Chemical composition of Desulfovibrio desulfuricans lipid A

Crypt residing bacteria and proximal colonic carcinogenesis in a mouse model of Lynch syndrome

Colorectal cancer is a multifactorial disease involving inherited DNA mutations, environmental factors, gut inflammation and intestinal microbiota. Certain germline mutations within the DNA mismatch repair system are associated with Lynch syndrome tumors including right-sided colorectal cancer with mucinous phenotype and presence of an inflammatory infiltrate. Such tumors are more often associated with bacterial biofilms, which may contribute to disease onset and progression. Inflammatory bowel diseases are also associated with colorectal cancer and intestinal dysbiosis. Herein we addressed the question, whether inflammation can aggravate colorectal cancer development under mismatch repair deficiency. MSH2loxP/loxP Vill-cre mice were crossed into the IL-10-/- background to study the importance of inflammation and mucosal bacteria as a driver of tumorigenesis in a Lynch syndrome mouse model. An increase in large bowel tumorigenesis was found in double knockout mice both under conventional housing and under specific pathogen-free conditions. This increase was mostly due to the development of proximal tumors, a hotspot for tumorigenesis in Lynch syndrome, and was associated with a higher degree of inflammation. Additionally, bacterial invasion into the mucus of tumor crypts was observed in the proximal tumors. Inflammation shifted fecal and mucosal microbiota composition and was associated with enrichment in Escherichia-Shigella as well as Akkermansia, Bacteroides and Parabacteroides genera in fecal samples. Tumor-bearing double knockout mice showed a similar enrichment for Escherichia-Shigella and Parabacteroides. Lactobacilli, Lachnospiraceae and Muribaculaceae family members were depleted upon inflammation. In summary, chronic inflammation aggravates colonic tumorigenesis under mismatch repair deficiency and is associated with a shift in microbiota composition.

Potential of Omega-3 Polyunsaturated Fatty Acids in Managing Chemotherapy- or Radiotherapy-Related Intestinal Microbial Dysbiosis

Chemotherapy- or radiotherapy-related intestinal microbial dysbiosis is one of the main causes of intestinal mucositis. Cases of bacterial translocation into peripheral blood and subsequent sepsis occur as a result of dysfunction in the intestinal barrier. Evidence from recent studies depicts the characteristics of chemotherapy- or radiotherapy-related intestinal microbial dysbiosis, which creates an imbalance between beneficial and harmful bacteria in the gut. Decreases in beneficial bacteria can lead to a weakening of the resistance of the gut to harmful bacteria, resulting in robust activation of proinflammatory signaling pathways. For example, lipopolysaccharide (LPS)-producing bacteria activate the nuclear transcription factor-κB signaling pathway through binding with Toll-like receptor 4 on stressed epithelial cells, subsequently leading to secretion of proinflammatory cytokines. Nevertheless, various studies have found that the omega-3 (n-3) polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid and eicosapentaenoic acid can reverse intestinal microbial dysbiosis by increasing beneficial bacteria species, including Lactobacillus, Bifidobacterium, and butyrate-producing bacteria, such as Roseburia and Coprococcus. In addition, the n-3 PUFAs decrease the proportions of LPS-producing and mucolytic bacteria in the gut, and they can reduce inflammation as well as oxidative stress. Importantly, the n-3 PUFAs also exert anticancer effects in colorectal cancers. In this review, we summarize the characteristics of chemotherapy- or radiotherapy-related intestinal microbial dysbiosis and introduce the contributions of dysbiosis to the pathogenesis of intestinal mucositis. Next, we discuss how n-3 PUFAs could alleviate chemotherapy- or radiotherapy-related intestinal microbial dysbiosis. This review provides new insights into the clinical administration of n-3 PUFAs for the management of chemotherapy- or radiotherapy-related intestinal microbial dysbiosis.

Distribution of endotoxins in full scale pharmaceutical wastewater treatment plants and its relationship with microbial community structure

Endotoxins are potential toxics impacting human health through respiration derived in wastewater treatment plants (WWTPs), yet the formation of endotoxins during wastewater treatment processes is still lacking research. In our study, the distribution of endotoxins and bacterial community structure in the wastewater of three full scale pharmaceutical WWTPs were explored using the limulus amebocyte lysate (LAL) test and MiSeq technique. Results showed that higher endotoxin activities in the influent of Plant A and Plant C (560 and 1140 EU/mL), stemming from the fermentation process, were found compared to that of Plant B (135 EU/mL), coming from the process of chemical synthesis. During the anaerobic treatment and the cyclic activated sludge system (CASS) in the three WWTPs, the endotoxin activity increased, while it declined in the aerobic treatment system. In all bioreactors, the relative abundance of Gram-negative bacteria accounted for 50.0-94.6%. Bacteria with high lipopolysaccharide (LPS) in LAL assay were found at the genus level of Bacteroides, Enterococcus, Desulfovibrio, and Megasphaera.

The chemical composition of endotoxin isolated from intestinal strain of Desulfovibrio desulfuricans

Desulfovibrio desulfuricans anaerobes are constituents of human alimentary tract microflora. There are suggestions that they take part in the pathogenesis of periodontitis and some gastrointestinal inflammatory disorders, such as ulcerative colitis or Crohn's disease. Endotoxin is one of Gram-negative bacteria cellular components that influence these microorganisms pathogenicity. Endotoxin is a lipid-polisaccharide heteropolymer consisting of three elements: lipid A, core oligosaccharide, and O-specific polysaccharide, also called antigen-O. The biological activity of lipopolysaccharide (LPS) is determined by its structure. In this study, we show that rhamnose, fucose, mannose, glucose, galactose, heptose, and 2-keto-3-deoxyoctulosonic acid (Kdo) are constituents of D. desulfuricans endotoxin oligosaccharide core and O-antigen. Lipid A of these bacteria LPS is composed of glucosamine disaccharide substituted by 3-acyloxyacyl residues: ester-bound 3-(dodecanoyloxy)tetradecanoic, 3-(hexadecanoyloxy)tetradecanoic acid, and amide-bound 3-(tetradecanoyloxy)tetradecanoic acid.