Changes in intestinal microflora of Caenorhabditis elegans following Bacillus nematocida B16 infection

The effect of pathogenic bacteria on a host and its symbiotic microbiota is vital and widespread in the biotic world. The soil-dwelling opportunistic bacterium Bacillus nematocida B16 uses a "Trojan horse" mechanism to kill Caenorhabditis elegans. The alterations in the intestinal microflora that occur after B16 infection remain unknown. Here, we analyzed the intestinal bacteria presented in normal and infected worms. The gut microbial community experienced a complex change after B16 inoculation, as determined through marked differences in species diversity, structure, distribution and composition between uninfected and infected worms. Regardless of the worm's origin (i.e., from soil or rotten fruits), the diversity of the intestinal microbiome decreased after infection. Firmicutes increased sharply, whereas Proteobacteria, Actinobacteria, Cyanobacteria and Acidobacteria decreased to different degrees. Fusobacteria was only present 12 h post-infection. After 24 h of infection, 1228 and 1109 bacterial species were identified in the uninfected and infected groups, respectively. The shared species reached 21.97%. The infected group had a greater number of Bacillus species but a smaller number of Pediococcus, Halomonas, Escherichia and Shewanella species (P < 0.01). Therefore, this study provides the first evaluation of the alterations caused by pathogenic bacteria on symbiotic microbiota using C. elegans as the model species.