PULSED-FIELD GEL-ELECTROPHORESIS IN THE STUDY OF MESOPHILIC AND PSYCHROPHILIC AEROMONAS SPP

Pulsed-field gel electrophoresis (PFGE) was used to study the genetic diversity of mesophilic Aeromonas hybridization group (HG) 1, HG 2, HG 3, HG 4, HG 5, HG 6, HG 7, HG 8/10 and HG 11, psychrophilic Aeromonas salmonicida subsp. salmonicida and atypical Aerom. salmonicida strain s. XbaI was chosen for restriction because it produced fragments whose numbers and size were appropriate for PFGE analysis of all studied HG s. All mesophilic Aeromonas strains within an HG had different banding patterns. No shared bands which could be used for identification of a n HG were found. Pulsed-held gel electrophoresis analysis further conf irmed the known genetic homogeneity of Aerom. salmonicida subsp. salmo nicida. Pulsed-field gel electrophoresis pattern analysis suggested th at the genomic size of Aerom. salmonicida subsp. salmonicida is smalle r than that of mesophilic Aeromonas spp, or atypical Aerom. salmonicid a. Aeromonas salmonicida subsp. salmonicida had only one large restric tion fragment (310 kb) and lacked other large fragments (>160 kb). Alt hough the PFGE patterns of atypical Aerom. salmonicida resembled the b anding patterns of mesophilic Aeromonas spp. they had several small fr agments (15-50 kb) shared with Aerom. salmonicida subsp. salmonicida s uggesting genetic relatedness.