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Tschitschko, B, Erdmann, S, DeMaere, MZ, Roux, S, Panwar, P, Allen, MA, Williams, TJ, Brazendale, S, Hancock, AM, Eloe-Fadrosh, EA & Cavicchioli, R 2018, 'Genomic variation and biogeography of Antarctic haloarchaea.', Microbiome, vol. 6, no. 1, pp. 113-113.View/Download from: UTS OPUS or Publisher's site
BACKGROUND:The genomes of halophilic archaea (haloarchaea) often comprise multiple replicons. Genomic variation in haloarchaea has been linked to viral infection pressure and, in the case of Antarctic communities, can be caused by intergenera gene exchange. To expand understanding of genome variation and biogeography of Antarctic haloarchaea, here we assessed genomic variation between two strains of Halorubrum lacusprofundi that were isolated from Antarctic hypersaline lakes from different regions (Vestfold Hills and Rauer Islands). To assess variation in haloarchaeal populations, including the presence of genomic islands, metagenomes from six hypersaline Antarctic lakes were characterised. RESULTS:The sequence of the largest replicon of each Hrr. lacusprofundi strain (primary replicon) was highly conserved, while each of the strains' two smaller replicons (secondary replicons) were highly variable. Intergenera gene exchange was identified, including the sharing of a type I-B CRISPR system. Evaluation of infectivity of an Antarctic halovirus provided experimental evidence for the differential susceptibility of the strains, bolstering inferences that strain variation is important for modulating interactions with viruses. A relationship was found between genomic structuring and the location of variation within replicons and genomic islands, demonstrating that the way in which haloarchaea accommodate genomic variability relates to replicon structuring. Metagenome read and contig mapping and clustering and scaling analyses demonstrated biogeographical patterning of variation consistent with environment and distance effects. The metagenome data also demonstrated that specific haloarchaeal species dominated the hypersaline systems indicating they are endemic to Antarctica. CONCLUSION:The study describes how genomic variation manifests in Antarctic-lake haloarchaeal communities and provides the basis for future assessments of Antarctic regional and global biogeography o...
Erdmann, S, Tschitschko, B, Zhong, L, Raftery, MJ & Cavicchioli, R 2017, 'A plasmid from an Antarctic haloarchaeon uses specialized membrane vesicles to disseminate and infect plasmid-free cells.', Nature Microbiology, pp. 1446-1455.View/Download from: UTS OPUS or Publisher's site
The major difference between viruses and plasmids is the mechanism of transferring their genomic information between host cells. Here, we describe the archaeal plasmid pR1SE from an Antarctic species of haloarchaea that transfers via a mechanism similar to a virus. pR1SE encodes proteins that are found in regularly shaped membrane vesicles, and the vesicles enclose the plasmid DNA. The released vesicles are capable of infecting a plasmid-free strain, which then gains the ability to produce plasmid-containing vesicles. pR1SE can integrate and replicate as part of the host genome, resolve out with fragments of host DNA incorporated or portions of the plasmid left behind, form vesicles and transfer to new hosts. The pR1SE mechanism of transfer of DNA could represent the predecessor of a strategy used by viruses to pass on their genomic DNA and fulfil roles in gene exchange, supporting a strong evolutionary connection between plasmids and viruses.An archaeal plasmid that can be transported in membrane vesicles, similar to a virus, and encodes proteins that can insert into host membranes and membrane vesicles, provides insights into the evolutionary link between plasmids and viruses.
Williams, TJ, Allen, M, Tschitschko, B & Cavicchioli, R 2017, 'Glycerol metabolism of haloarchaea.', Environmental microbiology, vol. 19, no. 3, pp. 864-877.View/Download from: UTS OPUS or Publisher's site
Haloarchaea are heterotrophic members of the Archaea that thrive in hypersaline environments, often feeding off the glycerol that is produced as an osmolyte by eucaryotic Dunaliella during primary production. In this study we analyzed glycerol metabolism genes in closed genomes of haloarchaea and examined published data describing the growth properties of haloarchaea and experimental data for the enzymes involved. By integrating the genomic data with knowledge from the literature, we derived an understanding of the ecophysiology and evolutionary properties of glycerol catabolic pathways in haloarchaea.
Tschitschko, B, Williams, TJ, Allen, MA, Zhong, L, Raftery, MJ & Cavicchioli, R 2016, 'Ecophysiological Distinctions of Haloarchaea from a Hypersaline Antarctic Lake as Determined by Metaproteomics', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 82, no. 11, pp. 3165-3173.View/Download from: Publisher's site