Molecular phylogeny of a commercially important thermophilic microalga Chlorella sorokiniana LWG002615 and associated bacterium Aquimonas sp. NBRI01 isolated from Jeori thermal spring, Shimla, India

Abstract

Thermophilic eukaryotic algae are rare in nature, but quite important owing to their faster growth rate, high lipid content and ability to withstand harsh environment. While screening Jeori thermal spring at Shimla for thermophilic algae we have isolated one eukaryotic chlorophycean microalga in addition to several populations of cyanophyceae. The microalga isolated from 44 °C temperature was identified as Chlorella sorokiniana based on morphology and 18S ribosomal RNA sequence analysis. The 18S rRNA sequence showed 100% similarity with C. sorokiniana isolate 34-2 (GenBank No. KU948991). Taxonomic analysis revealed that it belongs to phylum Chlorophyta, class Trebouxiophyceae and family Chlorellaceae. Phylogenetic reconstruction by ‘Maximum Likelihood’ showed that it was mostly clustered with different isolates of C. sorokiniana. The 18S rDNA sequence was submitted to NCBI GenBank (accession number MH382824). The alga was deposited in institutional herbarium as C. sorokiniana isolate LWG002615. One associated thermophilic bacteria Aquimonas sp. NBRI01 was also identified by 16S rRNA sequencing and assigned the NCBI gene bank accession number MH379673. Isolation of C. sorokiniana LWG002615 from natural thermal spring will encourage the outdoor cultivation of this important thermophilic alga in high temperature regions and will further strengthen its commercial application.