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Aminoacetone Formation and Utilization by Pseudomonads Grown on DL-1-Aminopropan-2-ol
Abstract
SUMMARY:
Pseudomonas sp. 8/IX isolated from soil and Pseudomonas sp. NCIB 8858 are capable of growth on DL-I-aminopropan-2-ol or aminoacetone as sole sources of carbon, nitrogen and energy. During growth on the amino alcohol, small amounts of aminoacetone initially accumulate in the medium but disappear during the early logarithmic phase. Aminoacetone accumulation is favoured by high pH and high growth-substrate concentrations.
Washed suspensions of the pseudomonads grown on DL-I-aminopropan-2-ol accumulate aminoacetone when incubated with the amino alcohol in the presence of metabolic inhibitors, and rapidly utilize aminoacetone in their absence. Aminoacetone formation is optimal at about pH 10 in the presence or absence of the most effective inhibitor iodoacetate.
Aminoacetone utilization occurs optimally at pH 7·7, the apparent K m for the amino ketone being about 0·1 mM. At an initial concn. of 1·0 mM, the rate of utilization is proportional to cell density up to at least 0·5 mg. dry wt organisms/ml. and is constant with time over almost the entire course of the reaction. The maximum rate of utilization is approximately 150 mμmoles/mg. dry wt organisms/min. at 30˚. The phenyl analogue 2'-aminoacetophenone is utilized at a comparable rate but 5-aminolaevulate is virtually unaffected. Anaerobic conditions and metabolic inhibitors prevent amino ketone utilization.
Growth conditions markedly affect the ability of suspensions both to accumulate and utilize aminoacetone. Of the growth substrates tested, only L-threonine enabled Pseudomonas sp. 8/IX to utilize aminoacetone, the rate being approx. 60 % of that found after growthon DL-I-aminopropan-2-ol
The patterns of oxidation of possible intermediates of DL-I-aminopropan-2-ol catabolism are similar using washed organisms grown on either the amino alcohol or aminoacetone. Organisms grown on acetate plus glycine oxidize such compounds at relatively low rates. Methylglyoxal is not a substrate for either growth or oxidation. Comparison of the rates of oxygen uptake and aminoacetone utilization, and measurement of the total oxygen consumed, indicate about 70% complete oxidation of the amino ketone by organisms grown on the amino alcohol.
Similar maximum crop-sizes are obtained in media in which ammonium sulphate or different relative amounts of D- and L-I-aminopropan-2-ol serve as the sole sources of growth-limiting nitrogen.
- Accepted:
- Published Online:
© Society for General Microbiology 1968