Literature Review: Antarctica, The Extreme Niche

CHAPTER 2

LITERATURE REVIEW

2.1 Antarctica, the extreme niche
Antarctica is known to be the world largest continent, with the area size around 14 million Km2. The continent is covered by two massive ice sheets, namely the East Antarctica, and the West Antarctica ice sheets. The two gigantic ice sheets are separated by a 3, 500 km long range, known as the Transantarctic Mountain, it is also known to be the largest ice-free area in the continent of Antarctica (~23, 000 km2).

Antarctica is the coldest region on Earth, this is due to the rarefied solar radiation expose to the continent, only 16% of that solar radiation at equatorial region is exposed to Antarctica. Not only that, the high average surface elevation surface of the ice sheets,

This phenomenon drastically blocks membrane-bound enzyme, slow down the diffusion rates and increase cluster formation of integral membrane protein. Microorganism overcomes the propensity for membranous to rigidity at low temperature by adapting to the conditions in order to maintain to a constant degree of membrane fluidity, or known as homeoviscous adaptation (Hazel, 1995). In order to achieve that, cold effect initials a coordinated response, whereby the fatty acid desaturase and the dehydrases are induced to increase the ratio of polyunsaturated to saturated fatty acids or decreases the length of the fatty acid chains in the membrane (Carty et al., 1999).

Protein synthesis is suppressed during the temperature downshift due to the growth arrest effect affecting the expression of CSPs, that is required for hypothermal adaptation (Rieder & Cole, 2002). Synthesis of the specific CSPs during temperature downshifts enhanced and ensured an accurate translation of specific mRNAs at low temperatures (Sahara et al., 2002). mRNA translation plays a crucial part in the cold shock responses. However, the overall mechanism of cold shock mediated inhibition of translation needed to be fully

According to Margesin (2009), there were at least 10 genome out of 398 cold adapted microorganism have been fully sequenced. All these genome data provide valuable information regarding cold adaptation. The genome of G. antarctica PI12 has been partially sequenced in the year 2007 using several Next Generation Sequencing (NGS) platforms, these NGS platforms, including Sanger technology, 454 Life Sciences, Roche and Illumina Hi-Seq (Murad, A. M. A., personal communication, 2011). By using various sequencing platforms, it helps to improve the sequencing output information by overcoming the limitations found in each sequencing platform. The genome of G. antarctica PI12 is approximately 22 million base pairs (20.4 Mb), comprised of 21 scaffolds, with about 467, 060 bp gaps, or equivalent to 2.3 % of the gaps in scaffold. However, the total number of chromosomes is yet to be determined. The total genome coverage was 116.4X, and the total length reads generated was 2.32 GB. Based on several ongoing studies, G. antarctica PI12 used in this project is possibly a haploid cell. It contains at least 10 chromosomes based on PFGE and telomere analysis (Zainuddin, N., personal communication, 2011). However, a much conclusive remark on the total chromosome numbers, and the ploidy state of G. antarctica PI12 is yet to be