Interactions between Campylobacter jejuni and Bacillus subtilisErega, Andi (Avtor) Smole Možina, Sonja (Mentor) Mandić Mulec, Ines (Komentor) Campylobacter jejuniBacillus subtilisbiofilm formationconfocal microscopyfood safetysecondary metabolitesThe gram-negative, foodborne pathogen Campylobacter jejuni is typically found in animals, such as birds, as an intestinal commensal, and also in food products, especially fresh poultry meat. Probiotics are one of the strategies that can be easily applied in animal feeding to attenuate Campylobacter problem in the food production and human nutrition. Here, we present a natural strain Bacillus subtilis PS-216, gram-positive, beneficial, spore forming potentially probiotic strain and reference strain C. jejuni NCTC 11168 in in vitro co-culture experimental model system. We hypothesize that B. subtilis secretes metabolites that reduce C. jejuni survival in a co-culture and that this interaction changes the growth dynamics and spatial distribution of both species in a multi-species biofilm during static, microaerobic conditions at 42 㓋C. We confirm this hypothesis by using microscale (confocal laser scanning microscopy), C. jejuni and B. subtilis mutants and colony counts of fluorescently labelled strains. We confirm that B. subtilis decreases the fitness of C. jejuni, reduces its biofilm prominence, and decreases the adhesion of C. jejuni to abiotic surfaces. Moreover, we show that the addition of B. subtilis cells to a pre-established C. jejuni biofilm induces its dispersal, that the antagonistic effect of B. subtilis is contact independent and involves non-ribosomal peptides bacillaen and bacylisin as a fully functional two-component system response regulator (ComA) for full antagonistic strength of B. subtilis PS-216 against C. jejuni during co-culture assay. Furthermore, B. subtilis two-time diluted CFS affects the faster formation of biofilm in response to B. subtilis extracellular components. Also, we showed importance of efflux apparatus system, quorum sensing and stress response of C. jejuni during interaction with B. subtilis PS-216 in co-culture and adhesion to abiotic surfaces. Altogether results indicate that mechanism of competitive exclusion is driven by interference competition between two competing strains which is in line with all three hypotheses. In conclusion, we show a strong potential of B. subtilis PS-216 to limit C. jejuni biofilm growth and adhesion to abiotic surfaces, which makes this strain interesting for application in pathogen biofilm control and as a potentially probiotic strain to be applied in animal feeding.[A. Erega]20212021-10-01 10:22:13Doktorsko delo/naloga131715UDK: 579.22/.26:579.6VisID: 199335COBISS_ID: 81643523sl