High throughput proteomic comparison of data for planktonic and biofilm-forming cells of Acidthiobacillus ferrooxidans ATCC 23270

摘要

Bioleaching is the extraction of metals, such as copper or gold, from sulfidic ores by microorganisms. Their energy for growth is obtained by oxidation of ferrous iron and/or reduced inorganic sulfur compounds. Bacterial attachment increases leaching activities, through the formation of special microenvironment between the bacterium and the metal sulfide surface, filled by extracellular polymeric substances ( EPS). Planktonic and sessile cells should significantly differ in their gene expression and proteomic patterns. High-throughput proteomic comparison of Acidithiobacillus ferrooxidans ATCC 23270 biofilm cells attached to pyrite ( FeS2 ) and planktonic cells was performed. A protocol for protein extraction from both bacterial sub-populations was developed. After separation by SDS page, gel lanes excision and tryptic protein digestion of gel slices, the resulting peptides were analyzed by high resolution mass spectrometry ( reverse-phase nano-UHPLC column coupled to an LTQOrbitrap XL). After statistical evaluation, more than 1300 and about 1200 proteins in total were reliably identified in planktonic and biofilm samples after 24 hours. Slightly lower amounts of proteins were identified in proteomes of cells incubated for 48 hours. Comparing these fractions, several proteins were found to be up-regulated in biofilm cells. When possible, functional categories and probable subcellular location were assigned. Outer membrane proteins probably involved in osmotic regulation, polysaccharide biosynthesis, efflux functions and protein secretion, lipoproteins and proteins with unknown functions were found to be upregulated in proteomes of biofilm cells. Several proteins encoding for a type IV secretion system were found in proteomes from both cell sub-populations. This first global proteomic study of early stages of biofilm formation on pyrite will provide new insights into At. ferrooxidans biofilm formation process and will assist in assigning functions to unknown proteins.