legionella steigerwaltii legionella steigerwaltii legionella steigerwaltii is a gram-negative bacterium from the genus legionella isolated from tap water in st. croix on the virgin islands. legionella steigerwaltii scientific classification domain: bacteria phylum: pseudomonadota class: gammaproteobacteria order: legionellales family: legionellaceae genus: legionella species: l. steigerwaltii binomial name legionella steigerwaltiibrenner et al. 1985 type strain atcc 35302, ccug 29674, ccug 56441, cip 103851, jcm 7558, nctc 11991, sc-18-c9