IRON SUPPLY OF STAPHYLOCOCCI AND OF MICROCOCCI BY ALPHA-KETOACIDS

Most of 232 strains of coagulase-negative staphylococci (CNS) belongin g to 16 species, and nine strains of micrococci belonging to four spec ies, could be distinguished by their growth on an iron-poor nutrient m edium. alpha-Keto-/alpha-hydroxyacids, as primary metabolites, facilit ated iron supply to CNS and micrococci under various iron-limited cond itions, as detected by different bioassay methods. Twelve selected CNS strains and two micrococcal strains produced significant amounts of a lpha-ketoacids in iron-poor liquid nutrient media. In particular, stra ins of Staphylococcus cohnii, S. xylosus and S. lentus unable to grow on iron-poor media, produced high amounts of pyruvic acid and alpha-ke toglutaric acid. In bioassays, the selected CNS strains being sideroph ore indicator strains were fed with alpha-ketoacids at different level s of iron limitation. Strains able to grow under iron deprivation appe ared to produce additional siderophores such as staphyloferrins under iron stress. alpha-Keto-/alpha-hydroxyacids may be additionally active in the iron supply of CNS and micrococci.