Colonization and mineralization of palmitic acid byPseudomonas pseudoflava

Pseudomonas pseudoflava and palmitic acid were used to investigate the role of bacterial colonization in the degradation of waterinsoluble organic compounds. Mineralization was measured by trapping the(14)CO2 produced from the labeled substrate, and colonization of the surface of the solid organic chemical was determined by epifluorescence microscopy. In a medium containing solid palmitic acid,P. pseudoflava mineralized the organic substrate at a logarithmic rate. Mineralization was evident before colonization of the surface of the chemical was detected. The rate of appearance of single cells and/or aggregations of cells on the surface of the palmitic acid was essentially the same as the doubling time of free cells in solution. At about 50 hours, mineralization and colonization of the surface stopped. In a salts solution containing solid palmitic acid,P. pseudoflava grew logarithmically in the solution and biphasically on the surface of the palmitic acid. We suggest that the bacterium first metabolizes soluble palmitic acid and later colonizes the solid when the substrate in solution has been depleted.