Destruction and formation of toxins by one bacterial species affect biodegradation by a second species

Two strains of Pseudomonas able to grow on phenol or p-nitrophenol (PNP) were isolated from sewage. Pseudomonas sp. PN101 mineralized and formed nitrite from PNP but did not mineralize phenol, and Pseudomonas sp. PH111 mineralized phenol but not PNP. Phenol increased the lag period before Pseudomonas sp. PN101 grew on and mineralized PNP, but this toxicity was reduced by inoculation of the medium with Pseudomonas sp. PH111. PNP inhibited growth of Pseudomonas sp. PH111 and slightly increased the length of the acclimation period for the mineralization of phenol by the bacterium. Inoculation of Pseudomonas sp. PN101 into solutions containing PNP and phenol increased the lag period prior to growth of Pseudomonas sp. PH111 on phenol and markedly lengthened the lag period for its mineralization of phenol. Coinciding with this delay in the onset of phenol degradation was the accumulation of an organic compound formed from PNP by Pseudomonas sp. PN101. This compound was not mineralized by the phenol-degrading bacterium. The data suggest that bacteria may interact during the decomposition of chemical mixtures by destroying or by forming toxins that affect the biodegradation of individual components of those mixtures.