MadSci Network: Cell Biology
Query:

Re: What are the effects of nitrates on chlorella?

Date: Wed Jul 26 11:37:53 2000
Posted By: Michael Maguire, Faculty,Case Western Reserve Univ.
Area of science: Cell Biology
ID: 963082203.Cb
Message:

 Chlorella, an algae, like most plants requires nitrogen for growth.  It can use 
nitrogen in the form of ammonia/ammonium directly.  However, it is not always 
available in that form.  Since we live in an oxygen atmosphere, nitrogen is 
usually available in the form of nitrate, which must be reduced to ammonia or a 
similar compound for use in synthesizing amino acids and thus proteins, among 
other uses.
  Reduction is by an enzyme called nitrate reductase, which in most cells is 
expressed only when nitrate is present.  In the presence of ammonia, the algae 
will grow well.  In the presence of ammonia plus nitrate, the organism will use 
ammonia preferentially, and then, if the ammonia runs out, will induce nitrate 
reductase and utilize nitrate.  In the absence of ammonia and presence of 
nitrate, the organism will induce the reductase.  Once this is done, it will 
begin to actively grow.Below are abstracts of some papers/reviews that may be of 
further help.=

 Enzyme Microb Technol 2000 Aug 1;27(3-5):312-318Heterotrophic production of 
biomass and lutein by Chlorella protothecoides onvarious nitrogen sources.Shi X, 
Zhang X, Chen FKey Laboratory of Microbiology of Agricultural Ministry, Huazhong 
AgriculturalUniversity, 430070, Wuhan, China

The effects of nitrate, ammonium, and urea as nitrogen sources on the 
heterotrophic growth of Chlorella protothecoides were investigated using 
flaskcultures. No appreciable inhibitory effect on the algal growth was observed 
overa nitrogen concentration range of 0.85-1.7 g l(-)(1). In contrast, 
differencesin specific growth rate and biomass production were found among the 
cultureswith the various nitrogen compounds. The influence of different nitrogen 
sourcesat a concentration equivalent to 1.7 g l(-)(1) nitrogen on the 
heterotrophicproduction of biomass and lutein by C. protothecoides was 
investigated using theculture medium containing 40 g l(-)(1) glucose as the sole 
carbon and energysource in fermentors. The maximum biomass concentrations in the 
three cultureswith nitrate, ammonium, and urea were 18.4, 18.9, and 19.6 g l(-
)(1) dry cells,respectively. The maximum lutein yields in these cultures were 
between 68.42 and83.81 mg l(-)(1). The highest yields of both biomass and lutein 
were achieved inthe culture with urea. It was therefore concluded that urea was 
the bestnitrogen source for the production of biomass and lutein. Based on 
theexperimental results, a group of kinetic models describing cell growth, 
luteinproduction, and glucose and nitrogen consumption were proposed and 
asatisfactory fit was found between the experimental results and predictedvalues. 
Dynamic analysis of models demonstrated that enhancing initial 
nitrogenconcentration in fermentor cultures, which correspondingly enhances cell 
growthand lutein formation, may shorten the fermentation cycle by 25-46%.

Plant Cell Physiol 2000 Apr;41(4):534-40Oxygen uptake, acidification of medium 
and nitrate uptake induced by blue lightin nitrate-starved Chlorella cells.Kamiya 
ALaboratory of Chemistry, Faculty of Pharmaceutical Sciences, Teikyo 
University,Sagamiko, Kanagawa, Japan.

Blue light-induced oxygen uptake of the colorless mutant of Chlorella 
kessleri(No. 9.80) was 30-40% higher in the presence of exogenous glycine than in 
itsabsence. None of the other amino acids tested had this effect. Moreover, 
mutantcells in which glutamine synthetase was inhibited by methionine 
sulphoximine,accumulated approximately 65% more ammonium ions under blue 
irradiation in thepresence of exogenous glycine than in its absence. The protein 
kinase C inhibitors, staurosporine or K252a, reduced the enhancement of oxygen 
uptake byapproximately 40%. The present results indicate that blue light-
dependentdeamination of endogenous glycine might be a prerequisite for enhanced 
oxygenuptake in Chlorella. This blue light-induced oxygen uptake was not 
influenced bythe inhibitors of protein phosphatase, calyculin A or okadaic acid. 
On thecontrary, calyculin A and okadaic acid had a marked effect on the 
acidificationof the suspension medium and nitrate uptake induced by blue light in 
Chlorellacells. The different responses to the inhibitors of protein kinase 
andphosphatase suggest the presence of different pathways among the blue 
lightsignal transduction operating on oxygen uptake, acidification of the medium 
andnitrate uptake in Chlorella.PMID: 10845468, UI: 203020784: Arch Biochem 
Biophys 1989 Nov 1;274(2):525-31Induction and synthesis of nitrate reductase in 
Chlorella vulgaris.Sherman TD, Funkhouser EADepartment of Biochemistry and 
Biophysics, Texas A&M University, College Station77843.Assimilatory nitrate 
reductase is an inducible, eukaryotic enzyme that respondsto a variety of 
environmental cues. When higher plants and green algae are grownwith ammonia as a 
nitrogen source, low levels of nitrate reductase activity arepresent. Transfer to 
nitrate-containing medium is accompanied by substantialincrease of nitrate 
reductase activity. Here it is shown immunologically that,in the green algae 
Chlorella vulgaris, nitrate reductase protein isover-produced as activity appears 
during induction. Immunoreactive protein isalso found in cells grown on ammonia. 
Low levels of translatable mRNA fornitrate reductase are present in ammonia-grown 
cells. These data suggest that:(i) nitrate reductase appearance is controlled 
primarily on a transcriptionallevel, but that transcription is not completely 
halted under repressingconditions; (ii) there is an overproduction of nitrate 
reductase protein earlyduring the induction period as previously suggested; and 
(iii) nascent protein,from in vitro translation, is of approximately the same 
molecular size as thenitrate reductase subunit and therefore little 
posttranslational modification isnecessary to generate the functional enzyme. 
Insertion of cofactors and assembly are probably the only post-translational 
events.



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