Chlorophyll Synthesis in Chlorella

Abstract

The degree of light limitation of growth is the primary controlling factor of chlorophyll synthesis during photoautotrophic growth of Chlorella. The chlorophyll content of the cells increases when light is limiting for growth as occurs in dense cultures, or in cultures under low incident light, or when the light is used less efficiently through partial inhibition of photosynthesis by 3-(p-chlorophenyl)-1, 1-dimethylurea. Most algae, Chlorella included, do not require light in order to carry out chlorophyll synthesis, and therefore, the regulation of chlorophyll synthesis in algae appears to be quite different from that involved in the greening of etiolated higher plants. There are, however, some common features of chlorophyll synthesis in algae and higher plants: 8-aminolevulinic acid synthetase, the putative first enzyme of chlorophyll synthesis, has not been detected in extracts of any green plant, including algae (3); chlorophyll synthesis in Chlorella appears to be dependent upon protein synthesis (2), as it is in higher plants (4, 5); mutants of Chlorella exist which behave like higher plants with respect to a light requirement for protochlorophyllide reduction and chlorophyll formation (7,8).Sargent (14) and Myers (10, 11) reported that Chlorella produced more chlorophyll under low light conditions than under high light conditions. This is perhaps related to the observations of Sestak (15) specifically suppressed when dilute cultures of Chloreilla were exposed to high light intensity, the effect being designated the lag phase of chlorophyll synthesis. The duration of the lag phase could be altered by changing the incident light intensity on the culture or the initial cell population density, and by the presence of certain sugars in the culture medium. A number of possible explanations were put forward concerning the physiological basis of the lag phase. First, the lag could be due to some intrinsic induction period required before the enzymes necessary for chlorophyll biosynthesis are produced within the cells. When a newly inoculated culture is placed in the light, perhaps some component of the chlorophyll biosynthetic system is destroyed and then resynthesized during the induction period. Second, perhaps light suppresses chlorophyll synthesis directly. Then the lag phase might reflect the time required for the cells to overcome the light-induced suppression of chorophyll synthesis, i.e., to adapt to the new light environment. Third, the lag phase might represent a feedback control exerted by a product of photosynthesis over another process, chlorophyll biosynthesis, which provides a key component of the photosynthetic apparatus, namely, chlorophyll. The cells might adjust their chlorophyll content in response to the light available for carrying ouLt photosynthesis. Fourth, inasmuch as growth rate and chlorophyll biosynthetic rate appear to be inversely related, perhaps there is a competition for a common precursor of chlorophyll and other cellular components.The experiments described in this pap...

Extracellular matrix production and calcium carbonate precipitation by coral cells in vitro

“…7) maintained high chlorophyll levels. These results suggest that glucose can suppress chlorophyll synthesis in zooxanthellae, possibly as a result of end-product inhibition (14)(15)(16) X. elongata, 87 Ϯ 2%), after which it started to decrease (day 26: M. digitata, 70 Ϯ 7%; X. elongata, 75 Ϯ 6%). After the first week, many of the epithelial cells formed aggregates that adhered to the plates.…”

Fluctuations in the Organic Carbon to Chlorophyll a Ratios for Estuarine Benthic Diatom Populations

“…Steemann-Nielsen and Hansen (1959), Rodhe et al (1966), Anderson (1969), Sayo et al (1969), Takahashi et al (1972), Eppley et al (1973) and Fee (1976) chlorophyll a increase under low light intensities. Harvey (1953), Brown and Richardson (1968), Beale and Appleman (1971) and Sheridan (1972) found an inverse proportion between light intensity and chlorophyll a concentrations for algal cells. Steele and Baird (1962), Antia et al (1963), Coombs et al (1967), Eppley (1968), Strickland et al (1969), Hobson and Pariser (1971), Thomas and Dodson (1972) and Peny (1976) showed that deficiency of P, N and Si could lead to a considerable increase in the organic carbon to chlorophyll a ratios.…”

Primary production of particulate protein amino acids : algal protein metabolism and its relationship to the composition of particulate organic matter

“…As noted in chapter 3 (Table 3- was enhanced relative to total biomass in low light adapted cultures, a commonly observed response of algae (e.g. Beale and Appleman, 1971;Beardall and Morris, 1976;Prezelin, 1976;Falkowski and Ovens, 1980;Perry et al, 1981;Richardson et al, 1983). The fact that the chlorophyll ~/proteln carbon ratio declined with decreasing growth rate under low light conditions indicates that nitrogen limitation suppressed the low light enhanced chlorophyll produc tion.…”