Role of Lipid A Phosphorylation on Prey Identification by Bdellovibrio Bacteria

Bdellovibrio bacteriovorus is a Gram-negative bacterium that preys on nearly all other Gram-negative bacteria except itself, but the mechanism of prey identification remains unknown. Since the vast majority of Gram-negative cells have lipopolysaccharide (LPS) molecules composing their outer membrane and the lipid A region of LPS is highly conserved across species, the chemical composition of lipid A could be a target. B. bacteriovorus itself has highly unusual lipid A structure in which both phosphate residues present in typical lipid A are substituted by mannose. Here, B. bacteriovorus was grown both in liquid buffer and on agar with three strains of potential prey cells: K-12 E. coli, which has conventional lipid A, and two other K-12 strains that produce mono-or non-phosphorylated lipid A. In addition, the liquid predator/prey suspension was pipetted onto filtration membranes and the membranes were imaged as a time series using AFM. In liquid buffer, B.bacteriovorus preys on all types of E. coli, although LPSphosphorylation level may impact how quickly predation occurs. Indouble layer agar plates, a clear preference for dephosphorylated over mono- or nonphosphorylated LPS is established, but under certainconditions B. bacteriovorus is still able to consume mono- and nonphosphorylated prey.