Identification of a novel nutrient-deprivation-induced Sinorhizobium meliloti gene (hmgA) involved in the degradation of tyrosine

Sinorhirobium meliloti strain N4 carries a Tn5luxAB insertion in a gene whi ch is induced by nitrogen and carbon deprivation as well as in the presence of tyrosine. The Tn5luxAB-tagged locus was found to share significant simi larity with the human hmgA gene and the corresponding Aspergillus nidulans gene, encoding the enzyme homogentisate dioxygenase, which is involved in t he degradation of tyrosine. Extended DNA sequence analysis of the tagged lo cus revealed the presence of several ORFs, including one encoding a polypep tide sharing a high degree of similarity with human and fungal maleylacetoa cetate isomerases. Strain N4 was found to be unable to use tyrosine as carb on source, to lack homogentisate dioxygenase activity, to produce a melanin -like pigment and to be affected in stationary-phase survival. This is beli eved to be the first report of a hmgA-homologous gene in bacteria.