Affiliation:
1. Department of Biochemistry, University of Kentucky Medical Center, Lexington, Kentucky 40506
Abstract
The composition of the membrane-bound electron transport system of
Haemophilus parainfluenzae
underwent modification in response to the terminal electron acceptor in the growth medium.
H. parainfluenzae
was able to grow with O
2
, nitrate, fumarate, pyruvate, and substrate amounts of nicotinamide adenine dinucleotide (NAD) as electron acceptors. When O
2
served as the electron acceptor and its concentration was lowered below 20 μ
m
, the bacteria formed more cytochromes
b, c, a
1
,
a
2
, and
o
than were present in the cells grown at 150 to 200 μ
m
O
2
. Nitrate and nitrite reductase activities also appeared during growth at the low O
2
concentrations in the absence of added nitrate. Cytochrome levels in cells grown anaerobically with fumarate, pyruvate, or NAD as terminal acceptors were similar to those formed in cells grown at low O
2
concentrations. Cells grown with nitrate had higher levels of cytochromes
c, b
, and
o
, and of nitrate and nitrite reductases, than did cells grown with the other acceptors. The formation of cytochrome oxidase
a
2
was repressed by the presence of nitrate in the growth medium. The critical O
2
concentration (the O
2
concentration at which the rate of O
2
uptake becomes demonstrably dependent on the O
2
concentration) was about 100 μ
m
in cells grown with nitrate and about 15 μ
m
in cells grown with the other acceptors. A mutant of
H. parainfluenzae
was found to make about 10% as much cytochrome
c
as the wild type, and its formation of cytochrome
a
2
was not repressed by nitrate. The critical O
2
concentration of the mutant was high when it was grown with nitrate, suggesting that the high levels of cytochrome
c
and the absence of cytochrome
a
2
from the wild type are not responsible for the high critical O
2
concentration. The modifications of the respiratory system induced by changing the terminal electron acceptor were inhibited by the presence of chloramphenicol, which suggests that protein synthesis is involved.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
55 articles.
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