Premium
LIGHT/DARK‐PHASED CELL DIVISION IN EUGLENA GRACILIS (Z) (EUGLENOPHYCEAE) IN PO 4 ‐LIMITED CONTINUOUS CULTURE 1
Author(s) -
Chisholm S. W.,
Stross Raymond G.,
Nobbs Paul A.
Publication year - 1975
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.1975.tb02798.x
Subject(s) - euglena gracilis , chemostat , biology , cell division , dilution , euglena , growth rate , population , botany , biophysics , zoology , cell , biochemistry , genetics , physics , bacteria , thermodynamics , geometry , mathematics , chloroplast , demography , sociology , gene
SUMMARY Eugene gracilis Klebs (Z) was grown in a cyclostat (continuous culture on a light/dark cycle) at growth limiting levels of phosphate. Cell division was restricted to the dark period regardless of the proportion of the cells dividing during each 24 h period. Growth rate, as reflected by the amplitude of the cell density oscillation, was correlated with dilution rate. The width of the division gate was analyzed using a phasing index and found to be narrowest at dilution rates where the mean generation time of the cell population was an even multiple of 24 h. The effect was attributed to enhanced phasing of the cell division process by the biological clock of Euglena . Residual phosphate levels in the cyclostat were less than 0.3 μM PO 4 at all submaximal growth rates. Cellular phosphorus concentration increased with dilution rate as described by a hyperbola saturating at D max = 0.74 day −1 with 8 × 10 −8 μM P/cell as the minimum intracellular phosphorus concentration for growth. The results are discussed, in terms of the inherent similarities and differences between a cyclostat and a steady state chemostat, and the advantages of the cyclostat for studies in phytoplankton ecology.