Endogenous nitric oxide in Pseudomonas fluorescens ZY2 as mediator against the combined exposure to zinc and cefradine.

A better understanding on the mechanism involved in bacterial resistance to combined exposure to antibiotics and heavy metals is helpful in implementing practices to mitigate their ecological risk and spread of resistance genes in microbial population. Pseudomonas fluorescens ZY2, a strain isolated from swine wastewater, was chosen to study its growth (bacterial density OD600), the formation of reactive oxygen species (ROS), nitric oxide (NO) and NO synthases (NOS) under Zn, cefradine or Zn + cefradine treatments. Using Zn and cefradine as representative heavy metal and antibiotic in this investigation, respectively, the resistance of P.

[Variations in the active characteristics of sludge during the operation of an aerobic membrane bioreactor and their effects on membrane fouling].

The present work investigated the variations in the active characteristics of sludge during the operation period of an aeration membrane bioreactor, as well as their effects on the fouling of membrane module. Through discharging the excess sludge, the concentration of the mixed liquor was maintained at around 4 000 mg x L(-1) for 75 days, during which the characteristics of sludge were carefully tested every day to reflect its variation. Results indicated the dehydrogenase activity increased with the prolonging operation time.

[Rapid enrichment and cultivation of denitrifying phosphate-removal bacteria and its identification by fluorescence in situ hybridization technology].

The present work focused on a rapid enrichment and cultivation of denitrifying phosphate-removal bacteria (DPB) in a membrane bio-reactor(MBR) by using A2/O anaerobic sludge from a wastewater treatment plant as seed, as well as providing an identification method. In the experiments, sodium acetate was used as the carbon source and a certain amount of nitrate was added to the MBR in the anoxic stage. Results showed that, with the efficient trap of the hollow-fiber membrane module, the proportion of DPB in all the phosphate-accumulating organisms (PAOs) increased from 24% to 93% within 35 days after two-stage's cultivation including anaerobic/aerobic and anaerobic/anoxic, during which the removal efficiency of nitrogen and phosphorus reached more than 90%.

[Synergistic effects of nano-sized magnetic particles and uncoupler to the characteristics of activated sludge].

For improving the performance and sludge settling property of an activated sludge reduction process with uncoupler, in this investigation, uncoupler and nano-sized magnetic particles were added simultaneously to a sequencing batch reactor for exploring their synergistic effects to the characteristics of activated sludge. The results showed that the volume reduction of sludge reached 41% with single 2,4,5-Trichlorophenol (TCP) Comparing with the control experiment, the biodegradability and settling properties of the activated sludge decreased. Under the actions of TCP combined with nano-sized magnetic particles, the volume reduction of sludge reached 34%, the removal efficiencies of COD, nitrogen, and phosphorus as well as the sludge settling property were not significantly influenced.

Efficient transformation of Legionella pneumophila by high-voltage electroporation.

A simple and reproducible method has been developed to transform Legionella pneumophila by electroporation. Effects of different conditions, including electric field strength, pulse length, DNA quality and cell density, were evaluated. Using our method, an efficiency of up to 6 x 10(7) transformants/microg DNA was obtained.