| Abstract |
SUMMARY
Two new
Chlorella
‐like microalgal strains, Mei‐3 and Mei‐4, were isolated from rock surfaces in the intertidal zone of Japan, a habitat with high irradiation, high salinity, and periodic dryness. The two strains grew well in a freshwater medium and showed high tolerance to photooxidative stress conditions. A phylogenetic analysis based on SSU rDNA‐ITS sequences revealed that the strains Mei‐3 and Mei‐4 belong to the family Chlorellaceae, and Mei‐4 represents an independent lineage within the family. Secondary structural analysis of ITS2 revealed compensatory base changes between Mei‐3 and its most closely related species in the genus
Chlorella
. Based on light and transmission electron microscopy, the mature cells of the two strains are spherical or oval shaped with smooth cell walls, and each cell contains a single pyrenoid penetrated by thylakoid membranes, a typical morphological feature of the family Chlorellaceae. However, Mei‐4 showed morphological changes in response to stress, with an accumulation of oil droplets along the extremely thickened cell wall. On the basis of molecular and morphological analyses, we propose
Chlorella intertidalis
sp. nov. for Mei‐3 and
Apricichlorella intertidalis
gen. et sp. nov. for Mei‐4.
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