The influence of a H2-utilizing organism, Vibrio succinogenes, on the fermentation of limiting amounts of glucose by a carbohydrate-fermenting, H2-producing organism, Ruminococcus albus, was studied in continuous cultures. Growth of V. succinogenes depended on the production of H2 from glucose by R. albus. V. succinogenes used the H2 produced by R. albus to obtain energy for growth by reducing fumarate in the medium. Fumarate was not metabolized by R. albus alone. The only products detected in continuous cultures of R. albus alone were acetate, ethanol, and H2. CO2 was not measured. The only products detected in the mixed cultures were acetate and succinate. No free H2 was produced. No formate or any other volatile fatty acid, no succinate or other dicarboxylic acids, lactate, alcohols other than ethanol, pyruvate, or other keto-acids, acetoin, or diacetyl were detected in cultures of R. albus alone or in mixed cultures. The moles of product per 100 mol of glucose fermented were approximately 69 for ethanol, 74 for acetate, 237 for H2 for R. albus alone and 147 for acetate and 384 for succinate for the mixed culture. Each mole of succinate is equivalent to the production of 1 mol of H2 by R. albus. Thus, in the mixed cultures, ethanol production by R. albus is eliminated with a corresponding increase in acetate and H2 formation. The mixed-culture pattern is consistent with the hypothesis that nicotinamide adenine dinucleotide (reduced form), formed during glycolysis by R. albus, is reoxidized during ethanol formation when R. albus is grown alone and is reoxidized by conversion to nicotinamide adenine dinucleotide and H2 when R. albus is grown with V. succinogenes. The ecological significance of this interspecies transfer of H2 gas and the theoretical basis for its causing changes in fermentation patterns of R. albus are discussed. Fermentation products, particularly ethanol and lactate, of pure cultures of a number of important rumen bacteria are not usually formed nor are they usually significant intermediates in the rumen fermentation (7). The major products of the fermentation of ingested food, mainly plant carbohydrates, by the mixed rumen microbial population are acetic, propionic, and butyric acids, and the gases CH, and CO2 (7). Hungate (7) suggested that, in the rumen, the electrons derived from the oxidation of fermentation substrates by carbohydrate-fermenting, ethanolor lactate-producing rumen

No abstract

Depletion of nonessential amino acids and its effect on the immune system can be studied by the administration of bacterial enzymes. Escherichia coli asparaginase hydrolyzes both asparagine and glutamine: administration of this enzyme to mice is rapidly immunosuppressive. Vibrio succinogenes asparaginase hydrolyzes only asparagine and has no apparent effect on immune system function. When the enzymes are rendered nonantigenic and nonimmunogenic by covalent attachment of polyethylene glycol, the effects on immune system function remain the same as described above with the native (nonmodified) enzymes. We believe the data reviewed justify the conclusion that glutamine deficiency is specifically immunosuppressive whereas asparagine deficiency is not. We further believe that enzymatic depletion of nonessential amino acids can be a useful tool for nutritional investigations.

A Gram-negative aerobic bacterium capable of using 2-chlorophenol (2-CP), 3-chlorophenol (3-CP) and 4-chlorophenol (4-CP) as sole carbon sources was isolated and characterized. The bacterium, designated LD1, was identified to be a Pseudomonas pickettii strain. LD1 was able to totally degrade and dechlorinate 2-CP (initial concentration: 1.51 mmol l-1), 3-CP (initial concentration: 0.57 mmol l-1) and 4-CP (initial concentration: 0.75 mmol l-1) within 30, 30 and 40 h of incubation, respectively, under growing-cell batch conditions. LD1 was also found to be able to metabolize chlorocatechols in growing- and resting-cell conditions. This suggests that the bacterium degrades monochlorophenols through a chlorocatechol pathway. In addition, LD1 was found to be capable of readily metabolizing other organic compounds such as phenol, benzoic acid, hydroxybenzoic acids and hydroquinone. Because of the broad spectrum of monochlorophenols and organic compounds that LD1 can degrade, this bacterium appears to have the potential for being successfully used in the biotreatment of wastewaters and in soil decontamination.

No abstract