NOVELTY - An isolated form of a pathogenic bacterium (I) (its progeny), which controls at least one of an alga or a cyanobacterium in water and which is at least substantially similar to a bacterium deposited in the ARS patent culture collection having the assigned number NRRL B-30043, is new.    USE - (I) Is useful for reducing or eliminating off-flavor in water, fish or other aquatic life forms. The off-flavor is caused directly or indirectly by the algae, the cyanobacterium, a bacterium or their metabolite or product; or by a chemical agent such as geosmin, 2-methylisoborneol, 2-methylenebornane, 2-methyl-2-bornene and their dehydrated forms, present in the water, fish or other aquatic life form. The method involves preparing a suspension comprising water and (I), prior to the treatment step. (I) Is bacterium SG-3 in the form of an isolate, a cultured bacterium, a concentrate, an immobilized cell preparation, an inoculate, a solid, a powder, a freeze-dried powder, a cell lysate, or a genetically engineered bacterium, and produces a lytic agent (such as protein or chemical agent) which lyses the algae, cyanobacterium or bacterium. (I) Is useful for reducing or eliminating off-flavor in an aqueous waste or aquaculture, by inoculating the aqueous waste or aquaculture with an inoculum comprising (I) to form a mixture, and incubating the mixture to increase a cellular titre of (I) in the mixture and to reduce or eliminate the off-flavor. (I) Is also useful for controlling, reducing or inhibiting the formation of scum in water; for controlling an amount of cyanobacteria, algae or undesired bacteria in water-containing environment (especially cyanobacteria in mixed population of cyanobacteria and algae); and for controlling susceptible pest bacteria such as Edwardsiella spp., Flexibacter spp., Aeromonas sp. and Pseudomonas sp. in water, fish or other aquatic life forms (all claimed). (I) Can be used to treat municipal or industrial waste.    ADVANTAGE - (I) Celectively controls cyanobacteria in mixed population of cyanobacteria and algae. (I) (Which is genetically engineered) possesses properties such as enhanced pathogenicity toward cyanobacteria, improved storage properties, improved formulation properties, improved growth or production characteristics, and increased spectrum of activity; and eliminates or reduces the expression of an undesired property, introduces or expresses a property not native to the bacterium, or contain genetic information from another organism.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method of controlling an amount of cyanobacteria, algae or undesired bacteria in water-containing environment, involves treating the cyanobacteria, algae or undesired bacteria with (I) and a pathogenic virus.