Analysis of Genes and Proteins in Acidithiobacillus ferrooxidans During Growth and Attachment on Pyrite Under Different Conditions

Abstract

Microbes are able to enhance the sulfide mineral decomposition, which lead to the formation of AMD. Attachment of bacterial cells to the mineral surface is an important process for pyrite oxidation by Acidithiobacillus ferrooxidans. The selective advantage of bacterial adhesion is considered to favor the surface localization of bacterial populations as nutritionally favorable. Environmental factors determine cell accumulation or dissociation of attachment. In our study, the amount of sessile cells increased rapidly during the initial stage of attachment on pyrite. Planktonic cells showed high activity leading to the accumulation of large colonies on the pyrite surface. We found three proteins to be up-regulated significantly. Additionally, by matching the sequences of the three proteins to the Pfam database, we found that they are related to adhesion, pili biosynthesis and movement. When we replaced pyrite with glass to provide an inert surface that abolished electrostatic forces, we found that cell attachment was maintained under nutrient-rich conditions but drastically reduced under conditions of limited nutrients or the presence of the inhibitor homoserinelactone. Our results are consistent with the idea that starvation may lead to inhibition of attachment by an unknown mechanism that allows bacteria to search for nutrient-rich habitats.

Keywords:

• Acidithiobacillus ferrooxidans
• surface attachment
• pyrite
• gene analysis
• proteomic
• two-dimensional electrophoresis

Acknowledgments

Authors Tu and Wang contributed equally to this work.

Thanks to Dr. Ruiyong Wang for his guidance and ideas in experimental design and Dr. Xingqing Zhao for identification of 16S rDNA. We also thank the Electronic Microscope Room of Jinling Hospital for TEM analysis. We gratefully acknowledge support from the foundations of the following programs: 973 programs (2007CB815603), the National Natural Science Foundation of China (40930742, 10979018) and the Scientific Research Foundation of Graduate School of Nanjing University (2010CL10).