Affiliation:
1. Department of Microbiology and Molecular Genetics, Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
Abstract
ABSTRACT
Rex factors are bacterial transcription factors thought to respond to the cellular NAD
+
/NADH ratio in order to modulate gene expression by differentially binding DNA. To date, Rex factors have been implicated in regulating genes of central metabolism, oxidative stress response, and biofilm formation. The genome of
Enterococcus faecalis
, a low-GC Gram-positive opportunistic pathogen, encodes
EF2638
, a putative Rex factor. To study the role of
E. faecalis
Rex, we purified EF2638 and evaluated its DNA binding activity
in vitro
. EF2638 was able to bind putative promoter segments of several
E. faecalis
genes in an NADH-responsive manner, indicating that it represents an authentic Rex factor. Transcriptome analysis of a Δ
EF2638
mutant revealed that genes likely to be involved in anaerobic metabolism were upregulated during aerobic growth, and the mutant exhibited an altered NAD
+
/NADH ratio. The Δ
EF2638
mutant also exhibited a growth defect when grown with aeration on several carbon sources, suggesting an impaired ability to cope with oxidative stress. Inclusion of catalase in the medium alleviated the growth defect. H
2
O
2
measurements revealed that the mutant accumulates significantly more H
2
O
2
than wild-type
E. faecalis
. In summary, EF2638 represents an authentic Rex factor in
E. faecalis
that influences the production or detoxification of H
2
O
2
in addition to its more familiar role as a regulator of anaerobic gene expression.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology