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Showing papers on "Bacteria published in 2008"


Journal ArticleDOI
TL;DR: Bacteria have existed on Earth for three billion years or so and have become adept at protecting themselves against toxic chemicals, so it is unsurprising that antibiotic resistance is now a major clinical problem all over the world.
Abstract: Bacteria have existed on Earth for three billion years or so and have become adept at protecting themselves against toxic chemicals. Antibiotics have been in clinical use for a little more than 6 decades. That antibiotic resistance is now a major clinical problem all over the world attests to the success and speed of bacterial adaptation. Mechanisms of antibiotic resistance in bacteria are varied and include target protection, target substitution, antibiotic detoxification and block of intracellular antibiotic accumulation. Acquisition of genes needed to elaborate the various mechanisms is greatly aided by a variety of promiscuous gene transfer systems, such as bacterial conjugative plasmids, transposable elements and integron systems, that move genes from one DNA system to another and from one bacterial cell to another, not necessarily one related to the gene donor. Bacterial plasmids serve as the scaffold on which are assembled arrays of antibiotic resistance genes, by transposition (transposable elements and ISCR mediated transposition) and site-specific recombination mechanisms (integron gene cassettes).The evidence suggests that antibiotic resistance genes in human bacterial pathogens originate from a multitude of bacterial sources, indicating that the genomes of all bacteria can be considered as a single global gene pool into which most, if not all, bacteria can dip for genes necessary for survival. In terms of antibiotic resistance, plasmids serve a central role, as the vehicles for resistance gene capture and their subsequent dissemination. These various aspects of bacterial resistance to antibiotics will be explored in this presentation.

794 citations


Journal ArticleDOI
TL;DR: The bacterial response towards antibiotic stress on altered membrane permeability is outlined and recent advances in molecular approaches that are improving knowledge of the physico-chemical parameters that govern the translocation of antibiotics through porin channels are discussed.
Abstract: Gram-negative bacteria are responsible for a large proportion of antibiotic-resistant bacterial diseases. These bacteria have a complex cell envelope that comprises an outer membrane and an inner membrane that delimit the periplasm. The outer membrane contains various protein channels, called porins, which are involved in the influx of various compounds, including several classes of antibiotics. Bacterial adaptation to reduce influx through porins is an increasing problem worldwide that contributes, together with efflux systems, to the emergence and dissemination of antibiotic resistance. An exciting challenge is to decipher the genetic and molecular basis of membrane impermeability as a bacterial resistance mechanism. This Review outlines the bacterial response towards antibiotic stress on altered membrane permeability and discusses recent advances in molecular approaches that are improving our knowledge of the physico-chemical parameters that govern the translocation of antibiotics through porin channels.

749 citations


Journal ArticleDOI
04 Apr 2008-Science
TL;DR: Bacteria subsisting on antibiotics are surprisingly phylogenetically diverse, and many are closely related to human pathogens, suggesting that this unappreciated reservoir of antibiotic-resistance determinants can contribute to the increasing levels of multiple antibiotic resistance in pathogenic bacteria.
Abstract: Antibiotics are a crucial line of defense against bacterial infections. Nevertheless, several antibiotics are natural products of microorganisms that have as yet poorly appreciated ecological roles in the wider environment. We isolated hundreds of soil bacteria with the capacity to grow on antibiotics as a sole carbon source. Of 18 antibiotics tested, representing eight major classes of natural and synthetic origin, 13 to 17 supported the growth of clonal bacteria from each of 11 diverse soils. Bacteria subsisting on antibiotics are surprisingly phylogenetically diverse, and many are closely related to human pathogens. Furthermore, each antibiotic-consuming isolate was resistant to multiple antibiotics at clinically relevant concentrations. This phenomenon suggests that this unappreciated reservoir of antibiotic-resistance determinants can contribute to the increasing levels of multiple antibiotic resistance in pathogenic bacteria.

522 citations


Journal ArticleDOI
TL;DR: This work uses gold nanorods that have been covalently linked to primary antibodies to selectively destroy the pathogenic Gram-negative bacterium, Pseudomonas aeruginosa, and finds that, following nanorod attachment to the bacterial cell surface, exposure to near-infrared radiation results in a significant reduction in bacterial cell viability.
Abstract: Increases in the prevalence of antibiotic resistant bacteria require new approaches for the treatment of infectious bacterial pathogens. It is now clear that a nanotechnology-driven approach using nanoparticles to selectively target and destroy pathogenic bacteria can be successfully implemented. We have explored this approach by using gold nanorods that have been covalently linked to primary antibodies to selectively destroy the pathogenic Gram-negative bacterium, Pseudomonas aeruginosa. We find that, following nanorod attachment to the bacterial cell surface, exposure to near-infrared radiation results in a significant reduction in bacterial cell viability.

466 citations


Journal ArticleDOI
TL;DR: It is shown that M. tuberculosis forms biofilms with specific environmental and genetic requirements distinct from those for planktonic growth, which contain an extracellular matrix rich in free mycolic acids, and harbour an important drug‐tolerant population that persist despite exposure to high levels of antibiotics.
Abstract: Successful treatment of human tuberculosis requires 6-9 months' therapy with multiple antibiotics. Incomplete clearance of tubercle bacilli frequently results in disease relapse, presumably as a result of reactivation of persistent drug-tolerant Mycobacterium tuberculosis cells, although the nature and location of these persisters are not known. In other pathogens, antibiotic tolerance is often associated with the formation of biofilms--organized communities of surface-attached cells--but physiologically and genetically defined M. tuberculosis biofilms have not been described. Here, we show that M. tuberculosis forms biofilms with specific environmental and genetic requirements distinct from those for planktonic growth, which contain an extracellular matrix rich in free mycolic acids, and harbour an important drug-tolerant population that persist despite exposure to high levels of antibiotics.

465 citations


Journal ArticleDOI
TL;DR: The results show that bacteria can couple the anaerobic oxidation of methane to denitrification without the involvement of Archaea.
Abstract: Recently, a microbial consortium was shown to couple the anaerobic oxidation of methane to denitrification, predominantly in the form of nitrite reduction to dinitrogen gas. This consortium was dominated by bacteria of an as yet uncharacterized division and archaea of the order Methanosarcinales. The present manuscript reports on the upscaling of the enrichment culture, and addresses the role of the archaea in methane oxidation. The key gene of methanotrophic and methanogenic archaea, mcrA, was sequenced. The associated cofactor F(430) was shown to have a mass of 905 Da, the same as for methanogens and different from the heavier form (951 Da) found in methanotrophic archaea. After prolonged enrichment (> 1 year), no inhibition of anaerobic methane oxidation was observed in the presence of 20 mM bromoethane sulfonate, a specific inhibitor of MCR. Optimization of the cultivation conditions led to higher rates of methane oxidation and to the decline of the archaeal population, as shown by fluorescence in situ hybridization and quantitative MALDI-TOF analysis of F(430). Mass balancing showed that methane oxidation was still coupled to nitrite reduction in the total absence of oxygen. Together, our results show that bacteria can couple the anaerobic oxidation of methane to denitrification without the involvement of Archaea.

423 citations


Journal ArticleDOI
29 Aug 2008-Science
TL;DR: Bioinformatic analysis coupled with gene expression studies in P. aeruginosa and Streptomyces coelicolor revealed that the majority of SoxR regulons in bacteria lack the genes required for stress responses, despite the fact that many of these organisms still produce redox-active small molecules, which indicates that red ox-active pigments play a role independent of oxidative stress.
Abstract: It is thought that bacteria excrete redox-active pigments as antibiotics to inhibit competitors. In Pseudomonas aeruginosa, the endogenous antibiotic pyocyanin activates SoxR, a transcription factor conserved in Proteo- and Actinobacteria. In Escherichia coli, SoxR regulates the superoxide stress response. Bioinformatic analysis coupled with gene expression studies in P. aeruginosa and Streptomyces coelicolor revealed that the majority of SoxR regulons in bacteria lack the genes required for stress responses, despite the fact that many of these organisms still produce redox-active small molecules, which indicates that redox-active pigments play a role independent of oxidative stress. These compounds had profound effects on the structural organization of colony biofilms in both P. aeruginosa and S. coelicolor, which shows that "secondary metabolites" play important conserved roles in gene expression and development.

391 citations


Journal ArticleDOI
TL;DR: Current knowledge of this mechanism and the roles of Gram-positive pili in the colonization of specific host tissues, modulation of host immune responses and the development of bacterial biofilms are reviewed.

388 citations


Journal ArticleDOI
TL;DR: Compared the pathogenic strain and the commensal E. coli strain MG1655 modes of metabolism in vitro, it is found that the two strains used the 13 sugars in a similar order and cometabolized as many as 9 sugars at a time.
Abstract: The carbon sources that support the growth of pathogenic Escherichia coli O157:H7 in the mammalian intestine have not previously been investigated. In vivo, the pathogenic E. coli EDL933 grows primarily as single cells dispersed within the mucus layer that overlies the mouse cecal epithelium. We therefore compared the pathogenic strain and the commensal E. coli strain MG1655 modes of metabolism in vitro, using a mixture of the sugars known to be present in cecal mucus, and found that the two strains used the 13 sugars in a similar order and cometabolized as many as 9 sugars at a time. We conducted systematic mutation analyses of E. coli EDL933 and E. coli MG1655 by using lesions in the pathways used for catabolism of 13 mucus-derived sugars and five other compounds for which the corresponding bacterial gene system was induced in the transcriptome of cells grown on cecal mucus. Each of 18 catabolic mutants in both bacterial genetic backgrounds was fed to streptomycin-treated mice, together with the respective wild-type parent strain, and their colonization was monitored by fecal plate counts. None of the mutations corresponding to the five compounds not found in mucosal polysaccharides resulted in colonization defects. Based on the mutations that caused colonization defects, we determined that both E. coli EDL933 and E. coli MG1655 used arabinose, fucose, and N-acetylglucosamine in the intestine. In addition, E. coli EDL933 used galactose, hexuronates, mannose, and ribose, whereas E. coli MG1655 used gluconate and N-acetylneuraminic acid. The colonization defects of six catabolic lesions were found to be additive with E. coli EDL933 but not with E. coli MG1655. The data indicate that pathogenic E. coli EDL933 uses sugars that are not used by commensal E. coli MG1655 to colonize the mouse intestine. The results suggest a strategy whereby invading pathogens gain advantage by simultaneously consuming several sugars that may be available because they are not consumed by the commensal intestinal microbiota.

327 citations


Journal ArticleDOI
TL;DR: Polyphenols appear to have potential to alter gut microecology and, by affecting the total number of beneficial microflora in the gut, may confer positive gut health benefits.

322 citations


Journal ArticleDOI
TL;DR: A beta-glucuronidase gene belonging to family 2 glycosyl hydrolases was detected in 10 of the 40 isolates based on degenerate PCR, suggesting that the degeneratePCR could provide a useful assay for the capacity to produce beta- Glucuronic acid in the gut community.

Journal ArticleDOI
TL;DR: The microbial population structure and function of natural anaerobic communities maintained in lab-scale continuously stirred tank reactors at different lactate to sulfate ratios and in the absence of sulfate were analyzed using an integrated approach of molecular techniques and chemical analysis.
Abstract: The microbial population structure and function of natural anaerobic communities maintained in lab-scale continuously stirred tank reactors at different lactate to sulfate ratios and in the absence of sulfate were analyzed using an integrated approach of molecular techniques and chemical analysis. The population structure, determined by denaturing gradient gel electrophoresis and by the use of oligonucleotide probes, was linked to the functional changes in the reactors. At the influent lactate to sulfate molar ratio of 0.35 mol mol−1, i.e., electron donor limitation, lactate oxidation was mainly carried out by incompletely oxidizing sulfate-reducing bacteria, which formed 80–85% of the total bacterial population. Desulfomicrobium- and Desulfovibrio-like species were the most abundant sulfate-reducing bacteria. Acetogens and methanogenic Archaea were mostly outcompeted, although less than 2% of an acetogenic population could still be observed at this limiting concentration of lactate. In the near absence of sulfate (i.e., at very high lactate/sulfate ratio), acetogens and methanogenic Archaea were the dominant microbial communities. Acetogenic bacteria represented by Dendrosporobacter quercicolus-like species formed more than 70% of the population, while methanogenic bacteria related to uncultured Archaea comprising about 10–15% of the microbial community. At an influent lactate to sulfate molar ratio of 2 mol mol−1, i.e., under sulfate-limiting conditions, a different metabolic route was followed by the mixed anaerobic community. Apparently, lactate was fermented to acetate and propionate, while the majority of sulfidogenesis and methanogenesis were dependent on these fermentation products. This was consistent with the presence of significant levels (40–45% of total bacteria) of D. quercicolus-like heteroacetogens and a corresponding increase of propionate-oxidizing Desulfobulbus-like sulfate-reducing bacteria (20% of the total bacteria). Methanogenic Archaea accounted for 10% of the total microbial community.

Journal ArticleDOI
TL;DR: The results support the potential of LAB as biocontrol agents against postharvest rot as well as previous reports of antifungal activity by LAB.
Abstract: Summary. This study evaluated the efficacy of lactic acid bacteria (LAB) isolated from fresh fruits and vegetables as biocontrol agents against the phytopathogenic and spoilage bacteria and fungi, Xanthomonas campestris, Erwinia carotovora, Penicillium expansum, Monilinia laxa, and Botrytis cinerea. The antagonistic activity of 496 LAB strains was tested in vitro and all tested microorganisms except P. expansum were inhibited by at least one isolate. The 496 isolates were also analyzed for the inhibition of P. expansum infection in wounds of Golden Delicious apples. Four strains (TC97, AC318, TM319, and FF441) reduced the fungal rot diameter of the apples by 20%; only Weissella cibaria strain TM128 decreased infection levels by 50%. Cell-free supernatants of selected antagonistic bacteria were studied to determine the nature of the antimicrobial compounds produced. Organic acids were the preferred mediators of inhibition but hydrogen peroxide was also detected when strains BC48, TM128, PM141 and FF441 were tested against E. carotovora. While previous reports of antifungal activity by LAB are scarce, our results support the potential of LAB as biocontrol agents against postharvest rot. [Int Microbiol 2008; 11(4):231-236].

Journal ArticleDOI
TL;DR: It is presented the case that survival of bacteria that inhabit dry-climate soils are highly dependent on mechanisms, which limit protein oxidation during dehydration, which is similar to that of sensitive bacteria.
Abstract: For extremely ionizing radiation-resistant bacteria, survival has been attributed to protection of proteins from oxidative damage during irradiation, with the result that repair systems survive and function with far greater efficiency during recovery than in sensitive bacteria. Here we examined the relationship between survival of dry-climate soil bacteria and the level of cellular protein oxidation induced by desiccation. Bacteria were isolated from surface soils of the shrub-steppe of the US Department of Energy's Hanford Site in Washington State. A total of 63 isolates were used for phylogenetic analysis. The majority of isolates were closely related to members of the genus Deinococcus, with Chelatococcus, Methylobacterium and Bosea also among the genera identified. Desiccation-resistant isolates accumulated high intracellular manganese and low iron concentrations compared to sensitive bacteria. In vivo, proteins of desiccation-resistant bacteria were protected from oxidative modifications that introduce carbonyl groups in sensitive bacteria during drying. We present the case that survival of bacteria that inhabit dry-climate soils are highly dependent on mechanisms, which limit protein oxidation during dehydration.

Journal ArticleDOI
TL;DR: It is indicated that de novo nucleotide biosynthesis represents the single most critical metabolic function for bacterial growth in blood and the corresponding enzymes as putative antibiotic targets for the treatment of bloodstream infections are revealed.
Abstract: Proliferation of bacterial pathogens in blood represents one of the most dangerous stages of infection. Growth in blood serum depends on the ability of a pathogen to adjust metabolism to match the availability of nutrients. Although certain nutrients are scarce in blood and need to be de novo synthesized by proliferating bacteria, it is unclear which metabolic pathways are critical for bacterial growth in blood. In this study, we identified metabolic functions that are essential specifically for bacterial growth in the bloodstream. We used two principally different but complementing techniques to comprehensively identify genes that are required for the growth of Escherichia coli in human serum. A microarray-based and a dye-based mutant screening approach were independently used to screen a library of 3,985 single-gene deletion mutants in all non-essential genes of E. coli (Keio collection). A majority of the mutants identified consistently by both approaches carried a deletion of a gene involved in either the purine or pyrimidine nucleotide biosynthetic pathway and showed a 20- to 1,000-fold drop in viable cell counts as compared to wild-type E. coli after 24 h of growth in human serum. This suggests that the scarcity of nucleotide precursors, but not other nutrients, is the key limitation for bacterial growth in serum. Inactivation of nucleotide biosynthesis genes in another Gram-negative pathogen, Salmonella enterica, and in the Gram-positive pathogen Bacillus anthracis, prevented their growth in human serum. The growth of the mutants could be rescued by genetic complementation or by addition of appropriate nucleotide bases to human serum. Furthermore, the virulence of the B. anthracis purE mutant, defective in purine biosynthesis, was dramatically attenuated in a murine model of bacteremia. Our data indicate that de novo nucleotide biosynthesis represents the single most critical metabolic function for bacterial growth in blood and reveal the corresponding enzymes as putative antibiotic targets for the treatment of bloodstream infections.

Journal ArticleDOI
TL;DR: Overall, differences in survival were observed for all bacteria studied, when submitted to the same environmental pressure, and this holds both for differences between indicators and pathogenic bacteria and between pathogenicacteria.

Journal ArticleDOI
TL;DR: Secreted PLA2s may be potentially useful new endogenous antibiotics to combat infections including those caused by antibiotic-resistant bacteria such as methicillin-resistant staphylococci and vancomysin-resistant enterococci.

Journal ArticleDOI
TL;DR: Lactic acid bacteria have been widely used as starter or nonstarter cultures in the dairy industry for over a thousand years and play an essential role in flavor formation during the fermentation of dairy products.
Abstract: Lactic acid bacteria (LAB) have been widely used as starter or nonstarter cultures in the dairy industry for over a thousand years. They play an essential role in flavor formation during the fermentation of dairy products. Several metabolic routes can lead to the formation of flavor compounds when

Journal ArticleDOI
TL;DR: It is proposed that OCC protein-encoding genes are suitable targets for molecular ecological studies on both aerobic and anaerobic ammonium-oxidizing bacteria.
Abstract: Bacterial aerobic ammonium oxidation and anaerobic ammonium oxidation (anammox) are important processes in the global nitrogen cycle. Key enzymes in both processes are the octahaem cytochrome c (OCC) proteins, hydroxylamine oxidoreductase (HAO) of aerobic ammonium-oxidizing bacteria (AOB), which catalyses the oxidation of hydroxylamine to nitrite, and hydrazine oxidoreductase (HZO) of anammox bacteria, which converts hydrazine to N(2). While the genomes of AOB encode up to three nearly identical copies of hao operons, genome analysis of Candidatus'Kuenenia stuttgartiensis' showed eight highly divergent octahaem protein coding regions as possible candidates for the HZO. Based on their phylogenetic relationship and biochemical characteristics, the sequences of these eight gene products grouped in three clusters. Degenerate primers were designed on the basis of available gene sequences with the aim to detect hao and hzo genes in various ecosystems. The hao primer pairs amplified gene fragments from 738 to 1172 bp and the hzo primer pairs amplified gene fragments from 289 to 876 bp in length, when tested on genomic DNA isolated from a variety of AOB and anammox bacteria. A selection of these primer pairs was also used successfully to amplify and analyse the hao and hzo genes in community DNA isolated from different ecosystems harbouring both AOB and anammox bacteria. We propose that OCC protein-encoding genes are suitable targets for molecular ecological studies on both aerobic and anaerobic ammonium-oxidizing bacteria.

Journal ArticleDOI
TL;DR: Of the 10 organic acids analyzed and quantified in coffee beans, acetic and lactic acids may have been generated by microbial activity, and Butyric acid was not detected in any sample.

Journal ArticleDOI
TL;DR: Grapefruit juice and furocoumarins could serve as a source to develop bacterial intervention strategies targeting microbial cell signaling processes, and inhibit biofilm formation by Escherichia coli O157:H7, Salmonella typhimurium and Pseudomonas aeruginosa.


Journal ArticleDOI
TL;DR: Results support the potential use of lactic acid bacteria as bioprotective agents against foodborne human pathogens in ready-to-eat fresh fruit and vegetable products.


Journal ArticleDOI
TL;DR: The genomes of four endophytic bacteria now available should promote discovery of other genes that contribute to this phenotype and help to understand the role of virulence factors in plant and animal pathogens.
Abstract: Non-plant pathogenic endophytic bacteria can promote plant growth, improve nitrogen nutrition, and, in some cases, are human pathogens. Recent work in several laboratories has shown that enteric bacteria are common inhabitants of the interior of plants. These observations led to the experiments that showed the entry into plants of enteric human pathogens such as Salmonella and E. coli O157:H7. The extent of endophytic colonization by strains is regulated by plant defenses and several genetic determinants necessary for this interior colonization in endophytic bacteria have been identified. The genomes of four endophytic bacteria now available should promote discovery of other genes that contribute to this phenotype. Common virulence factors in plant and animal pathogens have also been described in bacteria that can infect both plant and animal models. Future directions in all of these areas are proposed.

Journal ArticleDOI
TL;DR: In this paper, the authors detected an intimate association between Piriformospora indica and Rhizobium radiobacter, an α-Proteobacterium, using quantitative PCR, denaturating gradient gel electrophoresis and fluorescence in situ hybridization.
Abstract: Because of their beneficial impact on plants, the highly diverse mycorrhizal fungi grouped in the order Sebacinales lay claim to high ecological and agricultural significance. Here, we describe for the first time associations of Sebacinoid members with bacteria. Using quantitative PCR, denaturating gradient gel electrophoresis and fluorescence in situ hybridization, we detected an intimate association between Piriformospora indica and Rhizobium radiobacter, an α-Proteobacterium. The stability of the association, vertical transmission of the bacteria during asexual fungal reproduction and fungal plant colonization was monitored using R. radiobacter-specific primers. Treatment of mycelium or fungal protoplasts with antibiotics highly efficient against the free bacteria failed to cure the fungus. Barley seedlings dip-inoculated with R. radiobacter showed growth promotion and systemic resistance to the powdery mildew fungus Blumeria graminis comparable to P. indica inoculation. By screening additional isolates of the Sebacina vermifera complex, three species-specific associations with bacteria from the genera Paenibacillus, Acinetobacter and Rhodococcus were found. These findings suggest that Sebacinales species regularly undergo complex interactions involving host plants and bacteria reminiscent of other ectomycorrhizal and endomycorrhizal associations.

Journal ArticleDOI
TL;DR: The results show that amyloid adhesins were an abundant component of activated sludge extracellular polymeric substances and seem to have unexpected, divers functions.
Abstract: Amyloid proteins (fimbriae or other microbial surface-associated structures) are expressed by many types of bacteria, not yet identified, in biofilms from various habitats, where they likely are of key importance to biofilm formation and biofilm properties. As these amyloids are potentially of great importance to the floc properties in activated sludge wastewater treatment plants (WWTP), the abundance of amyloid adhesins in activated sludge flocs from different WWTP and the identity of bacteria producing these were investigated. Amyloid adhesins were quantified using a combination of conformationally specific antibodies targeting amyloid fibrils, propidium iodide to target all fixed bacterial cells, confocal laser scanning microscopy, and digital image analysis. The biovolume fraction containing amyloid adhesins ranged from 10 to 40% in activated sludge from 10 different WWTP. The identity of bacteria producing amyloid adhesins was determined using fluorescence in situ hybridization with oligonucleotide probes in combination with antibodies or thioflavin T staining. Among the microcolony-forming bacteria, amyloids were primarily detected among Alpha- and Betaproteobacteria and Actinobacteria. A more detailed analysis revealed that many denitrifiers (from Thauera, Azoarcus, Zoogloea, and Aquaspirillum-related organisms) and Actinobacteria-related polyphosphate-accumulating organisms most likely produced amyloid adhesins, whereas nitrifiers did not. Many filamentous bacteria also expressed amyloid adhesins, including several Alphaproteobacteria (e.g., Meganema perideroedes), some Betaproteobacteria (e.g., Aquaspirillum-related filaments), Gammaproteobacteria (Thiothrix), Bacteroidetes, Chloroflexi (e.g., Eikelboom type 1851), and some foam-forming Actinobacteria (e.g., Gordonia amarae). The results show that amyloid adhesins were an abundant component of activated sludge extracellular polymeric substances and seem to have unexpected, divers functions.

Journal ArticleDOI
TL;DR: Reports published up to date indicate that T3SS inhibitors have the potential to be developed into novel antibacterial therapeutics.
Abstract: In recent years mounting problems related to antibiotic-resistant bacteria have resulted in the prediction that we are entering the preantibiotic era. A way of preventing such a development would be to introduce novel antibacterial medicines with modes of action distinct from conventional antibiotics. Recent studies of bacterial virulence factors and toxins have resulted in increased understanding of the way in which pathogenic bacteria manipulate host cellular processes. This knowledge may now be used to develop novel antibacterial medicines that disarm pathogenic bacteria. The type III secretion system (T3SS) is known to be a potent virulence mechanism shared by a broad spectrum of pathogenic Gram-negative bacteria that interact with human, animal and plant hosts by injecting effector proteins into the cytosol of host cells. Diseases, such as bubonic plague, shigellosis, salmonellosis, typhoid fever, pulmonary infections, sexually transmitted chlamydia and diarrhoea largely depend on the bacterial proteins injected by the T3SS machinery. Recently a number of T3SS inhibitors have been identified using screening-based approaches. One class of inhibitors, the salicylidene acylhydrazides, has been subjected to chemical optimization and evaluation in several in vitro and ex vivo assays in multiple bacterial species including Yersinia spp., Chlamydia spp., Salmonella spp. and Pseudotuberculosis aeruginosa. Reports published up to date indicate that T3SS inhibitors have the potential to be developed into novel antibacterial therapeutics.

Journal ArticleDOI
TL;DR: Some features of the cellulosome of the anaerobic fungus Orpinomyces sp.
Abstract: Anaerobic fungi, first described in 1975 by Orpin, live in close contact with bacteria and other microorganisms in the rumen and caecum of herbivorous animals, where they digest ingested plant food. Seventeen distinct anaerobic fungi belonging to five different genera have been described. They have been found in at least 50 different herbivorous animals. Anaerobic fungi do not possess mitochondria, but instead have hydrogenosomes, which form hydrogen and carbon dioxide from pyruvate and malate during fermentation of carbohydrates. In addition, they are very oxygen- and temperature-sensitive, and their DNA has an unusually high AT content of from 72 to 87 mol%. My initial reason for studying anaerobic fungi was because they solubilize lignocellulose and produce all enzymes needed to efficiently hydrolyze cellulose and hemicelluloses. Although some of these enzymes are found free in the medium, most of them are associated with cellulosomal and polycellulosomal complexes, in which the enzymes are attached through fungal dockerins to scaffolding proteins; this is similar to what has been found for cellulosomes from anaerobic bacteria. Although cellulosomes from anaerobic fungi share many properties with cellulosomes of anaerobic cellulolytic bacteria and have comparable structures, their structures differ in their amino acid sequences. I discuss some features of the cellulosome of the anaerobic fungus Orpinomyces sp. PC-2 and some possible uses of its enzymes in industrial settings.

Journal ArticleDOI
TL;DR: The minimum inhibitory concentrations (MICs) of 6 different antibiotics were determined for 143 strains of lactic acid bacteria and bifidobacteria using the Etest, suggesting that most of the strains were either susceptible or intrinsically resistant to these antibiotics.
Abstract: The minimum inhibitory concentrations (MICs) of 6 different antibiotics (chloramphenicol, clindamycin, erythromycin, streptomycin, tetracycline and vancomycin) were determined for 143 strains of lactic acid bacteria and bifidobacteria using the Etest. Different MICs were found for different species and strains. Based on the distribution of these MIC values, most of the strains were either susceptible or intrinsically resistant to these antibiotics. However, the MIC range of some of these antibiotics showed a bimodal distribution, which suggested that some of the tested strains possess acquired antibiotic resistance. Screening for resistance genes was performed by PCR using specific primers, or using a DNA microarray with around 300 nucleotide probes representing 7 classes of antibiotic resistance genes. The genes identified encoded resistance to tetracycline [tet(M), tet(W), tet(O) and tet(O/W)], erythromycin and clindamycin [erm(B)] and streptomycin [aph(E) and sat(3)]. Internal portions of some of these determinants were sequenced and found to be identical to genes described in other bacteria. All resistance determinants were located on the bacterial chromosome, except for tet(M), which was identified on plasmids in Lactococcus lactis. The contribution of intrinsic multidrug transporters to the antibiotic resistance was investigated by cloning and measuring the expression of Bifidobacterium breve genes in L. lactis.