Stimulation of bacterial growth by heat-stable, norepinephrine-induced autoinducers

The ability of norepinephrine to increase the growth of Escherichia coli in a serum-based medium has previously been shown to be due to the production of an autoinducer of growth during early log phase. Seventeen Gram-negativ e and 6 Gram-positive clinical isolates were examined for a similar ability to respond to norepinephrine, and to synthesise autoinducer. The majority of Gram-negative strains both produced and responded to heat-stable norepin ephrine-induced autoinducers of growth. Most of these autoinducers showed a high degree of cross-species activity, suggesting the existence of a novel family of Gram-negative bacterial signalling molecules. In contrast, altho ugh a number of Gram-positive strains were able to respond to norepinephrin e, the majority failed to produce autoinducers in the presence of norepinep hrine. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.