Uptake of benzoate by Rhodopseudomonas palustris grown anaerobically in light

Journal Article · Sat Feb 01 04:00:00 EST 1986 · J. Bacteriol.; (United States)

OSTI ID:6138009

Harwood, C S; Gibson, J

The uptake and anaerobic metabolism of benzoate were studied in short-term experiments with phototrophic cells of Rhodopseudomonas palustris. Cells that were preincubated and assayed anaerobically in the presence of 1 mM dithiothreitol accumulated (7-/sup 14/C)benzoate at a rate of at least 0.5 nmol x min/sup -1/ x mg/sup -1/ of protein. Cells that were preincubated aerobically, or anaerobically in the absence of a reducing agent or an electron donor such as succinate, took up benzoate at reduced rates. Benzoate was removed from the external medium with remarkably high efficiency; initial uptake rates were independent of substrate concentration, and uptake remained linear down to concentrations of less than 1 ..mu..M. Uptake rates were not sensitive to external pH in the range of 6.5 to 8.1, and very little free benzoate was found associated with the cells. By contrast, benzoyl coenzyme A (CoA) was formed rapidly in cells exposed to labeled benzoate. Its appearance in such cells, together with the more gradual accumulation of other compounds tentatively identified as reduction products, is consistent with the identification of benzoyl CoA as an intermediate in the anaerobic reductive metabolism of benzoate. The very effective uptake of external benzoate can be explained by its conversion to benzoyl CoA immediately after its passage across the cell membrane by simple or facilitated diffusion. Such a chemical conversion would serve to maintain a downhill concentration gradient between the cell cytoplasm and the cell surroundings, even at very low external benzoate concentrations.

• Research Organization: Cornell Univ., Ithaca, NY
• OSTI ID: 6138009
• Journal Information: J. Bacteriol.; (United States), Journal Name: J. Bacteriol.; (United States) Vol. 165:2; ISSN JOBAA
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
BENZOIC ACID
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
COENZYMES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
METABOLISM
MICROORGANISMS
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PH VALUE
RHODOPSEUDOMONAS
TRACER TECHNIQUES
UPTAKE