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Genetics and Biosynthesis of Lipopolysaccharide O-Antigens
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Wendy J. Keenleyside, Chris Whitfield
In most gram-negative pathogens, and particularly in most wild-type members of the families Enterobacteriaceae, Pseudomonadaceae, Pasteurellaceae, and Vibrionaceae, the LPS core is capped by an O-polysaccharide (O-PS) side chain to form smooth LPS (S-LPS). Structural diversity in the O-PSs defines the O-antigen specificity used in serological classifications. Although the fine structure of a particular O-antigen determines the serospecificity of a given strain, there are examples where taxonomically distant species may express similar or identical polysaccharides. Serotype specificity is therefore important for classification and/or epidemiology within a species, and its genetic basis is of particular interest in terms of the evolution of O-antigenic diversity.
Biology of microbes
Published in Philip A. Geis, Cosmetic Microbiology, 2006
Serratia. The Serratia organism is not typically considered a pathogen because infections caused by it are rare. Serratia is a member of the Enterobacteriaceae family that includes Escherichia, Enterobacter, and Proteus, and comprises the largest of the three families cited in Section 5 of Bergey’s Manual (1984) focusing on the anaerobic Gram-negative rods (Vibrionaceae and Pasteurellaceae are the other two families). Like most members of the Enterobacteriaceae, Serratia degrade sugars to pyruvate by means of the Embden–Meyerhof pathway (glycolysis), then use the pyruvate as the terminal electron acceptor to yield a variety of end products in a fermentation process. Pyruvate is further reduced to butanediol, ethanol, and carbon dioxide.
Clinical Features of Colorectal Adenoma and Adenocarcinoma
Published in Peter Sagar, Andrew G. Hill, Charles H. Knowles, Stefan Post, Willem A. Bemelman, Patricia L. Roberts, Susan Galandiuk, John R.T. Monson, Michael R.B. Keighley, Norman S. Williams, Keighley & Williams’ Surgery of the Anus, Rectum and Colon, 2019
Jamie Murphy, Norman S. Williams
The bile-salt/bacteria theory gains credence when it is considered that the bile acids have a chemical structure similar to that of carcinogens such as methylcholanthrene. Furthermore, it is known that certain bacteria, particularly Clostridium paraputrificum, can dehydrogenate the steroid nucleus, an effect that might be important in the development of compounds with structures similar to that of known carcinogens. It is therefore of particular interest that some authors have found that C. paraputrificum is particularly prevalent in the intestinal flora of high-risk groups. Likewise, others have noted its presence in the faeces of colon cancer patients more often than in those of control subjects. Hill et al.55 also noted that the excretion of bile acids is greater and the ratio of anaerobic to aerobic bacteria in faeces is higher in subjects from countries with a high colorectal cancer incidence than in those with a low incidence. Certain anaerobes are more active in the degradation of bile acids, and it is found that excreted bile acids are more often degraded in high-incidence populations than in low-incidence ones. It thus appears that bacteria within the large bowel do have an important role in colon carcinogenesis. However, although certain organisms have been identified to be in higher concentrations within tumours as compared to normal colon (including Bacteroidaceae, Streptococcaceae, Fusobacteriaceae, Peptostreptococcaceae, Veillonellaceae and Pasteurellaceae species), there are no hard data linking a specific bacterium to the development of colorectal carcinoma.56 Many of the studies involve only small numbers of patients, and any given patient may have more than 400 identifiable species of bacteria in the gut. Thus, a number of practical factors make interpretation of these results difficult despite recent technical and conceptual advances in characterising the taxonomic composition, metabolic capacity and immunomodulatory activity of the human gut microbiota.
Altered composition of the oral microbiome in integrin beta 6-deficient mouse
Published in Journal of Oral Microbiology, 2022
Osamu Uehara, Jiarui Bi, Deshu Zhuang, Leeni Koivisto, Yoshihiro Abiko, Lari Häkkinen, Hannu Larjava
Next, we used the QIIME 2 database to analyze the genus-level alterations in the bacterial composition between the Itgb6−/− and WT mice at two different ages. All 24 samples were sequenced using MiSeq, and 7,542,554 total sequences were amplified, ranging from a minimum of 91,349 to a maximum of 409,155 sequences per sample, with a mean of 314,273 sequences per sample. QIIME2 detected a total of 86 different bacterial genera. The oral microbial composition between each individual mouse in different groups was remarkably similar (Figure 5a) with the phylum Proteobacteria dominating the samples at 70–90% in all samples (Figure 5). At the family level, Pasteurellaceae was the dominating family, followed by Streptococcaceae (Figure 5). Members of the Streptococcaceae family, considered early colonizers in the dental plaque biofilm [25], showed little differences among the four mouse groups (Figure 5). Supporting the observed differences from the PCoA analyses, the bacterial composition at the genus level showed differences among the four mouse groups (Figure 5). Interestingly, an unidentified bacterial genus from Rickettsiales was increased in 6-month-old WT mice but decreased in 6-month-old Itgb6−/− mice (Figure 5). The Lactobacillus from Lactobacillaceae family had higher abundance in 3-month-old WT mice compared to others (Figure 5).
MICROBIOTA INSIGHTS IN CLOSTRIDIUM DIFFICILE INFECTION AND INFLAMMATORY BOWEL DISEASE
Published in Gut Microbes, 2020
C. Rodríguez, E. Romero, L. Garrido-Sanchez, G. Alcaín-Martínez, RJ. Andrade, B. Taminiau, G. Daube, E. García-Fuentes
Several studies have reported an increase in the Pasteurellaceae and/or Enterobacteriaceae families in patients with CD.37–40,45-47,49,68 Gut inflammation and chronic colitis have been further associated with an important increase of Enterobacteriaceae family68 and an oxidative stress in the gut. A recent study goes beyond and suggests Enterobacteriaceae as stool biomarkers in IBD.45 There are several metabolic changes that promote oxidative stress at the mucosal surface of IBD patients and favor an increased level or depletion of different taxa that use mucin as a primary energy source.37,38 Specifically, the increase in components of the benzoate metabolic pathway (aminobenzoate and fluorobenzoate degradation) seems to be directly associated with Enterobacteriaceae growth, virulence, and stress response.40 Bacteria such as Salmonella or enterohemorrhagic E. coli would take advantage of these redox stresses and therefore proliferate to a large extent. Indeed, in the ileum mucosa of CD patients and in the fecal samples of UC patients,60 high numbers of adherent and invasive E. coli have been found, as well as a high prevalence of antibodies directed against E. coli outer membrane porin C (OmpC) and flagellin. It seems that E. coli acts as an opportunistic pathogen and is directly implicated in the disease, with the induction of the production of cytokines, such as tumor necrosis factor α (TNFα) and IL8,39 and an increase in mucin degradation.
The pathogenic oral–gut–liver axis: new understandings and clinical implications
Published in Expert Review of Clinical Immunology, 2021
Jin Imai, Sho Kitamoto, Nobuhiko Kamada
Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn’s disease (CD), is a chronic inflammatory disease of the gastrointestinal tract. Accumulating evidence suggests that aberrant immune responses to the gut microbiota are closely associated with the pathogenesis of IBD. It has been repeatedly demonstrated that atypical, potentially pathogenic members of commensal bacteria (pathobionts) are markedly enriched in the stool and the intestinal mucosa of IBD patients compared to non-IBD individuals [15,16]. The perturbed microbial community in the gut, so-called gut dysbiosis, is a hallmark of IBD [17]. For example, Gevers and colleagues analyzed the microbiome of newly diagnosed treatment-naïve pediatric patients with CD [18]. This study revealed a significant correlation between microbial alterations in the intestinal mucosa and disease status, with an increased abundance of Veillonellaceae, Pasteurellaceae, Enterobacteriaceae, Nisseriaceae, Gemellaceae, and Fusobacteriaceae, and a decreased abundance of Bacteroidales, Erysipelotrichales, and Clostridiales [12,18]). Notably, the enriched bacterial taxa are considered typical oral resident bacteria. Similarly, the accumulation of oral-derived bacteria in the gut is also reported in patients with UC. A cohort of new-onset, treatment-naïve pediatric UC patients with severe inflammation exhibited a striking increase in the abundance of oral bacteria, such as Veillonella dispar, Aggregatibacter segnis, Campylobacter spp, Lachnospiraceae, Veillonella parvula, Haemophilus parainfluenzae, and Megasphaera spp [19]. Thus, bacteria derived from the oral cavity ectopically colonize the gut in patients with IBD, both CD and UC (Figure 1).