Characterization of Erwinia chrysanthemi biovars in alpine water sources by biochemical properties, GLC fatty acid analysis and genomic DNA fingerprinting

E.J. COTHER, J.K. BRADLEY, M.R. GILLINGS AND P.C. FAHY. 1992. Erwinia chrysanthemi isolated from the headwaters of the Murrumbidgee River was shown to be different from strains isolated from the source of the Murray River only 140 km away. Biovar 5 (sensu Samson) was found consistently in the upper reaches of the Murrumbidgee River but was not detected in the Murray River where the majority of strains isolated were characterized biochemically as biovar 3. Fatty acid methyl ester analysis of 56 water strains by gas‐liquid chromatography and the Hewlett‐Packard Microbial Identification System confirmed the existence of a distinct biotype at the source of each river system. All Erw. chrysanthemi strains contained cis 9 hexadecanoic (16 : cis9), hexadecanoic (16 : 0), and tetradecanoic (12 : 0) acids. The majority of strains contained dodecanoic acid (12 : 0) in small amounts. Twenty‐six isolates (18 from water, six from potato, and two type cultures) selected for DNA digestion with Hae III or Hinf I were placed in 10 clonal lines based on restriction patterns. No clone was common to both river systems. Restriction patterns obtained by analysis of strains from soft‐rotting potatoes were identical to those obtained from cultures from the headwaters or upper reaches of both rivers. Biochemical, fatty acid and DNA characterization methods all supported the hypothesis that Erw. chrysanthemi is a natural component of the alpine aquatic microflora which could infect potatoes via irrigation water.