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Diurnal rhythm of a unicellular diazotrophic cyanobacterium under mixotrophic conditions and elevated carbon dioxide

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Title Diurnal rhythm of a unicellular diazotrophic cyanobacterium under mixotrophic conditions and elevated carbon dioxide
 
Creator GAUDANA, SB
ALAGESAN, S
CHETTY, M
WANGIKAR, PP
 
Subject Glycerol
CO2
Kai
Glycogen
Diazotroph
Cyanothece 51142
SP STRAIN ATCC-51142
NITROGEN-FIXING CYANOBACTERIA
SP ATCC 51142
GENUS CYANOTHECE
CONTINUOUS-LIGHT
CIRCADIAN CLOCK
FIXATION
GROWTH
RESPIRATION
DARK
 
Description Mixotrophic cultivation of cyanobacteria in wastewaters with flue gas sparging has the potential to simultaneously sequester carbon content from gaseous and aqueous streams and convert to biomass and biofuels. Therefore, it was of interest to study the effect of mixotrophy and elevated CO2 on metabolism, morphology and rhythm of gene expression under diurnal cycles. We chose a diazotrophic unicellular cyanobacterium Cyanothece sp. ATCC 51142 as a model, which is a known hydrogen producer with robust circadian rhythm. Cyanothece 51142 grows faster with nitrate and/or an additional carbon source in the growth medium and at 3 % CO2. Intracellular glycogen contents undergo diurnal oscillations with greater accumulation under mixotrophy. While glycogen is exhausted by midnight under autotrophic conditions, significant amounts remain unutilized accompanied by a prolonged upregulation of nifH gene under mixotrophy. This possibly supports nitrogen fixation for longer periods thereby leading to better growth. To gain insights into the influence of mixotrophy and elevated CO2 on circadian rhythm, transcription of core clock genes kaiA, kaiB1 and kaiC1, the input pathway, cikA, output pathway, rpaA and representatives of key metabolic pathways was analyzed. Clock genes' transcripts were lower under mixotrophy suggesting a dampening effect exerted by an external carbon source such as glycerol. Nevertheless, the genes of the clock and important metabolic pathways show diurnal oscillations in expression under mixotrophic and autotrophic growth at ambient and elevated CO2, respectively. Taken together, the results indicate segregation of light and dark associated reactions even under mixotrophy and provide important insights for further applications.
 
Publisher SPRINGER
 
Date 2014-10-16T13:48:39Z
2014-10-16T13:48:39Z
2013
 
Type Article
 
Identifier PHOTOSYNTHESIS RESEARCH, 118(1-2)51-57
0166-8595
1573-5079
http://dx.doi.org/10.1007/s11120-013-9888-0
http://dspace.library.iitb.ac.in/jspui/handle/100/15706
 
Language en