Sinorhizobium meliloti strain 1021 bioS and bdhA gene transcriptions are both affected by biotin available in defined medium

Sinorhizobium meliloti 1021 responds to external biotin signals from alfalf a plants through the bioS regulatory locus. Immunogold labeling and electro n microscopy revealed that the BioS protein is located within the S. melilo ti cytoplasm. Under biotin-limiting conditions the S. meliloti cell lumen w as filled with polyhydroxybutyrate (PHB) granules suggesting that either PH B synthesis or degradation are influenced by biotin. To test this hypothesi s a 3-hydroxybutyrate-dehydrogenase-lacZ (bdhA-lacZ) fusion was mobilized i nto S. meliloti. P-galactosidase tests revealed an overall 3.6-5.2-fold hig her bdhA transcription in the presence of added biotin. Comparison of the b dhA and the bioS promoter regions identified several common motifs. (C) 200 0 Federation of European Microbiological Societies. Published by Elsevier S cience B.V. All rights reserved.