[Influence of microcystin-LR on cell viability and surface characteristics of Pseudomonas putida].

In microcystin-LR (MC-LR) degradation system, the change in surface characteristics and cell viability of Pseudomonas putida was studied. The purpose of this study was to reveal the influence of MC-LR on P. putida and elucidate the toxicity of MC-LR on microorganisms. The result demonstrated that MC-LR enhanced the cytoplasmic membrane permeability, as well as affected the ion metabolism and protein release of P. putida. The soluble sugar and Na+, Cl-release increased with the rising concentration of MC-LR ranging from 0 mg x L(-1) to 2.0 mg x L(-1). Flow Cytometry Method(FCM) analysis revealed that MC-LR accelerated the death of P. putida, and the death rate increased with the ascending concentration of MC-LR. Compared with the control, the death rate on day 5 increased by nearly 30% when 2.5 mg x L(-1) MC-LR was added. Scanning electron microscopy (SEM) analysis showed that the cells were deformed under the toxicity of MC-LR. After 5-day exposure to 2.5 mg x L(-1) MC-LR, the majority of the cells were ruptured and the intracellular materials flew out. The cellular structure was severely damaged under this condition.

[Effect of heavy metal ions on triphenyltin enzymatic degradation].

The influence of different metal ions and different forms of addition on triphenyltin enzymatic degradation was investigated under conditions using enzyme obtained from Klebsiella pneumoniae. The objective of this study is to illuminate the mechanism of enzymatic degradation of triphenyltin (TPhT). The results demonstrated that the strain was able to tolerate K+, Mg2+, CU2+, Ca2+ and Fe3+ at high concentrations. High concentrations of Zn2+ and Fe2+ had some toxic effects on the strain, thus affecting its growth. The endoenzyme activity was enhanced by metal ions such as K+, Mg2+, Zn2+, Cu2+ and Fe2+ at certain concentrations. In the presence of 30 mg/L of Mg2+, the removal percentage of TPhT was up to 77.22%. Fe3+ restrained the enzyme activity at certain concentrations. Adding K+, Mg2+, Zn2+, Cu2+ into medium can promote the production of enzyme, among which Mg2+ demonstrated up to 85.66% of removal percentage of TPhT, suggesting some metal ions at the appropriate concentration range can be used as enzyme activator for the enzymatic degradation of triphenyltin. Metal ions showed no relevant impact on the cell growth and enzyme production. Certain metal ions can only serve as activators of endoenzyme and exhibited no similar effect towards exoenzyme.

[Characteristics of biodegradation of triphenyltin by Rhodopseudomonos spheroids].

The biodegradation of triphenyltin (TPT) by Rhodopseudomonos spheroids was investigated in this study. The results illuminated that R. spheroids was an effective strain for the biodegradation of TPT. The maximum removal ratio was attained when the growth temperature of R. spheroids was 30 degrees C. After treating for 3 hours, the removal ratios of 3 mg x L(-1) TPT were 13.82% to 47.29% using 0.49 g x L(-1) (based on dry weight) biomass of R. spheroids. The experiments on biodegradation of TPT were carried out in double-distilled water, simulated seawater,culture medium and river water, respectively. The results demonstrated that river water was optimal for the biodegradation since the indigenous microorganisms in water synergistically increased the removal ratios of TPT. Extracellular enzyme produced by R. spheroids was also effective on the degradation of TPT, and 71.64% of TPT was degraded by this way within 24 hours. The experiments also revealed that the biodegradation process of TPT included biosorption by cell wall, TPT entering cells, and initial degradation by intracellular enzyme, then the TPT and intermediate products backing out of cells to be degraded by extracellular enzyme.