MECHANISMS FOR NEGATIVE REGULATION BY IRON OF THE FATA OUTER-MEMBRANEPROTEIN GENE-EXPRESSION IN VIBRIO-ANGUILLARUM 775

Synthesis of the 86-kDa FatA outer membrane protein is repressed under iron-rich conditions. Complementation of transposition mutants derive d from clones containing the pJM1 iron uptake region revealed the exis tence of an antisense RNA, RNAalpha. This RNA is only expressed under iron-rich conditions and acts as a negative regulator of FatA synthesi s, with slight but discernible decrease in the steady-state level of f atA mRNA determined by RNase protection and by Northern blot analysis. Primer extension experiments revealed that the level of several possi ble fatA transcripts was reduced in the presence of RNAalpha. In addit ion, we found that fatA mRNA expression is slightly reduced in the pre sence of Escherichia coli Fur. We have identified and cloned a chromos omally encoded fur-like gene in Vibrio anguillarum.