Regulation of Pectate Lyase Synthesis in Pseudomonas fluorescens and Erwinia carotovora

Abstract

Inducible synthesis of extracellular pectate lyase occurs in Erwinia carotovora, a bacterial soft-rot pathogen of plants, and, to a lesser extent, in a nonpathogenic isolate of Pseudomonasfluorescens. A combination of pectin and a heat-labile factor in fresh potato tissue or acetone powders of the tissue provided the best carbon source for induction. Yields of inducible pectate lyase were much greater than those usually reported. The pathogen, but not the saprophyte, produced a small amount of constitutive enzyme when grown on glucose. The relatively low level or absence of constitutive synthesis in these bacteria did not result from catabolite repression. Attempts were made to relieve any existing catabolite repression by restricting growth through slow feeding of glucose or by growing the organisms on glycerol. These conditions did not significantly alter the differential rate of lyase synthesis compared with changes observed in the presence of inducers. Previous growth history did not affect induction in the pathogen. However, P. fluorescens previously cultured on glucose required 10 to 20 generations of growth on inducing medium before appreciable lyase synthesis occurred. Differences between the pathogen and nonpathogen suggest that regulation of pectate lyase synthesis is related to pathogenicity of soft-rot bacteria.

Pectolytic enzymes produced by Pseudomonas syringae pv. glycinea

“…glycinea is able to produce PL and PG when grown in an artificial medium with pectin-potato discs as the carbon source. The bacterium also produced small amounts of constitutive PL when grown on glucose, as reported for other phytopathogenic bacteria [8,16]. The biochemical characteristics (optimal pH, temperature and divalent cation requirement) of PL and PG from P.s.…”

“…Strains NCPPB 1245, NCPPB 1783, NCPPB 2411, NCPPB 2752 were received from the National Collection of Plant Pathogenic Bacteria, Harpenden, U.K.. Bacteria were maintained at 4°C on nutrient agar supplemented with 2% (v/v) glycerol. For enzyme production, the six strains were grown in 100 ml of a liquid medium [8] in 250 ml flasks. The medium consisted of a basal salt solution containing, per 1000 ml of distilled water, 2 g (NH4)2804, ' 4 g KH2PO4, 6 g NazHPO 4, 1 mg FeSO 4 • 7H20 , 400 mg MgSO 4 • 7H20, 1 mg CaCI2, 10/xg HzBO3, 10/zg MnSO4, 70/xg ZnSO4, 50/zg CuSO4, 10/zg MoO 3.…”

Virulence and Enzyme Production of Erwinia carotovora ssp. atroseptica on Potato Tuber Tissue

“…For estimating the growth rate (by measuring the turbidity against a numbered standard) the strains were cultured for 24 h at 20 °G on a reciprocal shaker in Erlenmeyer flasks containing 20 ml of pectin medium, pH 7.0, after ZuCKER and HANKIN (1970).…”

“…For the estimation of enzyme producibility a mineral salt medium, pH 7.0, after ZuCKER and HANKIN (1970) with 20% potato cell sap and 15 g/1 potato fibres (= potato medium) or with 10 g/1 glucose as single carbon source (= glucose medium) were used.…”

“…atroseptica (= Eca) is known to secrete several enzymes such as pectatelyase (PL), Cx-cellulase, proteinase, polygalacturonase (PC), and phosphatidase. Because of the high secretion rate, pectatelyase is regarded the most promising enzyme for inducing and governing tissue maceration (ZUCKER andHANKIN 1970, TSENG andMOUNT 1974). The enzyme production of Erwinia is induced by oligomere galacturonides derived from the plant cell wall pectin (CoLLMER and BATEMAN 1982).…”