Abstract
The soil-dwelling, opportunistic pathogenic bacterium "Bacillus nematocida" B16 exhibits strong killing activities against a variety of pathogenic nematodes via a “Trojan horse” mechanism that can kill worm species like Caenorhabditis elegans. The bacterial strain CPCC 101271 was previously isolated from the intestines of C. elegans that were recovered from natural habitats and can serve as a probiotic for C. elegans, while also assisting in resistance to infection by the pathogenic strain B16. In this study, the lifespan of C. elegans fed with strain CPCC 101271 cells was extended by approximately 40% compared with that of worms fed with Escherichia coli OP50 cells. In addition, the colonization of C. elegans by the pathogenic bacterium "B. nematocida" B16 was inhibited when pre-fed with strain CPCC 101271. Metagenomic sequence analysis of intestinal microbiota of C. elegans fed with strain CPCC 101271 and infected with B16 revealed that pre-feeding worms with CPCC 101271 improved the diversity of the intestinal bacteria. Moreover, community structure significantly varied in coordination with Stenotrophomonas spp. and Bacillus spp. abundances when competition between strains CPCC 101271 and B16 was evaluated. In conclusion, the nematode microbiota strain CPCC 101271 assisted in its host resistance to colonization by the pathogen "Bacillus nematocida" and can also promote life span-prolongation in C. elegans. These results underscore that understanding the interactions between C. elegans microbiota and pathogens can provide new insights into achieving effective biological control of agricultural pests.
Highlights
Nematodes are one kind of the most abundant worms and have a significant global impact on ecosystems, economies, agriculture, and human health
We report an intestinal bacterium Stenotrophomonas strain CPCC 101271, and the results of in vitro and in vivo experiments showed that "B. nematocida" B16 can inhibit the growth of CPCC 101271, while strain CPCC 101271 has the ability to inhibit the colonization of C. elegans by B16
Worms fed on CPCC 101271 lived approximately 40% longer than worms fed on E. coli or JCM 1 3333T, indicating that the nematodes fed on CPCC 101271 lived longer than those fed on E. coli OP50 or S. rhizophila JCM 1 3333T and had greatly increased survival rates (Fig. 1)
Summary
Nematodes are one kind of the most abundant worms and have a significant global impact on ecosystems, economies, agriculture, and human health. Plant parasitic nematodes cause huge economic losses to agriculture and forestry every year. It is of great importance to develop biological methods to control plant-parasitic nematodes, so as to deal with the environmental problems posed by chemical control methods (Duncan 1991). It has been reported that the intestinal flora in most nematodes plays an important role in host growth, physiological metabolism, and immune regulation (Nour et al 2003; Haegeman et al 2009). Since microbiota is thought to be key to the stability of biocontrol agents, understanding the functions of the intestinal flora in nematodes is of great significance for improving the activity of biocontrol agents
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