Novel polar lipid composition of Clostridium innocuum as the basis for an assessment of its taxonomic status.

The extractable polar lipids of Clostridium innocuum have been shown to consist of glycosyldiradylglycerols, phospholipids and phosphoglycolipids. The major glycosyldiradylglycerols are D-Glcp(alpha 1-3)radyl2Gro and D-Galp(alpha 1-2)D-Glcp(alpha 1-3)radyl2Gro. Both glycolipids have some 1-O-(alk-1-enyl)-2-O-acyl species, in addition to diacyl species. The phospholipids include bisphosphatidylglycerol (cardiolipin), lysocardiolipin and phosphatidylglycerol (PG). In addition, several novel lipids have been found, including a PG acetal of cardiolipin plasmalogen, smaller amounts of a lyso form of this lipid, a PG acetal of PG plasmalogen, and two phosphoglycolipids, which represent 65% of total polar lipids. The latter have been identified as 2'-amino-1',3'- dihydroxypropane-3'-P-6-D-Galp(alpha 1-2)D-Glcp(alpha 1-3)radyl2Gro and a derivative of this lipid containing an acyl chain esterified to O-6 of the glucopyranosyl ring. Based on rRNA sequence data, C. innocuum is considered to be a relative of the mycoplasmas. Its unique lipid composition permits an assessment of the taxonomic status of C. innocuum, since the lipid amphiphiles display marked differences from those of Acholeplasma laidlawii.