Supplementary Material for: Colonization of Caenorhabditis elegans by Bacillus nematocida B16, a Bacterial Opportunistic Pathogen

Background: Soil-dwelling Bacillus nematocida B16 can kill Caenorhabditis elegans via a Trojan horse-like mechanism. However, colonization is a key problem that must be solved during the infection process. Aims: To study the molecular mechanism involved in the colonization of B. nematocida B16 against the host C. elegans. Methods: GFP-expressing strain B16g was constructed and its nematocidal activity was assayed. ‘Feeding transfer’ experiments were carried out separately using of B16 and B16g strains to explore the colonization mode of the bacteria. Fluorescence microscopy was used to observe the interactions between fluorescent signal and the quantity of bacteria in the intestine. A mariner-based transposon called TnYLB-1 was also applied in the random mutagenesis of B16 to screen the mutants with impaired colonization of nematode worms and identify potential localization-related genes. Results and Conclusion: A small inoculum of the bacteria resulted in its proliferation in the C. elegans intestine. The fluorescence signal was enhanced with increasing bacterial density in the intestine. Several candidate genes with possibly important roles in colonization were found. These results provide a solid foundation for further elucidation of the infection process at the molecular level and enrichment of our knowledge of bacterial pathogenesis.