Bacterial Utilization of Low Concentrations of Organic Matter

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Abstract
Plate counts revealed that marine hetero-trophic bacteria multiply in. mineral solns. containing only 0.1 mgm./l. of peptone or glucose but the media were not clouded unless the conc. of organic matter was 10 to 100 mgm./l. The rate of multiplication and respiration in solns. containing < 10 mgm./l. was proportional to the . conc. of the substrate. Concs. of glucose, glycerol, ethanol, lac-tate, succinate, starch and asparagine ranging from 0.25 to 5 mgm./l. were quantitatively utilized by bacteria in 16-30 days at 22[degree]C. 60-70% of the organic matter was oxidized to CO2 and water and 30-40% converted into bacterial protoplasm. Using O2 consumption as a criterion, it was found that 70 pure cultures of marine bacteria utilized glucose although very few of them produced acid in standard methods media. The cultures attacked concs. as low as 0.1 mgm./l. Escherichia coli, Staphylococcus citreus, Bacillus megatherium, Proteus vulgaris and Lactobacillus lactis multiplied and respired in glucose solns. as dilute as 0.1 mgm./l. Solid surfaces promoted the bacterial utilization of low cones, of organic matter.