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Bai X, Wang H, Cheng W, Wang J, Ma M, Hu H, Song Z, Ma H, Fan Y, Du C, Xu J. Genomic Analysis of Leptolyngbya boryana CZ1 Reveals Efficient Carbon Fixation Modules. Plants (Basel) 2023; 12:3251. [PMID: 37765415 PMCID: PMC10536570 DOI: 10.3390/plants12183251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/20/2023] [Accepted: 09/11/2023] [Indexed: 09/29/2023]
Abstract
Cyanobacteria, one of the most widespread photoautotrophic microorganisms on Earth, have evolved an inorganic CO2-concentrating mechanism (CCM) to adapt to a variety of habitats, especially in CO2-limited environments. Leptolyngbya boryana, a filamentous cyanobacterium, is widespread in a variety of environments and is well adapted to low-inorganic-carbon environments. However, little is currently known about the CCM of L. boryana, in particular its efficient carbon fixation module. In this study, we isolated and purified the cyanobacterium CZ1 from the Xin'anjiang River basin and identified it as L. boryana by 16S rRNA sequencing. Genome analysis revealed that L. boryana CZ1 contains β-carboxysome shell proteins and form 1B of Rubisco, which is classify it as belonging to the β-cyanobacteria. Further analysis revealed that L. boryana CZ1 employs a fine CCM involving two CO2 uptake systems NDH-13 and NDH-14, three HCO3- transporters (SbtA, BicA, and BCT1), and two carboxysomal carbonic anhydrases. Notably, we found that NDH-13 and NDH-14 are located close to each other in the L. boryana CZ1 genome and are back-to-back with the ccm operon, which is a novel gene arrangement. In addition, L. boryana CZ1 encodes two high-affinity Na+/HCO3- symporters (SbtA1 and SbtA2), three low-affinity Na+-dependent HCO3- transporters (BicA1, BicA2, and BicA3), and a BCT1; it is rare for a single strain to encode all three bicarbonate transporters in such large numbers. Interestingly, L. boryana CZ1 also uniquely encodes two active carbonic anhydrases, CcaA1 and CcaA2, which are also rare. Taken together, all these results indicated that L. boryana CZ1 is more efficient at CO2 fixation. Moreover, compared with the reported CCM gene arrangement of cyanobacteria, the CCM-related gene distribution pattern of L. boryana CZ1 was completely different, indicating a novel gene organization structure. These results can enrich our understanding of the CCM-related gene arrangement of cyanobacteria, and provide data support for the subsequent improvement and increase in biomass through cyanobacterial photosynthesis.
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Affiliation(s)
- Xiaohui Bai
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
| | - Honghui Wang
- Huangshan Institute of Product Quality Inspection, Huangshan 245000, China;
| | - Wenbin Cheng
- School of Life Sciences, University of Science and Technology of China, Hefei 230027, China;
| | - Junjun Wang
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
| | - Mengyang Ma
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
| | - Haihang Hu
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
| | - Zilong Song
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
| | - Hongguang Ma
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
| | - Yan Fan
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
- School of Life Science and Technology, Henan Institute of Science and Technology, Xinxiang 453003, China
| | - Chenyu Du
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
| | - Jingcheng Xu
- College of Life and Environment Science, Huangshan University, Huangshan 245041, China; (J.W.); (M.M.); (H.H.); (Z.S.); (H.M.); (Y.F.); (C.D.)
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Aguiló-Nicolau P, Galmés J, Fais G, Capó-Bauçà S, Cao G, Iñiguez C. Singular adaptations in the carbon assimilation mechanism of the polyextremophile cyanobacterium Chroococcidiopsis thermalis. Photosynth Res 2023; 156:231-245. [PMID: 36941458 PMCID: PMC10154277 DOI: 10.1007/s11120-023-01008-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 02/16/2023] [Indexed: 05/03/2023]
Abstract
Cyanobacteria largely contribute to the biogeochemical carbon cycle fixing ~ 25% of the inorganic carbon on Earth. However, the carbon acquisition and assimilation mechanisms in Cyanobacteria are still underexplored regardless of being of great importance for shedding light on the origins of autotropism on Earth and providing new bioengineering tools for crop yield improvement. Here, we fully characterized these mechanisms from the polyextremophile cyanobacterium Chroococcidiopsis thermalis KOMAREK 1964/111 in comparison with the model cyanobacterial strain, Synechococcus sp. PCC6301. In particular, we analyzed the Rubisco kinetics along with the in vivo photosynthetic CO2 assimilation in response to external dissolved inorganic carbon, the effect of CO2 concentrating mechanism (CCM) inhibitors on net photosynthesis and the anatomical particularities of their carboxysomes when grown under either ambient air (0.04% CO2) or 2.5% CO2-enriched air. Our results show that Rubisco from C. thermalis possess the highest specificity factor and carboxylation efficiency ever reported for Cyanobacteria, which were accompanied by a highly effective CCM, concentrating CO2 around Rubisco more than 140-times the external CO2 levels, when grown under ambient CO2 conditions. Our findings provide new insights into the Rubisco kinetics of Cyanobacteria, suggesting that improved Sc/o values can still be compatible with a fast-catalyzing enzyme. The combination of Rubisco kinetics and CCM effectiveness in C. thermalis relative to other cyanobacterial species might indicate that the co-evolution between Rubisco and CCMs in Cyanobacteria is not as constrained as in other phylogenetic groups.
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Affiliation(s)
- Pere Aguiló-Nicolau
- Research Group on Plant Biology Under Mediterranean Conditions, Universitat de les Illes Balears, INAGEA, Ctra. Valldemossa km. 7.5, 07122, Palma, Balearic Islands, Spain
| | - Jeroni Galmés
- Research Group on Plant Biology Under Mediterranean Conditions, Universitat de les Illes Balears, INAGEA, Ctra. Valldemossa km. 7.5, 07122, Palma, Balearic Islands, Spain.
| | - Giacomo Fais
- Interdepartmental Centre of Environmental Science and Engineering, University of Cagliari, Via San Giorgio 12, 09124, Cagliari, Italy
| | - Sebastià Capó-Bauçà
- Research Group on Plant Biology Under Mediterranean Conditions, Universitat de les Illes Balears, INAGEA, Ctra. Valldemossa km. 7.5, 07122, Palma, Balearic Islands, Spain
| | - Giacomo Cao
- Interdepartmental Centre of Environmental Science and Engineering, University of Cagliari, Via San Giorgio 12, 09124, Cagliari, Italy
- Department of Mechanical, Chemical and Materials Engineering, University of Cagliari, Via Marengo 2, 09123, Cagliari, Italy
| | - Concepción Iñiguez
- Research Group on Plant Biology Under Mediterranean Conditions, Universitat de les Illes Balears, INAGEA, Ctra. Valldemossa km. 7.5, 07122, Palma, Balearic Islands, Spain
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Nawaly H, Matsui H, Tsuji Y, Iwayama K, Ohashi H, Nakajima K, Matsuda Y. Multiple plasma membrane SLC4s contribute to external HCO3- acquisition during CO2 starvation in the marine diatom Phaeodactylum tricornutum. J Exp Bot 2023; 74:296-307. [PMID: 36124754 DOI: 10.1093/jxb/erac380] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 09/16/2022] [Indexed: 06/15/2023]
Abstract
The availability of CO2 is one of the restrictions on aquatic photosynthesis. Solute carrier (SLC) 4-2, a plasma membrane HCO3- transporter has previously been identified in the marine diatom Phaeodactylum tricornutum. In this study, we discovered two paralogs, PtSLC4-1 and PtSLC4-4, that are both localized at the plasma membrane. Their overexpression stimulated HCO3- uptake, and this was inhibited by the anion channel blocker 4,4´-diisothiocyanostilbene-2,2´-disulfonic (DIDS). Similarly to SLC4-2, PtSLC4-1 specifically required Na+ of ~100 mM for its maximum HCO3- transport activity. Unlike PtSLC4-1 and PtSLC4-2, the HCO3- transport of PtSLC4-4 depended equally on Na+, K+, or Li+, suggesting its broad selectivity for cations. Transcript analyses indicated that PtSLC4-1 was the most abundant HCO3- transporter under CO2 concentrations below atmospheric levels, while PtSLC4-4 showed little transcript induction under atmospheric CO2 but transient induction to comparable levels to PtSLC4-1 during the initial acclimation stage from high CO2 (1%) to very low CO2 (<0.002%). Our results strongly suggest a major HCO3- transport role of PtSLC4-1 with a relatively minor role of PtSLC4-2, and that PtSLC4-4 operates under severe CO2 limitation unselectively to cations when the other SLC4s do not function to support HCO3- uptake.
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Affiliation(s)
- Hermanus Nawaly
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Hiroaki Matsui
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Yoshinori Tsuji
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Kazufumi Iwayama
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Hiroki Ohashi
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Kensuke Nakajima
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Yusuke Matsuda
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
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Sun Y, Harman VM, Johnson JR, Brownridge PJ, Chen T, Dykes GF, Lin Y, Beynon RJ, Liu LN. Decoding the Absolute Stoichiometric Composition and Structural Plasticity of α-Carboxysomes. mBio 2022;:e0362921. [PMID: 35343789 DOI: 10.1128/mbio.03629-21] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Carboxysomes are anabolic bacterial microcompartments that play an essential role in carbon fixation in cyanobacteria and some chemoautotrophs. This self-assembling organelle encapsulates the key CO2-fixing enzymes, Rubisco, and carbonic anhydrase using a polyhedral protein shell that is constructed by hundreds of shell protein paralogs. The α-carboxysome from the chemoautotroph Halothiobacillus neapolitanus serves as a model system in fundamental studies and synthetic engineering of carboxysomes. In this study, we adopted a QconCAT-based quantitative mass spectrometry approach to determine the stoichiometric composition of native α-carboxysomes from H. neapolitanus. We further performed an in-depth comparison of the protein stoichiometry of native α-carboxysomes and their recombinant counterparts heterologously generated in Escherichia coli to evaluate the structural variability and remodeling of α-carboxysomes. Our results provide insight into the molecular principles that mediate carboxysome assembly, which may aid in rational design and reprogramming of carboxysomes in new contexts for biotechnological applications. IMPORTANCE A wide range of bacteria use special protein-based organelles, termed bacterial microcompartments, to encase enzymes and reactions to increase the efficiency of biological processes. As a model bacterial microcompartment, the carboxysome contains a protein shell filled with the primary carbon fixation enzyme Rubisco. The self-assembling organelle is generated by hundreds of proteins and plays important roles in converting carbon dioxide to sugar, a process known as carbon fixation. In this study, we uncovered the exact stoichiometry of all building components and the structural plasticity of the functional α-carboxysome, using newly developed quantitative mass spectrometry together with biochemistry, electron microscopy, and enzymatic assay. The study advances our understanding of the architecture and modularity of natural carboxysomes. The knowledge learned from natural carboxysomes will suggest feasible ways to produce functional carboxysomes in other hosts, such as crop plants, with the overwhelming goal of boosting cell metabolism and crop yields.
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Chen T, Fang Y, Jiang Q, Dykes GF, Lin Y, Price GD, Long BM, Liu LN. Incorporation of Functional Rubisco Activases into Engineered Carboxysomes to Enhance Carbon Fixation. ACS Synth Biol 2022; 11:154-161. [PMID: 34664944 PMCID: PMC8787814 DOI: 10.1021/acssynbio.1c00311] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
![]()
The carboxysome is
a versatile paradigm of prokaryotic organelles
and is a proteinaceous self-assembling microcompartment that plays
essential roles in carbon fixation in all cyanobacteria and some chemoautotrophs.
The carboxysome encapsulates
the central CO2-fixing enzyme, ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco), using a polyhedral protein shell
that is selectively permeable to specific metabolites in favor of
Rubisco carboxylation. There is tremendous interest in repurposing
carboxysomes to boost carbon fixation in heterologous organisms. Here,
we develop the design and engineering of α-carboxysomes by coexpressing
the Rubisco activase components CbbQ and CbbO with α-carboxysomes
in Escherichia coli. Our results show
that CbbQ and CbbO could assemble into the reconstituted α-carboxysome
as intrinsic components. Incorporation of both CbbQ and CbbO within
the carboxysome promotes activation of Rubisco and enhances the CO2-fixation activities of recombinant carboxysomes. We also
show that the structural composition of these carboxysomes could be
modified in different expression systems, representing the plasticity
of the carboxysome architecture. In translational terms, our study
informs strategies for engineering and modulating carboxysomes in
diverse biotechnological applications.
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Affiliation(s)
- Taiyu Chen
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, U.K
- National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research, Huazhong Agricultural University, Wuhan 430070, China
| | - Yi Fang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, U.K
| | - Qiuyao Jiang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, U.K
| | - Gregory F. Dykes
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, U.K
| | - Yongjun Lin
- National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research, Huazhong Agricultural University, Wuhan 430070, China
| | - G. Dean Price
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, 134 Linnaeus Way, Acton, Australian Capital Territory 2601, Australia
| | - Benedict M. Long
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, 134 Linnaeus Way, Acton, Australian Capital Territory 2601, Australia
| | - Lu-Ning Liu
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, U.K
- College of Marine Life Sciences, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China
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Malerba ME, Marshall DJ, Palacios MM, Raven JA, Beardall J. Cell size influences inorganic carbon acquisition in artificially selected phytoplankton. New Phytol 2021; 229:2647-2659. [PMID: 33156533 DOI: 10.1111/nph.17068] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 11/02/2020] [Indexed: 06/11/2023]
Abstract
Cell size influences the rate at which phytoplankton assimilate dissolved inorganic carbon (DIC), but it is unclear whether volume-specific carbon uptake should be greater in smaller or larger cells. On the one hand, Fick's Law predicts smaller cells to have a superior diffusive CO2 supply. On the other, larger cells may have greater scope to invest metabolic energy to upregulate active transport per unit area through CO2 -concentrating mechanisms (CCMs). Previous studies have focused on among-species comparisons, which complicates disentangling the role of cell size from other covarying traits. In this study, we investigated the DIC assimilation of the green alga Dunaliella tertiolecta after using artificial selection to evolve a 9.3-fold difference in cell volume. We compared CO2 affinity, external carbonic anhydrase (CAext ), isotopic signatures (δ13 C) and growth among size-selected lineages. Evolving cells to larger sizes led to an upregulation of CCMs that improved the DIC uptake of this species, with higher CO2 affinity, higher CAext and higher δ13 C. Larger cells also achieved faster growth and higher maximum biovolume densities. We showed that evolutionary shifts in cell size can alter the efficiency of DIC uptake systems to influence the fitness of a phytoplankton species.
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Affiliation(s)
- Martino E Malerba
- School of Biological Sciences, Monash University, Clayton, Vic., 3800, Australia
- Centre of Geometric Biology, Monash University, Clayton, Vic., 3800, Australia
| | - Dustin J Marshall
- School of Biological Sciences, Monash University, Clayton, Vic., 3800, Australia
- Centre of Geometric Biology, Monash University, Clayton, Vic., 3800, Australia
| | - Maria M Palacios
- School of Biological Sciences, Monash University, Clayton, Vic., 3800, Australia
- Centre of Geometric Biology, Monash University, Clayton, Vic., 3800, Australia
| | - John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK
- Climate Change Cluster, University of Technology, Sydney, Ultimo, NSW, 2007, Australia
- School of Biological Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA, 2009, Australia
| | - John Beardall
- School of Biological Sciences, Monash University, Clayton, Vic., 3800, Australia
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Jensen EL, Maberly SC, Gontero B. Insights on the Functions and Ecophysiological Relevance of the Diverse Carbonic Anhydrases in Microalgae. Int J Mol Sci 2020; 21:E2922. [PMID: 32331234 PMCID: PMC7215798 DOI: 10.3390/ijms21082922] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 04/19/2020] [Accepted: 04/20/2020] [Indexed: 01/07/2023] Open
Abstract
Carbonic anhydrases (CAs) exist in all kingdoms of life. They are metalloenzymes, often containing zinc, that catalyze the interconversion of bicarbonate and carbon dioxide-a ubiquitous reaction involved in a variety of cellular processes. So far, eight classes of apparently evolutionary unrelated CAs that are present in a large diversity of living organisms have been described. In this review, we focus on the diversity of CAs and their roles in photosynthetic microalgae. We describe their essential role in carbon dioxide-concentrating mechanisms and photosynthesis, their regulation, as well as their less studied roles in non-photosynthetic processes. We also discuss the presence in some microalgae, especially diatoms, of cambialistic CAs (i.e., CAs that can replace Zn by Co, Cd, or Fe) and, more recently, a CA that uses Mn as a metal cofactor, with potential ecological relevance in aquatic environments where trace metal concentrations are low. There has been a recent explosion of knowledge about this well-known enzyme with exciting future opportunities to answer outstanding questions using a range of different approaches.
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Affiliation(s)
- Erik L. Jensen
- Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, FR3479, 31 Chemin J. Aiguier, CEDEX 20, 13 402 Marseille, France;
| | - Stephen C. Maberly
- UK Centre for Ecology & Hydrology, Lake Ecosystems Group, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP, UK;
| | - Brigitte Gontero
- Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, FR3479, 31 Chemin J. Aiguier, CEDEX 20, 13 402 Marseille, France;
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Abstract
Diatoms are a diverse group of unicellular algae that contribute significantly to global photosynthetic carbon fixation and export in the modern ocean, and are an important source of microfossils for paleoclimate reconstructions. Because of their importance in the environment, diatoms have been a focus of study on the physiology and ecophysiology of carbon fixation, in particular their CO2-concentrating mechanisms (CCMs) and Rubisco characteristics. While carbon fixation in diatoms is not as well understood as in certain model aquatic photoautotrophs, a greater number of species have been examined in diatoms. Recent work has highlighted a large diversity in the function, physiology, and kinetics of both the CCM and Rubisco between different diatom species. This diversity was unexpected since it has generally been assumed that CCMs and Rubiscos were similar within major algal lineages as the result of selective events deep in evolutionary history, and suggests a more recent co-evolution between the CCM and Rubisco within diatoms. This review explores our current understanding of the diatom CCM and highlights the diversity of both the CCM and Rubisco kinetics. We will suggest possible environmental, physiological, and evolutionary drivers for the co-evolution of the CCM and Rubisco in diatoms.
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Affiliation(s)
- Jodi N Young
- University of Washington, School of Oceanography, Seattle, WA 98105, USA
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Abstract
CO2-concentrating mechanisms (CCMs), based either on active transport of inorganic carbon (biophysical CCMs) or on biochemistry involving supplementary carbon fixation into C4 acids (C4 and CAM), play a major role in global primary productivity. However, the ubiquitous CO2-fixing enzyme in autotrophs, Rubisco, evolved at a time when atmospheric CO2 levels were very much higher than today and O2 was very low and, as CO2 and O2 approached (by no means monotonically), today's levels, at some time subsequently many organisms evolved a CCM that increased the supply of CO2 and decreased Rubisco oxygenase activity. Given that CO2 levels and other environmental factors have altered considerably between when autotrophs evolved and the present day, and are predicted to continue to change into the future, we here examine the drivers for, and possible timing of, evolution of CCMs. CCMs probably evolved when CO2 fell to 2-16 times the present atmospheric level, depending on Rubisco kinetics. We also assess the effects of other key environmental factors such as temperature and nutrient levels on CCM activity and examine the evidence for evolutionary changes in CCM activity and related cellular processes as well as limitations on continuity of CCMs through environmental variations.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK
- Functional Plant Biology and Climate Change Cluster, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - John Beardall
- School of Biological Sciences, Monash University, Building 18, Clayton Campus, Vic 3800, Australia
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Sandrini G, Cunsolo S, Schuurmans JM, Matthijs HCP, Huisman J. Changes in gene expression, cell physiology and toxicity of the harmful cyanobacterium Microcystis aeruginosa at elevated CO2. Front Microbiol 2015; 6:401. [PMID: 25999931 PMCID: PMC4419860 DOI: 10.3389/fmicb.2015.00401] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 04/17/2015] [Indexed: 12/31/2022] Open
Abstract
Rising CO2 concentrations may have large effects on aquatic microorganisms. In this study, we investigated how elevated pCO2 affects the harmful freshwater cyanobacterium Microcystis aeruginosa. This species is capable of producing dense blooms and hepatotoxins called microcystins. Strain PCC 7806 was cultured in chemostats that were shifted from low to high pCO2 conditions. This resulted in a transition from a C-limited to a light-limited steady state, with a ~2.7-fold increase of the cyanobacterial biomass and ~2.5-fold more microcystin per cell. Cells increased their chlorophyll a and phycocyanin content, and raised their PSI/PSII ratio at high pCO2. Surprisingly, cells had a lower dry weight and contained less carbohydrates, which might be an adaptation to improve the buoyancy of Microcystis when light becomes more limiting at high pCO2. Only 234 of the 4691 genes responded to elevated pCO2. For instance, expression of the carboxysome, RuBisCO, photosystem and C metabolism genes did not change significantly, and only a few N assimilation genes were expressed differently. The lack of large-scale changes in the transcriptome could suit a buoyant species that lives in eutrophic lakes with strong CO2 fluctuations very well. However, we found major responses in inorganic carbon uptake. At low pCO2, cells were mainly dependent on bicarbonate uptake, whereas at high pCO2 gene expression of the bicarbonate uptake systems was down-regulated and cells shifted to CO2 and low-affinity bicarbonate uptake. These results show that the need for high-affinity bicarbonate uptake systems ceases at elevated CO2. Moreover, the combination of an increased cyanobacterial abundance, improved buoyancy, and higher toxin content per cell indicates that rising atmospheric CO2 levels may increase the problems associated with the harmful cyanobacterium Microcystis in eutrophic lakes.
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Affiliation(s)
- Giovanni Sandrini
- Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of AmsterdamAmsterdam, Netherlands
| | - Serena Cunsolo
- Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of AmsterdamAmsterdam, Netherlands
| | - J. Merijn Schuurmans
- Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of AmsterdamAmsterdam, Netherlands
- Department of Aquatic Ecology, Netherlands Institute of EcologyWageningen, Netherlands
| | - Hans C. P. Matthijs
- Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of AmsterdamAmsterdam, Netherlands
| | - Jef Huisman
- Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of AmsterdamAmsterdam, Netherlands
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Abstract
The evolution of autotrophy is considered in relation to the availability of phosphorus (P), the ultimate elemental resource limiting biological productivity through Earth's history. Work on microbes and plants is emphasized, dealing in turn with the main uses for P in cells, namely nucleic acids, phospholipids, and water-soluble low molecular mass phosphate esters plus metabolically active inorganic orthophosphate. There is a greater minimum gene number and minimum DNA content in autotrophic than in osmochemoorganotrophic archaea and bacteria, as well as a lower rate of biomass increase per unit P (P-use efficiency) in autotrophs than in osmochemoorganotrophs, in eukaryotes as well as bacteria. This may be due to the diversion of rRNA from producing proteins common to all organisms to producing highly expressed proteins specific to autotrophs. The P requirement for phospholipids is decreased in oxygenic photolithotrophs, and some anoxygenic photolithotrophs, by substituting galactolipids and sulpholipids for phospholipids in the photosynthetic, and some other, membranes. The six different autotrophic inorganic carbon assimilation pathways have varying requirements for low molecular mass water-soluble phosphate esters. In oxygenic photolithotrophs, there is no clear evidence of a different P requirement for growth in the absence (diffusive CO2 entry) relative to the presence of CO2-concentrating mechanisms (CCMs). P limitation increases the expression of crassulacean acid metabolism (CAM) in facultative CAM plants, decreases the extent of inorganic carbon accumulation in algae with CCMs, and (usually) their inorganic carbon affinity and the water-use efficiency of growth of terrestrial plants, and the light-use efficiency of photolithotrophs.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK
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