The formation of phenol in the degradation ofp-hydroxybenzoic acid byKlebsiella aerogenes (Aerobacter aerogenes)

After growth ofK. aerogenes in chemically defined media consisting of mineral salts andp-hydroxybenzoate with or without glucose, phenol was found in the culture fluid at concentrations inhibiting further growth. Bacteria adapted to mineral salts medium containingp-hydroxybenzoate as sole source of carbon and energy produced small but isolable quantities of 3,4-dihydroxybenzoic acid and catechol and oxidized these substances as rapidly asp-hydroxybenzoate. Bacteria adapted to mineral salts medium containing glucose as sole carbon and energy source did not oxidizep-hydroxybenzoate, 3,4-dihydroxybenzoate or catechol. Bacteria adapted to glucose medium or top-hydroxybenzoate medium did not oxidize or utilize phenol as sole carbon and energy source. A metabolic pathway forp-hydroxybenzoate degradation is proposed and the formation of phenol is attributed to a side reaction.     

The non-oxidative decarboxylation ofp-hydroxybenzoic acid,gentisic acid,protocatechuic acid and gallic acid byKlebsiella aerogenes (Aerobacter aerogenes)

Klebsiella aerogenes adapted to a chemically-defined mineral salts medium with glucose orp-hydroxybenzoate as sole source of carbon and energy possessed constitutive decarboxylases for gentisate (2,5-dihydroxybenzoate), protocatechuate (3,4-dihydroxybenzoate) and gallate (3,4,5-trihydroxybenzoate) whose pH optima were respectively 5.9, 5.6 and 5.8. A decarboxylase for PHB was induced by PHB in both growing and resting cells; the induction was delayed or inhibited by chloramphenicol and by ultrasonic disruption of the bacteria. Crude ultrasonic preparations of PHB decarboxylase had an optimum pH of 6.0, a Michaelis constant of 4mm and an activation energy of 25,500 cal mole^–1 at 28 – 38 C. All four decarboxylations proceeded without O₂ and for every mole of phenolic acid decomposed one mole of CO₂ and one mole of the corresponding phenol were produced. The effects of ultrasonic disruption of the bacteria suggested that permeability barriers limited the rate of decarboxylation of PHB and 2,5-DHB but not of 3,4-DHB or 3,4,5-THB. During ultrasonic disintegration PHB and 3,4-DHB decarboxylases were retained solely by insoluble centrifugeable particles, whereas 2,5-DHB and 3,4,5-THB decarboxylases were gradually released into solution.The decarboxylation of protocatechuic acid is an essential stage in the assimilation ofp-hydroxybenzoic acid byK. aerogenes, whereas the decarboxylation ofp-hydroxybenzoate itself is an injurious side reaction.We wish to thank Mr. P. J. Wragg for technical assistance.     

The Action of 2, 4-dichlorophenoxyacetic Acid on Bacterium lactis aerogenes (Aerobacter aerogenes)

2, 4-Dichlorophenoxyacetic acid (2, 4-D) had little effect onthe growth of Bacterium lactis aerogenes at concentrations lowerthan 1,000 mg per 1. As the concentration was raised the lagincreased and the growth-rate decreased gradually. Serial subcultureat 5,000 mg per 1 caused an unusual pattern of behaviour. Firstthe lag at 5,000 mg per 1 fell gradually to a low level overabout 25 subcultures; then, although the lag did not increase,growth became gradually slower over a further 91 subcultures.During the first subculture in 5,000 mg per 1 of 2, 4-D, RNA/masswas low throughout, but DNA/mass and protein/mass were neverlower than normal; polysaccharide/mass passed through a maximumand cell size was unaffected. Possible mechanisms for the actionof the drug are discussed in view of the findings that (i) after1,000 generations of growth in drug the fermentative propertiesand the utilization of glucose by the cells were unimpairedand (ii) the concentration of magnesium ions had little effecton the action of 2, 4-D (unlike EDTA).