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Showing papers on "Bacteria published in 2019"


Journal ArticleDOI
TL;DR: The relative abundance of faecal Bacteroides was negatively correlated with an altered GABA-mediated response in a depression patient cohort and genome-based metabolic modelling of the human gut microbiota revealed multiple genera with the predicted capability to produce or consume GABA.
Abstract: The gut microbiota affects many important host functions, including the immune response and the nervous system1. However, while substantial progress has been made in growing diverse microorganisms of the microbiota2, 23-65% of species residing in the human gut remain uncultured3,4, which is an obstacle for understanding their biological roles. A likely reason for this unculturability is the absence in artificial media of key growth factors that are provided by neighbouring bacteria in situ5,6. In the present study, we used co-culture to isolate KLE1738, which required the presence of Bacteroides fragilis to grow. Bioassay-driven purification of B. fragilis supernatant led to the isolation of the growth factor, which, surprisingly, is the major inhibitory neurotransmitter GABA (γ-aminobutyric acid). GABA was the only tested nutrient that supported the growth of KLE1738, and a genome analysis supported a GABA-dependent metabolism mechanism. Using growth of KLE1738 as an indicator, we isolated a variety of GABA-producing bacteria, and found that Bacteroides ssp. produced large quantities of GABA. Genome-based metabolic modelling of the human gut microbiota revealed multiple genera with the predicted capability to produce or consume GABA. A transcriptome analysis of human stool samples from healthy individuals showed that GABA-producing pathways are actively expressed by Bacteroides, Parabacteroides and Escherichia species. By coupling 16S ribosmal RNA sequencing with functional magentic resonance imaging in patients with major depressive disorder, a disease associated with an altered GABA-mediated response, we found that the relative abundance levels of faecal Bacteroides are negatively correlated with brain signatures associated with depression.

488 citations


Journal ArticleDOI
20 Nov 2019-Nature
TL;DR: Bacterial symbionts of animals may contain antibiotics that are particularly suitable for development into therapeutics; one such compound, darobactin, is active against important Gram-negative pathogens both in vitro and in animal models of infection.
Abstract: The current need for novel antibiotics is especially acute for drug-resistant Gram-negative pathogens1,2. These microorganisms have a highly restrictive permeability barrier, which limits the penetration of most compounds3,4. As a result, the last class of antibiotics that acted against Gram-negative bacteria was developed in the 1960s2. We reason that useful compounds can be found in bacteria that share similar requirements for antibiotics with humans, and focus on Photorhabdus symbionts of entomopathogenic nematode microbiomes. Here we report a new antibiotic that we name darobactin, which was obtained using a screen of Photorhabdus isolates. Darobactin is coded by a silent operon with little production under laboratory conditions, and is ribosomally synthesized. Darobactin has an unusual structure with two fused rings that form post-translationally. The compound is active against important Gram-negative pathogens both in vitro and in animal models of infection. Mutants that are resistant to darobactin map to BamA, an essential chaperone and translocator that folds outer membrane proteins. Our study suggests that bacterial symbionts of animals contain antibiotics that are particularly suitable for development into therapeutics.

364 citations


Journal ArticleDOI
TL;DR: The acquisition of specific antimicrobial resistance can compromise or enhance biofilm formation in several species of Gram-negative bacteria, however, multidrug-resistant isolates do not show a trend to being greater biofilm producers than non-multiresistant isolates.
Abstract: Gram-negative microorganisms are a significant cause of infection in both community and nosocomial settings. The increase, emergence, and spread of antimicrobial resistance among bacteria are the most important health problems worldwide. One of the mechanisms of resistance used by bacteria is biofilm formation, which is also a mechanism of virulence. This study analyzed the possible relationship between antimicrobial resistance and biofilm formation among isolates of three Gram-negative bacteria species. Several relationships were found between the ability to form biofilm and antimicrobial resistance, being different for each species. Indeed, gentamicin and ceftazidime resistance was related to biofilm formation in Escherichia coli, piperacillin/tazobactam, and colistin in Klebsiella pneumoniae, and ciprofloxacin in Pseudomonas aeruginosa. However, no relationship was observed between global resistance or multidrug-resistance and biofilm formation. In addition, compared with other reported data, the isolates in the present study showed higher rates of antimicrobial resistance. In conclusion, the acquisition of specific antimicrobial resistance can compromise or enhance biofilm formation in several species of Gram-negative bacteria. However, multidrug-resistant isolates do not show a trend to being greater biofilm producers than non-multiresistant isolates.

180 citations


Journal ArticleDOI
TL;DR: LAB-treated silage enhanced the number of desirable Lactobacillus and inhibited the growth of undesirable microorganisms, such as Acinetobacter, in conclusion.

152 citations


Journal ArticleDOI
TL;DR: FCEO showed a significant reduction effect on the growth rate of surviving bacteria and lead to lysis of the cell wall, intracellular ingredient leakage, and consequently, cell death.
Abstract: In this work, antibacterial activity of finger citron essential oil (FCEO, Citrus medica L. var. sarcodactylis) and its mechanism against food-borne bacteria were evaluated. A total of 28 components in the oil were identified by gas chromatography-mass spectrometry, in which limonene (45.36%), γ-terpinene (21.23%), and dodecanoic acid (7.52%) were three main components. For in vitro antibacterial tests, FCEO exhibited moderately antibacterial activity against common food-borne bacteria: Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus. It showed a better bactericidal effect on Gram-positive bacteria than Gram-negative. Mechanisms of the antibacterial action were investigated by observing changes of bacteria morphology according to scanning electron microscopy, time-kill analysis, and permeability of cell and membrane integrity. Morphology of tested bacteria was changed and damaged more seriously with increased concentration and exposure time of FCEO. FCEO showed a significant reduction effect on the growth rate of surviving bacteria and lead to lysis of the cell wall, intracellular ingredient leakage, and consequently, cell death.

123 citations


Journal ArticleDOI
TL;DR: Results of available studies indicate the depolarization and alteration of membrane fluidity as mechanisms underlying the inhibition of pathogenicacteria by fruit PC, which reveal fruit PC have potential antimicrobial properties, which should be rationally exploited in solutions to control pathogenic bacteria.

120 citations


Journal ArticleDOI
TL;DR: The mechanisms implicated in iron uptake and the challenges associated with the design and utilization of siderophore-mimicking antibiotics are discussed.
Abstract: Iron is an essential nutrient for bacterial growth, replication, and metabolism. Humans store iron bound to various proteins such as hemoglobin, haptoglobin, transferrin, ferritin, and lactoferrin, limiting the availability of free iron for pathogenic bacteria. However, bacteria have developed various mechanisms to sequester or scavenge iron from the host environment. Iron can be taken up by means of active transport systems that consist of bacterial small molecule siderophores, outer membrane siderophore receptors, the TonB-ExbBD energy-transducing proteins coupling the outer and the inner membranes, and inner membrane transporters. Some bacteria also express outer membrane receptors for iron-binding proteins of the host and extract iron directly from these for uptake. Ultimately, iron is acquired and transported into the bacterial cytoplasm. The siderophores are small molecules produced and released by nearly all bacterial species and are classified according to the chemical nature of their iron-chelating group (ie, catechol, hydroxamate, α-hydroxyl-carboxylate, or mixed types). Siderophore-conjugated antibiotics that exploit such iron-transport systems are under development for the treatment of infections caused by gram-negative bacteria. Despite demonstrating high in vitro potency against pathogenic multidrug-resistant bacteria, further development of several candidates had stopped due to apparent adaptive resistance during exposure, lack of consistent in vivo efficacy, or emergence of side effects in the host. However, cefiderocol, with an optimized structure, has advanced and has been investigated in phase 1 to 3 clinical trials. This article discusses the mechanisms implicated in iron uptake and the challenges associated with the design and utilization of siderophore-mimicking antibiotics.

118 citations


Journal ArticleDOI
TL;DR: This work leveraged sequences from thousands of uncultivated organisms and identified protein families that co-occur in genomes that are likely foundational for lineage capacities, suggesting persistence of core sets of proteins since lineage divergence.
Abstract: Candidate phyla radiation (CPR) bacteria separate phylogenetically from other bacteria, but the organismal distribution of their protein families remains unclear. Here, we leveraged sequences from thousands of uncultivated organisms and identified protein families that co-occur in genomes, thus are likely foundational for lineage capacities. Protein family presence/absence patterns cluster CPR bacteria together, and away from all other bacteria and archaea, partly due to proteins without recognizable homology to proteins in other bacteria. Some are likely involved in cell-cell interactions and potentially important for episymbiotic lifestyles. The diversity of protein family combinations in CPR may exceed that of all other bacteria. Over the bacterial tree, protein family presence/absence patterns broadly recapitulate phylogenetic structure, suggesting persistence of core sets of proteins since lineage divergence. The CPR could have arisen in an episode of dramatic but heterogeneous genome reduction or from a protogenote community and co-evolved with other bacteria.

95 citations


Journal ArticleDOI
TL;DR: It is shown that conjugation and specific killing of targeted bacteria occurs in the microbiota of zebrafish and crustacean larvae, which are natural hosts for Vibrio spp.
Abstract: Targeted killing of pathogenic bacteria without harming beneficial members of host microbiota holds promise as a strategy to cure disease and limit both antimicrobial-related dysbiosis and development of antimicrobial resistance. We engineer toxins that are split by inteins and deliver them by conjugation into a mixed population of bacteria. Our toxin-intein antimicrobial is only activated in bacteria that harbor specific transcription factors. We apply our antimicrobial to specifically target and kill antibiotic-resistant Vibrio cholerae present in mixed populations. We find that 100% of antibiotic-resistant V. cholerae receiving the plasmid are killed. Escape mutants were extremely rare (10-6-10-8). We show that conjugation and specific killing of targeted bacteria occurs in the microbiota of zebrafish and crustacean larvae, which are natural hosts for Vibrio spp. Toxins split with inteins could form the basis of precision antimicrobials to target pathogens that are antibiotic resistant.

93 citations


Journal ArticleDOI
TL;DR: These findings demonstrate that L. monocytogenes uses EVs for toxin release and implicate these structures in mammalian cytotoxicity, and show that dynamic lipid structures are released from L.monocyTogenes during infection.

92 citations


Journal ArticleDOI
06 Nov 2019-Nature
TL;DR: A previously undescribed mechanism for interbacterial antagonism is revealed and a physiological role for the metabolite (p)ppApp in bacteria is demonstrated in bacteria.
Abstract: Bacteria have evolved sophisticated mechanisms to inhibit the growth of competitors1. One such mechanism involves type VI secretion systems, which bacteria can use to inject antibacterial toxins directly into neighbouring cells. Many of these toxins target the integrity of the cell envelope, but the full range of growth inhibitory mechanisms remains unknown2. Here we identify a type VI secretion effector, Tas1, in the opportunistic pathogen Pseudomonas aeruginosa. The crystal structure of Tas1 shows that it is similar to enzymes that synthesize (p)ppGpp, a broadly conserved signalling molecule in bacteria that modulates cell growth rate, particularly in response to nutritional stress3. However, Tas1 does not synthesize (p)ppGpp; instead, it pyrophosphorylates adenosine nucleotides to produce (p)ppApp at rates of nearly 180,000 molecules per minute. Consequently, the delivery of Tas1 into competitor cells drives rapid accumulation of (p)ppApp, depletion of ATP, and widespread dysregulation of essential metabolic pathways, thereby resulting in target cell death. Our findings reveal a previously undescribed mechanism for interbacterial antagonism and demonstrate a physiological role for the metabolite (p)ppApp in bacteria.

Journal ArticleDOI
11 Jan 2019-ACS Nano
TL;DR: Broad-spectrum bacterial inhibition was demonstrated for the polymeric antimicrobials, especially highly opportunistic Gram-negative bacteria, such as Pseudomona aeruginosa based on the synergy of physical destruction and photodynamic therapy, without detectable resistance.
Abstract: Highly pathogenic Gram-negative bacteria and their drug resistance are a severe public health threat with high mortality. Gram-negative bacteria are hard to kill due to the complex cell envelopes with low permeability and extra defense mechanisms. It is challenging to treat them with current strategies, mainly including antibiotics, peptides, polymers, and some hybrid materials, which still face the issue of drug resistance, limited antibacterial selectivity, and severe side effects. Together with precise bacteria targeting, synergistic therapeutic modalities, including physical membrane damage and photodynamic eradication, are promising to combat Gram-negative bacteria. Herein, pathogen-specific polymeric antimicrobials were formulated from amphiphilic block copolymers, poly(butyl methacrylate)- b-poly(2-(dimethylamino) ethyl methacrylate- co-eosin)- b-ubiquicidin, PBMA- b-P(DMAEMA- co-EoS)-UBI, in which pathogen-targeting peptide ubiquicidin (UBI) was tethered in the hydrophilic chain terminal, and Eosin-Y was copolymerized in the hydrophilic block. The micelles could selectively adhere to bacteria instead of mammalian cells, inserting into the bacteria membrane to induce physical membrane damage and out-diffusion of intracellular milieu. Furthermore, significant in situ generation of reactive oxygen species was observed upon light irradiation, achieving further photodynamic eradication. Broad-spectrum bacterial inhibition was demonstrated for the polymeric antimicrobials, especially highly opportunistic Gram-negative bacteria, such as Pseudomona aeruginosa ( P. aeruginosa) based on the synergy of physical destruction and photodynamic therapy, without detectable resistance. In vivo P. aeruginosa-infected knife injury model and burn model both proved good potency of bacteria eradication and promoted wound healing, which was comparable with commercial antibiotics, yet no risk of drug resistance. It is promising to hurdle the infection and resistance suffered from highly opportunistic bacteria.

Journal ArticleDOI
TL;DR: The identification of one Halomonas and one Bacillus isolate that, when used to inoculate young alfalfa seedlings, stimulate plant growth in the presence of 1% NaCl, a level that significantly inhibits growth of uninoculated plants is identified.
Abstract: Halophytes are plants that are adapted to grow in saline soils, and have been widely studied for their physiological and molecular characteristics, but little is known about their associated microbiomes. Bacteria were isolated from the rhizosphere and as root endophytes of Salicornia rubra, Sarcocornia utahensis, and Allenrolfea occidentalis, three native Utah halophytes. A total of 41 independent isolates were identified by 16S rRNA gene sequencing analysis. Isolates were tested for maximum salt tolerance, and some were able to grow in the presence of up to 4 M NaCl. Pigmentation, Gram stain characteristics, optimal temperature for growth, and biofilm formation of each isolate aided in species identification. Some variation in the bacterial population was observed in samples collected at different times of the year, while most of the genera were present regardless of the sampling time. Halomonas, Bacillus, and Kushneria species were consistently isolated both from the soil and as endophytes from roots of all three plant species at all collection times. Non-culturable bacterial species were analyzed by Illumina DNA sequencing. The most commonly identified bacteria were from several phyla commonly found in soil or extreme environments: Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, and Gamma- and Delta-Proteobacteria. Isolates were tested for the ability to stimulate growth of alfalfa under saline conditions. This screening led to the identification of one Halomonas and one Bacillus isolate that, when used to inoculate young alfalfa seedlings, stimulate plant growth in the presence of 1% NaCl, a level that significantly inhibits growth of uninoculated plants. The same bacteria used in the inoculation were recovered from surface sterilized alfalfa roots, indicating the ability of the inoculum to become established as an endophyte. The results with these isolates have exciting promise for enhancing the growth of inoculated alfalfa in salty soil.

Journal ArticleDOI
TL;DR: Characterizations of synthesized GO confirmed the transition of graphene to GO and the antibacterial activity of GO was concentration and time-dependent and loss of membrane integrity in bacteria was enhanced with increasing GO concentrations and this corresponded to the elevated release of LDH in the reaction medium.

Journal ArticleDOI
TL;DR: The activity of digestive tract was stronger than cultured gut bacteria, andEnzymatic similarity between oatmeal and cellulose diets, was shown, and all three plastics diet resulted in different activity in both, digestive tract and bacteria.

Journal ArticleDOI
TL;DR: A mutually beneficial interaction between two bacteria isolated from the gut microbiota of Drosophila, i.e., Acetobacter fabarum and Lactobacillus brevis is investigated, suggesting that one species consumes the waste products of the other, leading to greater productivity of the microbial community and modifying the nutrients available to the host.
Abstract: Interactions between species shape the formation and function of microbial communities. In the gut microbiota of animals, cross-feeding of metabolites between microbes can enhance colonization and influence host physiology. We examined a mutually beneficial interaction between two bacteria isolated from the gut microbiota of Drosophila, i.e., Acetobacter fabarum and Lactobacillus brevis. After developing an in vitro coculture assay, we utilized a genetic screen to identify A. fabarum genes required for enhanced growth with L. brevis. The screen, and subsequent genetic analyses, showed that the gene encoding pyruvate phosphate dikinase (ppdK) is required for A. fabarum to benefit fully from coculture. By testing strains with mutations in a range of metabolic genes, we provide evidence that A. fabarum can utilize multiple fermentation products of L. brevis. Mutualism between the bacteria in vivo affects gnotobiotic Drosophila melanogaster; flies associated with A. fabarum and L. brevis showed >1,000-fold increases in bacterial cell density and significantly lower triglyceride storage than monocolonized flies. Mutation of ppdK decreased A. fabarum density in flies cocolonized with L. brevis, consistent with the model in which Acetobacter employs gluconeogenesis to assimilate Lactobacillus fermentation products as a source of carbon in vivo. We propose that cross-feeding between these groups is a common feature of microbiota in Drosophila. IMPORTANCE The digestive tracts of animals are home to a community of microorganisms, the gut microbiota, which affects the growth, development, and health of the host. Interactions among microbes in this inner ecosystem can influence which species colonize the gut and can lead to changes in host physiology. We investigated a mutually beneficial interaction between two bacterial species from the gut microbiota of fruit flies. By coculturing the bacteria in vitro, we were able to identify a metabolic gene required for the bacteria to grow better together than they do separately. Our data suggest that one species consumes the waste products of the other, leading to greater productivity of the microbial community and modifying the nutrients available to the host. This study provides a starting point for investigating how these and other bacteria mutually benefit by sharing metabolites and for determining the impact of mutualism on host health.

Journal ArticleDOI
Guobin Qi1, Fang Hu1, Kenry1, Leilei Shi1, Min Wu1, Bin Liu1 
TL;DR: An aggregation-induced emission (AIE) bioprobe that can detect bacterial infection and kill bacteria surviving inside macrophages through a dynamic process, notably specific molecular tailoring of the probe by caspase-1 activation in infected macrophage and accumulation of the residue on phagosomes containing bacteria, leading to light-up fluorescent signals.
Abstract: The detection and elimination of intracellular bacteria remain a major challenge. In this work, we report an aggregation-induced emission (AIE) bioprobe that can detect bacterial infection and kill bacteria surviving inside macrophages through a dynamic process, notably specific molecular tailoring of the probe by caspase-1 activation in infected macrophages and accumulation of the residue on phagosomes containing bacteria, leading to light-up fluorescent signals. Moreover, the AIEgen can serve as a photosensitizer for generation of reactive oxygen species (ROS); and the average ROS indicator fluorescent signal intensity per unit area in the bacterial phagosomes is approximately 2.7-fold higher than that in the cytoplasm. This, in turn, induces bacteria killing with high efficiency and minimal cytotoxicity towards macrophages. We envision that this specific light-up bioprobe may provide a new approach for selective and sensitive detection and eradication of intracellular bacterial infections.

Journal ArticleDOI
23 Jul 2019-PeerJ
TL;DR: The IAA production potential of theacterial isolates can be enhanced by affecting optimum growth conditions for bacterial isolates and can be used for the optimal production of bacterial IAA and its utilization for plant growth improvement can lead to better yield in an eco-friendly manner.
Abstract: Background Auxin production by bacteria is one of the most important direct mechanisms utilized by plant growth-promoting bacteria (PGPB) for the betterment of plants naturally because auxin is a plant friendly secondary metabolite synthesized naturally by bacteria, and hence improves the growth of associated plants. So, the current study focuses on bacterial synthesis of Indole-3-acetic acid (IAA) for plant growth improvement. Methods In the current study, the PGPB were selected on the basis of their auxin production potential and their growth promoting attributes were evaluated. Indole-3-acetic acid producing potential of two selected bacterial isolates was observed by varying different growth conditions i.e., media composition, carbon sources (glucose, sucrose and lactose) and different concentrations of precursor. Influence of various physiological factors (temperature and incubation time period) on IAA production potential was also evaluated. Results Both the bacterial strains Bacillus cereus (So3II) and B. subtilis (Mt3b) showed variable potential for the production of bacterial IAA under different set of growth and environmental conditions. Hence, the IAA production potential of the bacterial isolates can be enhanced by affecting optimum growth conditions for bacterial isolates and can be used for the optimal production of bacterial IAA and its utilization for plant growth improvement can lead to better yield in an eco-friendly manner.

Journal ArticleDOI
TL;DR: It is shown that antibiotics can induce MVs through different routes in the important human pathogen Staphylococcus aureus, and evidence that the amount of DNA associated with MVs formed by phage lysis is greater than that for MV formed by β-lactam antibiotic-induced blebbing is presented.
Abstract: Bacterial membrane vesicle research has so far focused mainly on Gram-negative bacteria. Only recently have Gram-positive bacteria been demonstrated to produce and release extracellular membrane vesicles (MVs) that contribute to bacterial virulence. Although treatment of bacteria with antibiotics is a well-established trigger of bacterial MV formation, the underlying mechanisms are poorly understood. In this study, we show that antibiotics can induce MVs through different routes in the important human pathogen Staphylococcus aureus DNA-damaging agents and antibiotics inducing the SOS response triggered vesicle formation in lysogenic strains of S. aureus but not in their phage-devoid counterparts. The β-lactam antibiotics flucloxacillin and ceftaroline increased vesicle formation in a prophage-independent manner by weakening the peptidoglycan layer. We present evidence that the amount of DNA associated with MVs formed by phage lysis is greater than that for MVs formed by β-lactam antibiotic-induced blebbing. The purified MVs derived from S. aureus protected the bacteria from challenge with daptomycin, a membrane-targeting antibiotic, both in vitro and ex vivo in whole blood. In addition, the MVs protected S. aureus from killing in whole blood, indicating that antibiotic-induced MVs function as a decoy and thereby contribute to the survival of the bacterium.

Journal ArticleDOI
TL;DR: Conventional wastewater treatment is not sufficient for the removal of hygienically relevant bacteria and achieves only limited reductions, so metagenome analyses demonstrated the accumulation of facultative pathogenic bacteria, antibiotic resistance genes, virulence factor genes, and metabolic gene targets in the back flush retentates of the membranes, which opens further questions about retentate fluid material handling at urban wastewater treatment plants.
Abstract: Conventional wastewater treatment is not sufficient for the removal of hygienically relevant bacteria and achieves only limited reductions. This study focuses on the reduction efficiencies of two semi-industrial ultrafiltration units operating at a large scale municipal wastewater treatment plant. In total, 7 clinically relevant antibiotic resistance genes, together with 3 taxonomic gene markers targeting specific facultative pathogenic bacteria were analysed via qPCR analyses before and after advanced treatment. In parallel with membrane technologies, an ozone treatment (1 g ozone/g DOC) was performed for comparison of the different reduction efficiencies. Both ultrafiltration units showed increased reduction efficiencies for facultative pathogenic bacteria and antibiotic resistance genes of up to 6 log units, resulting mostly in a strong reduction of the bacterial targets. In comparison, the ozone treatment showed some reduction efficiency, but was less effective compared with ultrafiltration due to low ozone dosages frequently used for micro-pollutant removal at municipal wastewater treatment plants. Additionally, metagenome analyses demonstrated the accumulation of facultative pathogenic bacteria, antibiotic resistance genes, virulence factor genes, and metabolic gene targets in the back flush retentate of the membranes, which opens further questions about retentate fluid material handling at urban wastewater treatment plants.

Journal ArticleDOI
TL;DR: A fluorescent probe BacGO is presented, which shows the best universal selectivity for Gram-positive bacteria among known probes with a minimum staining procedure for sample detection and enrichment of the live bacteria.
Abstract: The rapid and sensitive classification of bacteria is the first step of bacterial community research and the treatment of infection. Herein, a fluorescent probe BacGO is presented, which shows the best universal selectivity for Gram-positive bacteria among known probes with a minimum staining procedure for sample detection and enrichment of the live bacteria. BacGO could also be used to assess of the Gram status in the bacterial community from wastewater sludge. Furthermore, BacGO could sensitively and selectively detect a Gram-positive bacterial infection, not only in vitro but also using an in vivo keratitis mouse model. BacGO provides an unprecedented research tool for the study of dynamic bacterial communities and for clinical application.

Journal ArticleDOI
TL;DR: To study the effect of bacteria on wheat tolerance to salinity stress, bread wheat seeds were inoculated with A. nitroguajacolicus and grown under salt stress condition and a considerable number of genes encoding secondary metabolites such as phenylpropanoids was detected.
Abstract: It is commonly accepted that bacteria actively interact with plant host and have beneficial effects on growth and adaptation and grant tolerance to various biotic and abiotic stresses. However, the mechanisms of plant growth promoting bacteria to communicate and adapt to the plant environment are not well characterized. Among the examined bacteria isolates from different saline soils, Arthrobacter nitroguajacolicus was selected as the best plant growth-promoting bacteria under salt stress. To study the effect of bacteria on wheat tolerance to salinity stress, bread wheat seeds were inoculated with A. nitroguajacolicus and grown under salt stress condition. Comparative transcriptome analysis of inoculated and un-inoculated wheat roots under salt stress showed up-regulation of 152 genes whereas 5 genes were significantly down-regulated. Many genes from phenylpropanoid, flavonoid and terpenoid porphyrin and chlorophyll metabolism, stilbenoid, diarylheptanoid metabolism pathways were differentially expressed within inoculated roots under salt stress. Also, a considerable number of genes encoding secondary metabolites such as phenylpropanoids was detected. They are known to take part in lignin biosynthesis of the cell wall as well as antioxidants.

Journal ArticleDOI
Chen Xingyu1, Zhan Hu1, Yun Qi1, Chunfeng Song1, Guanyi Chen1 
TL;DR: The results of microbial analysis showed that some dominant plant growth-promoting bacteria could secrete indole-3-acetic acid (IAA) to enhance the interaction between algae and bacteria, and the denitrifying bacteria that could coexist with microalgae also improved the efficiency of wastewater treatment in the symbiotic systems.

Journal ArticleDOI
TL;DR: Further extensive research on isolation and characterization of probiotic bacteria from local dairy products and their growth optimization might be necessity for development of probiotics enriched food supplement and human health benefits through prevention and controlling of bacterial infections.

Journal ArticleDOI
TL;DR: In vitro and in vivo data suggest that BBR directly affects bacteria to alter bile acid metabolism and activate FXR signaling, providing new insights into the link between intestinal bacteria, nuclear receptor signaling, and xenobiotics.
Abstract: Intestinal bacteria play an important role in bile acid metabolism and in the regulation of multiple host metabolic pathways (e.g., lipid and glucose homeostasis) through modulation of intestinal farnesoid X receptor (FXR) activity. Here, we examined the effect of berberine (BBR), a natural plant alkaloid, on intestinal bacteria using in vitro and in vivo models. In vivo, the metabolomic response and changes in mouse intestinal bacterial communities treated with BBR (100 mg/kg) for 5 days were assessed using NMR- and mass spectrometry-based metabolomics coupled with multivariate data analysis. Short-term BBR exposure altered intestinal bacteria by reducing Clostridium cluster XIVa and IV and their bile salt hydrolase (BSH) activity, which resulted in the accumulation of taurocholic acid (TCA). The accumulation of TCA was associated with activation of intestinal FXR, which can mediate bile acid, lipid, and glucose metabolism. In vitro, isolated mouse cecal bacteria were incubated with three doses of BBR (0.1, 1, and 10 mg/ml) for 4 hours in an anaerobic chamber. NMR-based metabolomics combined with flow cytometry was used to evaluate the direct physiologic and metabolic effect of BBR on the bacteria. In vitro, BBR exposure not only altered bacterial physiology but also changed bacterial community composition and function, especially reducing BSH-expressing bacteria like Clostridium spp. These data suggest that BBR directly affects bacteria to alter bile acid metabolism and activate FXR signaling. These data provide new insights into the link between intestinal bacteria, nuclear receptor signaling, and xenobiotics.

Journal ArticleDOI
TL;DR: The results indicated that the NTAPPJ treatment could be useful for preventing bacterial adhesion and biofilm formation on titanium dental implant surfaces, while the reductive potential on surfaces treated by theNTAPPJ could cause oxidation of bacteria, which could be more sensitive to gram-negative bacteria due to differences in the cell wall structure.
Abstract: Titanium is commonly used as a biomaterial for dental implants. In this study, we investigated the antibacterial properties of titanium samples following treatment with a non-thermal atmospheric pressure plasma jet (NTAPPJ) on bacteria with two different cell wall structures, including gram-positive and gram-negative bacteria. The hydrophilicity and surface energy of titanium surfaces were significantly increased after NTAPPJ treatment without altering topographical features. Changes in the chemical composition and reductive potential were observed on the NTAPPJ-treated titanium surfaces. The adhesion and biofilm formation rate of bacteria were significantly reduced on the NTAPPJ-treated titanium surfaces compared with the untreated samples, which was confirmed by fluorescent imaging. Regarding the comparison between gram-positive and gram-negative bacteria, both adhesion and the biofilm formation rate were significantly lower for gram-negative bacteria than gram-positive bacteria on samples treated for longer durations with the NTAPPJ. Transmission electron microscopy imaging showed a comparably more disruptive membrane structure of gram-negative bacteria than gram-positive bacteria on the NTAPPJ-treated surfaces. Our results indicated that the NTAPPJ treatment could be useful for preventing bacterial adhesion and biofilm formation on titanium dental implant surfaces, while the reductive potential on surfaces treated by the NTAPPJ could cause oxidation of bacteria, which could be more sensitive to gram-negative bacteria due to differences in the cell wall structure.

Journal ArticleDOI
TL;DR: Significant progress has been made to characterize the role of protein S-thiolation in redox-regulation and thiol protection of main metabolic and antioxidant enzymes, but the physiological roles of the pathways for regeneration are only beginning to emerge as well as their interactions with other cellular redox systems.
Abstract: Low molecular weight (LMW) thiols play an important role as thiol-cofactors for many enzymes and are crucial to maintain the reduced state of the cytoplasm. Most Gram-negative bacteria utilize glutathione (GSH) as major LMW thiol. However, in Gram-positive Actinomycetes and Firmicutes alternative LMW thiols, such as mycothiol (MSH) and bacillithiol (BSH) play related roles as GSH surrogates, respectively. Under conditions of hypochlorite stress, MSH and BSH are known to form mixed disulfides with protein thiols, termed as S-mycothiolation or S-bacillithiolation that function in thiol-protection and redox regulation. Protein S-thiolations are widespread redox-modifications discovered in different Gram-positive bacteria, such as Bacillus and Staphylococcus species, Mycobacterium smegmatis, Corynebacterium glutamicum and Corynebacterium diphtheriae. S-thiolated proteins are mainly involved in cellular metabolism, protein translation, redox regulation and antioxidant functions with some conserved targets across bacteria. The reduction of protein S-mycothiolations and S-bacillithiolations requires glutaredoxin-related mycoredoxin and bacilliredoxin pathways to regenerate protein functions. In this review, we present an overview of the functions of mycothiol and bacillithiol and their physiological roles in protein S-bacillithiolations and S-mycothiolations in Gram-positive bacteria. Significant progress has been made to characterize the role of protein S-thiolation in redox-regulation and thiol protection of main metabolic and antioxidant enzymes. However, the physiological roles of the pathways for regeneration are only beginning to emerge as well as their interactions with other cellular redox systems. Future studies should be also directed to explore the roles of protein S-thiolations and their redox pathways in pathogenic bacteria under infection conditions to discover new drug targets and treatment options against multiple antibiotic resistant bacteria.

Journal ArticleDOI
TL;DR: Self-assembly of an aggregation-induced emission active photosensitizer with a cell-penetrating peptide-decorated virus coat protein exhibits both ROS generation and a strong membrane-intercalating capacity, resulting in significantly enhanced PDI efficiency against bacteria.
Abstract: Antibiotic resistance has become one of the major threats to global health. Photodynamic inactivation (PDI) develops little antibiotic resistance; thus, it becomes a promising strategy in the control of bacterial infection. During a PDI process, light-induced reactive oxygen species (ROS) damage the membrane components, leading to the membrane rupture and bacteria death. Due to the short half-life and reaction radius of ROS, achieving the cell-membrane intercalation of photosensitizers is a key challenge for PDI of bacteria. In this work, a tetraphenylethylene-based discrete organoplatinum(II) metallacycle (1) acts as a photosensitizer with aggregation-induced emission. It self-assembles with a transacting activator of transduction (TAT) peptide-decorated virus coat protein (2) through electrostatic interactions. This assembly (3) exhibits both ROS generation and strong membrane-intercalating ability, resulting in significantly enhanced PDI efficiency against bacteria. By intercalating in the bacterial cell membrane or entering the bacteria, assembly 3 decreases the survival rate of gram-negative Escherichia coli to nearly zero and that of gram-positive Staphylococcus aureus to ∼30% upon light irradiation. This study has wide implications from the generation of multifunctional nanomaterials to the control of bacterial infection, especially for gram-negative bacteria.

Journal ArticleDOI
30 Jul 2019
TL;DR: Modified flavonoids could be used as a suitable alternative antimicrobial agent for the treatment of infectious diseases because of their antibacterial activity against pathogenic bacteria.
Abstract: The surge of resistant food pathogens is a major threat worldwide. Previous research conducted on phytochemicals has shown their antibacterial activity against pathogenic bacteria. The design of antimicrobial agents to curb pathogenic disease remains a challenge demanding critical attention. Flavonoids such as apigenin and quercetin were evaluated against Gram-positive and Gram-negative bacteria. The results indicated that the antibacterial activity of each flavonoid occurred at a different minimum inhibitory concentration. However, the antimicrobial activity results of the modified flavonoids were also reported, and it was observed that the Gram-positive bacteria were more susceptible in comparison to the Gram-negative bacteria. The cell wall structure of the Gram-positive and Gram-negative bacteria could be the main reason for the bacteria susceptibility. Modified flavonoids could be used as a suitable alternative antimicrobial agent for the treatment of infectious diseases. Our results indicated 100% inhibition of Listeria monocytogenes, Pseudomonas aeruginosa, and Aeromonas hydrophila with modified flavonoids.

Journal ArticleDOI
TL;DR: A simple and cost-effective colorimetric- and electrochemical-based bioassay capable of analyzing both the presence of E. coli and its relative level of antibiotic resistance and the capability of the presented biosensor in identifying drug-resistant bacteria with two artificially induced antibiotic- resistant bacteria is demonstrated.
Abstract: The facile and economical identification of pathogenic bacteria, especially their antibiotic-resistance, is crucial in the realm of human health and safety. The presence of Escherichia coli ( E. coli) is considered as an indicator of water contamination and is closely related to human health. Herein, inspired by the biocatalysis of bacterial surfaces, we developed a simple and cost-effective colorimetric- and electrochemical-based bioassay that is capable of analyzing both the presence of E. coli and its relative level of antibiotic resistance. In this approach, p-benzoquinone is used as a redox mediator to monitor the bacterial concentration and specifically distinguish E. coli from four other common clinical bacteria, namely, Staphylococcus aureus ( S. aureus), Enterococcus faecalis ( E. faecalis), Salmonella pullorum ( S. pullorum), and Streptococcus mutans ( S. mutans). A visible color change, captured with a smartphone using a "light box", without relying on any complex instruments, can reflect the concentration of bacteria. The accurate quantification of E. coli was investigated with an electrochemical system in the concentration ranges of 1.0 × 103 to 1.0 × 109 CFU/mL. We further demonstrated the capability of the presented biosensor in identifying drug-resistant bacteria with two artificially induced antibiotic-resistant bacteria. Therefore, the presented bioassay is not only capable of detecting E. coli with high sensitivity and specificity but also provides a rapid solution to evaluate E. coli antibiotic resistance.