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Kang W, Mu L, Hu X. Marine Colloids Boost Nitrogen Fixation in Trichodesmium erythraeum by Photoelectrophy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:9236-9249. [PMID: 38748855 DOI: 10.1021/acs.est.4c01849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Nitrogen fixation by the diazotrophic cyanobacterium Trichodesmium contributes up to 50% of the bioavailable nitrogen in the ocean. N2 fixation by Trichodesmium is limited by the availability of nutrients, such as iron (Fe) and phosphorus (P). Although colloids are ubiquitous in the ocean, the effects of Fe limitation on nitrogen fixation by marine colloids (MC) and the related mechanisms are largely unexplored. In this study, we found that MC exhibit photoelectrochemical properties that boost nitrogen fixation by photoelectrophy in Trichodesmium erythraeum. MC efficiently promote photosynthesis in T. erythraeum, thus enhancing its growth. Photoexcited electrons from MC are directly transferred to the photosynthetic electron transport chain and contribute to nitrogen fixation and ammonia assimilation. Transcriptomic analysis revealed that MC significantly upregulates genes related to the electron transport chain, photosystem, and photosynthesis, which is consistent with elevated photosynthetic capacities (e.g., Fv/Fm and carboxysomes). As a result, MC increase the N2 fixation rate by 67.5-89.3%. Our findings highlight a proof-of-concept electron transfer pathway by which MC boost nitrogen fixation, broadening our knowledge on the role of ubiquitous colloids in marine nitrogen biogeochemistry.
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Affiliation(s)
- Weilu Kang
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Carbon Neutrality Interdisciplinary Science Centre, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Li Mu
- Tianjin Key Laboratory of Agro-Environment and Product Safety, Key Laboratory for Environmental Factors Controlling Agro-Product Quality Safety (Ministry of Agriculture and Rural Affairs), Institute of Agro-Environmental Protection, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China
| | - Xiangang Hu
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Carbon Neutrality Interdisciplinary Science Centre, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
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2
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Qiu GW, Zheng WC, Yang HM, Wang YY, Qi X, Huang D, Dai GZ, Shi H, Price NM, Qiu BS. Phosphorus deficiency alleviates iron limitation in Synechocystis cyanobacteria through direct PhoB-mediated gene regulation. Nat Commun 2024; 15:4426. [PMID: 38789507 PMCID: PMC11126600 DOI: 10.1038/s41467-024-48847-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 05/14/2024] [Indexed: 05/26/2024] Open
Abstract
Iron and phosphorus are essential nutrients that exist at low concentrations in surface waters and may be co-limiting resources for phytoplankton growth. Here, we show that phosphorus deficiency increases the growth of iron-limited cyanobacteria (Synechocystis sp. PCC 6803) through a PhoB-mediated regulatory network. We find that PhoB, in addition to its well-recognized role in controlling phosphate homeostasis, also regulates key metabolic processes crucial for iron-limited cyanobacteria, including ROS detoxification and iron uptake. Transcript abundances of PhoB-targeted genes are enriched in samples from phosphorus-depleted seawater, and a conserved PhoB-binding site is widely present in the promoters of the target genes, suggesting that the PhoB-mediated regulation may be highly conserved. Our findings provide molecular insights into the responses of cyanobacteria to simultaneous iron/phosphorus nutrient limitation.
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Affiliation(s)
- Guo-Wei Qiu
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Wen-Can Zheng
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Hao-Ming Yang
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Yu-Ying Wang
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Xing Qi
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Da Huang
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Guo-Zheng Dai
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Huazhong Shi
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79409, USA
| | - Neil M Price
- Department of Biology, McGill University, 1205 Docteur Penfield, Montreal, Québec, H3A 1B1, Canada
| | - Bao-Sheng Qiu
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China.
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3
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Dai W, Du H, Zhou Q, Li S, Wang Y, Hou J, Guo C, Yang Q, Li C, Xie S, Li SC, Wu R. Metabolic profiles outperform the microbiota in assessing the response of vaginal microenvironments to the changed state of HPV infection. NPJ Biofilms Microbiomes 2024; 10:26. [PMID: 38509123 PMCID: PMC10954630 DOI: 10.1038/s41522-024-00500-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Accepted: 03/11/2024] [Indexed: 03/22/2024] Open
Abstract
There is a deficiency in population-based studies investigating the impact of HPV infection on vaginal microenvironment, which influences the risk of persistent HPV infection. This prospective study aimed to unravel the dynamics of vaginal microbiota (VM) and vaginal metabolome in reaction to the changed state of HPV infection. Our results propose that the vaginal metabolome may be a superior indicator to VM when assessing the impact of altered HPV state on the vaginal microenvironment.
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Affiliation(s)
- Wenkui Dai
- Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China
- Institute of Obstetrics and Gynecology, Shenzhen PKU-HKUST Medical Center, Shenzhen, China
- Shenzhen Key Laboratory on Technology for Early Diagnosis of Major Gynecologic Diseases, Shenzhen, China
| | - Hui Du
- Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China
- Institute of Obstetrics and Gynecology, Shenzhen PKU-HKUST Medical Center, Shenzhen, China
- Shenzhen Key Laboratory on Technology for Early Diagnosis of Major Gynecologic Diseases, Shenzhen, China
| | - Qian Zhou
- Department of Computer Science, City University of Hong Kong, Hong Kong, China
| | - Sumei Li
- Department of Pharmacology, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University, The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, China
| | - Yinan Wang
- Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China
- Institute of Obstetrics and Gynecology, Shenzhen PKU-HKUST Medical Center, Shenzhen, China
- Shenzhen Key Laboratory on Technology for Early Diagnosis of Major Gynecologic Diseases, Shenzhen, China
| | - Jun Hou
- Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China
- Institute of Obstetrics and Gynecology, Shenzhen PKU-HKUST Medical Center, Shenzhen, China
- Shenzhen Key Laboratory on Technology for Early Diagnosis of Major Gynecologic Diseases, Shenzhen, China
| | - Chunlei Guo
- Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China
- Institute of Obstetrics and Gynecology, Shenzhen PKU-HKUST Medical Center, Shenzhen, China
- Shenzhen Key Laboratory on Technology for Early Diagnosis of Major Gynecologic Diseases, Shenzhen, China
| | - Qing Yang
- Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China
- Institute of Obstetrics and Gynecology, Shenzhen PKU-HKUST Medical Center, Shenzhen, China
- Shenzhen Key Laboratory on Technology for Early Diagnosis of Major Gynecologic Diseases, Shenzhen, China
| | - Changzhong Li
- Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China
- Institute of Obstetrics and Gynecology, Shenzhen PKU-HKUST Medical Center, Shenzhen, China
- Shenzhen Key Laboratory on Technology for Early Diagnosis of Major Gynecologic Diseases, Shenzhen, China
| | - Shouxia Xie
- Department of Pharmacology, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University, The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, China
| | - Shuai Cheng Li
- Department of Computer Science, City University of Hong Kong, Hong Kong, China.
| | - Ruifang Wu
- Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China.
- Institute of Obstetrics and Gynecology, Shenzhen PKU-HKUST Medical Center, Shenzhen, China.
- Shenzhen Key Laboratory on Technology for Early Diagnosis of Major Gynecologic Diseases, Shenzhen, China.
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Mao Y, Lin T, Li H, He R, Ye K, Yu W, He Q. Aerobic methane production by phytoplankton as an important methane source of aquatic ecosystems: Reconsidering the global methane budget. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 907:167864. [PMID: 37866611 DOI: 10.1016/j.scitotenv.2023.167864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 10/09/2023] [Accepted: 10/13/2023] [Indexed: 10/24/2023]
Abstract
Biological methane, a major source of global methane budget, is traditionally thought to be produced in anaerobic environments. However, the recent reports about methane supersaturation occurring in oxygenated water layer, termed as "methane paradox", have challenged this prevailing paradigm. Significantly, growing evidence has indicated that phytoplankton including prokaryotic cyanobacteria and eukaryotic algae are capable of generating methane under aerobic conditions. In this regard, a systematic review of aerobic methane production by phytoplankton is expected to arouse the public attention, contributing to the understanding of methane paradox. Here, we comprehensively summarize the widespread phenomena of methane supersaturation in oxic layers. The remarkable correlation relationships between methane concentration and several key indicators (depth, chlorophyll a level and organic sulfide concentration) indicate the significance of phytoplankton in in-situ methane accumulation. Subsequently, four mechanisms of aerobic methane production by phytoplankton are illustrated in detail, including photosynthesis-driven metabolism, reactive oxygen species (ROS)-driven demethylation of methyl donors, methanogenesis catalyzed by nitrogenase and demethylation of phosphonates catalyzed by CP lyase. The first two pathways occur in various phytoplankton, while the latter two have been specially discovered in cyanobacteria. Additionally, the effects of four crucial factors on aerobic methane production by phytoplankton are also discussed, including phytoplankton species, light, temperature and crucial nutrients. Finally, the measures to control global methane emissions from phytoplankton, the precise intracellular mechanisms of methane production and a more complete global methane budget model are definitely required in the future research on methane production by phytoplankton. This review would provide guidance for future studies of aerobic methane production by phytoplankton and emphasize the potential contribution of aquatic ecosystems to global methane budget.
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Affiliation(s)
- Yufeng Mao
- Key Laboratory of Eco-Environment of Three Gorges Region, Ministry of Education, Chongqing University, Chongqing 400044, China; Key Laboratory of Hydraulic and Waterway Engineering, Ministry of Education, Chongqing Jiaotong University, Chongqing 400074, China; Lingzhi Environmental Protection Co., Ltd, Wuxi 214200, China
| | - Tong Lin
- Key Laboratory of Eco-Environment of Three Gorges Region, Ministry of Education, Chongqing University, Chongqing 400044, China
| | - Hong Li
- Key Laboratory of Eco-Environment of Three Gorges Region, Ministry of Education, Chongqing University, Chongqing 400044, China
| | - Ruixu He
- Key Laboratory of Hydraulic and Waterway Engineering, Ministry of Education, Chongqing Jiaotong University, Chongqing 400074, China
| | - Kailai Ye
- Key Laboratory of Hydraulic and Waterway Engineering, Ministry of Education, Chongqing Jiaotong University, Chongqing 400074, China
| | - Weiwei Yu
- Key Laboratory of Hydraulic and Waterway Engineering, Ministry of Education, Chongqing Jiaotong University, Chongqing 400074, China
| | - Qiang He
- Key Laboratory of Eco-Environment of Three Gorges Region, Ministry of Education, Chongqing University, Chongqing 400044, China.
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Colussi A, Bokhari SNH, Mijovilovich A, Koník P, Küpper H. Acclimation to medium-level non-lethal iron limitation: Adjustment of electron flow around the PSII and metalloprotein expression in Trichodesmium erythraeum IMS101. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2024; 1865:149015. [PMID: 37742749 DOI: 10.1016/j.bbabio.2023.149015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 09/15/2023] [Accepted: 09/18/2023] [Indexed: 09/26/2023]
Abstract
The aim of this study was to investigate how acclimation to medium-level, long-term, non-lethal iron limitation changes the electron flux around the Photosystem II of the oceanic diazotroph Trichodesmium erythraeum IMS101. Fe availability of about 5× and 100× lower than a replete level, i.e. conditions common in the natural environment of this cyanobacterium, were applied in chemostats. The response of the cells was studied not only in terms of growth, but also mechanistically, measuring the chlorophyll fluorescence of dark-adapted filaments via imaging fluorescence kinetic microscopy (FKM) with 0.3 ms time resolution. Combining these measurements with those of metal binding to proteins via online coupling of metal-free HPLC (size exclusion chromatography SEC) to sector-field ICP-MS allowed to track the fate of the photosystems, together with other metalloproteins. General increase of fluorescence has been observed, with the consequent decrease in the quantum yields φ of the PSII, while the efficiency ψ of the electron flux between PSII and the PSI remained surprisingly unchanged. This indicates the ability of Trichodesmium to cope with a situation that makes assembling the many iron clusters in Photosystem I a particular challenge, as shown by decreasing ratios of Fe to Mg in these proteins. The negative effect of Fe limitation on PSII may also be due to its fast turnover. A broader view was obtained from metalloproteomics via HPLC-ICP-MS, revealing a differential protein expression pattern under iron limitation with a drastic down-regulation especially of iron-containing proteins and some increase in low MW metal-binding complexes.
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Affiliation(s)
- Antonio Colussi
- Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Laboratory of Plant Biophysics and Biochemistry, České Budějovice, Czech Republic; University of South Bohemia, Faculty of Sciences, Department of Experimental Plant Biology, České Budějovice, Czech Republic
| | - Syed Nadeem Hussain Bokhari
- Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Laboratory of Plant Biophysics and Biochemistry, České Budějovice, Czech Republic
| | - Ana Mijovilovich
- Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Laboratory of Plant Biophysics and Biochemistry, České Budějovice, Czech Republic
| | - Peter Koník
- University of South Bohemia, Faculty of Sciences, Department of Chemistry, České Budějovice, Czech Republic
| | - Hendrik Küpper
- Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Laboratory of Plant Biophysics and Biochemistry, České Budějovice, Czech Republic; University of South Bohemia, Faculty of Sciences, Department of Experimental Plant Biology, České Budějovice, Czech Republic.
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6
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Eichner M, Inomura K, Pierella Karlusich JJ, Shaked Y. Better together? Lessons on sociality from Trichodesmium. Trends Microbiol 2023; 31:1072-1084. [PMID: 37244772 DOI: 10.1016/j.tim.2023.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 04/30/2023] [Accepted: 05/01/2023] [Indexed: 05/29/2023]
Abstract
The N2-fixing cyanobacterium Trichodesmium is an important player in the oceanic nitrogen and carbon cycles. Trichodesmium occurs both as single trichomes and as colonies containing hundreds of trichomes. In this review, we explore the benefits and disadvantages of colony formation, considering physical, chemical, and biological effects from nanometer to kilometer scale. Showing that all major life challenges are affected by colony formation, we claim that Trichodesmium's ecological success is tightly linked to its colonial lifestyle. Microbial interactions in the microbiome, chemical gradients within the colony, interactions with particles, and elevated mobility in the water column shape a highly dynamic microenvironment. We postulate that these dynamics are key to the resilience of Trichodesmium and other colony formers in our changing environment.
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Affiliation(s)
- Meri Eichner
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czech Republic.
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | | | - Yeala Shaked
- Freddy and Nadine Herrmann Institute of Earth Sciences, Hebrew University, Jerusalem, Israel; Interuniversity Institute for Marine Sciences, Eilat, Israel
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7
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Robicheau BM, Tolman J, Desai D, LaRoche J. Microevolutionary patterns in ecotypes of the symbiotic cyanobacterium UCYN-A revealed from a Northwest Atlantic coastal time series. SCIENCE ADVANCES 2023; 9:eadh9768. [PMID: 37774025 PMCID: PMC10541017 DOI: 10.1126/sciadv.adh9768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 08/28/2023] [Indexed: 10/01/2023]
Abstract
UCYN-A is a globally important nitrogen-fixing symbiotic microbe often found in colder regions and coastal areas where nitrogen fixation has been overlooked. We present a 3-year coastal Northwest Atlantic time series of UCYN-A by integrating oceanographic data with weekly nifH and16S rRNA gene sequencing and quantitative PCR assays for UCYN-A ecotypes. High UCYN-A relative abundances dominated by A1 to A4 ecotypes reoccurred annually in the coastal Northwest Atlantic. Although UCYN-A was detected every summer/fall, the ability to observe separate ecotypes may be highly dependent on sampling time given intense interannual and weekly variability of ecotype-specific occurrences. Additionally, much of UCYN-A's rarer diversity was populated by short-lived neutral mutational variants, therefore providing insight into UCYN-A's microevolutionary patterns. For instance, rare ASVs exhibited community composition restructuring annually, while also sharing a common connection to a dominant ASV within each ecotype. Our study provides additional perspectives for interpreting UCYN-A intraspecific diversity and underscores the need for high-resolution datasets when deciphering spatiotemporal ecologies within UCYN-A.
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Affiliation(s)
- Brent M. Robicheau
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jennifer Tolman
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Dhwani Desai
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- Integrated Microbiome Resource, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Julie LaRoche
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
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8
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Santoro M, Hassenrück C, Labrenz M, Hagemann M. Acclimation of Nodularia spumigena CCY9414 to inorganic phosphate limitation - Identification of the P-limitation stimulon via RNA-seq. Front Microbiol 2023; 13:1082763. [PMID: 36687591 PMCID: PMC9846622 DOI: 10.3389/fmicb.2022.1082763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 12/05/2022] [Indexed: 01/06/2023] Open
Abstract
Nodularia spumigena is a toxic, filamentous cyanobacterium capable of fixing atmospheric N2, which is often dominating cyanobacterial bloom events in the Baltic Sea and other brackish water systems worldwide. Increasing phosphate limitation has been considered as one environmental factor promoting cyanobacterial mass developments. In the present study, we analyzed the response of N. spumigena strain CCY9414 toward strong phosphate limitation. Growth of the strain was diminished under P-deplete conditions; however, filaments contained more polyphosphate under P-deplete compared to P-replete conditions. Using RNA-seq, gene expression was compared in N. spumigena CCY9414 after 7 and 14 days in P-deplete and P-replete conditions, respectively. After 7 days, 112 genes were significantly up-regulated in P-deplete filaments, among them was a high proportion of genes encoding proteins related to P-homeostasis such as transport systems for different P species. Many of these genes became also up-regulated after 14 days compared to 7 days in filaments grown under P-replete conditions, which was consistent with the almost complete consumption of dissolved P in these cultures after 14 days. In addition to genes directly related to P starvation, genes encoding proteins for bioactive compound synthesis, gas vesicles formation, or sugar catabolism were stimulated under P-deplete conditions. Collectively, our data describe an experimentally validated P-stimulon in N. spumigena CCY9414 and provide the indication that severe P limitation could indeed support bloom formation by this filamentous strain.
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Affiliation(s)
- Mariano Santoro
- Department of Biological Oceanography, Leibniz Institute for Baltic Sea Research, Warnemünde (IOW), Rostock, Germany,Department of Plant Physiology, Institute for Biosciences, University of Rostock, Rostock, Germany
| | - Christiane Hassenrück
- Department of Biological Oceanography, Leibniz Institute for Baltic Sea Research, Warnemünde (IOW), Rostock, Germany
| | - Matthias Labrenz
- Department of Biological Oceanography, Leibniz Institute for Baltic Sea Research, Warnemünde (IOW), Rostock, Germany
| | - Martin Hagemann
- Department of Plant Physiology, Institute for Biosciences, University of Rostock, Rostock, Germany,*Correspondence: Martin Hagemann,
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Yang N, Lin YA, Merkel CA, DeMers MA, Qu PP, Webb EA, Fu FX, Hutchins DA. Molecular mechanisms underlying iron and phosphorus co-limitation responses in the nitrogen-fixing cyanobacterium Crocosphaera. THE ISME JOURNAL 2022; 16:2702-2711. [PMID: 36008474 PMCID: PMC9666452 DOI: 10.1038/s41396-022-01307-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 08/04/2022] [Accepted: 08/09/2022] [Indexed: 12/15/2022]
Abstract
In the nitrogen-limited subtropical gyres, diazotrophic cyanobacteria, including Crocosphaera, provide an essential ecosystem service by converting dinitrogen (N2) gas into ammonia to support primary production in these oligotrophic regimes. Natural gradients of phosphorus (P) and iron (Fe) availability in the low-latitude oceans constrain the biogeography and activity of diazotrophs with important implications for marine biogeochemical cycling. Much remains unknown regarding Crocosphaera's physiological and molecular responses to multiple nutrient limitations. We cultured C. watsonii under Fe, P, and Fe/P (co)-limiting scenarios to link cellular physiology with diel gene expression and observed unique physiological and transcriptional profiles for each treatment. Counterintuitively, reduced growth and N2 fixation resource use efficiencies (RUEs) for Fe or P under P limitation were alleviated under Fe/P co-limitation. Differential gene expression analyses show that Fe/P co-limited cells employ the same responses as single-nutrient limited cells that reduce cellular nutrient requirements and increase responsiveness to environmental change including smaller cell size, protein turnover (Fe-limited), and upregulation of environmental sense-and-respond systems (P-limited). Combined, these mechanisms enhance growth and RUEs in Fe/P co-limited cells. These findings are important to our understanding of nutrient controls on N2 fixation and the implications for primary productivity and microbial dynamics in a changing ocean.
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Affiliation(s)
- Nina Yang
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Yu-An Lin
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Carlin A Merkel
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Michelle A DeMers
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Ping-Ping Qu
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Eric A Webb
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Fei-Xue Fu
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - David A Hutchins
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
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10
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Wrightson L, Yang N, Mahaffey C, Hutchins DA, Tagliabue A. Integrating the impact of global change on the niche and physiology of marine nitrogen-fixing cyanobacteria. GLOBAL CHANGE BIOLOGY 2022; 28:7078-7093. [PMID: 36054414 PMCID: PMC9826025 DOI: 10.1111/gcb.16399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 08/05/2022] [Accepted: 08/10/2022] [Indexed: 06/15/2023]
Abstract
Marine nitrogen fixation is a major source of new nitrogen to the ocean, which interacts with climate driven changes to physical nutrient supply to regulate the response of ocean primary production in the oligotrophic tropical ocean. Warming and changes in nutrient supply may alter the ecological niche of nitrogen-fixing organisms, or 'diazotrophs', however, impacts of warming on diazotroph physiology may also be important. Lab-based studies reveal that warming increases the nitrogen fixation-specific elemental use efficiency (EUE) of two prevalent marine diazotrophs, Crocosphaera and Trichodesmium, thus reducing their requirements for the limiting nutrients iron and phosphorus. Here, we coupled a new diazotroph model based upon observed diazotroph energetics of growth and resource limitation to a state-of-the-art global model of phytoplankton physiology and ocean biogeochemistry. Our model is able to address the integrated response of nitrogen fixation by Trichodesmium and Crocosphaera to warming under the IPCC high emission RCP8.5 scenario for the first time. Our results project a global decline in nitrogen fixation over the coming century. However, the regional response of nitrogen fixation to climate change is modulated by the diazotroph-specific thermal performance curves and EUE, particularly in the Pacific Ocean, which shapes global trends. Spatially, the response of both diazotrophs is similar with expansion towards higher latitudes and reduced rates of nitrogen fixation in the lower latitudes. Overall, 95%-97% of the nitrogen fixation climate signal can be attributed to the combined effect of temperature on the niche and physiology of marine diazotrophs, with decreases being associated with a reduced niche and increases resulting due to a combination of expanding niche and temperature driven changes to EUE. Climate change impacts on both the niche and physiology of marine diazotrophs interact to shape patterns of marine nitrogen fixation, which will have important implications for ocean productivity in the future.
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Affiliation(s)
- Lewis Wrightson
- Department of Earth, Ocean and Ecological SciencesUniversity of LiverpoolLiverpoolUK
| | - Nina Yang
- Department of Biological SciencesUniversity of Southern CaliforniaLos AngelesCaliforniaUSA
| | - Claire Mahaffey
- Department of Earth, Ocean and Ecological SciencesUniversity of LiverpoolLiverpoolUK
| | - David A. Hutchins
- Department of Biological SciencesUniversity of Southern CaliforniaLos AngelesCaliforniaUSA
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11
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Abstract
The dominant marine filamentous N2 fixer, Trichodesmium, conducts photosynthesis and N2 fixation during the daytime. Because N2 fixation is sensitive to O2, some previous studies suggested that spatial segregation of N2 fixation and photosynthesis is essential in Trichodesmium. However, this hypothesis conflicts with some observations where all the cells contain both photosystems and the N2-fixing enzyme nitrogenase. Here, we construct a systematic model simulating Trichodesmium metabolism, showing that the hypothetical spatial segregation is probably useless in increasing the Trichodesmium growth and N2 fixation, unless substances can efficiently transfer among cells with low loss to the environment. The model suggests that Trichodesmium accumulates fixed carbon in the morning and uses that in respiratory protection to reduce intracellular O2 during the mid-daytime, when photosynthesis is downregulated, allowing the occurrence of N2 fixation. A cell membrane barrier against O2 and alternative non-O2 evolving electron transfer also contribute to maintaining low intracellular O2. Our study provides a mechanism enabling N2 fixation despite the presence of photosynthesis across Trichodesmium. IMPORTANCE The filamentous Trichodesmium is a globally prominent marine nitrogen fixer. A long-standing paradox is that the nitrogen-fixing enzyme nitrogenase is sensitive to oxygen, but Trichodesmium conducts both nitrogen fixation and oxygen-evolving photosynthesis during the daytime. Previous studies using immunoassays reported that nitrogenase was limited in some specialized Trichodesmium cells (termed diazocytes), suggesting the necessity of spatial segregation of nitrogen fixation and photosynthesis. However, attempts using other methods failed to find diazocytes in Trichodesmium, causing controversy on the existence of the spatial segregation. Here, our physiological model shows that Trichodesmium can maintain low intracellular O2 in mid-daytime and achieve feasible nitrogen fixation and growth rates even without the spatial segregation, while the hypothetical spatial segregation might not be useful if substantial loss of substances to the environment occurs when they transfer among the Trichodesmium cells. Our study then suggests a possible mechanism by which Trichodesmium can survive without the spatial segregation.
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The marine nitrogen cycle: new developments and global change. Nat Rev Microbiol 2022; 20:401-414. [PMID: 35132241 DOI: 10.1038/s41579-022-00687-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2022] [Indexed: 12/25/2022]
Abstract
The ocean is home to a diverse and metabolically versatile microbial community that performs the complex biochemical transformations that drive the nitrogen cycle, including nitrogen fixation, assimilation, nitrification and nitrogen loss processes. In this Review, we discuss the wealth of new ocean nitrogen cycle research in disciplines from metaproteomics to global biogeochemical modelling and in environments from productive estuaries to the abyssal deep sea. Influential recent discoveries include new microbial functional groups, novel metabolic pathways, original conceptual perspectives and ground-breaking analytical capabilities. These emerging research directions are already contributing to urgent efforts to address the primary challenge facing marine microbiologists today: the unprecedented onslaught of anthropogenic environmental change on marine ecosystems. Ocean warming, acidification, nutrient enrichment and seawater stratification have major effects on the microbial nitrogen cycle, but widespread ocean deoxygenation is perhaps the most consequential for the microorganisms involved in both aerobic and anaerobic nitrogen transformation pathways. In turn, these changes feed back to the global cycles of greenhouse gases such as carbon dioxide and nitrous oxide. At a time when our species casts a lengthening shadow across all marine ecosystems, timely new advances offer us unique opportunities to understand and better predict human impacts on nitrogen biogeochemistry in the changing ocean of the Anthropocene.
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