%0 Journal Article %A Guffanti, Arthur A. %A Blanco, Robert %A Benenson, Robert A. %A Krulwich, Terry A. %T Bioenergetic Properties of Alkaline-tolerant and Alkalophilic Strains of Bacillus firmus %D 1980 %J Microbiology, %V 119 %N 1 %P 79-86 %@ 1465-2080 %R https://doi.org/10.1099/00221287-119-1-79 %I Microbiology Society, %X The protonmotive force, Na+/H+ antiport activity and a-aminoisobutyric acid transport were studied in alkaline-tolerant Bacillus firmus ATCC 14575 and in a newly isolated alkalophilic strain of the same species. The alkalophilic strain, which grew over a pH range from 8·0 to 10·5, maintained a cytoplasmic pH of 9·5 or below even at an external pH of 110. Evidence was obtained for an electrogenic Na+/H+ antiporter which could play a role in acidification of the cytoplasm as well as in generation of the transmembrane electrical potential. A non-alkalophilic strain, isolated after mutagenesis of the new alkalophile, lacked the Na+/H+ antiporter. The alkaline-tolerant strain of B. firmus, which grew at pH values between 6·5 and 8·5, did not maintain an acidified cytoplasm as the pH was raised above 8·0. A less active, apparently electroneutral, Na+/H+ exchange was found in this strain. Both the alkaline-tolerant and alkalophilic strains exhibited Na+-dependent transport of α-aminoisobutyric acid. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-119-1-79