ISSN:0008-4026    

DOI:10.1139/b98-062

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Carboxysomes containing the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) have been demonstrated in a variety of chemoautotrophic prokaryotes and cyanobacteria. The genes in theccmandcsooperon inSynechococcussp. PCC7942 andThiobacillus neapolitanus, respectively, code for several carboxysome polypeptides. The polypeptides CcmK and CsoS1 exhibit a high degree of conservation, and in turn show significant homology to the CchA and PduA polypeptides of the ethanolamine and propanediol operons of enteric bacteria. Probing Southern blots ofEscherichia coligenomic DNA withcsoS1Ashowed positive hybridization indicating the presence of acsoS1-like gene. GrowingSalmonella entericaandKlebsiella oxytocawith propanediol, andE.coliwith ethanolamine as the energy source under anaerobic conditions resulted in the formation of polyhedral bodies in these bacteria. The DNA - deduced amino acid sequence of three additionalcsoS1genes in bothThiobacillus intermediusandThiobacillus denitrificanswas determined. The nine CsoS1 polypeptides, which includes the three previously determined forT.neapolitanus, exhibited greater than 67% sequence identity. Identity and similarity comparisons and phylogenetic analysis of known polyhedral body CsoS1-like polypeptides indicate a close structural relationship between polyhedral bodies of potentially very different function.Key words: polyhedral bodies, carboxysomes, ribulose-1,5-bisphosphate carboxylase-oxygenase, cyanobacteria, thiobacilli, enteric bacteria.

ISSN:0008-4026    

DOI:10.1139/b98-088

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In this minireview we focus on certain aspects of the induction, function, and ecophysiological significance of the inorganic carbon-concentrating mechanism in cyanobacteria. Since this entire issue is dedicated to various aspects of this mechanism, we mainly discuss some of the recent studies in our laboratory and point to open questions and perspectives.Key words: CO2, cyanobacteria, inorganic carbon-concentrating mechanism, photosynthesis.

ISSN:0008-4026    

DOI:10.1139/b98-087

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In contrast to free-living photoautotrophs, endosymbiontic dinoflagellates of the genusSymbiodiniummust absorb their inorganic carbon from the cytoplasm of their host anthozoan cell rather then from seawater. The purpose of this paper is to review the present knowledge on the source of dissolved inorganic carbon supply for endosymbiont photosynthesis and the transport mechanisms involved.Symbiodiniumspp., generally known as zooxanthellae, live within the endodermal cells of their hosts, corals and sea anemones. They are separated from the surrounding seawater by the host tissues (oral ectodermal cell layer, collagenous basal membrane, endodermal cell, and perisymbiotic vesicles). The symbiotic association is therefore faced with the problem of delivering dissolved inorganic carbon to an endodermal site of consumption from an, essentially, ectodermal site of availability. Studies using original methods demonstrated that neither the internal medium (coelenteric fluid) nor paracellular diffusion could supply enough dissolved inorganic carbon for endosymbiont photosynthesis. A transepithelial active mechanism must be present in the host tissues to maintain the photosynthetic rate under saturating irradiance. A pharmacological approach led to propose a working model of dissolved inorganic carbon transport from seawater to zooxanthellae. This vectorial transport generates a pH gradient across the epithelium. The role of this gradient as well as the physiological adaptation ofSymbiodiniumspp. to symbiotic life are discussed.Key words: carbon concentrating mechanism, anthozoan, dinoflagellates, anion transport, symbiosis, transepithelial transport.

ISSN:0008-4026    

DOI:10.1139/b98-086

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

An inactivation library consisting of genomic fragments ligated within a modified bluescript vector was used to isolate several new high CO2requiring mutants ofSynechococcusPCC7942. The mutants described here were impaired in the ability to accumulate Ciinternally when supplied with HCO3-. The relevant genomic regions bearing novel genes involved in the ability to transport and to accumulate Ciwithin the cells and thus to grow under low-CO2conditions are presented. Some of the mutants were also impaired in ability to adjust to an elevated pH in their medium. We show that the use of inactivation libraries enabled cloning of genes encoding membrane-located proteins; we point to mutations introduced by the single cross-recombination events resulting in the formation of some of these mutants. Possible artifacts that may result in incorrect identification of genes, the inactivation of which could have led to the observed phenotype, are discussed.Key words: bicarbonate uptake, cyanobacteria, CO2, mutants, photosynthesis,Synechococcus.

ISSN:0008-4026    

DOI:10.1139/b98-085

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The unexpected finding that certain major marine photosynthetic microorganisms can serve as a source of CO2rather than a sink emerged during measurements of inorganic carbon fluxes associated with the CO2-concentrating mechanism. During steady-state photosynthesis, CO2was evolved at sustained rates up to 5-fold that of photosynthesis; the steady-state external CO2concentration reached was significantly higher than that at CO2-HCO3-equilibrium. The evolved CO2originated from HCO3-taken up and intracellularly converted to CO2in a light-dependent process. Our results bear implications for carbon cycling in the marine environment; the use of naturally-observed stable carbon isotope fractionations as paleobarometer and productivity probe; and for intracellular energy balance and pH regulation.Key words: carbonic anhydrase, CO2evolution, cyanobacteria, photosynthesis,Synechococcus.

ISSN:0008-4026    

DOI:10.1139/b98-084

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Cyanobacteria as well as eukaryotic algae possess a CO2concentrating mechanism that enables the cells to use low CO2concentrations very efficiently for photosynthesis. The efficiency of the CO2concentrating mechanism changes in response to environmental changes, especially the availability of inorganic carbon, but the underlying mechanisms that are involved in the regulation of the induction are unknown. This review deals with the occurrence of protein phosphorylation in cyanobacteria and highlights the possible involvement of post-translational modifications of existing proteins in the induction process, which leads to a high-affinity state of the CO2concentrating mechanism.Key words: cyanobacteria, CO2concentrating mechanism, protein kinase, protein phosphorylation, post-translational regulation.

ISSN:0008-4026    

DOI:10.1139/b98-083

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Carbonic anhydrase (CA) speeds up the equilibrium between CO2and HCO3-at physiological pH values and has been detected in almost every species of the animal and plant kingdoms. Among eucaryotic micro- and macro-algae the enzyme is widely distributed and plays an important role in photosynthetic CO2fixation. In some cases, different forms of carbonic anhydrases located extracellularly and intracellularly have been found to occur in the same cell. The expression of the genes encoding these CA isoforms are under the control of the inorganic carbon concentration in the medium, as the activities increase with decreasing the inorganic carbon content. Considerable progress has been made in recent years in isolating and characterizing the various forms of carbonic anhydrases on a biochemical and molecular level. Most of the data have been collected for microalgae likeChlamydomonas reinhardtii(Dangeard), while the situation in macroalgae is still descriptive. Therefore, this review summarizes the recent development with an emphasis on microalgae carbonic anhydrases.Key words: carbonic anhydrase, CO2concentrating mechanism, macroalgae, microalgae, photosynthesis.

ISSN:0008-4026    

DOI:10.1139/b98-082

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Cyanobacteria (blue-green algae) possess an environmental adaptation for survival at low CO2concentrations. The adaptation is known as a CO2concentrating mechanism (CCM), and it functions to actively transport and accumulate inorganic carbon ( and CO2; Ci) within the cell and then uses this Ci pool to provide elevated CO2concentrations around the primary CO2-fixing enzyme, ribulose bisphosphate carboxylase-oxygenase (Rubisco). It appears that the site of CO2elevation is within a unique microcompartment known as the carboxysome, which is a proteinaceous polyhedral body that contains most, if not all, of the Rubisco within the cell. This review covers comparative aspects of physiology, genetics, and proteins involved in the cyanobacterial CCM with particular focus on recent advances. This review highlights information on three strains of unicellular cyanobacteria, namelySynechocystisPCC6803 (freshwater strain; for which a full genome database is now available),SynechococcusPCC7002 (coastal marine strain) andSynechococcusPCC7942 (freshwater strain). Genes that may be involved in the CCM, directly or indirectly, are summarized in tabular form. ForSynechocystisPCC6803, the number of genes related to CCM activity is now in excess of 50; however, 19 of these components have the potential to code for several distinct type-1, NADH dehydrogenase complexes.Key words: cyanobacteria, CO2concentrating mechanism, carboxysomes, genes, photosynthesis, transporters.

ISSN:0008-4026    

DOI:10.1139/b98-081

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Unicellular algae acquire the ability to raise their internal CO2concentrations under low-CO2conditions because of the presence of a CO2concentrating mechanism (CCM). InChlamydomonas reinhardtii, this mechanism is induced when cells grown in high-CO2conditions are switched to low-CO2conditions. To elucidate the genes and proteins involved in this mechanism, we constructed a cDNA library from low CO2adapted cells and differentially screened the library for cDNAs upregulated under low-CO2conditions. Earlier studies identified six classes of clones specific to low CO2adapting cells. To identify other genes and proteins playing a role in this mechanism, we have systematically characterized the cDNA clones that appear to be upregulated by low-CO2adaptation but do not cross-hybridize with the six previously identified classes. We identified seven new classes of clones that are distinctly upregulated in low-CO2conditions. These clones were checked by Northern analyses, sequencing, and homology studies. One class of clone represents a novel gene,lci 3. We report on the seven classes of clones and the characterization oflci 3.Key words:Chlamydomonas, CO2concentrating mechanism, gene regulation, inducible genes, gene expression.

ISSN:0008-4026    

DOI:10.1139/b98-080

出版商:NRC Research Press    

年代:1998

数据来源: NRC