Explorations of Bdellovibrio bacteriovorus Films and Ubiquinone Expression
Authors:Hyeong-Jin Kim, Nicholas Thomas
Mentor:Eileen Spain, Professor of Chemistry, Occidental College
Bdellovibrio bacteriovorus is a Gram-negative Delta-proteobacteria that preys on other Gram-negative bacteria, including those which are pathogens of livestock and humans. When grown on nutrient-rich media, B. bacteriovorus develops into two phenotypes: host-dependent (HD) and host-independent (HI). HD strains are predatory, small, and highly motile; in contrast, HI strains are pleomorphic and do not require preying on Gram-negatives for sustenance. When inoculated onto a filter paper within a nutrient-rich agar, B. bacteriovorus self-organizes into a spatially-resolved biofilm with two concentric circles. We hypothesize a relationship between the ability of B. bacteriovorus to self-organize within biofilms and ubiquinone from prior research. Ubiquinone expression may explain the yellow color of the HD variant of B. bacteriovorus in biofilms as supported by the observed yellow color of ubiquinone upon isolation. Furthermore, ubiquinone may be involved in motility and in the digestion of prey components in the bdelloplast stage of predation. We investigated the expression of ubiquinone-metasynthesis genes, Bd0422 and Bd2350, through cDNA synthesis from total RNA of HD and HI samples taken from biofilms and gene amplification through RT-PCR and gel electrophoresis. We discover the expression of Bd0422 and Bd2350 in HD but not in HI variants. We present an interpretation of these findings within ecological and human health contexts.