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Journal of Bacteriology, December 2001, p. 7198-7205, Vol. 183, No. 24
Department of Microbiology, University of
Illinois, Urbana, Illinois 61801
Received 15 June 2001/Accepted 19 September 2001
Bacteroides thetaiotaomicron uses starch as a source
of carbon and energy. Early steps in the pathway of starch utilization, such as starch binding and starch hydrolysis, are encoded by
sus genes, which have been characterized previously. The
sus structural genes are expressed only if cells are
grown in medium containing maltose or higher oligomers of glucose.
Regulation of the sus structural genes is mediated by
SusR, an activator that is encoded by a gene located next to the
sus structural genes. A strain with a disruption in
susR cannot grow on starch but can still grow on maltose
and maltotriose. A search for transposon-generated mutants that could
not grow on maltose and maltotriose unexpectedly located a gene,
designated malR, which regulates expression of an
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.24.7198-7205.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
New Regulatory Gene That Contributes to Control of
Bacteroides thetaiotaomicron Starch Utilization
Genes
-glucosidase not controlled by SusR. Although a disruption in
susR did not affect expression of the
malR controlled gene, a disruption in
malR reduced expression of the sus
structural genes. Thus, MalR appears to participate with SusR in
regulation of the sus genes. Results of transcriptional
fusion assays and reverse transcription-PCR experiments showed that
malR is expressed constitutively. Moreover, multiple
copies of malR provided on a plasmid (5 to 10 copies per
cell) more than doubled the amount of
-glucosidase activity in cell
extracts. Our results demonstrate that the starch utilization system of
B. thetaiotaomicron is controlled on at least two levels
by the regulatory proteins SusR and MalR.
*
Corresponding author. Mailing address: Department of
Microbiology, 601 S. Goodwin Ave., CLSL 103, University of Illinois, Urbana, IL 61801. Phone: (217) 333-7378. Fax: (217) 244-8485. E-mail:
abigails{at}uiuc.edu.
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