K-126. The Role of Calcium in Bacteria: A Proteomic Approach

R. Lopes, D. C. Dominguez;
The Univ. of Texas, El Paso, TX.

The importance of calcium (Ca2+) as a cell regulator is well established in eukaryotes. However, little is known about the role of Ca2+ in prokaryotes. Recent experimental work has suggested that Ca2+ ions may play a regulatory role in prokaryotic organisms. The hypothesis that Ca2+ acts as a messenger is based on the observation that environmental signals induce changes in the level of cytosolic free Ca2+. Therefore, determining the levels of intracellular free Ca2+ ([Ca2+]i) and elucidating the mechanisms for regulating Ca2+ levels are crucial in establishing the role of Ca2+ in prokaryotic signal transduction. An essential step toward an increased understanding of the role of Ca2+ is the identification and characterization of Ca2+ binding proteins (CaBPs). In eukaryotes, CaBPs are involved in the regulation of multiple cellular events including: cell differentiation, gene expression, transport mechanisms and others. In an effort to identify CaBPs in B. subtilis 168, crude cell lysates were analyzed using different techniques including: proteomics, calcium 45 (Ca45Cl2) autoradiography, immunoblotting, mass spectrometry. Ca2+ chelators and ionophores treatments were performed to study Ca2+ regulation. Preliminary results indicate that B. subtilis 168 has several CaBPs identified by autoradiography, which also cross-react with monoclonal anti-calmodulin and/or polyclonal EF-hand antibodies. Based on these data we hypothesize that CaBPs play an important role in Ca2+ homeostasis and are associated to crucial intracellular mechanisms in bacteria. Further genomic analyses will be performed to investigate changes in gene expression in response to cytosolic Ca2+ levels.