Bacteriovorax stolpii strain UKi2, a facultative predator-parasite of larger Gram-negative bacteria, synthesizes distinct sphingophosphonolipids. These lipids are characterized by a direct P-C bond, the novel head group 1-hydroxy-2-aminoethylphosphonate, isobranched long chain bases and fatty acids, and fatty acids dominated by those with alpha-hydroxy groups. Myriocin, an inhibitor of serine:fatty acyl CoA transferase, reversibly blocked sphingophosplionolipid synthesis in B. stolpii UKi2. However, the inhibitor did not block cell proliferation indicating that these lipids are not vital for B. stolpii UKi2 viability and growth. When mixed with Escherichia coli prey cells, control predator-parasite bacteria were effective in forming large E coli bdelloplasts and cleared the suspension of the prey cells. Although myriocin-treated cells could attack prey cells and form bdelloplasts, their locomotory behavior was altered and fewer and smaller belelloplasts were produced. These observations open up the possibility for a role of sphingophosphonolipids in B. stolpii UKi2 complex behavior. (C) 2007 Elsevier Inc. All rights reserved.