This 1977 study describes the characterization of 47 yellow-pigmented, gram-negative rod bacteria isolated from human clinical specimens, hospital environments, and other sources. Using numerical taxonomic analysis of 68 phenotypic tests and DNA base composition analysis, the authors identified 29 strains as a new species of Pseudomonas, which they named Pseudomonas paucimobilis. The strains were strictly aerobic, heterotrophic organisms with a single polar flagellum, though motility was often difficult to demonstrate in standard culture media. Key biochemical characteristics included cytochrome oxidase production, hydrolysis of esculin, and β-galactosidase production. The DNA from 13 representative isolates showed a mean guanine-plus-cytosine content of 64.9 ± 1.4 mol%. The remaining 18 yellow-pigmented isolates could not be classified, except for two strains identified as Flavobacterium species. Notably, the pathogenicity of these bacteria for humans had not been established at the time of this study.

Key findings

• Twenty-nine yellow-pigmented bacterial strains isolated from clinical specimens and hospital environments represent a new species, formally named Pseudomonas paucimobilis, with 93.4% within-group similarity.
• P. paucimobilis is a strictly aerobic, gram-negative rod with a single polar flagellum and mean DNA G+C content of 64.9 ± 1.4 mol%, distinguishing it from Xanthomonas species with which it shares morphological similarities.
• The strains show consistent biochemical properties including positive cytochrome oxidase, esculin hydrolysis, and β-galactosidase production, with homogeneous antimicrobial susceptibility patterns.
• Motility was present in all 29 strains but was difficult to detect in standard nutrient broth; enhanced detection occurred in enriched minimal media.
• Two strains of previously unclassified Weaver group IIk, biotype 1 were identified as members of the new P. paucimobilis species.