Bacterial Community Shift in Two Sectors of a Tannery Plant and its Cr (VI) Removing Potential

Abstract

The bacterial community, analyzed by both 16S rRNA gene-based clone library and cultivation methods, changed in two different sectors of a tannery plant. Ten different bacterial phyla were detected through the clone library. The bacterial community of the tanning waste consisted of Gammaproteobacteria (34.8%), Bacteroidetes (20.9%), Betaproteobacteria (12.8%), Alphaproteobacteria (7.0%), Firmicutes (7.0%), Deinococcus-Thermus (7%), Planctomycetes (4.7%), Verrucomicrobia (2.3%), Epsilonproteobacteria (1.2%), Spirochaetes (1.2%), and that of the settling tank sludge consisted of Firmicutes (38.8%), Betaproteobacteria (27.1%), Gammaproteobacteria (11.8%), Bacteroidetes (9.4%), Alphaproteobacteria (4.7%), Deltaproteobacteria (3.5%), Actinobacteria (2.4%), Synergistes (1.2%). The tanning waste accommodated higher biodiversity than the downstream primary settling tank did. Cultivation conditions seriously influenced the culturability and isolation of bacterial strains: different levels of nutrients and Cr (VI) and temperatures resulted in isolation of different bacterial strains, which showed different removal of Cr (VI) (from 1.2% to 99.1%). In addition, supplementation of nutritious LB medium enhanced the Cr (VI) culturability of bacterial isolates. Several bacteria detected as operational taxonomy units (OTUs) by culture-independent analysis were isolated, yet many OTUs did not have their relative isolates. Among the isolates, Pseudochrobactrum, Shewanella, Marinobacter, Microbacterium, Psychrobacter and Agrococcus strains showed considerable Cr (VI) removal efficiencies and good potentials for Cr (VI) pollution treatment.

Keywords:

• tannery waste
• bacterial community
• clone library analysis
• bacterial cultivation
• Cr (VI) removal

Acknowledgments

This work was supported by the National Basic Research Program of China (No. 2007CB815601) and the National High Technology Research and Development Program of China (863 Program) (No. 2007AA021303). The authors are indebted to the help of Prof Guoying Li from Sichuan University for her valuable discussions and Mr Xu Liu from Zhaofeng Tannery for their samples.