Myxobacteria

Myxobacteria (literally "slime bacteria") can cause disease in both natural and hatchery fish. Diseases caused by these organisms include columnaris  and bacterial cold-water disease. Freshwater and anadromous fish are susceptible to myxobacterial infection, and large economic losses have occurred in populations of fish, from the diseases they cause. Nonpathogenic myxobacteria are present naturally on the skin and gills of fish.