Zooflagellates : Flagellate protozoa that do not have chlorophyll and are either holozoic, saprozoic, or symbiotic.

Zoogleal mass : Jellylike matrix in which microorganisms may be embedded.

Zoonosis (pl. zoonoses) : A disease primarily occurs in wild and domestic animals which can be transmitted to humans. (e.g., tularemia).

Zoophilic : Fungi that grow preferentially on animals.

Zoospore : A motile asexual spore.

Zooxanthella : A symbiotic dinoflagellate found living symbiotically within cnidarians and other invertebrates.

Zygomycetes : Group of fungi with nonseptate hyphae and spores produced within a sporangium.

Zygospore : A thick-walled sexual spore formed by the fusion of two gametangia in the Zygomycetes. Example: Rhizopus.

Zygote : The cell resulting from the fusion of male and female gametes; occurs in the mosquito stomach (Plasmodium spp.).

Zymogenous : Fermentation production. In environmental microbiology, the term refers to microorganisms, often transient or alien, that respond rapidly by enzyme production and growth when simple organic substrates become available.