Uncoupling by acetic acid limits growth of and acetogenesis by Clostridium thermoaceticum

Journal Article · Sat Dec 01 04:00:00 EST 1984 · Appl. Environ. Microbiol.; (United States)

OSTI ID:5960053

Baronofsky, J J; Schreurs, W J.A.; Kashket, E R

The internal pH of growing cells was measured and compared with that of nongrowing cells incubated in the absence of acetic acid. Growing cells maintained an interior about 0.6 pH units more alkaline than the exterior throughout most of batch growth (i.e., ..delta..pH = 0.6). The transmembrane electrical potential (..delta.. PSI) was also measured and was found to decrease from 140 mV at pH 7 at the beginning of growth to 80 mV when the medium had reached pH 5. The proton motive force, therefore, was 155 mV at pH 7, decreasing to 120 mV at pH 5. When further fermentation acidifed the medium below pH 5, both the ..delta..pH and the ..delta.. PSI collapsed, indicating that these cells require an internal pH of at least 5.5 to 5.7. Cells harvested from stationary phase and suspended in citrate-phosphate buffer maintained a ..delta..pH of 1.5 at external pH 5.0. This ..delta..pH was dissipated by acetic acid (at the concentrations found in the growth medium) and other weak organic acids, as well as by ionophores and inhibitors of glycolysis and of the H/sup +/-ATOase. Nongrowing cells had a ..delta.. PSI which ranged from about 116 mV at external pH 7 to about 55 mV at external pH 5 and which also was sensitive to ionophores. Since acetic acid, in its un-ionized form, diffuses passively across the cytoplasmic membrane, it effectively renders the membrane permeable to protons. It therefore seems unlikely that mutations at one or a few loci would result in C. thermoaceticum cells significantly more acetic acid tolerant than their parental type.

• Research Organization: Boston Univ. School of Medicine, MA
• OSTI ID: 5960053
• Journal Information: Appl. Environ. Microbiol.; (United States), Journal Name: Appl. Environ. Microbiol.; (United States) Vol. 48:6; ISSN AEMID
• Country of Publication: United States
• Language: English

Related Subjects

560302* -- Chemicals Metabolism & Toxicology-- Microorganisms-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACETIC ACID
ACIDIFICATION
ALDEHYDES
BACTERIA
BATCH CULTURE
BIOCONVERSION
BIOLOGICAL EFFECTS
CARBOHYDRATES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
CLOSTRIDIUM
CYTOPLASM
DECOMPOSITION
FERMENTATION
GLUCOSE
GLYCOLYSIS
HEXOSES
INHIBITION
MEMBRANE TRANSPORT
MICROORGANISMS
MONOCARBOXYLIC ACIDS
MONOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
PH VALUE
PRODUCTIVITY
SACCHARIDES
TOLERANCE