Abstract
UV irradiation is known to cause harmful effects on microorganisms. As the result, microorganisms have developed protection against exposure to harmful UV irradiation. We suggested that resistance to UV might be specific characteristic of certain genera of microorganisms. So, the aim of the work is to assess whether there is a correlation between UV resistance and the taxonomic position of microorganisms or is it the adaptation of cells to extreme conditions. There were studied 67 strains from extreme ecosystems (phytocenoses and оrnithogenic soil of the Antarctic, hypersaline ecosystems of the Crimea and the Dead Sea, the lake Baikal). Sequence of 16S rRNA genes, phylogenetic analysis and UV resistance were performed according to standard procedures. Phylogenetic analysis revealed live representatives of the following genera: Pseudomonas, Serratia, Rheinheimera, Aeromonas, Buttiauxella, Brevundimonas, Sphingomonas, Sphingopyxis, Dermacoccus, Frondihabitans, Microbacterium, Rhodococcus, Janthinobacterium, Arthrobacter, Micrococcus, Kocuria, Sphingobacterium, Flavobacterium, Chryseobacterium, Bacillus, Staphylococcus, Paenibacillus, Sporosarcina. Gram-positive bacteria were significantly more resistant to UV irradiation (LD99.99 750–1400 J/m2). Gram-negative had lower resistance (LD99.99 35–150 J/m2). Most pigmented strains were more resistant to UV than non-pigmented ones. According to the values of lethal doses of UV irradiation we suggest that investigated microorganisms have effective mechanisms to repair DNA damages. Resistance of microorganisms to UV, as a rule, was not related to the ecological features of their habitat. Thus, there is a correlation between the resistance of microorganisms to UV irradiation and their taxonomic position, which allows to consider UV resistance as a diagnostic feature at the genus level.
Highlights
The investigation of ultraviolet radiation influence on microorganisms is becoming an increasingly relevant topic of research today
Phylogenetic analysis based on 16S rRNA gene sequencing revealed the affiliation of bacterial isolates from the extreme regions to the following family: Micrococcaceae, Nocardiaceae, Dermacoccaceae, Microbacteriaceae, Pseudomonadaceae, Xanthomonadaceae, Enterobacteriaceae, Chromatiaceae, Aeromonadaceae, Caulobacteraceae, Sphingomonadaceae, Alcaligenaceae, Oxalobacteraceae, Sphingobacteriaceae, Flavobacteriaceae, Bacillaceae, Staphylococcaceae, Paenibacillaceae, Planococcaceae
The taxonomic position of bacterial isolates was established by phylogenetic analysis using the 16S rRNA gene sequence
Summary
The investigation of ultraviolet radiation influence on microorganisms is becoming an increasingly relevant topic of research today It is related with the growing anthropogenic impact on the atmosphere. Ultraviolet radiation on the Earth’s surface is noted to be increased from about 5% to 20% (depending on latitude) by the end of the 21st century (Zepp et al, 2011) Such intensity may affect a significant part of living organisms having a great ecological importance in biochemical cycles. UV rays cause various physiological effects depending on the spectrum and dose of radiation They adversely affect all living organisms, including bacteria, damaging such vital biomolecules as proteins, lipids and DNA (Ayala et al, 2014; Gabani, et al, 2013; Santos et al, 2013; Wynn-Williams et al, 2002). According to the literature (Sinha et al, 1998), cyanobacteria have developed mechanisms for counteraction to UV radiation
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