Synchrotron radiation based STXM analysis and micro-XRF mapping of differential expression of extracellular thiol groups by Acidithiobacillus ferrooxidans grown on Fe2Â + and S0

The differential expression of extracellular thiol groups by Acidithiobacillus ferrooxidans grown on substrates Fe2 + and S0 was investigated by using synchrotron radiation based scanning transmission X-ray microscopy (STXM) imaging and microbeam X-ray fluorescence (μ-XRF) mapping. The extracellular thiol groups (SH) were first alkylated by iodoacetic acid forming Protein-SCH2COOH and then the P-SCH2COOH was marked by calcium ions forming P-SCH2COOCa. The STXM imaging and μ-XRF mapping of SH were based on analysis of SCH2COO-bonded Ca2 +. The results indicated that the thiol group content of A. ferrooxidans grown on S0 is 3.88 times to that on Fe2 +. Combined with selective labeling of SH by Ca2 +, the STXM imaging and μ-XRF mapping provided an in situ and rapid analysis of differential expression of extracellular thiol groups.