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

Summary: The extractable polar lipids of Clostridium innocuum have been shown to consist of glycosyldiradylglycerols, phospholipids and phosphoglycolipids. The major glycosyldiradylglycerols are d-Glcp(α1-3)radyl2Gro and d-Galp(α1-2)d-Glcp(α1-3)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(α1-2)d-Glcp(α1-3)radyl2Gro and a derivative of this lipid containing an acyl chain esterified to 0-6 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.