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de cassia pessotti 4 & Valeska Villegas-escobar 1* the world is in the midst of an antimicrobial resistance crisis, driving a need to discover novel antibiotic substances. Using chemical cues as inducers to unveil a microorganism's full metabolic potential is considered a successful strategy. to this end, we investigated an inducible antagonistic behavior in multiple isolates of the order Bacillales, where large inhibition zones were produced against Ralstonia solanacearum only when grown in the presence of the indicator triphenyl tetrazolium chloride (ttc). this bioactivity was produced in a ttc-dose dependent manner. Escherichia coli and Staphylococcus sp. isolates were also inhibited by Bacillus sp. strains in ttc presence, to a lesser extent. Knockout mutants and transcriptomic analysis of B. subtilis NCIB 3610 cells revealed that genes from the L-histidine biosynthetic pathway, the purine, pyrimidine de novo synthesis and salvage and interconversion routes, were significantly upregulated. Chemical space studied through metabolomic analysis, showed increased presence of nitrogenous compounds in extracts from induced bacteria. the metabolites orotic acid and L-phenylalaninamide were tested against R. solanacearum, E. coli, Staphylococcus sp. and B. subtilis, and exhibited activity against pathogens only in the presence of ttc, suggesting a biotransformation of nitrogenous compounds in Bacillus sp. cells as the plausible cause of the inducible antagonistic behavior.

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Objectives To characterize the gut microbiome and build a collection of strains capable of metabolizing a specific dietary source rich in choline, from pregnant and lactating women of the region of Antioquia, Colombia Methods Fecal and blood samples were simultaneously collected from volunteers. Microbial cells were anaerobically isolated from fecal samples in an Egg Based Selective (EBS) medium, incubating at 37°C for 7 days. Afterwards, the colony-forming units per gram of fecal sample (CFU/g) were calculated for each volunteer, as the total biomass of culturable microorganisms capable of metabolizing a nutritional source rich in choline. Each bacterial morphology purified in EBS medium and Brain Heart Infusion (BHI) medium was cryopreserved at −80°C. Additionally, blood samples were analyzed by Abad Laboratorio obtaining the lipid profile of each volunteer. Data of CFU/g were analyzed using a non-parametric test. Correlation matrices of the total biomass and the physiological state of the volunteers, each of them with the lipid profile values, were performed in R software. Results Nineteen bacterial morphologies have been isolated, creating the first entries of the strains bank of choline metabolizing microorganisms. Total biomass values were between 1.89E + 08 and 2.10E + 10 CFU/g (± 6.96E + 09) and the Kruskal-Wallis test of total biomass in CFU/g denotes statistical significance among volunteers (P = 0,04). Besides, a significant correlation between the physiological state of volunteers and HDL was found, meaning that the lipid profile is affected during pregnancy and postpartum, as is widely recognized. Nevertheless, a non-previously reported correlation between total cholesterol, LDL and triglycerides with the total culturable choline-metabolizing microbial biomass from pregnant and lactating women was also found. Conclusions Total biomass of culturable choline-metabolizing microbiota is significantly variable among individuals and results suggest it being independent of the physiological state. Lactating and pregnancy states have an impact in the lipid profile, as has been previously reported. However, a novel finding in this study is that culturable microorganisms capable of metabolizing a nutritional source rich in choline as egg, impact the components of the lipidic profile. Funding Sources Universidad EAFIT Abad Laboratorio.