Vol 92, No 4 (2023)

Abstract—Planctomycetes are common inhabitants of northern wetland ecosystems. In this study, a new planctomycete of the genus Paludisphaera, strain Pla2^T, was isolated from a boreal fen in Russia. The novel isolate was represented by nonmotile, pink-pigmented, spherical cells that multiplied by budding and occurred singly or were assembled in small aggregates. Strain Pla2^T was a chemoorganotrophic, psychrotolerant mesophile with a growth optimum at pH 5.5‒6 and 15‒20°C. The preferred growth substrates were polysaccharides, including xylan, xanthan gum, and phytagel, as well as some sugars. The 16S rRNA gene sequence of strain Pla2T displayed the highest similarity (97.9%) to that of ‘Paludisphaera soli’ JC670^T isolated from highland soil of the western Himalayas. With other members of the genus Paludisphaera, “P. rhizosphaerae” JC665^T and P. borealis PX4^T, this similarity was 97.0 and 93.8%, respectively. The genome of strain Pla2^T was 8.21 Mb in size and contained about 6500 protein-coding genes and 3 copies of the rRNA operon. The DNA G + C content was 67 mol %. The average nucleotide identity between the genome sequence of strain Pla2^T and those of previously described members of the genus Paludisphaera was between 79.4 and 82.6%. This genotypic distance as well as several phenotypic differences allowed classifying the new planctomycete from a fen as representing a novel species of the genus Paludisphaera, Paludisphaera mucosa sp. nov. with the type strain Pla2^T (=KCTC92668^T = VKM B-3698^T).

Abstract—The role of groESL and dnaJ structural genes and hrcA regulatory gene, encoding the synthesis of heat shock proteins, in biosurfactant synthesis by R. pyridinivorans 5Ар was determined. The CIRCE binding sites for the regulatory protein coded by hrcA gene were revealed in the promoter regions of groESL, groEL2, and fmdB genes. GroESL and groEL2 genes expression during the late exponential phase in the medium with hexadecane at 42°C was higher than at 28°C (4.4 and 5.3 times, respectively). At the same time, no changes in expression of hrcA and fmdB genes were observed at two different temperature modes (28 and 42°C). In the absence of the negative regulator HrcA, groESL expression increased 14.4 and 3.5 times, that of groEL2, 9.6 and 2.7 times, and that of fmdB, 1.82 and 2.52 times at 28 and 42°C, respectively. Products of dnaJ and hrcA genes were required for trehalolipid synthesis at different temperature modes, with their role increasing at higher temperature (synthesis of trehalolipids by the mutant with impaired dnaJ gene decreased 1.8 and 2.5 times compared to 1.5 and 6.6 times, for the mutant with impaired hrcA at 28 and 42°C, respectively). At the same time, emulsifying activity of all mutant variants did not change at 28°C and decreased 1.4 and 1.9 times 42°C for the mutants with impaired groESL and hrcA genes, respectively. Our results indicated the complex chemical nature of the biosurfactants produce by R. pyridinivorans 5Ар (emulsifiers, including trehalolipids and compounds of other chemical composition). The Gro chaperones and the HrcA regulatory protein play the key roles in synthesis of these compounds at different temperature modes, while the dnaJ is required only for trehalolipid synthesis.

Abstract—The Ррх1 exopolyphosphatase of yeast is a constitutive protein localized predominantly in the cytoplasm. The purified enzyme hydrolyzes inorganic polyphosphates with high activity; however, in the knockout ∆ppx1 mutant of Saccharomyces cerevisiae the increase in the polyphosphate level was small, and no changes in physiological properties of this mutant were observed. To elucidate the functions of Ppx1, we studied the physiological characteristics of the S. cerevisiae strain overexpressing this enzyme. When cultivated in the YPD medium, the strain overexpressing Ppx1 showed no growth features different from those of the parental strain. The following physiological features of the strain overexpressing Ppx1 were observed at the stationary stage of growth: the level of ATP increased by nine times, the activity of vacuolar ATPase significantly decreased, and the sensitivity to peroxide increased compared to the parental strain. The level of reactive oxygen species doubled, while the degree of lipid oxidation remained the same as in parental strain. Since overexpression of Ppx1 under the culture conditions used did not affect the polyphosphate level, these polymers were not the regulators of the changes described above. Response to oxidative stress and vacuolar ATPase activity in yeasts is known to be regulated by cAMP, while Ppx1 is capable of hydrolyzing this signaling compound. We suggest that one of the functions of Ppx1 in yeasts is participation in the regulation of cAMP level.

Abstract—Wild-type cells of Rhodococcus pyridinivorans 5Ар were found to be highly efficient naphthalene degraders, completely utilizing this compound (500 mg/L) after 3 days, and may be used for remediation of naphthalene-contaminated aquatic ecosystems. Inactivation of the biodegradation genes narAa (encoding the large subunit of naphthalene dioxygenase) and narB (encoding cis-naphthalene dihydrodiol dehydrogenase) resulted it the loss of ability to use naphthalene as the sole energy source, which indicated the absence in the genome of R. pyridinivorans 5Ар of the determinants responsible for alternative pathways of naphthalene oxidation. Moreover, narB inactivation resulted in accumulation of a polar colored compound (probably a product of primary naphthalene oxidation) in the medium.