1.Bacterial Community Structure In Cooling Water And Biofilm In An Industrial Recirculating Cooling Water System2. Isolation And Characterization Of Atrazine-degrading Arthrobacter Sp.Wjm3from An Agricultural Soil

Microbial fouling is a serious problem in open recirculating cooling water systems. Its causing bacterial communities have not been fully understood. In this study, we analyzed community structure of free-living bacteria and particle-attached bacteria in cooling water, and bacteria in biofilm collected from the wall of water reservoir in an industrial recirculating cooling water system by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis PCR-DGGE and construction of the16S rRNA gene clone library. Based on amplified ribosomal DNA restriction analysis, clones of all three libraries were clustered into45operational taxonomic units (OTUs). Thirteen OTUs displaying91-96%sequence similarity to a type strain might be novel bacterial species. Sequences fell into11major lineages of the domain Bacteria:Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Bacteroidetes, Acidobacteria,Actinobacteria, Planctomycetes, Gemmatimonadetes,Cyanobacteria, Candidate division OD1.Noted differences in community structure were observed among the three libraries. The relative species richness of the free-living bacteria in cooling water was much lower than that of particle-attached bacteria and bacteria in biofilm. The majority of the free-living bacterial community (99.0%) was Betaproteobacteria. The predominant bacteria in the particle-attached bacterial community were Alphaproteobacteria (20.5%), Betaproteobacteria (27.8%) and Planctomycetacia (42.0%), while those in the biofilm bacterial community were Alphaproteobacteria (47.9%), Betaproteobacteria (11.7%), Acidobacteria (13.1%) and Gemmatimonadetes (11.3%). To control microbial fouling in industrial recirculating cooling water systems, additional physiological and ecological studies of these species will be essential. Atrazine has been a pollutant of great environmental concern due to its high potential to contaminate soil and waters. Isolation of a high-efficiency atrazine degrader whose degradation ability is not inhibited by organic matters and fertilziers in the soils is of practical importance for bioremediation of contaminated soils. A bacterial strain (wjm3) capable of utilizing atrazine as sole carbon and nitrogen source for growth was isolated from an agricultural soil in Shandong Province, China. The isolate was identified as Arthrobacter sp. according to its phenotypic features, physiologic and biochemical characteristics, and phylogenetic analysis. The strain wjm3could degrade86.8%of250mg·L-1atrazine within12h. Adding extra carbon and nitrogen source did not inhibite the degradation of atrazine. The strain demonstrated a very high efficiency of atrazine biodegradation with a broad optimum pH and temperature ranges and could not be inhibite by addition of both carbon and nitrogen source suggesting its huge potential for remediation of atrazine-contaminated soils and waters. This work might provide some new insights on atrazine remediation. Furthermore, this work helps us in the better understanding of the strain evolution by comparing the metabolic ability and gene characteristics of strain wjm3with other geographically distinct atrazine-degrading strains and contributes to the limited pool of knowledge on the function of Arthrobacter species.