Molecular Genetic and Functional Analysis of the Genes Encoding Alkane 1-Monooxygenase Synthesis in Members of the Genus Rhodococcus

• Published in: Microbiology (New York) 2023-04, Vol.92 (2), p.242-255
• Main Authors: Bukliarevich, H. A., Gurinovich, A. S., Filonov, A. E., Titok, M. A.
• Format: Article
• Language: English
• Subjects: Alkane 1-monooxygenase; alkanes; Biomedical and Life Sciences; biosurfactants; Chromosomes; Experimental Articles; Genes; Genetic analysis; Genomes; genus; Life Sciences; Localization; Medical Microbiology; Microbiology; Mutants; operon; Operons; oxidoreductases; Phylogenetics; Phylogeny; Proteins; regulatory proteins; Rhodococcus; Rubredoxin reductase; Surfactants; temperature; transcription (genetics); Trehalose
• ISSN: 0026-2617; 1608-3237
• DOI: 10.1134/S0026261722603311

— Organization and localization of the alkB genes and of alkane 1-monooxygenases they encode in members of the genus Rhodococcus was investigated. All members of a phylogenetic group were found to possess specific types of alkB genes ( alkB1 -type in the operons containing rubredoxin-coding genes, rubredoxin reductase, and a regulatory protein and/or alkB2 -type in the operons lacking the rubredoxin-reductase-coding gene, and additionally, separately located determinants of the alkB3 ‒ alkB8 type). The alkB1 -type genes were present in the chromosomes of bacteria of the groups B1 ( R. aetherivorans, R. ruber ), C ( R. opacus , R. jostii, R. wratislaviensis, R. koreensis ), D ( R. erythropolis , R. qingshengii ), G ( R. triatomae ), and E ( R. fascians ). The alkB2 -type genes occurred in strictly specified loci of the chromosomes of members of the phylogenetic groups A ( R. hoagii / R. equi ), B2 ( R. coprophilus, R. pyridinivorans, R. rhodochrous ), and D ( R. erythropolis , R. qingshengii ). The separately located alkB3 ‒ alkB5 genes were present in the chromosomes of members of the group D ( alkB5 was found only in R. qingshengii ); the alkB6 genes occurred in members of the groups B1 and B2, and alkB7‒alkB8 were present in members of the group E. The proteins encoded by alkB1 and alkB2 genes belonged to three phylogenetic groups. The first one comprised AlkB1-type proteins of members of groups B1 and C and the AlkB2-type proteins of members of the groups D and A. The second one was represented by AlkB2-type proteins of bacteria of the group B2. The third cluster comprised AlkB1-type proteins of members of the groups G and D. Alkane 1-monooxygenases encoded by separately located alkB3 ‒ alkB8 genes were represented by three phylogenetic lineages: AlkB3‒AlkB5, AlkB6, and AlkB7‒AlkB8. In the genome of R. pyridinivorans 5Ap, the alkB2 and alkB6 genes characteristic of group B1 were revealed. It was shown that these determinants are required for biosurfactant synthesis. Emulsifying activity of the mutant with an inactivated alkB2 gene growing at 28 and 42°C was 16 and 3 times lower, respectively, while the amount of trehalose-containing surfactants decreased 7 and 3 times, respectively. Irrespective of the cultivation temperature, the mutant with an inactivated alkB6 gene exhibited 1.2 times lower emulsifying activity and more than twofold decrease in the synthesis of trehalose-containing surfactants. These results suggest that alkB2 plays a key role in bio