FEMS Microbiology Letters 48 (1987) 401-406 401 Published by Elsevier FEM 03030 Characterization of hemin antibacterial action on Staphylococcus aureus Yeshayahu Nitzan, Hava Ladan, Shoshana Gozansky and Zvi Malik Health Sciences Research Center, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52100, Israel Received 10 June 1987 Revision received 8 September 1987 Accepted 9 September 1987 Key words: Staphylococcus aureus; Heroin inactivation; Antibacterial activity; Thiols protection; Serum protection 1. SUMMARY The mechanism of inactivation of Staphylococ- cas aureus cells by hemin is described. Protection experiments by sulfhydryl reagents such as cy- steine, mercaptoethanol, glutathione or thioglyco- late in their reduced form prevent S. aureus bacteria from inactivation by heroin (1.5 × 10 5 M). The treatment of bacteria by hemin in the presence of one of those reagents (1 × 10 -2 M) showed that the growth rate and viability of the culture remained unchanged. On the other hand sulfhydryl reagents did not prevent the binding of hemin to the bacteria. When cysteine or glutath- ione were introduced to a culture after exposure to hemin it could neither reverse the damage done to the cells nor shorten the time of the culture's recovery. Another type of protection was obtained by addition of serum albumin which prevented hemin molecules from binding to the bacterial envelopes. Furthermore, when albumin was intro- duced after the bacteria were treated by hemin it Correspondence to: Y. Nitzan, Health Sciences Research Center, Department of Life Sciences, Bar-llan University, Ramat-Gan 52100, Israel. prevented further damage to the survivors and thus shortened the time required for recovery. None of the singlet oxygen quenchers or hydroxyl radical scavengers could protect the bacteria from hemin inactivation. The mechanism by which hemin affects S. aureus is assumed to be by oxidizing a major system within the cell. 2. INTRODUCTION Hemin, the iron-containing porphyrin, is synthesized by most bacterial species. It functions as a prostetic group in proteins that have the capacity to bind or transfer oxygen and in cyto- chromes. Haemophilus influenzae is unable to pro- duce the tetrapyrrole molecule, and requires exog- enous hemin for its growth [1]. Hemin is needed in some other bacteria for its iron atom [2-4]. In- creased amounts of hemin regulate the porphyrin biosynthetic pathway by a negative feedback mechanism in Rhodopseudomonas sphaeroides [5]. Addition of exogenous hemin to the growth medium of S. epidermidis increases the cellular content of catalase and cytochromes, which are porphyrin-containing proteins [6]. In S. aureus, 0378-1097/87/$03.50 © 1987 Federation of European Microbiological Societies