Answer:

anaerobe

Answer	Crossword Clue
ANAEROBE	Certain bacterium
ANAEROBE	Septic tank bacterium, e.g.
ANAEROBE	Oxygen-shunning organism

ANAEROBE	Deep-sea bacterium
ANAEROBE	Fermentation facilitator
ANAEROBE	Septic tank organism, e.g.
ANAEROBE	Bacterium that can exist without air.
ANAEROBE	Organism requiring no air
ANAEROBE	Oxygen eschewer
ANAEROBE	Biology lab organism
ANAEROBE	Bacterium that doesn't need oxygen

ANAEROBE	Organism that doesn't require oxygen
ANAEROBE	Septic tank resident
ANAEROBE	Septic tank worker?
ANAEROBE	It doesn't need oxygen
ANAEROBE	It requires no oxygen for growth