Detection and identification of Bacteriovorax stolpii UKi2 Sphingophosphonolipid molecular species

Bacteriovorax stolpii is a predator of larger gram-negative bacteria and lives as a parasite in the intraperiplasmic space of the host cell. This bacterium is unusual among prokaryotes in that sphingolipids comprise a large proportion of its lipids. We here report the presence of 18 molecular species of B. stolpii UKi2 sphingophosphonolipids (SPNLs). (31)P NMR spectroscopy and analysis of P(i) released by a differential hydrolysis protocol confirmed the phosphonyl nature of these lipids. The SPNLs were dominated by those with 1-hydroxy-2-aminoethane phosphonate (hydroxy-aminoethylphosphonate) polar head groups; aminoethylphosphonate was also detected in minor SPNL components. The long-chain bases (LCBs) were dominated by C(17) iso-branched phytosphingosine; C(17) iso-branched dihydrosphingosine was also present in some SPNLs. The N-linked fatty acids were predominantly iso-branched and most contained an alpha-hydroxy group (C(15) alpha-hydroxy fatty acid was the major fatty acid). Minor molecular species containing nonhydroxy fatty acids were also detected. The definitive iso-structures of the predominant fatty acids and LCBs present in the B. stolpii SPNLs were established using (13)C and (3)H nuclear magnetic resonance spectroscopy; less than 20% were unbranched. Detection and analyses of intact compounds by MS-MS were performed by a hybrid quadrupole time-of-flight (Q-TOF-II) MS equipped with an electrospray ionization source. Analyses of peracetylated derivatives verified the structural assignments of these lipids.