pseudomonas gessardii pseudomonas gessardii pseudomonas gessardii is a fluorescent, gram-negative, rod-shaped bacterium isolated from natural mineral waters in france. based on 16s rrna analysis, p. gessardii has been placed in the p. fluorescens group. pseudomonas gessardii scientific classification domain: bacteria phylum: pseudomonadota class: gammaproteobacteria order: pseudomonadales family: pseudomonadaceae genus: pseudomonas species: p. gessardii binomial name pseudomonas gessardiiverhille, et al., 1999 type strain cip 105469 cfml 95-251