CHEMOTAXONOMIC DIFFERENTIATION BETWEEN THE BACILLUS-CEREUS GROUP AND BACILLUS-SUBTILIS BY PHOSPHOLIPID EXTRACTS ANALYZED WITH ELECTROSPRAY-IONIZATION TANDEM MASS-SPECTROMETRY

Electrospray ionization tandem mass spectrometry (ESI MS-MS) was devel oped for analysis of bacterial glycerophospholipids and was applied to bacterial differentiation. Bacillus anthracis, B. cereus, B. thuringi ensis (referred to as the B. cereus group) and B. subtilis are four cl osely related members of the Bacillus genus. Conventional taxonomic me thods, as well as whole cell carbohydrate profiling and fatty acid pro filing are sufficient to differentiate between the B. cereus group and B. subtilis. Phospholipids are the main source of fatty acids in the bacterial cell and therefore should maintain the discriminating power of the fatty acid data. Under negative ionization conditions, phosphol ipids form predominantly deprotonated molecular ions. The principal ba cterial phospholipids detected using negative ion ESI are phosphatidyl glycerols (PGs). Chloroform:methanol extraction of whole bacterial cel ls resulted in ESI mass spectra. The product ion mass spectra of depro tonated PGs provided the molecular weights of the fatty acid moieties. The distribution of fatty acids for the different PG species, as well as the different profiles of PGs, allowed differentiation between the B. cereus group and B. subtilis and this could provide a chemotaxonom ic method for bacterial differentiation. (C) 1997 Elsevier Science B.V .