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Journal of Bacteriology, May 1999, p. 3172-3177, Vol. 181, No. 10
Thermophile and Microbial Biochemistry and
Biotechnology Unit,
Received 17 November 1998/Accepted 2 March 1999
A strain of Bacillus designated TA2.A1, isolated from a
thermal spring in Te Aroha, New Zealand, grew optimally at pH 9.2 and
70°C. Bacillus strain TA2.A1 utilized glutamate as a sole carbon and energy source for growth, and sodium chloride (>5 mM) was
an obligate requirement for growth. Growth on glutamate was inhibited
by monensin and amiloride, both inhibitors that collapse the sodium
gradient (
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Sodium-Dependent Glutamate Uptake by an
Alkaliphilic, Thermophilic Bacillus Strain, TA2.A1
pNa) across the cell membrane.
N,N-Dicyclohexylcarbodiimide inhibited
the growth of Bacillus strain TA2.A1, suggesting that an
F1F0-ATPase (H type) was being used to generate
cellular ATP needed for anabolic reactions. Vanadate, an inhibitor of
V-type ATPases, did not affect the growth of Bacillus
strain TA2.A1. Glutamate transport by Bacillus strain
TA2.A1 could be driven by an artificial membrane potential (
),
but only when sodium was present. In the absence of sodium, the rate of

-driven glutamate uptake was fourfold lower. No glutamate
transport was observed in the presence of
pNa alone (i.e., no

). Glutamate uptake was specifically inhibited by monensin, and
the Km for sodium was 5.6 mM. The Hill plot had
a slope of approximately 1, suggesting that sodium binding was
noncooperative and that the glutamate transporter had a single binding
site for sodium. Glutamate transport was not affected by the
protonophore carbonyl cyanide m-chlorophenylhydrazone, suggesting that the transmembrane pH gradient was not required for
glutamate transport. The rate of glutamate transport increased with
increasing glutamate concentration; the Km for
glutamate was 2.90 µM, and the Vmax was 0.7 nmol · min
1 mg of protein. Glutamate transport was
specifically inhibited by glutamate analogues.
*
Corresponding author. Mailing address: Department of
Biological Sciences, University of Waikato, Private Bag 3105, Hamilton, New Zealand. Phone: 64 7 8384705. Fax: 64 7 8384324. E-mail:
h.morgan{at}waikato.ac.nz.
Journal of Bacteriology, May 1999, p. 3172-3177, Vol. 181, No. 10
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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