Abstract
BackgroundMembers of the bacterial genus Arthrobacter are both readily cultured and commonly identified in Antarctic soil communities. Currently, relatively little is known about the physiological traits that allow these bacteria to survive in the harsh Antarctic soil environment. The aim of this study is to investigate if Antarctic strains of Arthrobacter owe their resilience to substantial genomic changes compared to Arthrobacter spp. isolated from temperate soil environments.ResultsQuantitative PCR-based analysis revealed that up to 4% of the soil bacterial communities were comprised of Arthrobacter spp. at four locations in the Ross Sea Region. Genome analysis of the seven Antarctic Arthrobacter isolates revealed several features that are commonly observed in psychrophilic/psychrotolerant bacteria. These include genes primarily associated with sigma factors, signal transduction pathways, the carotenoid biosynthesis pathway and genes induced by cold-shock, oxidative and osmotic stresses. However, these genes were also identified in genomes of seven temperate Arthrobacter spp., suggesting that these mechanisms are beneficial for growth and survival in a range of soil environments. Phenotypic characterisation revealed that Antarctic Arthrobacter isolates demonstrate significantly lower metabolic versatility and a narrower salinity tolerance range compared to temperate Arthrobacter species. Comparative analyses also revealed fewer protein-coding sequences and a significant decrease in genes associated with transcription and carbohydrate transport and metabolism in four of the seven Antarctic Arthrobacter isolates. Notwithstanding genome incompleteness, these differences together with the decreased metabolic versatility are indicative of genome content scaling.ConclusionsThe genomes of the seven Antarctic Arthrobacter isolates contained several features that may be beneficial for growth and survival in the Antarctic soil environment, although these features were not unique to the Antarctic isolates. These genome sequences allow further investigations into the expression of physiological traits that enable survival under extreme conditions and, more importantly, into the ability of these bacteria to respond to future perturbations including climate change and human impacts.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1220-2) contains supplementary material, which is available to authorized users.
Highlights
Members of the bacterial genus Arthrobacter are both readily cultured and commonly identified in Antarctic soil communities
The three objectives of this study were (1) to investigate the abundance and diversity of Arthrobacter species found in soil microbial communities at four locations in the Ross Sea Region (RSR), (2) to compare genomes of seven Antarctic Arthrobacter isolates with seven temperate Arthrobacter spp., focusing on traits that may contribute to survival and growth in the Antarctic soil environment, and (3) to investigate the metabolic versatility and salinity tolerance range of Antarctic Arthrobacter isolates compared to three temperate, soil-dwelling Arthrobacter species
Abundance and diversity of Arthrobacter spp. in soils of RSR A total of eight samples from two soil depths at four locations within the RSR was investigated by quantitative PCR (qPCR) (Figure 1) to determine the relative abundance of members of the phylum Actinobacteria and genus Arthrobacter
Summary
Members of the bacterial genus Arthrobacter are both readily cultured and commonly identified in Antarctic soil communities. Just four studies have investigated psychrophilic/psychrotolerant organisms isolated from Antarctic environments including Methanococcoides burtonii from Ace Lake, Vestfold Hills [15,16], Exiguobacterium antarcticum from microbial mats, Lake Fryxell [17], Octadecabacter antarcticus from Antarctic sea ice [18], and Cellulophaga algicola from the surface of a sea-ice diatom Melosira, East Antarctica [19] These studies have reported the presence of cold adaptation relating to membrane modification, compatible solute accumulation, reactive oxygen species (ROS) detoxification, and significant changes in bacterial protein sequences including reduction in charged residues, hydrophobic clusters and proline content. FB24, A. nitroguajacolicus Rue61a, A. phenanthrenivorans Sphe, and A. arilaitensis re117 [22]
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