HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Busch, J. E. Articles by Stutzenberger, F. J. Search for Related Content PubMed Articles by Busch, J. E. Articles by Stutzenberger, F. J. Agricola Articles by Busch, J. E. Articles by Stutzenberger, F. J.

Repression and inactivation of -amylase in Thermomonospora species during growth on cellobiose

Department of Microbiology, Clemson University, Clemson, SC 29631-1909, USA

Author for correspondence: F. J. Stutzenberger. Tel: + 1 864 656 3057. Fax: + 1 864 656 1127. e-mail: SFRED@Clemson.Clemson.edu

ABSTRACT

Thermophilic actinomycetes establish themselves as numerically dominant bacterial populations in selected high temperature environments by virtue of their exoenzymic ability to degrade the complex polysaccharides in thermogenic plant biomass. When Thermomonospora curvata and Thermomonospora fusca were grown on a mixture of cellulose and starch in mineral salts minimal medium, -amylase was repressed via inhibition of maltose uptake by cellobiose. Addition of cellobiose to exponential phase cells growing on maltose or maltotriose triggered rapid degradation of extant amylase in the culture fluid of wild-type cells, but not in a protease-deficient mutant of T. fusca. A serine protease purified from T. fusca caused inactivation of the amylase in culture fluid of the mutant when added at a concentration approximating to that of the wild-type strain. The chelating agent, EDTA, accelerated inactivation by the protease, while the presence of calcium or amylase reaction products protected the amylase. Therefore, during growth in an environment containing multiple polysaccharides, these thermophiles control the levels of their extracellular depolymerizing enzymes via both inducer exclusion and proteolytic inactivation.