Buisson, C. | bioRxiv Science

bioRxiv2026

Environmental history shapes host-associated dynamics of sporulating and non-sporulating bacterial subpopulations during infection

Host-associated environments represent ecological contexts that can structure microbial population dynamics, yet their effects on sporulating pathogens remain poorly understood. We investigated how passage through a natural insect host shapes population-level traits in the entomopathogen Bacillus thuringiensis. Using Galleria mellonella larvae, we compared the characteristics of bacterial populations extracted from insect cadavers with those maintained under in vitro conditions. Passage through the host generated a distinct population structure, characterized by the stable coexistence of sporulating and non-sporulating bacteria and a larger non-sporulating fraction than in in vitro cultures. Host-extracted bacteria exhibited a different morphology and higher virulence than in vitro-grown populations, the latter being largely due to the non-sporulating fraction of the population, as shown by reinfection experiments with each subpopulation isolated via fluorescence-activated cell sorting. On the other hand, all subpopulations persisted similarly in the host and completed the infection cycle. Host-extracted subpopulations also showed increased tolerance to oxidative stress, consistent with an adaptation to conditions encountered within insect cadavers. Furthermore, competition assays revealed that non-sporulating bacteria from insect cadavers outcompeted sporulating cells, whereas the opposite was observed for in vitro-grown bacteria. In addition, spores produced in the host displayed reduced heat resistance but germinated more efficiently than laboratory-derived spores, highlighting environment-dependent properties which may affect transmission potential. Together, these results demonstrate that the host-associated ecological context drives functional differentiation within bacterial populations and modulates key traits linked to survival, competition, stress tolerance and persistence, emphasizing the importance of host-associated environments in structuring ecological properties of sporulating pathogens.

microbiology↗

bioRxiv2023

Reduction, removal or replacement of sodium nitrite in a model of cured and cooked meat: a joint evaluation of consequences on microbiological issues in food safety, colon ecosystem and colorectal carcinogenesis

ScopeEpidemiological and experimental evidence reported that processed meat consumption is associated with colorectal cancer (CRC) risk. Several studies suggest the involvement of nitrite or nitrate additives via N-nitroso-compound formation (NOCs). Methods and resultsCompared to the reference level (120 mg/kg of ham), the effects of sodium nitrite reduction (90 mg/kg of ham), removal and replacement were analysed on ham characteristics and in a CRC rat model. Sodium nitrite removal and reduction induced a similar decrease in CRC preneoplastic lesions, but only reduction led to (i) an inhibitory effect on Listeria monocytogenes growth comparable to that obtained using the reference nitrite level of 120 mg/kg and (ii) an effective control of lipid peroxidation. Among the three alternatives tested, none led to a significant gain when compared to the 120 mg/kg ham reference level: vegetable stock, due to nitrate presence, was very similar to this reference nitrite level, yeast extract induced a strong luminal peroxidation and no decrease in preneoplastic lesions despite the absence of NOCs, and polyphenol rich extract induced the clearest downward trend on preneoplastic lesions but the concomitant presence of nitrosyl iron in feces. Except vegetable stock, other alternatives were less efficient than sodium nitrite ([≥] 90 mg/kg) in reducing L. monocytogenes growth. ConclusionNitrite reduction (90mg/kg) effectively reduced CRC risk through limiting NOC formation and lipid peroxidation, while mitigating L. monocytogenes risks from cooked hams. Going further in reduction should be possible if accompanied by antioxidants to limit lipid peroxidation and appropriate use-by dates.

pathology↗