They are called decomposers although they may have more specific names than that the general term is decomposer or more scientifically saprobes and detritivores
parasites
an organism that feeds on dead organic matter especially a fungus or bacterium
A detrivore feeds on dead things.
Sparotrophic feeders means any organism, esp a fungus or bacterium, that lives and feeds on dead organic matter
when is bacterium defined as dead
Scavenger.
yes it feeds on wastes and eat other dead things
An organism, usually a bacterium or fungus, that breaks down the cells of dead plants and animals into simpler substances. The decomposer feeds on dead materials. Dust mites or spider mites are animals that are decomposers.
DECOMPOSER
Decomposers feed on dead and decayingt matter, breaking it down.
a composer is an organism that feeds on living organism
If your are asking about the virus which feeds on bacteria then it is BACTERIOPHAGE