THE ABILITY TO BIND ALBUMIN IS CORRELATED WITH NITRIC-OXIDE SENSITIVITY IN MORAXELLA-CATARRHALIS

Moraxella catarrhalis is sensitive to NO generators, e.g. S-nitroso-N- acetylpenicillamine (SNAP) and sodium nitroprusside (SNP), but can spo ntaneously develop higher SNP tolerance. Using SDS-PAGE of outer membr ane proteins and immunoblotting for serum albumin, we found that the w ild strain bound more blood-medium-derived albumin than the SNP-resist ant variant did. There was a negative correlation between NO tolerance and the presence of serum albumin in the medium. We suggest that M. c atarrhalis can change its surface properties to avoid binding albumin and thereby increase its resistance to NO. Growth of Moraxella is affe cted by iron, and that may have influenced our results. Using chrome a zurol S plates as an indicator, we noted that both albumin and SNP hav e a strong affinity for iron(III). (C) 1998 Federation of European Mic robiological Societies. Published by Elsevier Science B.V. All rights reserved.