Hemoproteins of Enterococcus faecalis

Sammanfattning: The gram-positive bacterium Enterococcus faecalis is a commensal organism, often found in the gut of humans and other animals. It can cause opportunistic disease and it frequently causes nosocomial infections. Treatment of such infections is often impaired by this organisms broad intrinsic and acquired resistance to antibiotics. E. faecalis uses homo-lactic fermentation for energy production. Work done in the 1970’ies indicated that production of cytochromes and respiratory activity occur if the cells are supplied with heme. A decade later, heme-dependent catalase activity was reported. This thesis describes the identification of a cytochrome bd and a catalase in E. faecalis. These two enzymes are synthesized only if heme is supplied in the growth medium. The cytochrome bd most likely functions as terminal oxidase in an aerobic respiratory chain present in E. faecalis under some conditions. The E. faecalis catalase was overproduced, purified and its major biochemical characteristics were determined. In addition, a catalase-deficient mutant was constructed. The newly acquired knowledge about the E. faecalis catalase was used to establish an in vivo system for production of artificial hemoproteins. It was demonstrated that E. faecalis cells can take up a variety of heme analogues from the growth medium and integrate them into the cytoplasmic catalase protein.