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Schoffman H, Keren N. Function of the IsiA pigment-protein complex in vivo. PHOTOSYNTHESIS RESEARCH 2019; 141:343-353. [PMID: 30929163 DOI: 10.1007/s11120-019-00638-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 03/18/2019] [Indexed: 06/09/2023]
Abstract
The acclimation of cyanobacterial photosynthetic apparatus to iron deficiency is crucial for their performance under limiting conditions. In many cyanobacterial species, one of the major responses to iron deficiency is the induction of isiA. The function of the IsiA pigment-protein complex has been the subject of intensive research. In this study of the model Synechocystis sp. PCC 6803 strain, we probe the accumulation of the pigment-protein complex and its effects on in vivo photosynthetic performance. We provide evidence that in this organism the dominant factor controlling IsiA accumulation is the intracellular iron concentration and not photo-oxidative stress or redox poise. These findings support the use of IsiA as a tool for assessing iron bioavailability in environmental studies. We also present evidence demonstrating that the IsiA pigment-protein complex exerts only small effects on the performance of the reaction centers. We propose that its major function is as a storage depot able to hold up to 50% of the cellular chlorophyll content during transition into iron limitation. During recovery from iron limitation, chlorophyll is released from the complex and used for the reconstruction of photosystems. Therefore, the IsiA pigment-protein complex can play a critical role not only when cells transition into iron limitation, but also in supporting efficient recovery of the photosynthetic apparatus in the transition back out of the iron-limited state.
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Affiliation(s)
- Hanan Schoffman
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, Israel
| | - Nir Keren
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, Israel.
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2
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Li Q, Huisman J, Bibby TS, Jiao N. Biogeography of Cyanobacterial isiA Genes and Their Link to Iron Availability in the Ocean. Front Microbiol 2019; 10:650. [PMID: 31024472 PMCID: PMC6460047 DOI: 10.3389/fmicb.2019.00650] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 03/14/2019] [Indexed: 11/15/2022] Open
Abstract
The cyanobacterial iron-stress-inducible isiA gene encodes a chlorophyll-binding protein that provides flexibility in photosynthetic strategy enabling cells to acclimate to low iron availability. Here, we report on the diversity and abundance of isiA genes from 14 oceanic stations encompassing large natural gradients in iron availability. Synechococcus CRD1 and CRD2-like isiA genes were ubiquitously identified from tropical and subtropical waters of the Pacific, Atlantic, and Indian Oceans. The relative abundance of isiA-containing Synechococcus cells ranged from less than 10% of the total Synechococcus population in regions where iron is replete such as the North Atlantic subtropical gyre, to over 80% in low-iron but high-nitrate regions of the eastern equatorial Pacific. Interestingly, Synechococcus populations in regions with both low iron and low nitrate concentrations such as the subtropical gyres in the North Pacific and South Atlantic had a low relative abundance of the isiA gene. Indeed, fitting our data into a multiple regression model showed that ∼80% of the variation in isiA relative abundances can be explained by nitrate and iron concentrations, whereas no other environmental variables (temperature, salinity, Chl a) had a significant effect. Hence, isiA has a predictable biogeographical distribution, consistent with the perceived biological role of IsiA as an adaptation to low-iron conditions. Understanding such photosynthetic strategies is critical to our ability to accurately estimate primary production and map nutrient limitation on global scales.
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Affiliation(s)
- Qian Li
- State Key Laboratory of Marine Environmental Sciences, Institute of Marine Microbes and Ecosphere, College of Ocean and Earth Sciences, Xiamen University, Xiamen, China
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands
- Center for Microbial Oceanography: Research and Education, Department of Oceanography, University of Hawai’i at Mānoa, Honolulu, HI, United States
| | - Jef Huisman
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands
| | - Thomas S. Bibby
- School of Ocean and Earth Science, National Oceanography Centre Southampton, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, United Kingdom
| | - Nianzhi Jiao
- State Key Laboratory of Marine Environmental Sciences, Institute of Marine Microbes and Ecosphere, College of Ocean and Earth Sciences, Xiamen University, Xiamen, China
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3
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González A, Sevilla E, Bes MT, Peleato ML, Fillat MF. Pivotal Role of Iron in the Regulation of Cyanobacterial Electron Transport. Adv Microb Physiol 2016; 68:169-217. [PMID: 27134024 DOI: 10.1016/bs.ampbs.2016.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron-containing metalloproteins are the main cornerstones for efficient electron transport in biological systems. The abundance and diversity of iron-dependent proteins in cyanobacteria makes those organisms highly dependent of this micronutrient. To cope with iron imbalance, cyanobacteria have developed a survey of adaptation strategies that are strongly related to the regulation of photosynthesis, nitrogen metabolism and other central electron transfer pathways. Furthermore, either in its ferrous form or as a component of the haem group, iron plays a crucial role as regulatory signalling molecule that directly or indirectly modulates the composition and efficiency of cyanobacterial redox reactions. We present here the major mechanism used by cyanobacteria to couple iron homeostasis to the regulation of electron transport, making special emphasis in processes specific in those organisms.
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Affiliation(s)
| | - E Sevilla
- University of Zaragoza, Zaragoza, Spain
| | - M T Bes
- University of Zaragoza, Zaragoza, Spain
| | | | - M F Fillat
- University of Zaragoza, Zaragoza, Spain.
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4
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Ismaiel MMS, El-Ayouty YM, Piercey-Normore MD. Antioxidants characterization in selected cyanobacteria. ANN MICROBIOL 2013. [DOI: 10.1007/s13213-013-0763-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Behrenfeld MJ, Milligan AJ. Photophysiological expressions of iron stress in phytoplankton. ANNUAL REVIEW OF MARINE SCIENCE 2013; 5:217-46. [PMID: 22881354 DOI: 10.1146/annurev-marine-121211-172356] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Iron is essential for all life, but it is particularly important to photoautotrophs because of the many iron-dependent electron transport components in photosynthetic membranes. Since the proliferation of oxygenic photosynthesis in the Archean ocean, iron has been a scarce commodity, and it is now recognized as a limiting resource for phytoplankton over broad expanses of the open ocean and even in some coastal/continental shelf waters. Iron stress does not impair photochemical or carbon fixation efficiencies, and in this respect it resembles the highly tuned photosynthetic systems of steady-state macronutrient-limited phytoplankton. However, iron stress does present unique photophysiological challenges, and phytoplankton have responded to these challenges through major architectural changes in photosynthetic membranes. These evolved responses include overexpression of photosynthetic pigments and iron-economic pathways for ATP synthesis, and they result in diagnostic fluorescence properties that allow a broad appraisal of iron stress in the field and even the detection of iron stress from space.
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Affiliation(s)
- Michael J Behrenfeld
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331-2902, USA.
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Bullerjahn GS, Boyanapalli R, Rozmarynowycz MJ, McKay RML. Cyanobacterial bioreporters as sensors of nutrient availability. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2010; 118:165-188. [PMID: 20091289 DOI: 10.1007/10_2009_23] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Due to their ubiquity in aquatic environments and their contribution to total biomass, especially in oligotrophic systems, cyanobacteria can be viewed as a proxy for primary productivity in both marine and fresh waters. In this chapter we describe the development and use of picocyanobacterial bioreporters to measure the bioavailability of nutrients that may constrain total photosynthesis in both lacustrine and marine systems. Issues pertaining to bioreporter construction, performance and field applications are discussed. Specifically, luminescent Synechococcus spp. and Synechocystis spp. bioreporters are described that allow the bioavailability of phosphorus, nitrogen and iron to be accurately measured in environmental samples.
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Affiliation(s)
- George S Bullerjahn
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, 43403, USA
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8
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Bibby TS, Zhang Y, Chen M. Biogeography of photosynthetic light-harvesting genes in marine phytoplankton. PLoS One 2009; 4:e4601. [PMID: 19240807 PMCID: PMC2644788 DOI: 10.1371/journal.pone.0004601] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Accepted: 01/03/2009] [Indexed: 01/05/2023] Open
Abstract
Background Photosynthetic light-harvesting proteins are the mechanism by which energy enters the marine ecosystem. The dominant prokaryotic photoautotrophs are the cyanobacterial genera Prochlorococcus and Synechococcus that are defined by two distinct light-harvesting systems, chlorophyll-bound protein complexes or phycobilin-bound protein complexes, respectively. Here, we use the Global Ocean Sampling (GOS) Project as a unique and powerful tool to analyze the environmental diversity of photosynthetic light-harvesting genes in relation to available metadata including geographical location and physical and chemical environmental parameters. Methods All light-harvesting gene fragments and their metadata were obtained from the GOS database, aligned using ClustalX and classified phylogenetically. Each sequence has a name indicative of its geographic location; subsequent biogeographical analysis was performed by correlating light-harvesting gene budgets for each GOS station with surface chlorophyll concentration. Conclusion/Significance Using the GOS data, we have mapped the biogeography of light-harvesting genes in marine cyanobacteria on ocean-basin scales and show that an environmental gradient exists in which chlorophyll concentration is correlated to diversity of light-harvesting systems. Three functionally distinct types of light-harvesting genes are defined: (1) the phycobilisome (PBS) genes of Synechococcus; (2) the pcb genes of Prochlorococcus; and (3) the iron-stress-induced (isiA) genes present in some marine Synechococcus. At low chlorophyll concentrations, where nutrients are limited, the Pcb-type light-harvesting system shows greater genetic diversity; whereas at high chlorophyll concentrations, where nutrients are abundant, the PBS-type light-harvesting system shows higher genetic diversity. We interpret this as an environmental selection of specific photosynthetic strategy. Importantly, the unique light-harvesting system isiA is found in the iron-limited, high-nutrient low-chlorophyll region of the equatorial Pacific. This observation demonstrates the ecological importance of isiA genes in enabling marine Synechococcus to acclimate to iron limitation and suggests that the presence of this gene can be a natural biomarker for iron limitation in oceanic environments.
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Affiliation(s)
- Thomas S. Bibby
- School of Ocean and Earth Sciences, National Oceanography Centre, Southampton, United Kingdom
- School of Biological Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Yinan Zhang
- School of Biological Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Min Chen
- School of Biological Sciences, University of Sydney, Sydney, New South Wales, Australia
- * E-mail:
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Foster JS, Green SJ, Ahrendt SR, Golubic S, Reid RP, Hetherington KL, Bebout L. Molecular and morphological characterization of cyanobacterial diversity in the stromatolites of Highborne Cay, Bahamas. ISME JOURNAL 2009; 3:573-87. [DOI: 10.1038/ismej.2008.129] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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10
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Dufresne A, Ostrowski M, Scanlan DJ, Garczarek L, Mazard S, Palenik BP, Paulsen IT, de Marsac NT, Wincker P, Dossat C, Ferriera S, Johnson J, Post AF, Hess WR, Partensky F. Unraveling the genomic mosaic of a ubiquitous genus of marine cyanobacteria. Genome Biol 2008; 9:R90. [PMID: 18507822 PMCID: PMC2441476 DOI: 10.1186/gb-2008-9-5-r90] [Citation(s) in RCA: 214] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Revised: 05/17/2008] [Accepted: 05/28/2008] [Indexed: 12/20/2022] Open
Abstract
Local niche occupancy of marine Synechococcus lineages is facilitated by lateral gene transfers. Genomic islands act as repositories for these transferred genes. Background The picocyanobacterial genus Synechococcus occurs over wide oceanic expanses, having colonized most available niches in the photic zone. Large scale distribution patterns of the different Synechococcus clades (based on 16S rRNA gene markers) suggest the occurrence of two major lifestyles ('opportunists'/'specialists'), corresponding to two distinct broad habitats ('coastal'/'open ocean'). Yet, the genetic basis of niche partitioning is still poorly understood in this ecologically important group. Results Here, we compare the genomes of 11 marine Synechococcus isolates, representing 10 distinct lineages. Phylogenies inferred from the core genome allowed us to refine the taxonomic relationships between clades by revealing a clear dichotomy within the main subcluster, reminiscent of the two aforementioned lifestyles. Genome size is strongly correlated with the cumulative lengths of hypervariable regions (or 'islands'). One of these, encompassing most genes encoding the light-harvesting phycobilisome rod complexes, is involved in adaptation to changes in light quality and has clearly been transferred between members of different Synechococcus lineages. Furthermore, we observed that two strains (RS9917 and WH5701) that have similar pigmentation and physiology have an unusually high number of genes in common, given their phylogenetic distance. Conclusion We propose that while members of a given marine Synechococcus lineage may have the same broad geographical distribution, local niche occupancy is facilitated by lateral gene transfers, a process in which genomic islands play a key role as a repository for transferred genes. Our work also highlights the need for developing picocyanobacterial systematics based on genome-derived parameters combined with ecological and physiological data.
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Affiliation(s)
- Alexis Dufresne
- Université Paris 6 and CNRS, UMR 7144, Station Biologique, 29682 Roscoff, France.
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11
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Singh AK, Sherman LA. Reflections on the function of IsiA, a cyanobacterial stress-inducible, Chl-binding protein. PHOTOSYNTHESIS RESEARCH 2007; 93:17-25. [PMID: 17375369 DOI: 10.1007/s11120-007-9151-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Accepted: 02/19/2007] [Indexed: 05/14/2023]
Abstract
The isiA gene encodes a protein that is similar to the Photosystem II chlorophyll-binding protein CP43, but lacks the entire large lumenal loop of over 100 amino acids. What is the function of this IsiA protein? Research on IsiA has traveled a long and interesting path since it was first discovered by its large accumulation during growth under iron-limited conditions. What appeared to be a simple on-off switch for isiA based on iron concentration has developed into a much richer and more intriguing set of possibilities that involve its expression and function. We provide an overview of isiA transcriptional regulation by many environmental factors and its proposed functions. We also describe the response to oxidative stress by cells that lack the IsiA protein. It is now clear that isiA expression can be de-repressed in the presence of normal iron levels and that the regulatory mechanisms can be linked to the inter-relationship between iron homeostasis and oxidative stress. The de facto transcriptional control of isiA expression has expanded to include regulation at both the transcriptional and post-transcriptional levels.
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Affiliation(s)
- Abhay K Singh
- Department of Biological Sciences, Purdue University, Hansen Hall, West Lafayette, IN 47907, USA
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12
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Cheng Y, Li JH, Shi L, Wang L, Latifi A, Zhang CC. A pair of iron-responsive genes encoding protein kinases with a Ser/Thr kinase domain and a His kinase domain are regulated by NtcA in the Cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2006; 188:4822-9. [PMID: 16788191 PMCID: PMC1482992 DOI: 10.1128/jb.00258-06] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The filamentous cyanobacterium Anabaena sp. strain PCC 7120 can fix N(2) when combined nitrogen is not available in the growth medium. It has a family of 13 genes encoding proteins with both a Ser/Thr kinase domain and a His kinase domain. The function of these enzymes is unknown. Two of them are encoded by pkn41 (alr0709) and pkn42 (alr0710). These two genes are separated by only 72 bp on the chromosome, and our results indicate that they are cotranscribed. The expression of pkn41 and pkn42 is induced by iron deprivation irrespective of the nature of the nitrogen source. Mutants inactivating either pkn41, pkn42, or both grow similarly to the wild type under normal conditions, but their growth is impaired either in the presence of an iron chelator or under conditions of nitrogen fixation and iron limitation, two situations where the demand for iron is particularly strong. Consistent with these results, these mutants display lower iron content than the wild type and a higher level of expression for nifJ1 and nifJ2, which encode pyruvate:ferredoxin oxidoreductases. Both nifJ1 and nifJ2 are known to be induced by iron limitation. NtcA, a global regulatory factor for different metabolic pathways, binds to the putative promoter region of pkn41, and the induction of pkn41 in response to iron limitation no longer occurs in an ntcA mutant. Our results suggest that ntcA not only regulates the expression of genes involved in nitrogen and carbon metabolism but also coordinates iron acquisition and nitrogen metabolism by activating the expression of pkn41 and pkn42.
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Affiliation(s)
- Yong Cheng
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, People's Republic of China
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Nosenko T, Lidie KL, Van Dolah FM, Lindquist E, Cheng JF, Bhattacharya D. Chimeric Plastid Proteome in the Florida “Red Tide” Dinoflagellate Karenia brevis. Mol Biol Evol 2006; 23:2026-38. [PMID: 16877498 DOI: 10.1093/molbev/msl074] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Current understanding of the plastid proteome comes almost exclusively from studies of plants and red algae. The proteome in these taxa has a relatively simple origin via integration of proteins from a single cyanobacterial primary endosymbiont and the host. However, the most successful algae in marine environments are the chlorophyll c-containing chromalveolates such as diatoms and dinoflagellates that contain a plastid of red algal origin derived via secondary or tertiary endosymbiosis. Virtually nothing is known about the plastid proteome in these taxa. We analyzed expressed sequence tag data from the toxic "Florida red tide" dinoflagellate Karenia brevis that has undergone a tertiary plastid endosymbiosis. Comparative analyses identified 30 nuclear-encoded plastid-targeted proteins in this chromalveolate that originated via endosymbiotic or horizontal gene transfer (HGT) from multiple different sources. We identify a fundamental divide between plant/red algal and chromalveolate plastid proteomes that reflects a history of mixotrophy in the latter group resulting in a highly chimeric proteome. Loss of phagocytosis in the "red" and "green" clades effectively froze their proteomes, whereas chromalveolate lineages retain the ability to engulf prey allowing them to continually recruit new, potentially adaptive genes through subsequent endosymbioses and HGT. One of these genes is an electron transfer protein (plastocyanin) of green algal origin in K. brevis that likely allows this species to thrive under conditions of iron depletion.
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Affiliation(s)
- Tetyana Nosenko
- The Roy J. Carver Center for Comparative Genomics, Department of Biological Sciences, University of Iowa, IA, USA
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Geiss U, Selig U, Schumann R, Steinbruch R, Bastrop R, Hagemann M, Schoor A. Investigations on cyanobacterial diversity in a shallow estuary (Southern Baltic Sea) including genes relevant to salinity resistance and iron starvation acclimation. Environ Microbiol 2004; 6:377-87. [PMID: 15008815 DOI: 10.1111/j.1462-2920.2004.00569.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cyanobacterial diversity in the pelagic of a shallow estuary at the Southern Baltic Sea has been investigated by a combination of classical morphological data and a polymerase chain reaction (PCR)-based molecular approach. The aim of the study was to investigate possible changes in the composition of the cyanobacterial community along the salinity and nutrient gradients. For this purpose partial gene sequences of cyanobacterial 16S rDNA and of two functional genes (ggpS- salinity tolerance marker, isiA- iron starvation marker) were amplified and compared with total community DNA. Random distribution of ggpS genotypes along the salinity gradient suggests that synthesis of the osmolyte glucosylglycerol is not restricted to higher salinity sampling sites. Most of the isiA sequences formed a new homogenous cluster in a phylogenetic tree, which indicates that the indigenous cyanobacterial community comprises a group of unknown species. Minimum iron concentrations, which can activate isiA transcription in model cyanobacteria, occurred at a few sampling sites with high phytoplankton biomass and moderate salinity. Nevertheless, isiA expression could be detected at all sampling sites, which indicated restricted iron supply to cyanobacterial phytoplankton in summer.
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Affiliation(s)
- Ulrike Geiss
- University of Rostock, Department Biological Sciences, Aquatic Ecology, Albert-Einstein-Str. 3a, D-18051 Rostock, Germany.
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15
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Geiss U, Bergmann I, Blank M, Schumann R, Hagemann M, Schoor A. Detection of Prochlorothrix in brackish waters by specific amplification of pcb genes. Appl Environ Microbiol 2004; 69:6243-9. [PMID: 14532086 PMCID: PMC201227 DOI: 10.1128/aem.69.10.6243-6249.2003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prochlorothrix hollandica is the only filamentous chlorophyll b (Chlb)-containing oxyphotobacterium that has been found in freshwater habitats to date. Chlb serves as a light-harvesting pigment which is bound to special binding proteins (Pcb). Even though Prochlorothrix was initially characterized as a highly salt-sensitive species, we detected it in a brackish water environment that is characterized by salinities of up to 12 practical salinity units. Using PCR and reverse transcription, we amplified pcb gene fragments of phytoplankton samples taken along a salinity gradient in the eutrophic Darss-Zingst estuary (southern Baltic Sea). After sequencing, high levels of homology to the pcbB and pcbC genes of P. hollandica were found. Furthermore, autofluorescence of Prochlorothrix-like filaments that indicated that Chlb was present was detected in enrichment cultures prepared from the estuarine phytoplankton. The detection of Chlb-containing filaments, as well as the pcb and 16S ribosomal DNA sequences, suggests that Prochlorothrix is an indigenous genus in the Darss-Zingst estuary and may also inhabit many other brackish water environments. The potential of using pcb gene detection to differentiate Prochlorothrix from morphologically indistinguishable species belonging to the genera Pseudanabaena and Planktothrix (Oscillatoria) in phytoplankton analyses is discussed.
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Affiliation(s)
- Ulrike Geiss
- Department of Aquatic Ecology, Institute of Biodiversity Research, Fachbereich Biowissenschaften, Universität Rostock, D-18051 Rostock, Germany.
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Michel KP, Pistorius EK. Adaptation of the photosynthetic electron transport chain in cyanobacteria to iron deficiency: The function of IdiA and IsiA. PHYSIOLOGIA PLANTARUM 2004; 120:36-50. [PMID: 15032875 DOI: 10.1111/j.0031-9317.2004.0229.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In this review we give an overview on the adaptational responses of photosystem (PS) II and PSI in cyanobacteria to iron starvation, mainly summarizing our results with the mesophilic Synechococcus elongatus PCC 7942. We also discuss this process with respect to the strong interrelationship between iron limitation and oxidative stress that exists in cyanobacteria as oxygenic photosynthetic organisms. The adaptation of the multiprotein complexes PSII and PSI to iron starvation is a sequential process, which is characterized by the enhanced expression of two major iron-regulated proteins, IdiA (iron deficiency induced protein A) and IsiA (iron stress induced protein A). Our results suggest that IdiA protects the acceptor side of PSII against oxidative stress under conditions of mild iron limitation in a currently unclear way, whereas prolonged iron deficiency leads to the synthesis of a chlorophyll a antenna around PSI-trimers consisting of IsiA molecules. The physiological consequences of these alterations under prolonged iron starvation, as shown by acridine yellow fluorescence measurements, are a reduction of linear electron transport activity through PSII and an increase of cyclic electron flow around PSI as well as an increase in respiratory activity. IdiA and IsiA expression are mediated by two distinct helix-turn-helix transcriptional regulators of the Crp/Fnr family. IdiB positively regulates expression of idiA under iron starvation, and Fur represses transcription of isiA under iron-sufficient conditions. Although both transcriptional regulators seem to operate independently of each other, our results indicate that a cross-talk between the signal transduction pathways exists. Moreover, IdiA as well as IsiA expression are affected by hydrogen peroxide. We suggest that due to the interdependence of iron limitation and the formation of reactive oxygen species, peroxide stress might be the superior trigger that leads to expression of these proteins under iron starvation. The modifications of PSII and PSI under iron starvation influence the redox state of redox-sensitive components of the electron transport chain, and thus the activity of metabolic pathways being regulated in dependence of the redox state of these components.
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Affiliation(s)
- Klaus-Peter Michel
- Biologie VIII: Molekulare Zellphysiologie, Universität Bielefeld, D-33501 Bielefeld, Germany
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Kunert A, Vinnemeier J, Erdmann N, Hagemann M. Repression by Fur is not the main mechanism controlling the iron-inducibleisiABoperon in the cyanobacteriumSynechocystissp. PCC 6803. FEMS Microbiol Lett 2003; 227:255-62. [PMID: 14592717 DOI: 10.1016/s0378-1097(03)00689-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The iron deficiency-dependent regulation of isiAB transcription in Synechocystis sp. PCC 6803 was analyzed by fusion of modified isiAB promoter fragments to gfp and in vivo quantification of Gfp fluorescence. For the putative Fur box only a slight repressing impact on promoter activity could be shown. In a heteroallelic fur mutant a corresponding incomplete repression of isiAB transcription under iron-replete conditions confirmed the role of Fur in isiAB regulation. However, a 90 bp region upstream of the putative -35 box of the isiAB promoter was essential for full promoter activity under iron-deplete conditions. This pattern indicates a dual promoter regulation by both a repressing mechanism exhibited via the Fur system and an unknown activating mechanism.
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Affiliation(s)
- Anja Kunert
- Fachbereich Biowissenschaften, Universität Rostock, Einsteinstr. 3a, D-18051, Rostock, Germany
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Xu WL, Jeanjean R, Liu YD, Zhang CC. pkn22(alr2502) encoding a putative Ser/Thr kinase in the cyanobacteriumAnabaenasp. PCC 7120 is induced by both iron starvation and oxidative stress and regulates the expression ofisiA. FEBS Lett 2003; 553:179-82. [PMID: 14550569 DOI: 10.1016/s0014-5793(03)01019-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In cyanobacteria, the isiA gene is required for cell adaptation to oxidative damage caused by the absence of iron. We show here that a putative Ser/Thr kinase gene, pkn22 (alr2052), is activated by iron deficiency and oxidative damage in Anabaena sp. PCC 7120. A pkn22 insertion mutant is unable to grow when iron is limiting. pkn22 regulates the expression of isiA (encoding CP43'), but not of isiB (encoding flavodoxin) and psbC (CP43). Fluorescence measurement at 77 K reveals the absence of the typical signature of CP43' associated with photosystem I in the mutant under iron-limiting conditions. We propose that Pkn22 is required for the function of isiA/CP43' and constitutes a regulatory element necessary for stress response.
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Affiliation(s)
- Wen-Liang Xu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, PR China
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Abstract
During the twenty years or so since the discovery of tiny photosynthetic cells of the genus Synechococcus in marine oceanic systems, a tremendous expansion of interest has been seen in the literature pertaining to these organisms. The fact that they are ubiquitous and abundant in major oceanic regimes underlies their ecological importance as significant contributors to marine C fixation. Recent advances in the physiology and biochemistry of these organisms are presented here, focusing on strains of the MC-A and MC-B clusters; it is stressed that the data contained herein should be put into the context of the ecological niche occupied by particular genotypes in situ. This system is ripe for joining the often separate disciplines of molecular ecology and microbial physiology and provides a great opportunity to tease out the underlying processes that both mediate organism evolution and also the environmental factors that dictate this.
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Affiliation(s)
- David J Scanlan
- Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
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Durham KA, Porta D, Twiss MR, McKay RML, Bullerjahn GS. Construction and initial characterization of a luminescent Synechococcus sp. PCC 7942 Fe-dependent bioreporter. FEMS Microbiol Lett 2002; 209:215-21. [PMID: 12007808 DOI: 10.1111/j.1574-6968.2002.tb11134.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A Synechococcus sp. PCC 7942 bioreporter strain capable of sensing bioavailable Fe was constructed by fusing the Fe-responsive isiAB promoter to the Vibrio harveyi luxAB genes. Monitoring luxAB-dependent luminescence through the growth curve demonstrated that in Fe-replete media, transcription from the isiAB promoter was induced transiently in the mid-exponential phase of growth. The initiation of transcription was the functional response to a 10-fold depletion of intracellular Fe to approximately 12 amol Fe per cell. Constitutive isiAB-dependent transcription was observed in Fe-depleted growth media. A dose-response relationship of the bioreporter was generated using trace metal-buffered Fraquil medium and was best represented by a sigmoidal curve having a linear component extending between pFe 21.1 (Fe3+=10(-21.1) M) and pFe 20.6 (Fe3+)=10(-20.6) M). Initial field trials conducted using water sampled from Lake Erie demonstrate that the bioreporter can serve as a quantitative tool to assess Fe deficiency in natural freshwater environments.
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Affiliation(s)
- Kathryn A Durham
- Department of Biological Sciences, Life Sciences Building, Bowling Green State University, OH 43403-0212, USA
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