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Evaluation of the Relationship Between the 18S rRNA / rDNA Ratio and Population Growth in the Marine Diatom Skeletonema tropicum via the Application of an Exogenous Nucleic Acid Standard
Author(s) -
Lin YunChi,
Kang LeeKuo,
Shih ChiYu,
Gong GwoChing,
Chang Jeng
Publication year - 2018
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/jeu.12521
Subject(s) - biology , diatom , phosphorus , ribosomal rna , population , 18s ribosomal rna , food science , botany , biochemistry , chemistry , demography , organic chemistry , sociology , gene
Ribosomal RNA ( rRNA ) has been regarded as a proxy for metabolic activity and population growth in microbes, but the limitations and assumptions of this approach should be better defined, particularly in eukaryotic microalgae. In this study, the 18S rRNA / rDNA ratio of a marine diatom, Skeletonema tropicum, was examined in batch and semi‐continuous cultures subjected to low nitrogen and phosphorus treatments at a temperature of 20 °C. In the semi‐continuous cultures, the measured 18S rRNA / rDNA ratio ranged from 4.0 × 10 2 to 5.0 × 10 3 , and the logarithmic form of this ratio increased linearly with the population growth rate under both low nitrogen and low phosphorus conditions. In batch cultures grown under low nitrogen or low phosphorus conditions, log ( rRNA / rDNA ) also increased linearly with growth rate when the latter ranged between −0.4 and 1.5 day −1 . The 18S rRNA / rDNA ratios of Skeletonema sampled from in the southern East China Sea were substantially lower than measured from laboratory cultures. Among the field samples, ratios obtained at a coastal station were higher than those obtained farther offshore. These results imply higher growth rate at the coastal station, but the influences of other factors, such as cell size and temperature, cannot be ruled out.