NAD-dependent epimerase/dehydratase affects cell surface properties, virulence and extracellular enzyme production in the soft rot phytopathogen, Pectobacterium carotovorum
Pectobacterium carotovorum (formerly, Erwinia carotovora subsp. carotovora) is a gram negative bacterium that, together with other soft rot Enterobacteriaceae causes soft rot disease in vegetables, fruits and ornamental plants. Soft rot disease occurs when the pathogen secrets cell wall-degrading exoenzymes resulting in water-soaked tissues and maceration. Virulence levels of soft rot bacteria are proportional to the levels of exoenzymes secretion. Virulence is regulated by many factors including temperature, moisture, host and bacterial chemical signals, and complex network of regulatory genes in the pathogen. Strain KD100 of P. carotovorum was mutagenized using transposon containing a promoterless lacZ (mini-Tn5 lacZ1) and two mutants with reduced levels of production of exoenzymes pectate lyase, protease, polygalacturonase, and cellulase were isolated. We compared to their parent KD100, the mutants were less virulent on celery petioles and carrot disks. Complementation of the mutants also restore the function same as parent. The inactivated gene responsible for the reduced virulent phenotype in both mutants was identified as wcaG. The gene wcaG encodes NAD-dependent epimerase/dehydratase which is homologous to GDP-fucose synthetase of E.coli. The GDP -fucose synthetase is involved in Colanic acid (CA) and lipopolysaccharide (LPS) biosynthesis. The wcaG mutants of P. carotovorum formed enhanced level of biofilm in comparison to their parent. In hydrophobicity test the mutants showed more hydrophobicity than the parent in hexane and hexadecane as solvents. The mutants were also more resistance to hydrogen peroxide in different time duration. These data implicate that NAD-dependent epimerase/dehydratase plays vital rule in cell surface properties, exoenzyme production and virulence in P. carotovorum.
Microbiology|Plant sciences|Plant pathology
"NAD-dependent epimerase/dehydratase affects cell surface properties, virulence and extracellular enzyme production in the soft rot phytopathogen, Pectobacterium carotovorum"
ETD Collection for Tennessee State University.