Affiliation:
1. Department of Biosciences, Tokyo University of Agriculture, Setagaya-ku, Tokyo 156-8502, Japan
2. Department of Food Science and Technology, Tokyo University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan
Abstract
ABSTRACT
Clostridium acetobutylicum
and
Clostridium aminovalericum
, both obligatory anaerobes, grow normally after growth conditions are changed from anoxic to microoxic, where the cells consume oxygen proficiently. In
C. aminovalericum
, a gene encoding a previously characterized H
2
O-forming NADH oxidase, designated
noxA
, was cloned and sequenced. The expression of
noxA
was strongly upregulated within 10 min after the growth conditions were altered to a microoxic state, indicating that
C. aminovalericum
NoxA is involved in oxygen metabolism. In
C. acetobutylicum
, genes suggested to be involved in oxygen metabolism and genes for reactive oxygen species (ROS) scavenging were chosen from the genome database. Although no clear orthologue of
C. aminovalericum
NoxA was found, Northern blot analysis identified many O
2
-responsive genes (e.g., a gene cluster [
CAC2448
to
CAC2452
] encoding an NADH rubredoxin oxidoreductase-A-type flavoprotein-desulfoferrodoxin homologue-MerR family-like protein-flavodoxin, an operon [
CAC1547
to
CAC1549
] encoding a thioredoxin-thioredoxin reductase-glutathione peroxidase-like protein, an operon [
CAC1570
and
CAC1571
] encoding two glutathione peroxidase-like proteins, and genes encoding thiol peroxidase, bacterioferritin comigratory proteins, and superoxide dismutase) whose expression was quickly and synchronously upregulated within 10 min after flushing with 5% O
2.
The corresponding enzyme activities, such as NAD(P)H-dependent peroxide (H
2
O
2
and alkyl hydroperoxides) reductase, were highly induced, indicating that microoxic growth of
C. acetobutylicum
is associated with the expression of a number of genes for oxygen metabolism and ROS scavenging.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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