Proteomic characterization of selenite resistance in a strain of Enterobacter cloacae

Abstract

A multimetal resistant strain of Enterobacter cloacae (E. cloacae) grew in the presence of 40mM selenite and demonstrated the ability to transform it into a red precipitate. Established growth curve studies in M-9 minimal salts medium showed that the E. cloacae strain grew in the presence of selenite only when the medium was supplemented with L-cysteine. During early log-phase, selenite or water was added. One hour later, cells were harvested for protein analysis by two dimensional gel electrophoresis (2DGE). Protein profiles of cultures grown under the resistant (cysteine) and sensitive (no cysteine) conditions were compared, and differentially expressed polypeptide spots were excised and sent to Ohio State University for identification by mass spectrometry. The identified proteins were classified under three possible functions: 1) oxidative stress response, 2) selenium processing and 3) selenite efflux. None of the identified proteins indicated a possible role for cysteine in selenite resistance.