Molecular and genetic characterization of the Pseudomonas chlororaphis subsp. aurantiaca mutant strain with increased resistance to hydrogen peroxide

A whole genome sequencing of natural and mutant producer strains is the best way to analyze the genome and to search for mutations that could cause the acquisition of a number of properties valuable for biotechnological and pharmaceutical industry.

The main goal of current research was to identify mutations that had been induced by chemical mutagenesis in the genome of the mutant strain Рseudomonas chlororaphis subsp. aurantiaca B-162/15 resistant to hydrogen peroxide. It would give an opportunity to discover new genes potentially participating in phenazine compounds biosynthesis. Such an approach also makes it possible to identify genes, whose products do not directly participate in the phenazine synthesis, but influence the phenazine detoxification, excretion, and optimization of antioxidant system activity. Most of all, it could help us to discover new unpredicted enzyme systems that might be involved into this process.

The genome size of P. chlororaphis subsp. aurantiaca B-162/15 was 7109863 b. p. It contained 6493 open reading frames and 66 sequences encoding transport and ribosomal RNA. Comparison of a wild-type strain and B-162/15 mutant genomes revealed 16 mutations, 13 of which were located in coding sequences and 3 were located in intergenic regions. Six mutations led to radical replacements in amino acid sequences of coded proteins (with a Grantham distance of more than 80). We managed to identify four potential gene-candidates, which could influence the phenazine metabolism and provided the ability of mutant strain to superproductivity. They were arginine N-succinyltransferase, phosphoenolpyruvate synthase, iron-contain-ing redox enzyme family protein, membrane-associated proteins in eicosanoid and glutathione metabolism. Three prophage regions were identified, two regions of which were intact and one region was incomplete. The prophage genes, as well as the bacterial genes were inside these regions. We also managed to identify two genes of Agrobacterium tumefaciens inside prophage region 2. It was possible that these regions were introduced into the genome of studied strain by viral transduction. 

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