Phenotypic Diversification Of Terrestrial Cyanobacteria From Selected Habitats On Signy Island, South Orkney Islands, Antarctica
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Date
2020-12
Authors
Radzi, Ranina Alya Mohamad
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Publisher
Universiti Sains Malaysia
Abstract
A floristic study was conducted on cyanobacteria from terrestrial habitats in Signy Island (60.7170° S, 45.6000° W), South Orkney Islands during the expedition of British Antarctic Survey (BAS) in austral summer of 2015/2016. Samples were collected following the previous 120 locations that was provided by Broady (1979). Thirty seven out of 120 collection sites established by Broady (1979) were successfully obtained and compared in this study. Changes in the cyanobacteria community at sites previously studied by Broady (1979) will provide excellent baseline information on the status of Antarctic terrestrial cyanobacteria diversity and dispersal. It is crucial to understand how the Antarctic life form is responding to current environmental change and what the continent was like in the past. This study has integrated traditional morphological and modern molecular taxonomic approaches providing new insights into the taxonomy of Antarctic cyanobacteria. Seventeen morphospecies belonging to 14 genera; Chamaesiphon, Cyanosarcina, Desmonostoc, Leptolyngbya, Microcoleus, Nodosilinea, Nostoc, Oscillatoria, Phormidium, Phormidesmis, Pseudanabaena, Synechocystis, Trichocoleus and Wilmottia have been recorded with robust descriptions by using streaking and most probable number techniques. Ten morphospecies recorded were similar to records by Broady (1979). Seven of the morphospecies; Leptolyngbya cf. subcapitata, Nodosilinea signiensis, Oscillatoria cf. subsala, Phormidium uncinatum, Trichocoleus cf. hospitus, Wilmotia murrayi M1 and Wilmottia murrayi M2 are new records for Signy Island. A novel species of Nodosilinea, Nodosilinea signiensis sp. nov. R. Radzi & F. Merican 2019 have been reported based on a polyphasic assessment of the strain in culture. This member of the genus Nodosilinea is well separated from the other Nodosilinea species in the 16S rDNA phylogenetic tree. Morphologically, the strain also showed difference in its morphological characteristics especially in cell size, cell shape, filament attenuation, sheath morphology and granulation. The D1-D1’ helix of the 16S – 23S ITS region analyses showed that N. signiensis is genetically distinct from other recorded species of Nodosilinea. Two cyanobacterial morphotypes were also successfully isolated and characterized using a polyphasic assesment. Both showed similar morphological characteristic to the genus Phormidium, in particular with simple, uniseriate and unbranched trichomes. However, 16S rDNA phylogenetic analyses showed a clear separation from members in the Phormidium. Both strains were grouped within the major clade of the Wilmottia murrayi. Interestingly, there are two lineages within the major clade of W. murrayi separating tropical species with those from the cold regions. To date, this genus at present contains only three species, W. murrayi, W. stricta and W. koreana. In this study, the occurrence of both W. murrayi M1 and M2 were first described from Signy Island. Therefore, the morphospecies recorded in this study have significantly provide a valuable information towards the diversity and dispersal of terrestrial cyanobacteria in Antarctica.
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Natural history