Characteristics of Myxobacteria Associated with Some Freshwater Fish Diseases in Japan

Abstract

Morphological, cultural and biochemical characteristics of 12 cultures of myxobacteria isolated mainly from eels with ‘branchionephritis’ and cyprinids with ‘ulcer disease’ were studied.These organisms were gram-negative, slender rods which exhibited gliding motility on agar medium. All cultures were able to grow at 5°, 10°, 20° and 27°, and tolerated a sodium chloride concentration of 1% for growth. They were uniform in their biochemical properties, though diverse in the production of cytochrome oxidase and in the reduction of nitrate. Some distinguishing features of the organisms were as follows: Degradation of starch, esculin and chitin; utilization of glucose, galactose and citrate; decomposition of tyrosine; nonproduction of hydrogen sulfide; negative reaction to Congo red. They are physiologically similar to the myxobacteria isolated from the Amerian hatchery-raised salmonids with gill disease, tail rot or other myxobacterial infections.The histopathological features of experimentally infected eels resembled those of salmonids with ‘hemorrhagic type of gill disease’ described by WOOD and YASUTAKE.