title: Coupling of Cellular Processes and Their Coordinated Oscillations under Continuous Light in Cyanothece sp. ATCC 51142, a Diazotrophic Unicellular Cyanobacterium.
abstract: Unicellular diazotrophic cyanobacteria such as Cyanothece sp. ATCC 51142 (henceforth Cyanothece), temporally separate the oxygen sensitive nitrogen fixation from oxygen evolving photosynthesis not only under diurnal cycles (LD) but also in continuous light (LL). However, recent reports demonstrate that the oscillations in LL occur with a shorter cycle time of ~11 h. We find that indeed, majority of the genes oscillate in LL with this cycle time. Genes that are upregulated at a particular time of day under diurnal cycle also get upregulated at an equivalent metabolic phase under LL suggesting tight coupling of various cellular events with each other and with the cell's metabolic status. A number of metabolic processes get upregulated in a coordinated fashion during the respiratory phase under LL including glycogen degradation, glycolysis, oxidative pentose phosphate pathway, and tricarboxylic acid cycle. These precede nitrogen fixation apparently to ensure sufficient energy and anoxic environment needed for the nitrogenase enzyme. Photosynthetic phase sees upregulation of photosystem II, carbonate transport, carbon concentrating mechanism, RuBisCO, glycogen synthesis and light harvesting antenna pigment biosynthesis. In Synechococcus elongates PCC 7942, a non-nitrogen fixing cyanobacteria, expression of a relatively smaller fraction of genes oscillates under LL condition with the major periodicity being 24 h. In contrast, the entire cellular machinery of Cyanothece orchestrates coordinated oscillation in anticipation of the ensuing metabolic phase in both LD and LL. These results may have important implications in understanding the timing of various cellular events and in engineering cyanobacteria for biofuel production.
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, India.
authors.forename: S
authors.initials: S
authors.lastname: Krishnakumar
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, India.
authors.forename: Sandeep B
authors.initials: SB
authors.lastname: Gaudana
authors.affiliation: School of Information Technology, Federation University Australia, Gippsland Campus, Victoria, 3841, Australia.
authors.forename: Nguyen X
authors.initials: NX
authors.lastname: Vinh
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, India; DBT Pan IIT Center for Bioenergy Indian Institute of Technology Bombay, Powai, Mumbai, India.
authors.forename: Ganesh A
authors.initials: GA
authors.lastname: Viswanathan
authors.affiliation: School of Information Technology, Federation University Australia, Gippsland Campus, Victoria, 3841, Australia.
authors.forename: Madhu
authors.initials: M
authors.lastname: Chetty
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, India; DBT Pan IIT Center for Bioenergy Indian Institute of Technology Bombay, Powai, Mumbai, India; Wadhwani Research Center for Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, India.
authors.forename: Pramod P
authors.initials: PP
authors.lastname: Wangikar
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001683:Biological Clocks / Q000235:genetics / Q000528:radiation effects*; D002244:Carbon / Q000378:metabolism; D002940:Circadian Rhythm / Q000235:genetics; D002952:Citric Acid Cycle / Q000235:genetics / Q000528:radiation effects; D046889:Cyanothece / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D015964:Gene Expression Regulation, Bacterial; D006003:Glycogen / Q000096:biosynthesis; D006019:Glycolysis / Q000235:genetics / Q000528:radiation effects; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism; D058977:Molecular Sequence Annotation; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation / Q000235:genetics / Q000528:radiation effects*; D009591:Nitrogenase / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010427:Pentose Phosphate Pathway / Q000235:genetics / Q000528:radiation effects; D010788:Photosynthesis / Q000235:genetics / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D002244:Carbon; D006003:Glycogen; D009591:Nitrogenase; D009584:Nitrogen; D010100:Oxygen