The esterase activity of a pigmented bacterial group belonging to the Pseudomonas genus

: Bacteria belonging to the Pseudomonas genus and isolated from zonal soils in different geographical zones of the USSR as well as from the rhizosphere of cultivated and wild plants were tested for their esterase activity. The studied collection of cultures included 205 strains of different pigmented Pseudomonas species which, according to the conventional taxonomy, were assigned to the so-called "Pseudomonas fluorescens complex". As was shown in this study, many Pseudomonas species are potential producers of nonspecific esterases. P. maltophilia and P. geniculata synthesizing pyomelanin have the highest activity of esterase. The activity of esterase correlates with the formation of a melanin-like pigment in Pseudomonas cultures. It also correlates with the species to which a culture belongs, which makes it possible to use this property as an additional criterion for the identification of Pseudomonas species.