The Major Glycerophospholipids of the Predatory and Parasitic Bacterium Bdellovibrio bacteriovorus HID5

Abstract

Bdellovibrio are small motile bacteria that attack and parasitize larger Gram-negative bacteria and since they might have practical applications, these organisms are attracting the attention of researchers as indicated by the sequencing of the B. bacteriovorus genome. There is an earlier report showing that B. bacteriovorus scavenges fatty acids from the host cell during its parasitic phase otherwise the biochemical nature of its lipids, particularly its complex lipids, remains unknown. We here report on the phospholipid classes of an axenically cultured host-independent strain (HID5). Phospholipids and fatty acids were identified by a variety of chromatographic procedures and high-resolution mass spectrometric techniques. Phosphatidylethanolamine was the major phospholipid and phosphatidylserine, cardiolipin, phosphatidylglycerol, and N-acylphosphatidylethanolamine were also identified. The major fatty acids were 16:0, 16:1, 18:1, and 9,10-Mt C16:0 (cyC17:0). Unlike another predatory bacterium, Bacteriovorus stolpii strain UKi2, sphingolipids were not detected in B. bacteriovorus by the procedures used in this study. This is consistent with the apparent lack of genes coding for sphingolipid biosynthesis enzymes in the B. bacteriovorus genome database. The results are consistent with the separation of Bdellovibrio and Bacteriovorus into separate genera.

Bacterial Predators Possess Unique Membrane Lipid Structures

“…Furthermore, we were able to determine the presence of NAPtdEth in B. bacteriovorus HD100, as proposed in another study [12]. In this context, the only amide bound fatty acids found in the NAPtdEth were cyclopropane FA.…”

“…The results for B. stolpii are consistent with the data published by Steiner et al [10]. However, we could not confirm the high proportion of phosphatidylserine found in B. bacteriovorus HD100 by Nguyen et al [12].…”

“…Nevertheless, other unusual lipid structures were found in these two members of the BALO group. Nguyen et al already reported phosphatidylserines in B. bacteriovorus HD100, as well as an additional lipid class for which the identification as N-acylphosphatidylethanolamines (NAPtdEth) was proposed [12]. Experimental proof for this assumption other than accurate masses was not provided.…”

“…Very uncommon for prokaryotes, sphingolipids were found in the cell wall of B. stolpii, which were shown to be phosphonolipids [9][10][11]. The only other BALO which has been analyzed so far in respect to its phospholipids is B. bacteriovorus [12].…”

Bdellovibrio and Like Organisms

“…In contrast, attachment by Bacteriolyticum stolpii is indifferent to prey LPS composition but is reduced in the absence of particular porins (outer membrane proteins, OMPs) such as OmpF and OmpC in E. coli (Schelling and Conti 1986;Varon and Shilo 1969). BALOs synthesize unique membrane lipid structures that greatly vary between taxa: in B. bacteriovorus, the lipid A is completely devoid of negatively charged groups and possesses a-D-mannopyranose residues instead of phosphate groups; B. stolpii contains sphingophospholipids with unique 2-amino-3-phosphonopropanate heads; and Peridibacter starrii's lipids include phosphatidylethanolamine structures with an additional N-glutamyl residue (Muller et al 2011;Nguyen et al 2008). The varied composition of lipids implies that predator's membrane fluidity and permeability…”