Congratulations Dr Habibu Aliyu

Posted on May 25, 2016

Microorganisms in Antarctic dry soils have evolved features which compensate for the physicochemical constraints imposed on their cellular function by extreme cold, alkalinity, aridity, salinity, starvation and UV irradiation. Nesterenkonia sp. AN1 is the first member of the genus Nesterenkonia isolated from Antarctic soils.

A combination of genomic and comparative genomic analyses was applied to elucidate the genetic determinants underlying survival strategies of Nesterenkonia sp. AN1. To highlight psychrotolerance mechanisms, I also compared, via RNA-seq analyses, the transcriptome of the Nesterenkonia sp. AN1grown at 5 ºC and 21 ºC.

The draft genome of Nesterenkonia sp. AN1 represents the first genome sequence of a cold adapted member of the genus Nesterenkonia. The genome comprised of 3.04 Mb assembled in forty-one contigs and encodes 2,852 proteins. These proteins include those putatively involved in cold shock, cold acclimation, osmotic and oxidative stress responses as well as the modulation of membrane fluidity.

Genome-wide comparison of the Nesterenkonia sp. AN1 and three mesophilic strains of Nesterenkonia revealed that members of the genus Nesterenkonia encodes an open pan-genome, which is consistent with their ecological diversity and niche specializations. Further evaluation of the pan-genome compartments showed that the majority of the adaptation genes are shared by all the strains, suggesting that members of the genus are naturally resilient to environmental stresses. The genome of Nesterenkonia sp. AN1, however, encodes unique adaptation proteins within the strain-specific genome fraction and also showed evidence of molecular evolution in a large number of the core genes. These events indicate that Nesterenkonia sp. AN1 genome had significant evolutionary innovations which involved the acquisition of adaptive genes and incorporation of advantageous mutations in the ancestral genetic stock.

Transcriptome data of Nesterenkonia sp. AN1 revealed that ~ 97% of the genes predicted in Nesterenkonia sp. AN1 were expressed under the experimental conditions. Analyses of the transcriptome showed that there was significant induction of transcripts that code for proteins associated with antioxidants activity at 5 ºC. There was also overexpression of universal stress protein genes related to uspA, along with genes encoding other characterised cold stress features. Genes encoding key enzymes of the glyoxylate cycle were also induced at 5 ºC, suggesting possible adaptation strategies for energy metabolism in cold habitats.

Taken together, the combined data revealed the presence of pervasive adaptation strategies which likely determine niche specialization of Nesterenkonia sp. AN1 and its survival in the highly dynamic arid soils of Antarctica.

Published by Alacia Armstrong

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