A variable response of degrading bacteria to phosphorus added to natural water

Abstract

The effect of inorganic phosphorus (P) on the degradation of 10 mg l-1 of para-nitrophenol (PNP) or 2,4-dichlorophenoxyacetic acid (2,4-D) by three test bacteria inoculated into Nile water samples was investigated. The response of the organisms to P depended mainly on their affinity for the available P. Thus, Corynebacterium sp. at an initial density of 3.3 x 10(4) cells ml-1 readily degraded 10 mg l-1 of PNP in filter-sterilized Nile water supplemented with 22.8 mg l-1 of P. The same effect was observed when Pseudomonas cepacia was inoculated into Nile water amended with PNP and supplemented with 2.28-22.8 mg l-1 of P. The bacteria grew in Nile water and the final densities were related to the level of the added P. On the other hand, the addition of P, at concentrations ranging from 2.28 to 22.8 mg l-1, to sterile Nile water inoculated with Pseudomonas sp. and amended with 10 mg l-1 of 2,4-D did not stimulate the degradation compared with that obtained with the unsupplemented samples. The affinity of the three strains to P was demonstrated in P-deficient medium amended with PNP or 2,4-D as a sole carbon source. The pH of the medium was adjusted with 0.1 mol l-1 Tris buffer. Pseudomonas sp. at an initial density of 3.3 x 10(4) cells ml-1 degraded 10 mg l-1 of 2,4-D in non-sterile Nile water without added P. A slight enhancement of degradation was observed in water samples amended with a high concentration of P.(ABSTRACT TRUNCATED AT 250 WORDS)

Biodegradation Kinetics of 2,4-Dichlorophenoxyacetic Acid (2,4-D) in South Saskatchewan River Water

“…In both experiments, the acclimation period was approximately l8 days and the biodegradation period less than l0 days. In their work with lakewater, Chen and Alexander (1989) and other scientists have observed similar results in freshwater experiments (Mangat and Elefsiniotis, 1999;Ka et al, 1994;Ramadan, 1994). Health and Welfare Canada (1993) reported an average half-life of 2,4-D in water of less than one week.…”

Catabolite repression of the toluene degradation pathway in Pseudomonas putida harboring pWW0 under various conditions of nutrient limitation in chemostat culture

“…The present results provide additional grounds for avoiding nutrient-limiting conditions during the biotechnological treatment of complex wastewaters and polluted soils. P limitation, which often occurs in freshwater habitats (16,24,28), especially seems to be an unfavorable condition for expression of a pathway subject to catabolite repression. The relatively high expression levels of the TOL pathway under O 2 -limiting conditions does not imply that mineralization of toluene and xylenes will actually occur in the presence of primary substrates; the Michaelis constants for oxygen of purified oxygenases like C23O (0.3 to 2 mg of O 2 liter Ϫ1 [32]) are generally higher than those reported for the electron transport chain (0.01 to 0.04 mg of O 2 liter Ϫ1 [17]).…”

“…From the environmental point of view, these results are not particularly relevant since maximal growth rate conditions do not, in general, occur under field conditions. In soil and surface water, the degradation of xenobiotics is often limited by the available concentration of oxygen (4, 6), phosphate (16,24,28), or nitrogen (2,16). We mimicked these limiting conditions in chemostat cultures of P. putida(pWW0) growing on a succinate-mineral medium and studied the inducibility of the TOL pathway in response to the nonmetabolizable inducer o-xylene.…”