Characteristics of Psychrotolerant Pseudomonads Isolated from Organogenic Clay Deposits of the Mramornaya Cave (Primorskii Krai)

Abstract

The community of cultured pseudomonads isolated from clayey organogenic deposits of the Mramornaya Cave (Primorskii krai) was investigated. The bacterial strains isolated in this work were eurythermal and psychrotolerant. Their taxonomic position was determined by high-throughput sequencing of the 16S rRNA gene fragments. Members of the genus Pseudomonas are known to inhabit all the ecological niches on Earth and, accordingly, have a wide range of adaptive functions. Microscopic techniques were used to establish the changes in the character of motility and the cell size stability with changes in the cultivation temperature. The studied strains are of scientific and applied interest due to their enzymatic activity against several substrates simultaneously at different temperatures (25 and 4°C), as well as to the ability to secrete cold-active pectinase, protease, and lipase. However, phosphate-solubilizing activity both at 4 and at 25°C became preferable for the strains. The Mramornaya Cave is of karst origin and is characterized by carbonate karst, which explains the preference for calcium phosphate in the studied strains. Analysis of the obtained data showed that the collection of cultivated bacteria obtained in the present work included both typical psychrotolerant ones, which exhibited enzymatic activity at optimal growth temperature, and unique ones, capable of synthesizing a wide range of enzymes under the temperature different from their growth optimum.