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Theses

Rôle de l’activité inhibitrice des propionibactéries dans la structuration des populations microbiennes

Abstract : To study the influence of habitat on the frequency and the specificity of bacterial competition, we examined a model of phylogenetically close species of propionibacteria living in two very different habitats: dairy propionibacteria (Propionibacterium spp., Acidipropionibacterium spp.) and cutaneous propionibacteria (Cutibacterium spp.). The frequency of competition was studied by complementary, phenotypic and genotypic approaches. The frequency of antagonisms was significantly different depending on the type of habitat and was directly influenced by bacterial genus. Indeed, 25 % of Cutibacterium strains and 22.5 % of Acidipropionibacterium strains inhibited at least one target strain, whereas Propionibacterium sp. were completely devoid of inhibitory activity. In accordance with phenotypic findings, no antagonistic metabolite biosynthetic gene cluster were found in 34 genomes of Propionibacterium freudenreichii, whereas the majority of Cutibacterium sp. and some Acidipropionibacterium sp. genomes contained at least one antagonistic gene cluster. The exemple of P. freudenreichii suggests that very selective habitats, with a high number of abiotic stress, like swiss-type cheeses, favours very resistant but not antagonistic species, as the number of potential concurrents is very limited in these conditions. On the contrary, Acidipropionibacterium sp. and a fortiori Cutibacterium sp. are characteristic of less selective habitats, with high bacterial diversity, and they present a high proportion of antagonistic strains. Cutibacterium sp. genomes contain a high diversity of antimicrobial components gene clusters (NRPS, bacteriocins) which may give them a competitive advantage to face a diversified panel of concurrents. During phenotypic screenging, we detected an important inhibitory activity of one strain of dairy Acidipropionibacterium against a pathogenic strain of Streptococcus pyogenes. The antibacterial substance detected in Acidipropionibacterium jensenii CIRM-BIA 1785 culture supernatant had an apparent molecular weight of less than 3.5 kDa. It was resistant to proteolysis, to temperature and to pH variations. In the genome of A. jensenii CIRM-BIA 1785, we detected several clusters of antimicrobial metabolite genes, including a lasso peptide which could potentially be responsible for anti-streptococcal activity. The characteristics of the substance make it a good candidate for therapeutic use in eradication of S. pyogenes carriage with the aim of reducing its reservoir and the probability of recurrent infections.
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Theses
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http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2019_0253_DUDA_FERRAND.pdf
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https://hal.univ-lorraine.fr/tel-02556063
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Submitted on : Monday, April 27, 2020 - 5:53:09 PM
Last modification on : Thursday, January 7, 2021 - 3:40:40 PM

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  • HAL Id : tel-02556063, version 1

Citation

Janina Duda-Ferrand. Rôle de l’activité inhibitrice des propionibactéries dans la structuration des populations microbiennes. Ingénierie des aliments. Université de Lorraine, 2019. Français. ⟨NNT : 2019LORR0253⟩. ⟨tel-02556063⟩

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