A total of 119 isolates of Edwardsiella ictaluri collected over the last 7 years from several states were biochemically characterized. Although not very reactive biochemically, this bacterium shows a high degree of homogeneity. Differences were found only in the production of gas from formate or from glucose at 37C and in the production of hydrogen sulfide as detected by lead acetate paper. Analysis of E. ictaluri by year or geographic area indicated that some differences existed, but no clear-cut biotypic variations were found. All isolates studied were capable of degrading chondroitin sulfate, a major component of cartilage, which may be an important virulence factor in the formation of the hole-in-the-head lesion characteristic of infected fish.

A total 291 strains of motile members of the genus Aeromonas were classified according to the taxonomic scheme proposed by POPOFF and VERON (1976). Forty three were indetified as A. hydrophila biovar hydrophila, 9 as A. hydrophila biovar anaerogenes, and 52 as A. sobria. The remaining 187 strains could not be identified. Thirty seven (86%) of 43 A. hydrophila biovar hydrophila, 3 (33 %) of 9 A. hydrophila biovar anaerogenes, 32 (62 %) of 52 A. sobria, and 65 (35%) of the 187 unidentified originated from fishes. All 6 A. hydrophila biovar hydrophila examined fell in the category of high virulence. The Japanese loach injected with them were killed earlier than those injected with the other motile Aeromonas, and the difference of mean time to death was statistically significant (P <0.01). The difference of average value of proteolytic activity of the broth culture filtrate between A. hydrophila biovar hydrophila and the other was significant (P <0.01), also. Exophthalumus and scale protru sion were evident only among fish injected with the sonicated cell extracts of A. hydrophila biovar hydrophila.

A procedure is described to prepare uniformly labelled D-[14C]ribulose 1,5-bisphosphate enzymically from uniformly labelled D-[14C]glucose through the coupled reactions catalysed by hexokinase (EC 2.7.1.1), glucose 6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44) and 5-phosphoribulokinase (EC 2.7.1.19). All reagents utilized in the method are commercially available. The procedure is a reliable preparative-scale method for synthesizing the dibarium salt of D-[14C]ribulose 1,5-biphosphate with a specific radioactivity up to 7 mCi/mmol and a purity near 90%. The final product was free of other 14C-labelled sugars, sugar phosphate esters, Pi and nucleotides.

A simple quantitative plate assay was used to study the proteolytic activity of Aeromonas hydrophila complex. All the A. hydrophila complex strains hydrolyzed albumin, casein, and fibrinogen; most of the strains also digested gelatin (99.9 %), hemoglobin (94.3%), and elastin (73.2 %). None of the strains hydrolyzed collagen. The activity on each substrate varied from isolate to isolate. By using correlation analysis a close relationship was obtained among these proteolytic reactions, especially with albumin, casein, fibrinogen, gelatin, and hemoglobin hy drolysis. The elastin hydrolysis demonstrated a lower correlation with the other 5 proteolytic activities and implied a different enzymatic system. A higher casein and elastin hydrolytic re sponse was found in the strains derived from human, fish, and other animal sources than those from water environments.

Enzymatic characterization of 48 Aeromonas hydrophila complex isolates from various sources was determined with the API ZYM system (Analytab Products, Plainview, N.Y.). All isolates lacked valine and cystine aminopeptidases, chymotrypsin, a-mannosidase, ot-fucosidase, ot-galactosidase, and f-glucuronidase but possessed caprylate esterase-lipase, leucine aminopeptidase, acid phosphatase, phosphoamidase, and N-acetyl-,B-glucosaminidase. Variability was found ia the presence of alkaline phosphatase, butyrate esterase, myristate lipase, trypsin, Igalactosidase, cx-glucosidase, and 3-glucosidase. No significant differences were evident among the enzymatic profiles of isolates from various sources.

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