ANALYSIS OF CONDUCTANCE RESPONSES DURING DEPOLYMERIZATION OF PECTATE BY SOFT-ROT ERWINIA SPP AND OTHER PECTOLYTIC BACTERIA ISOLATED FROM POTATO-TUBERS

Different bacteria isolated from potato tubers were screened for their pectolytic properties by examining pitting in polypectate agar, recor ding conductance responses in polypectate medium and performing potato tuber soft rot tests. For bacteria found positive in conductimetry, t he role of polygalacturonase (PG) and pectate lyase (PL) in the genera tion of conductance changes in a polygalacturonic acid (PGA) medium wa s further analysed using enzyme activity staining after gel electropho resis and high-performance anion exchange chromatography. The extent o f the conductance changes during depolymerization of PGA was dependent on the amounts of galacturonate monomers and oligomers accumulated in the medium. In comparison with an unidentified saprophyte and a Klebs iella strain, both mainly having PL activity, soft rot Erwinia spp, ra pidly produced larger conductance responses, due to a combined action of multiple forms of PG and FL. The responses of Erwinia spp. were ini tially associated with the accumulation of large amounts of monomers a nd saturated dimers to heptamers, due to PG activity. Subsequently, as well as monomers and saturated dimers, large amounts of unsaturated d imers were also detected, due to PL activity. The role of PG as an imp ortant conductimetric factor was also demonstrated for a pectinase pre paration derived from Aspergillus niger. Besides detection, automated conductimetric assays in pectate media may also be useful for monitori ng of pectolytic activity in pectinase preparations and for screening of pectolytic activity of microorganisms under different media and gro wth conditions.