legionella donaldsonii legionella donaldsonii legionella donaldsonii is a gram-negative, aerobic, non-spore-forming bacterium from the genus legionella. legionella donaldsonii scientific classification domain: bacteria phylum: pseudomonadota class: gammaproteobacteria order: legionellales family: legionellaceae genus: legionella species: l. donaldsonii binomial name legionella donaldsoniilo presti et al. 1999