EXTRACELLULAR PROTEINS AND OTHER COMPONENTS AS OBLIGATE INTERMEDIATESIN THE INDUCTION OF A RANGE OF ACID TOLERANCE AND SENSITIZATION RESPONSES IN ESCHERICHIA-COLI

Several acid tolerance responses of Escherichia coli were associated w ith secretion into the growth media of components (frequently proteins ) which altered acid tolerance of other cultures. First, medium filtra tes from cultures induced to acid tolerance by several conditions conv erted pH 7.0-grown organisms to tolerance and, for most such responses , filtrate proteins were needed for full induction. Secondly, filtrate s from cultures induced to acid sensitivity at alkaline pH produced se nsitisation of resistant cultures. Thirdly, filtrates from inherently tolerant or sensitive strains altered tolerance or sensitivity of norm al strains. In many cases, filtrate components were essential for the original response, e.g. acid habituation at pH 5.0. Extracellular comp onents may function as intermediates only in stress tolerance response s, but other adaptive responses must be tested as such components may function in other inducible processes. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rig hts reserved.