Ecophysiological adaptations of anaerobic bacteria to low pH. [Sarcina ventriculi; Lactobacillus helveticus]
The ecological and physiological adaptations of anaerobic bacteria to low pH were investigated in field and laboratory studies. Determinations of hydrogen kinetic parameters demonstrated that overall hydrogen metabolism was inhibited in acid ecosystems. In particular, hydrogen metabolism became progressively uncoupled at low pH. This uncoupling resulted in a slowing of carbon flow during anaerobic digestion and the accumulation of intermediary metabolites. The addition of carbon electron donors to acid bog sediments resulted in the accumulation of hydrogen and a slowing of the overall rates of anaerobic digestion. As an adaptation to low pH, anaerobic bacterial populations shifted from production of acid intermediary metabolites (e.g. acetate and lactate) to the production of neutral intermediary metabolites (e.g. ethanol). This shift was observed both in situ and in pure cultures of hydrolytic strains isolated from bog sediments. Detailed physiological studies of Sarcina ventriculi showed an adaptation to growth at low pH by mechanisms which allowed the continued production of ethanol from glucose and the maintenance of a proton motive force at low cytoplasmic pH values. Further physiological studies Lactobacillus helveticus showed that the accumulation of acidic end-product (lactic acid) strongly influenced cellular electrochemical parameters. Based on the results of computer simulations and laboratory studies of the physiology of the organism in the presence of organic acids, a new model for the passive coupling of energy conservation to the efflux of lactic acid in an electroneutral process is proposed.
- Research Organization:
- Wisconsin Univ., Madison (USA)
- OSTI ID:
- 6981020
- Country of Publication:
- United States
- Language:
- English
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ACIDIFICATION
ALCOHOLS
ALDEHYDES
ANAEROBIC DIGESTION
BACTERIA
BIOCONVERSION
BIOLOGICAL ADAPTATION
BIOSYNTHESIS
CARBOHYDRATES
CARBOXYLIC ACIDS
COMPUTERIZED SIMULATION
DATA
DIGESTION
ELEMENTS
ETHANOL
EXPERIMENTAL DATA
GLUCOSE
HEXOSES
HYDROGEN
HYDROXY ACIDS
HYDROXY COMPOUNDS
INFORMATION
INHIBITION
LACTIC ACID
MANAGEMENT
METABOLISM
METABOLITES
MICROORGANISMS
MONOSACCHARIDES
NONMETALS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
PH VALUE
PHYSIOLOGY
PROCESSING
SACCHARIDES
SIMULATION
SYNTHESIS
WASTE MANAGEMENT
WASTE PROCESSING