Effects of increasing concentration of salts on the expression of omp40 gene encoding a major porin of Acidithiobacillus ferrooxidans

Effects of increasing concentration of NaCl, KCl and Na₂SO₄ on the growth of Acidithiobacillus ferrooxidans cells and on the expression of omp40 gene, encoding one of the major outer membrane proteins of A. ferrooxidans, were examined to obtain information on the response of A. ferrooxidans NASF-1 cells to environmental changes and to improve the bioleaching system operated in salt-containing environments. Although NaCl and KCl inhibited growth of A. ferrooxidans NASF-1 cells at the concentration of 0.3 M, A. ferrooxidans NASF-1 could grow in medium supplemented with 0.5 M Na₂SO₄. An analysis of outer membrane proteins by a polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate revealed that the relative amount of Omp40 was increased when cells were grown in Fe²⁺-medium supplemented with NaCl. Northern blot hybridization analyses also revealed that the transcription of omp40 gene was stimulated in cells incubated in medium supplemented with NaCl and KCl, but not with Na₂SO₄.