Humic-like substances of bacterial origin. I. Some aspects of the formation and nature of humic-like substances produced by Pseudomonas.

Two bacterial strains Pseudomonas acidovorans No 26 and Pseudomonas sp. No 4 grown in Conn and yeast extract-glucose media, or in the media enriched with tyrosine, were found to produce dark brown pigment. It was shown that in the bacterial cultures numerous phenolic and quinone-type compounds were formed and transformed to humic-like polymers. Formation of humic-like substances started in the bacterial cells and was accompanied by the presence of phenyloxidases in the bacterial cultures. The bacterial "humic acids" were obtained from the supernatants in amounts varing from 0.05 to 0.865 mg/1 mg of dry weight of cells and from the cells in amounts of 0.02 to 0.165 mg/1 mg of dry weight of cells, depending on the medium used and time of incubation. The IR spectra of the bacterial "humic acids" appeared to be very similar to IR spectrum of the synthetic humic acids (Fluka A.G.) and contained the same chemical groups as the soil humic acids. The culture medium after growth of the strain No 26 was fractionated into "fulvic, hymatomelanic and humic acid" fractions. The hydrolysates from the obtained fractions contained amino acids and uronic acids. The amino acid composition appeared to be very similar to that of soil humic acids.