The impact of motility on the localization of Lactobacillus agilis in the murine gastrointestinal tract

Abstract Background While the overall composition of the mammalian gut microbiota has been intensively studied, the characteristics and ecologies of individual gut species are incompletely understood. Lactobacilli are considered beneficial commensals in the gastrointestinal mucosa and are relatively well-studied except for the uncommon species which exhibit motility. In this study, we evaluate the importance of motility on gut colonization by comparing motile and non-motile strains of Lactobacillus agilis in mice models. Results A flagellated but non-motile L. agilis strain was constructed by mutation of the motB gene. Colonization of the wild type and the mutant strain was assessed in both antibiotic-treated female Balb/c mice and gnotobiotic mice. The results suggest that the motile strain is better able to persist and/or localize in the gut mucosa. Chemotaxis assays indicated that the motile L. agilis strain is attracted by mucin, which is a major component of the intestinal mucus layer in animal guts. Conclusions Motility and chemotactic ability likely confer advantages in gut colonization to L. agilis. These findings suggest that the motile lactobacilli have unique ecologies compared to non-motile commensals of the lactic acid bacteria

Negative chemotaxis of Ligilactobacillus agilis BKN88 against gut-derived substances

Abstract Ligilactobacillus agilis is a motile lactic acid bacterium found in the gastrointestinal tracts of animals. The findings of our previous study suggest that the motility of L. agilis BKN88 enables gut colonization in murine models. However, the chemotactic abilities of motile lactobacilli remain unknown. This study aimed to identify the gut-derived chemoeffectors and their corresponding chemoreceptors in L. agilis BKN88. Chemotaxis assays with chemotactic and non-chemotactic (ΔcheA) L. agilis strains revealed that low pH, organic acids, and bile salts served as repellents. L. agilis BKN88 was more sensitive to bile and acid than the gut-derived non-motile lactobacilli, implying that L. agilis might utilize motility and chemotaxis instead of exhibiting stress tolerance/resistance. L. agilis BKN88 contains five putative chemoreceptor genes (mcp1–mcp5). Chemotaxis assays using a series of chemoreceptor mutants revealed that each of the five chemoreceptors could sense multiple chemoeffectors and that these chemoreceptors were functionally redundant. Mcp2 and Mcp3 sensed all tested chemoeffectors. This study provides further insights into the interactions between chemoreceptors and ligands of motile lactobacilli and the unique ecological and evolutionary features of motile lactobacilli, which may be distinct from those of non-motile lactobacilli

Molecular Approach for Tracing Dissemination Routes of Shiga Toxin-Producing Escherichia coli O157 in Bovine Offal at Slaughter

Bovine offal is currently recognized as one of the sources of human Shiga toxin-producing Escherichia coli (STEC) infection in Japan. Here, the prevalence and genetic characterization of STEC O157 in bovine feces, offal, and carcasses at slaughtering were examined between July and October in 2006. STEC O157 was detected in 31 of 301 cattle feces (10.3%) delivered from 120 farms. Simultaneously, 60 bovine-originated offal (tongue, liver, and omasum) and carcasses were randomly selected and the detection of O157 STEC was examined as well. STEC O157 was isolated from 4 tongues (6.7%), 1 liver (1.7%), 3 omasa (5.0%), and 2 carcasses (3.3%), respectively. All the O157 isolates were positive for eae and hlyA genes, and 37 of 41 isolates (90.2%) exhibited stx2c genotype. PFGE analysis revealed the identical macrogenotypes of 4-tongue- and 1-liver-originated isolates and among 2 fecal isolates from animals slaughtered consecutively. Considering their continuous detection according to the slaughtering order, we concluded that these distributions of O157 in bovine offal and feces might be due to cross-contamination at (pre)slaughter. Our data thus reposes implication of better sanitary control in diapedesis from both upper and lower sites to prevent spread of this pathogen to bovine offal at slaughtering

Different response of the knockout mice lacking b-series gangliosides against botulinum and tetanus toxins

AbstractWe assessed the response in knockout mice lacking the b-series (GD2, GD1b, GT1b and GQ1b) gangliosides against Clostridium botulinum (types A, B and E) and tetani toxins. We found that botulinum toxins were fully toxic, while tetanus toxin was much less toxic in the knockout mice. Combining the present results with our previous finding that tetanus toxin and botulinum types A and B toxins showed essentially no toxic activity in the knockout mice lacking both the a-series and b-series gangliosides (complex gangliosides), we concluded that the b-series gangliosides is the major essential substance for tetanus toxin, while b-series gangliosides may be not the essential substance for botulinum toxins, at the initial step during the intoxication process in mouse

Insights into Detoxification of Tolaasins, the Toxins Behind Mushroom Bacterial Blotch, by Microbacterium foliorum NBRC 103072T

Tolaasins are lipodepsipeptides secreted by Pseudomonas tolaasii, the causal agent of brown blotch disease of mushroom, and are the toxins that cause the brown spots. We previously reported that Microbacterium foliorum NBRC 103072T is an effective tolaasin-detoxifying bacterium. In this study, we aimed to characterize the tolaasin-detoxification process of M. foliorum NBRC 103072T. The tolaasin detoxification by M. foliorum NBRC 103072T was carried out by hydrolyzation of tolaasins at two specific sites in the peptide moiety of tolaasins by its cells, and the resulting fragments were released from bacterial cells. The tolaasin-hydrolyzing activity can be extracted by a neutral detergent solution from M. foliorum NBRC 103072T cells. Moreover, tolaasin adsorption to the bacterial cells occurred prior to hydrolyzation of tolaasins, which might contribute to the effective tolaasin detoxification by M. foliorum NBRC 103072T. It is notable that the tolaasin-degradation process by M. foliorum NBRC 103072T is carried out by hydrolyzation at specific sites in the peptide moiety of lipopeptide by bacterial cells as a novel biological degradation process of cyclic lipopeptides.[Graphic: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license

Identification of the <em>hcb</em> gene operon Involved in catalyzing aerobic hexachlorobenzene dechlorination in <em>Nocardioides</em> sp strain PD653

Erratum: Page 8, Fig. 3 legend, lines 6 and 7: “No-RT and genomic DNA, used as negative and positive controls, respectively, are presented in lanes − and +, respectively” should read “No-RT and genomic DNA, used as negative and positive controls, respectively, are presented in lanes − and g, respectively. cDNA from strain PD653 cells exposed to hexachlorobenzene for 3 h was used as the template and is shown in lane +.” https://doi.org/10.1128/AEM.02257-17International audienceNocardioides sp. strain PD653 was the first identified aerobic bacterium capable of mineralizing hexachlorobenzene (HCB). In this study, strain PD653-B2, which was unexpectedly isolated from a subculture of strain PD653, was found to lack the ability to transform HCB or pentachloronitrobenzene into pentachlorophenol. Comparative genome analysis of the two strains revealed that genetic rearrangement had occurred in strain PD653-B2, with a genomic region present in strain PD653 being deleted. In silico analysis allowed three open reading frames within this region to be identified as candidate genes involved in HCB dechlorination. Assays using recombinant Escherichia coli cells revealed that an operon is responsible for both oxidative HCB dechlorination and pentachloronitrobenzene denitration. The metabolite pentachlorophenol was detected in the cultures produced in the E. coli assays. Significantly less HCB-degrading activity occurred in assays under oxygen-limited conditions ([O-2] < 0.5 mg liter(-1)) than under aerobic assays, suggesting that monooxygenase is involved in the reaction. In this operon, hcbA1 was found to encode a monooxygenase involved in HCB dechlorination. This monooxygenase may form a complex with the flavin reductase encoded by hcbA3, increasing the HCB-degrading activity of PD653. IMPORTANCE The organochlorine fungicide HCB is widely distributed in the environment. Bioremediation can effectively remove HCB from contaminated sites, but HCB-degrading microorganisms have been isolated in few studies and the genes involved in HCB degradation have not been identified. In this study, possible genes involved in the initial step of the mineralization of HCB by Nocardioides sp. strain PD653 were identified. The results improve our understanding of the protein families involved in the dechlorination of HCB to give pentachlorophenol