legionella nautarum legionella nautarum legionella nautarum is a gram-negative bacterium from the genus legionella which was isolated from a hot water tap in london. legionella nautarum scientific classification domain: bacteria phylum: pseudomonadota class: gammaproteobacteria order: legionellales family: legionellaceae genus: legionella species: l. nautarum binomial name legionella nautarumdennis et al. 1993 type strain atcc 49506, ccug 44900, cip 105270, nctc 12375, thacker 1224