Isolation and Characterization of Unsaturated Fatty Acids Auxotrophs of Streptococcus pneumonie

ALTABE, SILVIA GRACIELA; DE MENDOZA, D

Pinamar. Buenos Aires

Congreso; 41 th Annual Meeting..XLI. Reunión anual de la SAIB; 2005

SAIB

Unsaturated fatty acids (UFAs) biosynthesis is essential for the maintenance of membrane structure and function in many groups of anaerobic bacteria.  Like  E. coli,  St. pneumoniae, produce the straight chain saturated (SFA) and monosaturated fatty acids.  In E. coli UFAs synthesis  requires the action of two gene products, fabA the essential isomerase/dehydratase and fabB an elongation condensing enzyme. St. pneumoniae lack both genes and  instead employs a unique enzyme with only an isomerase function encoded  by the fabM  gene. Although the function of FabM has been deduce in vitro, no mutants in St. pneumoniae have been isolated. We report the isolation of such mutant , St. pneumoniae SH3 by gene disruption using a cloramphenicol resistance cassette.  This mutant can not be grown in complex medium and the defect could be overcome by supplementing the media with oleic acid (C18:1). The  St. pneumoniae SH3 did not have detectable levels of monosaturated fatty acids as determined by GC-MS and  thin-layer chromatographic analysis of the phospholipid fatty acid composition. Therefore our experiments demonstrate that FabM is essential for growth of St. pneumoniae and provides the basis for developing new antibacterial strategies.