Morphology and phylogenetic relationships of two Antarctic strains within the genera Carolibrandtia and Chlorella (Chlorellaceae, Trebouxiophyceae)

Hyunsik Chae, Eun Jae Kim, Han Soon Kim, Han Gu Choi, Sanghee Kim, Ji Hee Kim

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The genera Carolibrandtia and Chlorella have been described as small green algae with spherical cell shapes that inhabit various environments. Species of these genera are often difficult to identify because of their simple morphology and high phenotypic plasticity. We investigated two small coccoid strains from Antarctica based on morphology, molecular phylogeny by two alignment methods which have been applied to previous phylogenetic studies of the genus Chlorella, and comparison of the secondary structures of nuclear small subunit (SSU) and internal transcribed spacer (ITS) rDNA sequences. Light microscopy of two strains revealed spherical cells containing chloroplasts with pyrenoids, and the morphological characteristics of the strains were nearly identical to those of other Chlorella species. However, based on the phylogenetic analyses of nuclear SSU and ITS rDNA sequences, it was determined that the Antarctic micro-algal strains belonged to two genera, as the Chlorella and Carolibrandtia. In addition, the secondary structures of the SSU and ITS2 sequences were analyzed to detect compensatory base changes (CBCs) that were used to identify and describe the two strains. A unique CBC in the SSU rDNA gene was decisive for distinguishing strain CCAP 211/45. The ITS2 rDNA sequences for each strain were compared to those obtained previously from other closely related species. Following the comparison of morphological and molecular characteristics, we propose KSF0092 as a new species, Chlorella terrestris sp. nov., and the reassignment of the strain Chlorella antarctica CCAP 211/45 into Carolibrandtia antarctica comb. nov.

Original languageEnglish
Pages (from-to)241-252
Number of pages12
JournalAlgae
Volume38
Issue number4
DOIs
StatePublished - Dec 2023

Keywords

  • Antarctica
  • Carolibrandtia
  • Chlorella
  • morphology
  • nuclear SSU and ITS rDNA

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