Showing papers in "Current Microbiology in 2020"

A Brief Review on the Non-protein Amino Acid, Gamma-amino Butyric Acid (GABA): Its Production and Role in Microbes.

Abstract: Gamma-Aminobutyric acid (GABA) is a non-protein amino acid widely distributed in nature. It is produced through irreversible α-decarboxylation of glutamate by enzyme glutamate decarboxylase (GAD). GABA and GAD have been found in plants, animals, and microorganisms. GABA is distributed throughout the human body and it is involved in the regulation of cardiovascular conditions such as blood pressure and heart rate, and plays a role in the reduction of anxiety and pain. Although researchers had produced GABA by chemical method earlier it became less acceptable as it pollutes the environment. Researchers now use a more promising microbial method for the production of GABA. In the drug and food industry, demand for GABA is immense. So, large scale conversion of GABA by microbes has got much attention. So this review focuses on the isolation source, production, and functions of GABA in the microbial system. We also summarize the mechanism of action of GABA and its shunt pathway.

Omics Approaches to Pesticide Biodegradation.

Abstract: Pesticides are xenobiotic molecules necessary to control pests in agriculture, home, and industry. However, water and soil can become contaminated as a consequence of their extensive use. Therefore, because of its eco-friendly characteristics and efficiency, bioremediation of contaminated sites is a powerful tool with advantages over other kinds of treatments. For an efficient pesticides bioremediation, it is necessary to take into account different aspects related to the microbial metabolism and physiology. In this respect, OMICs studies such as genomics, transcriptomics, proteomics, and metabolomics are essential to generate relevant information about the genes and proteins involved in pesticide degradation, the metabolites generated by microbial pesticide degradation, and the cellular strategies to contend against stress caused by pesticide exposition. Pesticides as organochlorines and organophosphorus are the more commonly studied using OMIC approaches. To date, many genomes of microorganisms capable of degrading pesticides have been published, mainly bacterial strains from Burkholderia, Pseudomonas, and Rhodococcus genera. Following the genomic reports, transcriptomic studies, using microarrays and more recently next-generation sequencing technology RNA-Seq, in pesticide microbial degradation are the most numerous. Proteomics, metabolomics, as well as studies that combine different OMIC are gained interest. This review aims to describe a brief overview of pesticide biodegradation mechanisms; new tools to study microorganisms in natural environments; basic concepts of the OMICs approaches; as well as advances in methodologies associated with the analysis of that tools. Additionally, the most recent reports on genomics, transcriptomics, proteomics, and metabolomics during the degradation of pesticides are also analyzed.

Cholesterol-Lowering Effects of Lactobacillus Species.

Abstract: Probiotics are the living and non-pathogenic microbial supplements which, upon administration in adequate quantities, influence the host organism positively by improving gut health and enhancing intestinal mucosal integrity. They suppress potentially pathogenic microorganisms by competing with them for nutrients as well as space for gut adherence. Lactobacillus species are the most commonly used bacteria in the probiotic preparations and studies show that they have cholesterol-lowering effects on the hosts. Lipids are biological molecules that are insoluble in water and bile salts play a major role in their digestion as they are synthesized and conjugated to taurine or glycine in the liver. Bile salt hydrolase deconjugates taurine or glycine from bile salts. Cholesterol metabolism is influenced by the effect of Lactobacillus species on microbial populations as well as overall metabolic activity of human intestinal microflora. Deconjugation of bile salt, concentration of short-chain fatty acids and molar proportion of propionate constitute the major processes by which cholesterol lowering is brought about by Lactobacillus species. This review summarizes the cholesterol-lowering properties of this species. A significant number of Lactobacillus strains have been known to display substantial bile salt hydrolase activities and identifying those strains for use in therapeutic purposes can be a great advancement. Here, this identification is done using phylogenetic relationship for different identified potential probiotic Lactobacillus strains.

The Effect of Auxin and Auxin-Producing Bacteria on the Growth, Essential Oil Yield, and Composition in Medicinal and Aromatic Plants.

Abstract: Aromatic plants had been used since ancient times for their preservative and medicinal properties, and to impart aroma and flavor to food. Also their secondary metabolites are economically important as drugs, flavor and fragrances, pharmaceuticals, agrochemicals, dye, and pigments, pesticides, cosmetics, food additives, other industrially biochemical, and also play a major role in the adaptation of plants to their environment. Indole acetic acid-producing rhizobacteria inoculations increase in stomatal density and level of secondary metabolite and have a synergistic effect on monoterpene biosynthesis. Bacterial inoculation significantly affected and increased the chemical composition of essential oil, citronellol, and geraniol content in rose-scented geranium; essential oil composition and total phenolic content in marigold; density, number, and size of glandular trichomes in sweet wormwood and peppermint essential oil components such as geranyl acetate, limonene, and β–pinene in coriander; oil yield and content in calendula; yield of the herb in hyssop; oxygenated compounds, essential oil content and yield, anethol and changing the chemical composition in fennel; growth, number of glandular trichomes and essential oil yield, root branching and length, and total amount of essential oil, production of monoterpenes such as pulegone, menthol, menthone, menthofuran, and terpineol content, biosynthesis of secondary metabolites in peppermint; growth and essential oil yield in marjoram; glandular hair abundance, essential oil yield, and monoterpene biosynthesis in basil; phellandrene, limonene, borneol, and campor in rosemary; carvacrol, thymol, linalool, and borneol in oregano; and α-thujene, α-pinene, α-terpinene, p-simen, β–pinene, and γ-terpinene contents and essential oil yield in summer savory. Inoculation with IAA-producing bacteria medicinal roots increased the valerenic acid in valerian, essential oil and quality in vetiver, curcumin content in turmeric alkaloid and ginsenoside content in ginseng, and inulin content in Jerusalem artichoke.

Metagenomics Approaches in Discovery and Development of New Bioactive Compounds from Marine Actinomycetes

Abstract: Marine actinomycetes are prolific sources of marine drug discovery system contributing for several bioactive compounds of biomedical prominence. Metagenomics, a culture-independent technique through its sequence- and function-based screening has led to the discovery and synthesis of numerous biologically significant compounds like polyketide synthase, Non-ribosomal peptide synthetase, antibiotics, and biocatalyst. While metagenomics offers different advantages over conventional sequencing techniques, they also have certain limitations including bias classification, non-availability of quality DNA samples, heterologous expression, and host selection. The assimilation of advanced amplification and screening methods such as φ29 DNA polymerase, Next-Generation Sequencing, Cosmids, and recent bioinformatics tools like automated genome mining, anti-SMASH have shown promising results to overcome these constrains. Consequently, functional genomics and bioinformatics along with synthetic biology will be crucial for the success of the metagenomic approach and indeed for exploring new possibilities among the microbial consortia for the future drug discovery process.

Novel Biosynthesis of Copper Nanoparticles Using Zingiber and Allium sp. with Synergic Effect of Doxycycline for Anticancer and Bactericidal Activity

Abstract: Copper nanoparticles (CuNPs), due to their cost-effective synthesis, interesting properties, and a wide range of applications in conductive inks, cooling fluids, biomedical field, and catalysis, have attracted the attention of scientific community in recent years. The aim of the present study was to develop and characterize antibacterial and anticancer CuNPs synthesized via chemical and biological methods, and further synthesize CuNPs conjugated with doxycycline to study their synergic effect. During the chemical synthesis, ascorbic acid was used as a stabilizing agent, while Zingiber officinale and Allium sativum-derived extracts were used during the biological methods for synthesis of CuNPs. Characterization of CuNPs was performed by transmission electron microscopy (TEM), UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray crystallography (XRD). Antimicrobial evaluation of the nanomaterials against Pseudomonas aeruginosa and Escherichia coli was performed by using disk diffusion method, while anticancer behavior against HeLa and HepG2 cell lines was studied by MTT assay. TEM revealed spherical-shaped nanoparticles with mean size of 22.70 ± 5.67, 35.01 ± 5.84, and 19.02 ± 2.41 nm for CuNPs, Gin-CuNPs, and Gar-CuNPs, respectively, and surface plasmon resonance peaks were obtained at 570 nm, 575 nm, and 610 nm for CuNPs, Gar-CuNPs, and Gin-CuNPs, respectively. The results of FTIR confirmed the consumption of biomolecules from the plant extracts for the synthesis of CuNPs. XRD analysis also confirmed synthesis of CuNPs. Doxycycline-conjugated NPs exhibited more antibacterial effects than doxycycline or CuNPs alone. Copper nanoparticles prepared by biological synthesis are cost-effective and eco-friendly as compared to their chemical counterparts. The chemically synthesized nanoparticles displayed more significant antimicrobial activity when capped with doxycycline than Z. officinale and A. sativum-mediated CuNPs; however, green-synthesized nanoparticles showed greater anticancer activity than their chemical counterparts.

Moringa Oleifera Oil Modulates Rumen Microflora to Mediate In Vitro Fermentation Kinetics and Methanogenesis in Total Mix Rations.

Abstract: This study was conducted to evaluate potential of Moringa oleifera seed oil (MOSO) to modulate rumen microflora to mitigate methane (CH4) production in different total mixed rations (TMRs). Three TMRs with different roughage (R) to concentrate (C) ratio were used as substrates (R70:C30, R50:C50 and R30:C70) for in vitro fermentation study using batch culture technique. Results revealed that supplementation of MOSO in different rations with variable roughage to concentrates ratio altered (P < 0.05) CH4 production and fermentation parameters. M. oleifera seed oil at 3 and 4% increased (P < 0.01) microbial protein (MCP) and propionate concentration for all rations but decreased acetate concentration in R70:C30 TMR. Two levels of MOSO (3 and 4%) quadratically increased (P = 0.001) MCP and decreased acetate in R30:C70 while all levels increased propionate. For R30:C70 and R50:C50 rations, MOSO linearly and quadratically decreased (P < 0.001) protozoa and methanogen counts; however, protozoa, methanogens and bacteria were significantly increased in R70:C30 ration without any change in fungal counts. Supplementation of higher level of MOSO (4%) in high roughage ration (R70:C30) showed negative effects on diversity (Shannon index) and evenness of bacterial species as compared to control and lower oil level. Moreover, it also decreased Firmicutes to Bacteroidetes ratio in high roughage rations more obviously at lower levels. Moringa oil also stimulated Prevotella in both high and low roughages diets that indicates its potential to mediate rumen acidosis. Conclusively, MOSO enhanced fermentation kinetics and decreased CH4 production through effective modulation of rumen microbiome.

Lactobacillus Cell Surface Proteins Involved in Interaction with Mucus and Extracellular Matrix Components

Abstract: The gut microbiota is a complex microbial ecosystem where bacteria, through mutual interactions, cooperate in maintaining of wellbeing and health. Lactobacilli are among the most important constituents of human and animal intestinal microbiota and include many probiotic strains. Their presence ensures protection from invasion of pathogens, as well as stimulation of the immune system and protection of the intestinal flora, often exerted through the ability to interact with mucus and extracellular matrix components. The main factors responsible for mediating adhesion of pathogens and commensals to the gut are cell surface proteins that recognize host targets, as mucus layer and extracellular matrix proteins. In the last years, several adhesins have been reported to be involved in lactobacilli-host interaction often miming the same mechanism used by pathogens.

Probiotic Potential of Lactobacillus paracasei CT12 Isolated from Water Kefir Grains (Tibicos)

Abstract: The water kefir grains are a multi-species starter culture used to produce fermented beverages of sucrose solution with or without fruit extracts. The water kefir grains are known in Mexico as Tibicos, which are mainly used to produce Tepache, a traditional Mexican drink made by fermenting pineapple peel. The microbiota of Tibicos mainly include lactic acid bacteria (LAB) and since most probiotics belong to this group, Tibicos may represent a potential source of probiotic bacteria. Moreover, several bacteria isolated from kefir samples have been recognized as probiotics. Hence, the aim of this study was to assess the probiotic properties of a Lactobacillus strain isolated from Tibicos. The isolated, designed as CT12, was identified as Lactobacillus paracasei by sequencing 16S RNA gene. L. paracasei CT12 showed a survival rate of ca. 57% and 40% following simulated gastric and intestinal digestion, respectively. Besides, the strain was sensitive to ampicillin and erythromycin, and exhibited hydrophobicity (97-99%), autoaggregation (ca. 70%) and mucin adhesion properties (up to 90%), while no possessed haemolytic capacity. Furthermore, its cell-free supernatant displayed relevant antimicrobial, antifungal and antioxidant capacity. Hence, L. paracasei CT12 appears to possess a potential probiotic value.

Saccharomyces boulardii CNCM I-745: A Non-bacterial Microorganism Used as Probiotic Agent in Supporting Treatment of Selected Diseases

Abstract: The yeast Saccharomyces boulardii CNCM I-745 is a unique, non-bacterial microorganism classified as a probiotic agent. In this review article, at first, we briefly summarized the mechanisms responsible for its probiotic properties, e.g. adhesion to and elimination of enteropathogenic microorganisms and their toxins; extracellular cleavage of pathogens’ virulent factors; trophic and anti-inflammatory effects on the intestinal mucosa. The efficacy of S. boulardii administration was tested in variety of human diseases. We discussed the results of S. boulardii CNCM I-745 use in the treatment or prevention of Helicobacter pylori infections, diarrhoea (Clostridium difficile infections, antibiotic-associated diarrhoea, and traveller’s diarrhoea), inflammatory bowel diseases, irritable bowel syndrome, candidiasis, dyslipidemia, and small intestine bacterial overgrowth in patients with multiple sclerosis. In case of limited number of studies regarding this strain, we also presented studies demonstrating properties and efficacy of other strains of S. boulardii. Administration of S. boulardii CNCMI I-745 during antibiotic therapy has certain advantage over bacterial probiotics, because—due to its fungal natural properties—it is intrinsically resistant to the antibiotics and cannot promote the spread of antimicrobial resistance. Even though cases of fungemia following S. boulardii CNCM I-745 administration were reported, it should be treated as a widely available and safe probiotic strain.

Effect of Salinity Stress on Lipid Accumulation in Scenedesmus sp. and Chlorella sp.: Feasibility of Stepwise Culturing

Abstract: The enhanced lipid accumulation in microalgae is envisioned under special stress conditions with the cost of algal growth, which in turn affects the overall lipid productivity. The selection of suitable stress conditions facilitates better lipid productivity without any harmful effect on microalgae growth and algal biomass production. In the present study, we have attempted to select the best salinity conditions towards better growth, biomass accumulation, and lipid productivity of microalgae. The study also envisaged testing the feasibility of the stepwise salinity stress-induced cultivation approach to minimize the growth penalty effect of microalgae. The highest specific growth rate (0.129, 0.133, 0.113 µday−1) and doubling per day (0.185, 0.193, 0.163 per day) were obtained at salinity concentration of 40 mM NaCl in BG-11 medium for Scenedesmus quadricauda (Sq19), Scenedesmus dimorphus (Sd12), and Chlorella sp. (Chl16), respectively. Maximal lipid content of 18.28, 30.70, and 32.19%, and lipid productivity of 8.59, 13.81, and 10.27 mg l−1 day−1 were achieved at 160 mM of NaCl in BG-11 media with the Sq19, Sd12, and Chl16 algal isolates, respectively. The utilization of stepwise salinity stress (160 mM) induced cultivation of Sd12 algal isolate results in higher lipid content (39.42%) and slightly improved lipid productivity than the control (without any stress, 20.4% lipid content). The results indicate the feasibility of enhancing the lipid content and productivity through the salinity-induced stepwise cultivation strategy.

Growth Performance and Intestinal Microbiota Diversity in Pacific White Shrimp Litopenaeus vannamei Fed with a Probiotic Bacterium, Honey Prebiotic, and Synbiotic

Abstract: This study aimed to evaluate the growth performance and intestinal microbiota composition in Pacific white shrimp after probiotic, honey prebiotic, or synbiotic treatment. Pacific white shrimp were treated for 45 days with probiotic (1% (v/w) of Bacillus sp. NP5 RfR probiotic), prebiotic (0.5% (v/w) of honey prebiotic), synbiotic (1% (v/w) of probiotic and 0.5% (v/w) prebiotic), or control (without addition of probiotic and prebiotic). Next-generation sequencing (NGS) was used to assess the effects of these treatments on growth performance and intestinal microbial diversity. The administration of a probiotic, prebiotic, or synbiotic led to increases in specific growth rate, feed conversion ratio, and digestive enzyme activities of amylase, protease, and lipase in Pacific white shrimp. The prebiotic treatment demonstrated the greatest effect, with values of growth rate of 3.09 ± 0.02 (% day−1), feed conversion ratio of 1.45 ± 0.00, and enzyme activities of 1.388 ± 0.0211 IU mg−1 protein for amylase, 0.055 ± 0.0004 IU mg−1 protein for protease, and 0.152 ± 0.0025 IU mg−1 protein for lipase. Analysis of the intestinal microbiota diversity revealed that prebiotic administration caused dominance of the phylum Bacteroidetes, whereas the probiotic and synbiotic treatments caused dominance of the phylum Proteobacteria. Moreover, prebiotic treatment was able to increase the diversity of Microbacterium, Lactobacillus, and Neptunomonas, which are established probiotic candidates in aquaculture. The probiotic, prebiotic, and synbiotic treatments induced a number of operational taxonomic units (OTUs) significantly higher than control treatment, that is, 470, 480, 451, and 344 OTU, respectively.

Shiga Toxin-Producing and Enteroaggregative Escherichia coli in Animal, Foods, and Humans: Pathogenicity Mechanisms, Detection Methods, and Epidemiology.

Abstract: The main Enterobacteriaceae habitat is the mammal gastrointestinal tract. In most cases, this group of species displays a symbiotic relationship with its hosts. However, some groups may be pathogenic to humans, such as Shiga toxin-producing Escherichia coli and enteroaggregative Escherichia coli. The presence of these groups represents a direct risk to consumers, and recent serotypes displaying the presence of pathogenic genes in both groups are a novel challenge for food production. Thus, microbiological control strategies presenting accurate detection methodologies are required. However, with the appearance of mutations among different species, knowledge, genetic monitoring, and bioinformatics techniques must be expanded. In addition, as a strategy to ensure safe products on an industrial scale, the monitoring by different techniques and fundamentals should be applied throughout the entire processing chain. Therefore, the aim of this review is to describe the pathogenesis mechanisms of different groups, mutant strain dispersion, and current and alternative epidemiological investigation methods.

An Insight into Diversity and Functionalities of Gut Microbiota in Insects

Abstract: The gut microbiota has long been of research interests due to its nutritional importance for many insects. It has been demonstrated that diversity of gut microbiota in insects can be modulated by many factors, including habitats, feeding preference, etc. Besides, the community structure of gut microbiota could also be altered during the different life stages of host insects. With development of conventional culture-dependent technologies and advanced culture-independent technologies, comprehensive and deep understanding of the functions of gut microbiota and their relationship with host insects were achieved, especially for the nutrient metabolic process mediated by them. In this review, we summarized the gut microbiota composition, major methods for gut microbiota characterization, and vital nutrient metabolic process mediated by gut microbiota in different insects. The increasing knowledge on the modulation of gut microbiota will help us for the comprehension of the contribution of gut microbiota to the nutritional metabolism of insects, prompting their growth and health.

Role of Inorganic Phosphate Solubilizing Bacilli Isolated from Moroccan Phosphate Rock Mine and Rhizosphere Soils in Wheat (Triticum aestivum L) Phosphorus Uptake

Abstract: This work aimed to assess the ability of plant growth-promoting Bacilli isolated from wheat rhizosphere and rock phosphate mine soils to convert inorganic phosphate (Pi) from Moroccan natural phosphate (NP) to soluble forms. The effect of these bacteria on wheat plants in order to increase their phosphorus (P) uptake in vitro was also investigated. Bacteria were isolated from wheat rhizosphere and natural rock phosphate soils and screened for their ability to solubilize Tri-Calcium Phosphate (TCP) and Natural Rock Phosphate (NP), to produce indole-3-acetic acid (IAA), siderophores and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Isolates were identified by 16S rRNA sequencing and tested for their capacity to increase wheat plants growth and their phosphorus uptake.Twenty-four strains belonging to Bacillus genus isolated from both biotopes were screened for their ability to solubilize Pi. The highest NP solubilization was showed by strains isolated from wheat rhizosphere. Solubilization of Pi was accompanied by organic acid production. Strains produce IAA, siderophore and ACC deaminase. Inoculation assays using efficient NP-solubilizing bacilli strains from both sources showed the ability of these isolates to increase wheat growth and the phosphorus uptake under in vitro conditions. Bacilli strains isolated from rhizosphere soil and natural rock phosphorus soil showed effective solubilization of Pi from rock phosphate. Phosphate solubilizing Bacilli were evaluated for their plant growth promotion under in vitro conditions. Results revealed the positive effect of all strains on biometric parameters and P content of wheat seedlings.

Curtailing Quorum Sensing in Pseudomonas aeruginosa by Sitagliptin

Abstract: Pseudomonas aeruginosa coordinates the secretion of virulence factors through quorum sensing. Quorum sensing inhibitors can attenuate the pathogenesis of bacteria and help the immune system to eradicate them without targeting the bacterial growth. This study aimed to explore the anti-quorum sensing and anti-virulence activities of sitagliptin against P. aeruginosa PAO1 strain. Sub-inhibitory concentration of sitagliptin significantly inhibited the virulence factors pyocyanin, hemolysin, protease and elastase in addition to blocking swimming, swarming and twitching motilities and biofilm formation. In silico analysis showed that sitagliptin interacted with LasR receptors by hydrogen bonding and hydrophobic interaction, mainly with the amino acids leucine present at positions 40 and 125, tyrosine at position 56, serine at position 129, tryptophan at position 60, alanine at position 50 and phenyl alanine at position 101. qRT-PCR confirmed the anti-quorum sensing activity by reducing the expression level of QS genes lasI, lasR, rhlI, rhlR, pqsA and pqsR. In conclusion, sitagliptin is a novel anti-quorum sensing agent that can be used for treating P. aeruginosa infections.

The Degradation of Phenanthrene, Pyrene, and Fluoranthene and Its Conversion into Medium-Chain-Length Polyhydroxyalkanoate by Novel Polycyclic Aromatic Hydrocarbon-Degrading Bacteria

Abstract: Screening of high-efficient polycyclic aromatic hydrocarbon (PAH)-degrading bacteria is important due to environmental contamination by PAHs. In this study, sediment contaminated with phenanthrene (Phe), pyrene (Pyr), and fluoranthene (Fluo) was used as a source of bacteria. The ability of these isolated bacteria to convert PAHs into valuable products was determined. Based on a primary screening, 20 bacterial isolates were obtained; however, only three strains showed a good PAH-degrading ability, and were identified as Pseudomonas aeruginosa, Pseudomonas sp., and Ralstonia sp. PAH-degrading genes were detected in all isolates. Notably, all selected strains could degrade PAHs using the ortho or meta cleavage pathways due to the presence of catechol dioxygenase genes. The ability of isolated strains to convert PAHs into polyhydroxyalkanoate (PHA) was also evaluated in both single and mixed cultures. Single cultures of P. aeruginosa PAH-P02 showed 100% degradation of PAHs, with the highest biomass (1.27 ± 0.02 g l−1) and PHA content (38.20 ± 1.92% dry cell weight). However, degradative ability and PHA production were decreased when mixtures of PAHs were used. This study showed that P. aeruginosa, Pseudomonas sp., and Ralstonia sp. were able to degrade PAHs and convert them into medium-chain-length (mcl)-PHA. A high content of 3-hydroxydecanoate (3HD, C10) was observed in this study. The formation of mcl-PHA with high 3HD content from Pyr and Fluo, and the assessment of mixed cultures converting PAHs to mcl-PHA, were novel contributions.

Decolorization of Reactive Black 5 and Reactive Red 152 Azo Dyes by New Haloalkaliphilic Bacteria Isolated from the Textile Wastewater.

Abstract: Textile wastewaters are usually alkali and saline, so using haloalkaliphilic bacteria can be the best option for the treatment of wastewater. This study aimed at the decolorization of textile Reactive Black 5 and Reactive Red 152 dyes using new haloalkaliphilic bacteria isolated from the textile wastewater. Among 50 strains of bacteria isolated from the effluent of Kashan textile industry, three bacterial strains, namely D1, D2 and E49, exhibited high decolorization abilities for Reactive Black 5 and Reactive Red 152 dyes. Decolorization was evaluated through spectrophotometry at maximum absorbance wavelengths of 607 and 554 nm for Reactive Black 5 and Reactive Red 152, respectively. The highest decolorization percentage was observed at a dye concentration of 50 mg L−1. Aerobic conditions, 5% of the yeast extract and salt, 10% of peptone and glucose as nitrogen and carbon sources, respectively, and a pH range of 9–12 were considered as the optimal conditions for decolorization. The consortium of three haloalkaliphilic isolates showed a remarkable ability for decolorization of the Reactive Black 5 (87%) and Reactive Red 152 (85%) dyes. The consortium exhibited higher decolorization ability for the textile effluent, compared to individual bacterial inoculations. According to phenotypic characterization experiments and phylogenetic analyses based on comparing 16S rDNA sequence, the mentioned strains belonged to the genus Halomonas.

Augmented Biodegradation of Textile Azo Dye Effluents by Plant Endophytes: A Sustainable, Eco-Friendly Alternative.

Abstract: Textile industry consumes a large proportion of available water and releases huge amounts of toxic azo dye effluents, leading to an inevitable situation of acute environmental pollution that has been a significant threat to mankind. Decolorization or detoxification of harmful azo dyes has become a global priority to overcome the disastrous consequences and salvage the ecosystem. Biodegradation of textile azo dyes by endophytes stands to be a lucrative and viable alternative over conventional physico-chemical methods, owing to their eco-friendliness, cost-competitive and non-toxic nature. Especially, plant endophytic microbes exhibit promising biodegradation potential which has wired up the effective removal of textile azo dyes, attributing to their ability to produce dye degrading enzymes, laccases, peroxidases and azoreductases. Although both bacterial and fungal endophytes have been tried for azo dye degradation, endophytic fungi find broader application over bacteria. Despite of the advancements made in microbe-mediated biodegradation, there is still a need to fill the gap in lab to in situ translation of biodegradation research. This review concisely accentuates the xenobiotics of textile azo dyes and microbial mechanisms of biodegradation of textile azo dyes, positing plant endophytic community, especially bacterial and fungal endophytes as the potential dye degraders, highlighting currently reported dye degrading endophytic species.

Production of Mannosylerythritol Lipids (MELs) to be Used as Antimicrobial Agents Against S. aureus ATCC 6538

Abstract: Antimicrobial resistance (AMR) is a current major health issue, both for the high rates of resistance observed in bacteria that cause common infections and for the complexity of the consequences of AMR. Pathogens like Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Mycobacterium tuberculosis among others are clear examples of antibiotic-resistant threats. Biosurfactants have recently emerged as a potential new generation of anti-adhesive and anti-biofilm agents; mannosylerythritol lipids (MELs) are biosurfactants produced by a range of fungi. A range of structural variants of MELs can be formed and the proportion of each isomer in the fermentation depends on the yeast used, the carbon substrate used for growth and the duration of the fermentation. In order to allow assessment of the possible functions of MELs as antimicrobial molecules, small quantities of MEL were produced by controlled fermentation. Fermentations of the yeast Pseudozyma aphidis using rapeseed oil as a carbon source yielded up to 165 gMELs/kgSubstrate. The MELs formed by this strain was a mixture of MEL-A, MEL-B, MEL-C and MEL-D. The MELs produced were tested against S. aureus ATCC 6538 on pre-formed biofilm and on co-incubation biofilm experiments on silicone discs; showing a disruption of biomass, reduction of the biofilm metabolic activity and a bacteriostatic/bactericidal effect confirmed by a release of oxygen uptake [Formula: see text], the reduction of citrate synthase activity and scanning electron microscopy. The results show that MELs are promising antimicrobial molecules for biomedical technological applications that could be studied in detail in large-scale systems and in conjunction with animal tissue models.

Endophytic Bacteria Associated with Medicinal Plant Vernonia anthelmintica: Diversity and Characterization.

Abstract: Increasing evidence shows that endophytic bacteria living inside plant tissue may possess similar biological activity and produce similar metabolites to their hosts. This study aimed to determine the diversity of endophytic bacteria associated with Vernonia anthelmintica and to evaluate their biological activity. The bacteria were isolated from the plant tissue using culture-dependent techniques. Comparison of the 16S rRNA gene sequences of endophytic bacteria isolated from V. anthelmintica showed that isolates belong to the species Micrococcus endophyticus VERA1, Bacillus megaterium VERA2, Pseudomonas chlororaphis VERA3, P. kilonensis VERA4, Stenotrophomonas pavanii VERA5, B. endophyticus VERA6, S. maltophilia VERA7, Pantoea ananatis VERA8, B. atrophaeus VERA9 and M. flavus VERA10. Activity studies showed that the endophytic bacteria share several similar biological properties with their host plant including antimicrobial, anti-vitiligo and antidiabetic activities. These findings indicate that plant phytochemical compounds and activity play an important role in the physiological properties of their endophytes.

Selenate Reduction and Selenium Enrichment of Tea by the Endophytic Herbaspirillum sp. Strain WT00C

Abstract: Herbaspirillum sp. WT00C is a tea-plant-specific endophytic bacterium. A genomic survey revealed an intact pathway for selenocompound metabolism in the genome of this bacterium. When it was cultured with sodium selenate, Herbaspirillum sp. WT00C was able to turn the culture medium to red. Electron microscopy and energy-dispersive X-ray spectroscopy confirmed that Herbaspirillum sp. WT00C reduced selenite (Se6+) to elemental selenium (Se0), and selenium nanoparticles (SeNPs) were secreted outside bacterial cells and grew increasingly larger to form Se-nanospheres and finally crystallized to form selenoflowers. Biochemical assays showed that selenospheres contained proteins but not carbohydrates or lipids. The improvement of selenium enrichment of tea plants by Herbaspirillum sp. WT00C was also tested. After Herbaspirillum sp. WT00C was inoculated into tea seedlings via needle injection and soaking tea-cutting methods, this endophytic bacterium markedly enhanced selenium enrichment of tea. When the tea seedlings inoculated by soaking tea-cutting mode were cultivated in the selenium-containing soils, selenium contents of tea leaves in three experimental groups were more than twofold compared to those of control groups. Our study demonstrates that the endophytic bacterium Herbaspirillum sp. WT00C has the ability to reduce selenate and improve selenium enrichment of tea.

Glutathione is Involved in Detoxification of Peroxide and Root Nodule Symbiosis of Mesorhizobium huakuii

Abstract: Legumes interact with symbiotic rhizobia to produce nitrogen-fixation root nodules under nitrogen-limiting conditions. The contribution of glutathione (GSH) to this symbiosis and anti-oxidative damage was investigated using the M. huakuii gshB (encoding GSH synthetase) mutant. The gshB mutant grew poorly with different monosaccharides, including glucose, sucrose, fructose, maltose, or mannitol, as sole sources of carbon. The antioxidative capacity of gshB mutant was significantly decreased by these treatments with H2O2 under the lower concentrations and cumene hydroperoxide (CUOOH) under the higher concentrations, indicating that GSH plays different roles in response to organic peroxide and inorganic peroxide. The gshB mutant strain displayed no difference in catalase activity, but significantly lower levels of the peroxidase activity and the glutathione reductase activity than the wild type. The same level of catalase activity could be associated with upregulation of the transcriptional activity of the catalase genes under H2O2-induced conditions. The nodules infected by the gshB mutant were severely impaired in abnormal nodules, and showed a nodulation phenotype coupled to a 60% reduction in the nitrogen fixation capacity. A 20-fold decrease in the expression of two nitrogenase genes, nifH and nifD, is observed in the nodules induced by gshB mutant strain. The symbiotic deficiencies were linked to bacteroid early senescence.

The Function and Mechanism of Enterovirus 71 (EV71) 3C Protease.

Abstract: Enterovirus 71 (EV71) is the main pathogen of the hand, foot, and mouth disease. It was firstly isolated from sputum specimens of infants with central nervous system diseases in California in 1969, and has been repeatedly reported in various parts of the world, especially in the Asia-Pacific region. EV71 3C protein is a 183 amino acid cysteine protease that can cleave most structural and non-structural proteins of EV71. Based on the analysis and understanding of EV71 3C protease, it is helpful to study and treat diseases caused by EV71 virus infection. The EV71 3C protease promotes virus replication by cleaving EV71 synthesis or host proteins. Moreover, EV71 3C protease inhibits the innate immune system and causes apoptosis. At present, in order to deal with the damage caused by the EV71, it is urgent to develop antiviral drugs targeting 3C protease. This review will focus on the structure, function, and mechanism of EV71 3C protease.

Characterization of Extracellular Protease from the Haloarcheon Halococcus sp. Strain GUGFAWS-3 (MF425611)

Abstract: Halococcus agarilyticus GUGFAWS-3 (MF425611) was isolated from a marine white sponge of Haliclona sp., inhabiting the rocks in the intertidal region of Anjuna, Goa, India. Uniquely, the microbe simultaneously produces two halo-extremozymes in 25% NaCl, namely protease and lipase at 49.5 ± 0.4 and 3.67 ± 0.02 (U mL−1), respectively. The protease is constitutively produced in starch mineral salts medium with consistent 4 ± 1.0 mm zone of enzyme production, regardless of the non-availability of protein as substrate. The ethanol precipitated enzyme on dialysis and Sephadex G-200 gel filtration chromatography was partially purified to 12.26-fold and was active between 20 and 80 °C, 0–5 M NaCl, and pH 3–13. Optimum activity, however, was at 70 °C, 3 M NaCl, and pH 7. The enzyme was thermo stable at 70 °C with 50.26 ± 2.40% of relative enzyme activity at 75 min. Furthermore, it was stable in the presence of polar and non-polar organic solvents, detergents, and hydrocarbons. Several metal cations enhanced its activity in the order of Ca2+ > Ni2+ > Fe3+ > Co2+ > Mg2+ > Cu2+ > Mn2+. Dependence of enzyme on cysteine; serine, and metal ions was confirmed by β-mercaptoethanol; PMSF and EDTA, respectively which induced its partial inhibition. Additionally, protease inhibited in vitro biofilm formation in Staphylococcus aureus. Conclusively, the production of a neutral halo-thermophilic protease is reported for the first time in the genus Halococcus.

Biocompatible PHB Production from Bacillus Species Under Submerged and Solid-State Fermentation and Extraction Through Different Downstream Processing

Abstract: Catastrophic global accumulation of non-biodegradable plastic has led to efforts for production of alternative eco-friendly biopolymer. Here, we attempted to produce a biodegradable, cytocompatible and eco-friendly polyhydroxy-butyrate (PHB) from a pigmented Bacillus sp. C1 (2013) (KF626477) through submerged (SmF) and solid-state fermentation (SSF). Under SmF and SSF, 0.60 g l−1 and 1.56 g l−1 of PHB with 0.497 g l−1 of yellow fluorescent pigment (YFP) was produced. Fourier transform infrared (FTIR) absorption bands at 1719–1720 cm−1 indicate the presence of C=O group of PHB. Nuclear magnetic resonance (NMR) exhibited the typical chemical shift patterns of PHB, and crystallinity was confirmed from X-ray diffraction (XRD). The melting temperature (Tm), degradation temperature (Td) and crystallinity (Xc) of extracted PHB were found to be 171 °C, 288 °C and 35%, respectively. FACS (Fluorescence-activated cell sorting) confirmed cytocompatibility of PHB at 400 µg ml−1 in mouse fibroblast line. Moreover, biodegradability and elevated cytocompatibility of the PHB produced through SSF make them highly potential biomaterials to be used as a drug delivery carrier in future.

Phage Transduction is Involved in the Intergeneric Spread of Antibiotic Resistance-Associated bla CTX-M , mel, and tetM Loci in Natural Populations of Some Human and Animal Bacterial Pathogens

Abstract: The horizontal genetic transfer (HGT) of antibiotic resistance genes (ARGs) mediated by species-specific bacteriophages contributes to the emergence of antibiotic-resistant strains in natural populations of human and animal bacterial pathogens posing a significant threat to global public health. However, it is unclear and needs to be determined whether polyvalent bacteriophages play any role in the intergeneric transmission of ARGs. In this study, we examined the genome sequences of 2239 bacteriophages from different sources for the presence of ARGs. The identified ARG-carrying bacteriophages were then analyzed by PHACTS, PHAST, and HostPhinder programs to determine their lifestyles, genes coding for bacterial cell lysis, recombinases, and a spectrum of their potential host species, respectively. We employed the SplitsTree, RDP4 and SimPlot software packages in recombination tests to identify HGT events of ARGs between these bacteriophages and bacteria. In our analyses, some ARG-carrying bacteriophages exhibited temperate and/or polyvalent patterns. The bootstrap values (97–100) for the SplitsTree-generated parallelograms, fit values (97–100) for splits networks, Phi P values (< 10−17 to 3.9 × 10−16), RDP4 P values (≤ 7.8 × 10−03), and the SimPlot results, provided strong statistical evidence for the phage transduction events of blaCTX-M, mel, and tetM loci on inter-species level. These events involved several host species such as Escherichia coli, Salmonella enterica, Shigella sonnei, Streptococcus pneumoniae and Bacillus coagulans. HGT of mel loci between Erysipelothrix and Streptococcus phages were also detected. These results firmly suggest that certain bacteriophages possibly with temperate properties induce the intergeneric dissemination of blaCTX-M, mel and tetM in the above species.

Complete Genome Sequence of Sphingobacterium psychroaquaticum Strain SJ-25, an Aerobic Bacterium Capable of Suppressing Fungal Pathogens

Abstract: Using antagonistic bacterium is an effective method to control plant disease by fungal pathogens. An aerobic bacterium designated SJ-25, capable of suppressing Fusarium graminearum, Exserohilum turcicum, Pythium aphanidermatum, and Cochliobolus sativus, was isolated from farmland soil. The phylogenetic analysis revealed that strain SJ-25 belongs to the species of Sphingobacterium psychroaquaticum. The genome of strain SJ-25 consists of a 4,396,535-bp chromosome with a G+C content of 41.7 mol%; including 3696 CDS, 64 tRNA genes and six rRNA operons. Genomic analysis revealed that its genome contains multiple genes responsible for biosynthesis of siderophore, methyl 4-hydroxybenzoate, chitinase, giving strain SJ-25 the antagonistic ability on fungi pathogen. Strain SJ-25 harbors sets genes responsible for production of 2, 3-butanediol and salicylic acid, which could elicit the induced systemic resistance of the host plant. This genome sequence could be used as a basis material for further exploration of antagonistic mechanisms on fungi, widening our understanding of the ecological role of the genus Sphingobacterium in farmland ecosystem.

Oxidative Stress Influences Pseudomonas aeruginosa Susceptibility to Antibiotics and Reduces Its Pathogenesis in Host

Abstract: Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes serious infections in humans, notably cystic fibrosis. P. aeruginosa faces various stresses such as oxidative stress either in the environment or within the host during infection. In the present study, the influence of oxidative stress on both Pseudomonas antibiotic susceptibility and host pathogenesis was characterized. Prior exposure to H2O2 significantly altered P. aeruginosa susceptibility to tested antibiotics; colistin, ciprofloxacin, tobramycin, and ceftazidime. The minimum inhibitory concentrations (MICs) of tested antibiotics either increased or decreased following H2O2 exposure. Importantly, RT-qPCR revealed that expression of quorum sensing genes, that regulate virulence factors production in P. aeruginosa, was significantly higher in unstressed relative to H2O2-stressed cells. The impact of P. aeruginosa exposure to oxidative stress by H2O2 on bacterial pathogenesis was investigated using in vivo mice infection model. Interestingly, exposure to oxidative stress markedly reduces P. aeruginosa pathogenesis in mice. Unstressed P. aeruginosa was able to kill more mice as compared to H2O2-stressed bacteria. In addition, body weight of mice infected with unstressed P. aeruginosa was lower than that of mice inoculated with stressed bacteria. Isolated organs (spleen, liver, and kidney) from mice infected with unstressed bacteria exhibited increased weight as well as bacterial load in comparison with mice infected with stressed bacteria. In summary, current data highlight the impact of oxidative stress on P. aeruginosa antibiotic susceptibility as well as host pathogenesis. These findings could be helpful in treatment of infections caused by this important pathogen.

Exploring the Role of Bacterial Extracellular Polymeric Substances for Sustainable Development in Agriculture.

Abstract: The incessant need to increase crop yields has led to the development of many chemical fertilizers containing NPK (nitrogen–phosphorous–potassium) which can degrade soil health in the long term. In addition, these fertilizers are often leached into nearby water bodies causing algal bloom and eutrophication. Bacterial secondary metabolites exuded into the extracellular space, termed extracellular polymeric substances (EPS) have gained commercial significance because of their biodegradability, non-toxicity, and renewability. In many habitats, bacterial communities faced with adversity will adhere together by production of EPS which also serves to bond them to surfaces. Typically, hygroscopic, EPS retain moisture in desiccating conditions and modulate nutrient exchange. Many plant growth-promoting bacteria (PGPR) combat harsh environmental conditions like salinity, drought, and attack of pathogens by producing EPS. The adhesive nature of EPS promotes soil aggregation and restores moisture thus combating soil erosion and promoting soil fertility. In addition, these molecules play vital roles in maintaining symbiosis and nitrogen fixation thus enhancing sustainability. Thus, along with other commercial applications, EPS show promising avenues for improving agricultural productivity thus helping to address land scarcity as well as minimizing environmental pollution.