1.8.52
COORDINATE REGULATION OF EXOENZYMES AND MOTILITY IN ERWINIA CAROTOVORA

YL SHIH, S HARRIS, S BENTLEY and GPC SALMOND

Department of Biochemistry, University of Cambridge, Downing Site, Tennis Court Road, Cambridge CB2 1QW, UK

Background and objectives
Exoenzymes, such as pectate lyases (Pels) and cellulases (Cels), and motility contribute to the virulence of the soft rot pathogen Erwinia carotovora. These virulence factors are coordinately regulated in order to respond to changing environmental signals [1]. This study aims to establish the coordinated regulatory system in E. carotovora.

Results and conclusions
Exoenzyme and motility mutants of E. carotovora subsp. carotovora (Ecc) and E. carotovora subsp. atroseptica (Eca) were generated via transposon mutagenesis. Two regulatory mutants, hexA and hexY, in which exoenzymes and motility are up-regulated, were isolated in both cases. HexA is a LysR-type transcriptional regulator, and HexY is a novel regulatory protein which possesses very strong effects on virulence factors. Several non-motile mutants, including flhDC and fliA, are also defective in the production of exoenzymes. The flhDC and fliA genes are reported as regulators among flagellar genes in several bacterial systems. Our data indicate that their activity is not only specific for motility but also widely influences other virulence factors in this microorganism. Through gene-fusion and Nothern experiments, we have demonstrated that these regulators can modulate the expression of each other at the transcription level. Here we present a regulatory circuit of virulence factors, including exoenzymes and motility, in E. carotovora.

Reference
1. Hugouvieux-Cotte-Pattat N, Condemine G, Nasser W, Reverchon S, 1996. Annual Review of Microbiology 50, 213-257.