The Genus Bacteroides

Wexler, Hannah M.

doi:10.1007/978-3-642-38954-2_129

Cited by 16 publications

(22 citation statements)

References 173 publications

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“…Outside its colonic niche, B. fragilis is an opportunistic pathogen; B. fragilis only accounts for 2% of the total gut Bacteroides yet it is the agent of >70% of Bacteroides infections. B. fragilis is the main cause of anaerobic bacteremia and intraabdominal abscesses, implicated in serious gynecological, soft tissue infections, peritonitis, brain abscess (Wexler, 2014 ) and surgical site infections (SSIs) following colorectal surgery (Solomkin et al, 2010 ). Even B. fragilis strains isolated as normal gut microbiota possess many genes associated with virulence; as the expression of virulent genes constitutes a form of stress response of pathogenic bacteria during host infection, we would expect differential regulation of the multitude of genes involved in virulence, survival, and host colonization (Louwen et al, 2014 ).…”

Section: Introductionmentioning

confidence: 99%

CRISPR-Cas Systems in Bacteroides fragilis, an Important Pathobiont in the Human Gut Microbiome

Tajkarimi

Wexler

2017

Front. Microbiol.

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Background: While CRISPR-Cas systems have been identified in bacteria from a wide variety of ecological niches, there are no studies to describe CRISPR-Cas elements in Bacteroides species, the most prevalent anaerobic bacteria in the lower intestinal tract. Microbes of the genus Bacteroides make up ~25% of the total gut microbiome. Bacteroides fragilis comprises only 2% of the total Bacteroides in the gut, yet causes of >70% of Bacteroides infections. The factors causing it to transition from benign resident of the gut microbiome to virulent pathogen are not well understood, but a combination of horizontal gene transfer (HGT) of virulence genes and differential transcription of endogenous genes are clearly involved. The CRISPR-Cas system is a multi-functional system described in prokaryotes that may be involved in control both of HGT and of gene regulation.Results: Clustered regularly interspaced short palindromic repeats (CRISPR) elements in all strains of B. fragilis (n = 109) with publically available genomes were identified. Three different CRISPR-Cas types, corresponding most closely to Type IB, Type IIIB, and Type IIC, were identified. Thirty-five strains had two CRISPR-Cas types, and three strains included all three CRISPR-Cas types in their respective genomes. The cas1 gene in the Type IIIB system encoded a reverse-transcriptase/Cas1 fusion protein rarely found in prokaryotes. We identified a short CRISPR (3 DR) with no associated cas genes present in most of the isolates; these CRISPRs were found immediately upstream of a hipA/hipB operon and we speculate that this element may be involved in regulation of this operon related to formation of persister cells during antimicrobial exposure. Also, blood isolates of B. fragilis did not have Type IIC CRISPR-Cas systems and had atypical Type IIIB CRISPR-Cas systems that were lacking adjacent cas genes.Conclusions: This is the first systematic report of CRISPR-Cas systems in a wide range of B. fragilis strains from a variety of sources. There are four apparent CRISPR-Cas systems in B. fragilis—three systems have adjacent cas genes. Understanding CRISPR/Cas function in B. fragilis will elucidate their role in gene expression, DNA repair and ability to survive exposure to antibiotics. Also, based on their unique CRISPR-Cas arrays, their phylogenetic clustering and their virulence potential, we are proposing that blood isolates of B. fragilis be viewed a separate subgroup.

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Section: Introductionmentioning

confidence: 99%

CRISPR-Cas Systems in Bacteroides fragilis, an Important Pathobiont in the Human Gut Microbiome

Tajkarimi

Wexler

2017

Front. Microbiol.

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“…The presence of carbohydrate-degrading enzymes allows the digestion of substrates from plant, algae, or animal sources. Together with the high tolerance to bile salts in the gut, these conditions influence a beneficial relationship with the host ( Wexler, 2014 ). In this study, this family was affected by sodium butyrate and CP as an indicator of the microbes’ response to gut environmental conditions.…”

Section: Discussionmentioning

confidence: 99%

Caeca Microbial Variation in Broiler Chickens as a Result of Dietary Combinations Using Two Cereal Types, Supplementation of Crude Protein and Sodium Butyrate

et al. 2021

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The intestinal microbiome can influence the efficiency and the health status of its host’s digestive system. Indigestible non-starch polysaccharides (NSP) serve as substrates for bacterial fermentation, resulting in short-chain fatty acids like butyrate. In broiler’s nutrition, dietary crude protein (CP) and butyrate’s presence is of particular interest for its impact on intestinal health and growth performance. In this study, we evaluated the effect on the microbial ecology of the ceca of dietary supplementations, varying the cereal type (maize and wheat), adequate levels of CP and supplementation of sodium butyrate on broiler chickens with 21 days. The overall structure of bacterial communities was statistically affected by cereal type, CP, and sodium butyrate (p = 0.001). Wheat in the diet promoted the presence of Lactobacillaceae, Bifidobacteriaceae and Bacteroides xylanisolvens, which can degrade complex carbohydrates. Maize positively affected the abundance of Bacteroides vulgatus. The addition of CP promoted the family Rikenellaceae, while sodium butyrate as feed supplement was positively related to the family Lachnospiraceae. Functional predictions showed an effect of the cereal type and a statistical significance across all supplementations and their corresponding interactions. The composition of diets affected the overall structure of broilers’ intestinal microbiota. The source of NSP as a substrate for bacterial fermentation had a stronger stimulus on bacterial communities than CP content or supplementation of butyrate.

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“…It has been previously suggested that, in Bacteroides, the production of propionate through the succinate/propionate pathway could be a cell response to optimize cell energy production while keeping the intracellular redox balance [ 18 , 19 ]. Although B. fragilis has the capacity to metabolize moderate amounts of lactic acid [ 27 ] as well as amino acids [ 28 ], our work was performed in a minimal medium, so that no amino acid sources were available and the scarce consumption of lactic acid that may occur does not explain the growth and metabolic activity of the bacterium in such conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Although we know that the presence of both EPS stimulates the production of α-glucosidase by B. fragilis , the high molar mass polymer of the EPS R1 fraction lacks the α-linkages targeted by this enzymatic activity [ 29 ]. This together with the inability of B. fragilis to ferment rhamnose [ 28 ], could pose difficulties for the use as fermentable substrate of the EPS R1 by this microorganism.…”

Section: Discussionmentioning

confidence: 99%

Bacteroides fragilis metabolises exopolysaccharides produced by bifidobacteria

et al. 2016

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BackgroundBacteroides fragilis is the most frequent species at the human intestinal mucosal surface, it contributes to the maturation of the immune system although is also considered as an opportunistic pathogen. Some Bifidobacterium strains produce exopolysaccharides (EPS), complex carbohydrate polymers that promote changes in the metabolism of B. fragilis when this microorganism grows in their presence. To demonstrate that B. fragilis can use EPS from bifidobacteria as fermentable substrates, purified EPS fractions from two strains, Bifidobacterium longum E44 and Bifidobacterium animalis subsp. lactis R1, were added as the sole carbon source in cultures of B. fragilis DSMZ 2151 in a minimal medium. Bacterial counts were determined during incubation and the evolution of organic acids, short chain fatty acids (SCFA) and evolution of EPS fractions was analysed by chromatography.ResultsGrowth of B. fragilis at early stages of incubation was slower in EPS than with glucose, microbial levels remaining higher in EPS at prolonged incubation times. A shift in metabolite production by B. fragilis occurred from early to late stages of growth, leading to the increase in the production of propionate and acetate whereas decrease lactate formation. The amount of the two peaks with different molar mass of the EPS E44 clearly decreased along incubation whereas a consumption of the polymer R1 was not so evident.ConclusionsThis report demonstrates that B. fragilis can consume some EPS from bifidobacteria, with a concomitant release of SCFA and organic acids, suggesting a role for these biopolymers in bacteria-bacteria cross-talk within the intestine.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0773-9) contains supplementary material, which is available to authorized users.

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The Genus Bacteroides

Cited by 16 publications

References 173 publications

CRISPR-Cas Systems in Bacteroides fragilis, an Important Pathobiont in the Human Gut Microbiome

CRISPR-Cas Systems in Bacteroides fragilis, an Important Pathobiont in the Human Gut Microbiome

Caeca Microbial Variation in Broiler Chickens as a Result of Dietary Combinations Using Two Cereal Types, Supplementation of Crude Protein and Sodium Butyrate

Bacteroides fragilis metabolises exopolysaccharides produced by bifidobacteria

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