Affiliation:
1. Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida 32610
Abstract
ABSTRACT
The phosphoenolpyruvate:sugar phosphotransferase system (PTS) is the major sugar uptake system in oral streptococci. The role of EIIAB
Man
(encoded by
manL
) in gene regulation and sugar transport was investigated in
Streptococcus mutans
UA159. The
manL
knockout strain, JAM1, grew more slowly than the wild-type strain in glucose but grew faster in mannose and did not display diauxic growth, indicating that EIIAB
Man
is involved in sugar uptake and in carbohydrate catabolite repression. PTS assays of JAM1, and of strains lacking the inducible (
fruI
) and constitutive (
fruCD
) EII fructose, revealed that
S. mutans
EIIAB
Man
transported mannose and glucose and provided evidence that there was also a mannose-inducible or glucose-repressible mannose PTS. Additionally, there appears to be a fructose PTS that is different than FruI and FruCD. To determine whether EIIAB
Man
controlled expression of the known virulence genes, glucosyltransferases (
gtfBC
) and fructosyltransferase (
ftf
) promoter fusions of these genes were established in the wild-type and EIIAB
Man
-deficient strains. In the
manL
mutant, the level of chloramphenicol acetyltransferase activity expressed from the
gtfBC
promoter was up to threefold lower than that seen with the wild-type strain at pH 6 and 7, indicating that EIIAB
Man
is required for optimal expression of
gtfBC
. No significant differences were observed between the mutant and the wild-type background in
ftf
regulation, with the exception that under glucose-limiting conditions at pH 7, the mutant exhibited a 2.1-fold increase in
ftf
expression. Two-dimensional gel analysis of batch-grown cells of the EIIAB
Man
-deficient strain indicated that the expression of at least 38 proteins was altered compared to that seen with the wild-type strain, revealing that EIIAB
Man
has a pleiotropic effect on gene expression.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
85 articles.
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