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Fang J, Zhang Y, Zhu T, Li Y. Scramblase activity of proteorhodopsin confers physiological advantages to Escherichia coli in the absence of light. iScience 2023; 26:108551. [PMID: 38125024 PMCID: PMC10730872 DOI: 10.1016/j.isci.2023.108551] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 05/11/2023] [Accepted: 11/20/2023] [Indexed: 12/23/2023] Open
Abstract
Microbial rhodopsins are widely distributed in the aqua-ecosystem due to their simple structure and multifaceted functions. Conventionally, microbial rhodopsins are considered to be exclusively light active. Here, we report the discovery of light-independent function of a proteorhodopsin from a psychrophile Psychroflexus torquis (ptqPR). ptqPR could improve the growth and viability of Escherichia coli cells under stressful conditions in the absence of light, and this was achieved by improving the energy maintenance, membrane potential, membrane fluidity, and membrane integrity. We further show that this non-canonical function of PR is related to its scramblase activity. PR mutants which lost scramblase activities also lost their ability to confer physiological advantages in E. coli. These findings shed light on why microbial rhodopsins are widely distributed in ecological systems where light is inaccessible.
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Affiliation(s)
- Jiayu Fang
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yanping Zhang
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Taicheng Zhu
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Yin Li
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
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2
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Abstract
For billions of years, life has continuously adapted to dynamic physical conditions near the Earth’s surface. Fossils and other preserved biosignatures in the paleontological record are the most direct evidence for reconstructing the broad historical contours of this adaptive interplay. However, biosignatures dating to Earth’s earliest history are exceedingly rare. Here, we combine phylogenetic inference of primordial rhodopsin proteins with modeled spectral features of the Precambrian Earth environment to reconstruct the paleobiological history of this essential family of photoactive transmembrane proteins. Our results suggest that ancestral microbial rhodopsins likely acted as light-driven proton pumps and were spectrally tuned toward the absorption of green light, which would have enabled their hosts to occupy depths in a water column or biofilm where UV wavelengths were attenuated. Subsequent diversification of rhodopsin functions and peak absorption frequencies was enabled by the expansion of surface ecological niches induced by the accumulation of atmospheric oxygen. Inferred ancestors retain distinct associations between extant functions and peak absorption frequencies. Our findings suggest that novel information encoded by biomolecules can be used as “paleosensors” for conditions of ancient, inhabited niches of host organisms not represented elsewhere in the paleontological record. The coupling of functional diversification and spectral tuning of this taxonomically diverse protein family underscores the utility of rhodopsins as universal testbeds for inferring remotely detectable biosignatures on inhabited planetary bodies.
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Affiliation(s)
- Cathryn D Sephus
- NASA Center for Early Life and Evolution, University of Wisconsin-Madison, Madison, WI, USA
| | - Evrim Fer
- NASA Center for Early Life and Evolution, University of Wisconsin-Madison, Madison, WI, USA.,Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.,Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI, USA
| | - Amanda K Garcia
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Zachary R Adam
- Department of Geoscience, University of Wisconsin-Madison, Madison, WI, USA.,Blue Marble Space Institute of Science, Seattle, WA, USA
| | - Edward W Schwieterman
- Blue Marble Space Institute of Science, Seattle, WA, USA.,Department of Earth and Planetary Sciences, University of California, Riverside, CA, USA
| | - Betül Kaçar
- NASA Center for Early Life and Evolution, University of Wisconsin-Madison, Madison, WI, USA.,Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
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3
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Gallagher GE, Waldbauer JR. Proteome Expression and Survival Strategies of a Proteorhodopsin-Containing Vibrio Strain under Carbon and Nitrogen Limitation. mSystems 2022;:e0126321. [PMID: 35384695 DOI: 10.1128/msystems.01263-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 11/23/2022] Open
Abstract
Photoheterotrophy is a widespread mode of microbial metabolism, notably in the oligotrophic surface ocean, where microbes experience chronic nutrient limitation. One especially widespread form of photoheterotrophy is based on proteorhodopsin (PR), which uses light to generate proton motive force that can drive ATP synthesis, flagellar movement, or nutrient uptake. To clarify the physiological benefits conferred by PR under nutrient stress conditions, we quantified protein-level gene expression of Vibrio campbellii CAIM 519 under both carbon and nitrogen limitation and under both light and dark conditions. Using a novel membrane proteomics strategy, we determined that PR expression is higher under C limitation than N limitation but is not light regulated. Despite expression of PR photosystems, V. campbellii does not exhibit any growth or survival advantages in the light and only a few proteins show significant expression differences between light and dark conditions. While protein-level proteorhodopsin expression in V. campbellii is clearly responsive to nutrient limitation, photoheterotrophy does not appear to play a central role in the survival physiology of this organism under these nutrient stress conditions. C limitation and N limitation, however, result in very different survival responses: under N-limited conditions, viability declines, cultivability is lost rapidly, central carbon flux through the Entner-Doudoroff pathway is increased, and ammonium is assimilated via the GS-GOGAT pathway. In contrast, C limitation drives cell dwarfing with maintenance of viability, as well as utilization of the glyoxylate shunt, glutamate dehydrogenase and anaplerotic C fixation, and a stringent response mediated by the Pho regulon. IMPORTANCE Understanding the nutrient stress responses of proteorhodopsin-bearing microbes like Vibrio campbellii yields insights into microbial contributions to nutrient cycling, lifestyles of emerging pathogens in aquatic environments, and protein-level adaptations implemented during times of nutrient limitation. In addition to its broad taxonomic and geographic prevalence, the physiological role of PR is diverse, so we developed a novel proteomics strategy to quantify its expression at the protein level. We found that proteorhodopsin expression levels in this wild-type photoheterotroph under these experimental conditions, while higher under C than under N limitation, do not afford measurable light-driven growth or survival advantages. Additionally, this work links differential protein expression patterns between C- and N-limited cultures to divergent stationary-phase survival phenotypes.
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Pontiller B, Pérez-Martínez C, Bunse C, Osbeck CMG, González JM, Lundin D, Pinhassi J. Taxon-Specific Shifts in Bacterial and Archaeal Transcription of Dissolved Organic Matter Cycling Genes in a Stratified Fjord. mSystems 2021; 6:e0057521. [PMID: 34904860 DOI: 10.1128/mSystems.00575-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 11/20/2022] Open
Abstract
A considerable fraction of organic matter derived from photosynthesis in the euphotic zone settles into the ocean’s interior and, as it progresses, is degraded by diverse microbial consortia that utilize a suite of extracellular enzymes and membrane transporters. Still, the molecular details that regulate carbon cycling across depths remain little explored. As stratification in fjords has made them attractive models to explore patterns in biological oceanography, we here analyzed bacterial and archaeal transcription in samples from five depth layers in the Gullmar Fjord, Sweden. Transcriptional variation over depth correlated with gradients in chlorophyll a and nutrient concentrations. Differences in transcription between sampling dates (summer and early autumn) were strongly correlated with ammonium concentrations, which potentially was linked with a stronger influence of (micro-)zooplankton grazing in summer. Transcriptional investment in carbohydrate-active enzymes (CAZymes) decreased with depth and shifted toward peptidases, partly a result of elevated CAZyme transcription by Flavobacteriales, Cellvibrionales, and Synechococcales at 2 to 25 m and a dominance of peptidase transcription by Alteromonadales and Rhodobacterales from 50 m down. In particular, CAZymes for chitin, laminarin, and glycogen were important. High levels of transcription of ammonium transporter genes by Thaumarchaeota at depth (up to 18% of total transcription), along with the genes for ammonia oxidation and CO2 fixation, indicated that chemolithoautotrophy contributed to the carbon flux in the fjord. The taxon-specific expression of functional genes for processing of the marine pool of dissolved organic matter and inorganic nutrients across depths emphasizes the importance of different microbial foraging mechanisms over spatiotemporal scales for shaping biogeochemical cycles. IMPORTANCE It is generally recognized that stratification in the ocean strongly influences both the community composition and the distribution of ecological functions of microbial communities, which in turn are expected to shape the biogeochemical cycling of essential elements over depth. Here, we used metatranscriptomics analysis to infer molecular detail on the distribution of gene systems central to the utilization of organic matter in a stratified marine system. We thereby uncovered that pronounced shifts in the transcription of genes encoding CAZymes, peptidases, and membrane transporters occurred over depth among key prokaryotic orders. This implies that sequential utilization and transformation of organic matter through the water column is a key feature that ultimately influences the efficiency of the biological carbon pump.
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Nakajima Y, Kojima K, Kashiyama Y, Doi S, Nakai R, Sudo Y, Kogure K, Yoshizawa S. Bacterium Lacking a Known Gene for Retinal Biosynthesis Constructs Functional Rhodopsins. Microbes Environ 2021; 35. [PMID: 33281127 PMCID: PMC7734400 DOI: 10.1264/jsme2.me20085] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [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: 12/14/2022] Open
Abstract
Microbial rhodopsins, comprising a protein moiety (rhodopsin apoprotein) bound to the light-absorbing chromophore retinal, function as ion pumps, ion channels, or light sensors. However, recent genomic and metagenomic surveys showed that some rhodopsin-possessing prokaryotes lack the known genes for retinal biosynthesis. Since rhodopsin apoproteins cannot absorb light energy, rhodopsins produced by prokaryotic strains lacking genes for retinal biosynthesis are hypothesized to be non-functional in cells. In the present study, we investigated whether Aurantimicrobium minutum KNCT, which is widely distributed in terrestrial environments and lacks any previously identified retinal biosynthesis genes, possesses functional rhodopsin. We initially measured ion transport activity in cultured cells. A light-induced pH change in a cell suspension of rhodopsin-possessing bacteria was detected in the absence of exogenous retinal. Furthermore, spectroscopic analyses of the cell lysate and HPLC-MS/MS analyses revealed that this strain contained an endogenous retinal. These results confirmed that A. minutum KNCT possesses functional rhodopsin and, hence, produces retinal via an unknown biosynthetic pathway. These results suggest that rhodopsin-possessing prokaryotes lacking known retinal biosynthesis genes also have functional rhodopsins.
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Affiliation(s)
- Yu Nakajima
- Microbial and Genetic Resources Research Group, Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST).,Atmosphere and Ocean Research Institute (AORI), The University of Tokyo
| | - Keiichi Kojima
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University
| | | | - Satoko Doi
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University
| | - Ryosuke Nakai
- Microbial Ecology and Technology Research Group, Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
| | - Yuki Sudo
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University
| | - Kazuhiro Kogure
- Atmosphere and Ocean Research Institute (AORI), The University of Tokyo
| | - Susumu Yoshizawa
- Atmosphere and Ocean Research Institute (AORI), The University of Tokyo
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6
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Kula-Maximenko M, Zieliński KJ, Ślesak I. The Role of Selected Wavelengths of Light in the Activity of Photosystem II in Gloeobacter violaceus. Int J Mol Sci 2021; 22:4021. [PMID: 33924720 DOI: 10.3390/ijms22084021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 01/03/2023] Open
Abstract
Gloeobacter violaceus is a cyanobacteria species with a lack of thylakoids, while photosynthetic antennas, i.e., phycobilisomes (PBSs), photosystem II (PSII), and I (PSI), are located in the cytoplasmic membrane. We verified the hypothesis that blue–red (BR) light supplemented with a far-red (FR), ultraviolet A (UVA), and green (G) light can affect the photosynthetic electron transport chain in PSII and explain the differences in the growth of the G. violaceus culture. The cyanobacteria were cultured under different light conditions. The largest increase in G. violaceus biomass was observed only under BR + FR and BR + G light. Moreover, the shape of the G. violaceus cells was modified by the spectrum with the addition of G light. Furthermore, it was found that both the spectral composition of light and age of the cyanobacterial culture affect the different content of phycobiliproteins in the photosynthetic antennas (PBS). Most likely, in cells grown under light conditions with the addition of FR and G light, the average antenna size increased due to the inactivation of some reaction centers in PSII. Moreover, the role of PSI and gloeorhodopsin as supplementary sources of metabolic energy in the G. violaceus growth is discussed.
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7
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Koedooder C, Van Geersdaële R, Guéneuguès A, Bouget FY, Obernosterer I, Blain S. The interplay between iron limitation, light and carbon in the proteorhodopsin-containing Photobacterium angustum S14. FEMS Microbiol Ecol 2020; 96:5847691. [DOI: 10.1093/femsec/fiaa103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Accepted: 05/25/2020] [Indexed: 01/01/2023] Open
Abstract
ABSTRACTIron (Fe) limitation is known to affect heterotrophic bacteria within the respiratory electron transport chain, therefore strongly impacting the overall intracellular energy production. We investigated whether the gene expression pattern of the light-sensitive proton pump, proteorhodopsin (PR), is influenced by varying light, carbon and Fe concentrations in the marine bacterium Photobacterium angustum S14 and whether PR can alleviate the physiological processes associated with Fe starvation. Our results show that the gene expression of PR increases as cells enter the stationary phase, irrespective of Fe-replete or Fe-limiting conditions. This upregulation is coupled to a reduction in cell size, indicating that PR gene regulation is associated with a specific starvation-stress response. We provide experimental evidence that PR gene expression does not result in an increased growth rate, cell abundance, enhanced survival or ATP concentration within the cell in either Fe-replete or Fe-limiting conditions. However, independent of PR gene expression, the presence of light did influence bacterial growth rates and maximum cell abundances under varying Fe regimes. Our observations support previous results indicating that PR phototrophy seems to play an important role within the stationary phase for several members of the Vibrionaceae family, but that the exact role of PR in Fe limitation remains to be further explored.
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Affiliation(s)
- Coco Koedooder
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
- The Fredy and Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Rémy Van Geersdaële
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
| | - Audrey Guéneuguès
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
| | - François-Yves Bouget
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
| | - Ingrid Obernosterer
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
| | - Stéphane Blain
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, Banyuls/mer, France
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8
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Alonso-Sáez L, Morán XAG, González JM. Transcriptional Patterns of Biogeochemically Relevant Marker Genes by Temperate Marine Bacteria. Front Microbiol 2020; 11:465. [PMID: 32265888 PMCID: PMC7098952 DOI: 10.3389/fmicb.2020.00465] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [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: 07/17/2019] [Accepted: 03/04/2020] [Indexed: 11/13/2022] Open
Abstract
Environmental microbial gene expression patterns remain largely unexplored, particularly at interannual time scales. We analyzed the variability in the expression of marker genes involved in ecologically relevant biogeochemical processes at a temperate Atlantic site over two consecutive years. Most of nifH transcripts, involved in nitrogen (N) fixation, were affiliated with the symbiotic cyanobacterium Candidatus Atelocyanobacterium thalassa, suggesting a key role as N providers in this system. The expression of nifH and amoA (i.e., marker for ammonia oxidation) showed consistent maxima in summer and autumn, respectively, suggesting a temporal succession of these important N cycling processes. The patterns of expression of genes related to the oxidation of carbon monoxide (coxL) and reduced sulfur (soxB) were different from that of amoA, indicating alternate timings for these energy conservation strategies. We detected expression of alkaline phosphatases, induced under phosphorus limitation, in agreement with the reported co-limitation by this nutrient at the study site. In contrast, low-affinity phosphate membrane transporters (pit) typically expressed under phosphorus luxury conditions, were mainly detected in post-bloom conditions. Rhodobacteraceae dominated the expression of soxB, coxL and ureases, while Pelagibacteraceae dominated the expression of proteorhodopsins. Bacteroidetes and Gammaproteobacteria were major contributors to the uptake of inorganic nutrients (pit and amt transporters). Yet, in autumn, Thauma- and Euryarchaeota unexpectedly contributed importantly to the uptake of ammonia and phosphate, respectively. We provide new hints on the active players and potential dynamics of ecologically relevant functions in situ, highlighting the potential of metatranscriptomics to provide significant input to future omics-driven marine ecosystem assessment.
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Affiliation(s)
- Laura Alonso-Sáez
- Marine Research Division, AZTI, Sukarrieta, Spain.,Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía (IEO), Gijón/Xixón, Spain
| | - Xosé Anxelu G Morán
- Biological and Environmental Sciences and Engineering Division, Red Sea Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - José M González
- Department of Microbiology, University of La Laguna, La Laguna, Spain
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Chen Q, Arents J, Schuurmans JM, Ganapathy S, de Grip WJ, Cheregi O, Funk C, Branco Dos Santos F, Hellingwerf KJ. Functional Expression of Gloeobacter Rhodopsin in PSI-Less Synechocystis sp. PCC6803. Front Bioeng Biotechnol 2019; 7:67. [PMID: 30984754 PMCID: PMC6450040 DOI: 10.3389/fbioe.2019.00067] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [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] [Received: 12/28/2018] [Accepted: 03/11/2019] [Indexed: 01/30/2023] Open
Abstract
The approach of providing an oxygenic photosynthetic organism with a cyclic electron transfer system, i.e., a far-red light-driven proton pump, is widely proposed to maximize photosynthetic efficiency via expanding the absorption spectrum of photosynthetically active radiation. As a first step in this approach, Gloeobacter rhodopsin was expressed in a PSI-deletion strain of Synechocystis sp. PCC6803. Functional expression of Gloeobacter rhodopsin, in contrast to Proteorhodopsin, did not stimulate the rate of photoheterotrophic growth of this Synechocystis strain, analyzed with growth rate measurements and competition experiments. Nevertheless, analysis of oxygen uptake and—production rates of the Gloeobacter rhodopsin-expressing strains, relative to the ΔPSI control strain, confirm that the proton-pumping Gloeobacter rhodopsin provides the cells with additional capacity to generate proton motive force. Significantly, expression of the Gloeobacter rhodopsin did modulate levels of pigment formation in the transgenic strain.
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Affiliation(s)
- Que Chen
- Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands.,Center of Synthetic Biochemistry, Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Jos Arents
- Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
| | - J Merijn Schuurmans
- Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands
| | - Srividya Ganapathy
- Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Willem J de Grip
- Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | | | | | - Filipe Branco Dos Santos
- Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
| | - Klaas J Hellingwerf
- Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
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10
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Zhang C, Lin S. Initial evidence of functional siRNA machinery in dinoflagellates. Harmful Algae 2019; 81:53-58. [PMID: 30638498 DOI: 10.1016/j.hal.2018.11.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [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: 04/11/2018] [Revised: 11/23/2018] [Accepted: 11/23/2018] [Indexed: 06/09/2023]
Abstract
Dinoflagellates are a major group of protists widely distributed in the aquatic environments. Many species in this lineage are able to form harmful algal blooms (HAB), some even producing toxins, making this phylum the most important contributors of HAB in the marine ecosystem. Despite the ecological importance, the molecular mechanisms underpinning the basic biology and HAB formation of dinoflagellates are poorly understood. While the high-throughput sequencing studies have documented a large and growing number of genes in dinoflagellates, their functions remained to be experimentally proven using a functional genetic tool. Unfortunately, no such tool is yet available. This study was aimed to adopt the RNA interference (RNAi) gene-silencing tool for dinoflagellate research, and to investigate the potential effects of RNAi-based silencing of proton-pump rhodopsin and CO2-fixing enzyme Rubisco encoding genes in dinoflagellates. It was found that RNAi treatment caused a significant decrease in growth rate in both species. Compared with the non- endogenous target (GFP-siRNA) and the blank control, RNAi treatments also suppressed the expression of the target genes. These results constitute the first experimental evidence of the existence and operation of siRNA in two species of dinoflagellates, present initial evidence that dinoflagellate rhodopsins are functional as a supplemental energy acquisition mechanism, and provide technical information for future functional genetic research on dinoflagellates.
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Affiliation(s)
- Chao Zhang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Southern Medical University and Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, China
| | - Senjie Lin
- Department of Marine Sciences, University of Connecticut, Groton, CT 06340, USA.
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11
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Inoue K, Tahara S, Kato Y, Takeuchi S, Tahara T, Kandori H. Spectroscopic Study of Proton-Transfer Mechanism of Inward Proton-Pump Rhodopsin, Parvularcula oceani Xenorhodopsin. J Phys Chem B 2018; 122:6453-6461. [DOI: 10.1021/acs.jpcb.8b01279] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Keiichi Inoue
- PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Shinya Tahara
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | | | - Satoshi Takeuchi
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | - Tahei Tahara
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
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12
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Vader A, Laughinghouse HD, Griffiths C, Jakobsen KS, Gabrielsen TM. Proton-pumping rhodopsins are abundantly expressed by microbial eukaryotes in a high-Arctic fjord. Environ Microbiol 2018; 20:890-902. [PMID: 29266690 DOI: 10.1111/1462-2920.14035] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2017] [Revised: 11/21/2017] [Accepted: 12/18/2017] [Indexed: 01/07/2023]
Abstract
Proton-pumping rhodopsins provide an alternative pathway to photosynthesis by which solar energy can enter the marine food web. Rhodopsin genes are widely found in marine bacteria, also in the Arctic, and were recently reported from several eukaryotic lineages. So far, little is known about rhodopsin expression in Arctic eukaryotes. In this study, we used metatranscriptomics and 18S rDNA tag sequencing to examine the mid-summer function and composition of marine protists (size 0.45-10 µm) in the high-Arctic Billefjorden (Spitsbergen), especially focussing on the expression of microbial proton-pumping rhodopsins. Rhodopsin transcripts were highly abundant, at a level similar to that of genes involved in photosynthesis. Phylogenetic analyses placed the environmental rhodopsins within disparate eukaryotic lineages, including dinoflagellates, stramenopiles, haptophytes and cryptophytes. Sequence comparison indicated the presence of several functional types, including xanthorhodopsins and a eukaryotic clade of proteorhodopsin. Transcripts belonging to the proteorhodopsin clade were also abundant in published metatranscriptomes from other oceanic regions, suggesting a global distribution. The diversity and abundance of rhodopsins show that these light-driven proton pumps play an important role in Arctic microbial eukaryotes. Understanding this role is imperative to predicting the future of the Arctic marine ecosystem faced by a changing light climate due to diminishing sea-ice.
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Affiliation(s)
- Anna Vader
- University Centre in Svalbard, Longyearbyen, Norway
| | | | | | - Kjetill S Jakobsen
- Department of Biosciences, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
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13
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Osunla CA, Okoh AI. Vibrio Pathogens: A Public Health Concern in Rural Water Resources in Sub-Saharan Africa. Int J Environ Res Public Health 2017; 14:E1188. [PMID: 28991153 DOI: 10.3390/ijerph14101188] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Revised: 09/29/2017] [Accepted: 10/04/2017] [Indexed: 12/12/2022]
Abstract
Members of the Vibrio genus are autochthonous inhabitants of aquatic environments and play vital roles in sustaining the aquatic milieu. The genus comprises about 100 species, which are mostly of marine or freshwater origin, and their classification is frequently updated due to the continuous discovery of novel species. The main route of transmission of Vibrio pathogens to man is through drinking of contaminated water and consumption inadequately cooked aquatic food products. In sub-Saharan Africa and much of the developing world, some rural dwellers use freshwater resources such as rivers for domestic activities, bathing, and cultural and religious purposes. This review describes the impact of inadequately treated sewage effluents on the receiving freshwater resources and the associated risk to the rural dwellers that depends on the water. Vibrio infections remain a threat to public health. In the last decade, Vibrio disease outbreaks have created alertness on the personal, economic, and public health uncertainties associated with the impact of contaminated water in the aquatic environment of sub-Saharan Africa. In this review, we carried out an overview of Vibrio pathogens in rural water resources in Sub-Saharan Africa and the implication of Vibrio pathogens on public health. Continuous monitoring of Vibrio pathogens among environmental freshwater and treated effluents is expected to help reduce the risk associated with the early detection of sources of infection, and also aid our understanding of the natural ecology and evolution of Vibrio pathogens.
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Chen Q, Arents J, Ganapathy S, de Grip WJ, Hellingwerf KJ. Functional Expression of Gloeobacter Rhodopsin inSynechocystissp. PCC6803. Photochem Photobiol 2017; 93:772-781. [DOI: 10.1111/php.12745] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/07/2017] [Indexed: 12/22/2022]
Affiliation(s)
- Que Chen
- Molecular Microbial Physiology; Swammerdam Institute for Life Sciences; University of Amsterdam; Amsterdam The Netherlands
| | - Jos Arents
- Molecular Microbial Physiology; Swammerdam Institute for Life Sciences; University of Amsterdam; Amsterdam The Netherlands
| | - Srividya Ganapathy
- Biophysical Organic Chemistry; Leiden Institute of Chemistry; Leiden University; Leiden The Netherlands
| | - Willem J. de Grip
- Biophysical Organic Chemistry; Leiden Institute of Chemistry; Leiden University; Leiden The Netherlands
| | - Klaas J. Hellingwerf
- Molecular Microbial Physiology; Swammerdam Institute for Life Sciences; University of Amsterdam; Amsterdam The Netherlands
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Boeuf D, Lami R, Cunnington E, Jeanthon C. Summer Abundance and Distribution of Proteorhodopsin Genes in the Western Arctic Ocean. Front Microbiol 2016; 7:1584. [PMID: 27790192 PMCID: PMC5061748 DOI: 10.3389/fmicb.2016.01584] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [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: 06/02/2016] [Accepted: 09/21/2016] [Indexed: 11/13/2022] Open
Abstract
Proteorhodopsins (PR) are phylogenetically diverse and highly expressed proton pumps in marine bacterial communities. The phylogenetic diversity and in situ expression of the main PR groups in polar off-shore, coastal and estuarine waters is poorly known and their abundance has not yet been reported. Here, we show that PR gene sequences of the southern Beaufort Sea including MacKenzie shelf and estuary are mainly affiliated to Gammaproteobacteria, Alphaproteobacteria, and Bacteroidetes. Substantial overlap (78%) between DNA- and cDNA-based librairies indicated in situ PR transcription within a large fraction of PR-containing community. Sets of specific qPCR primers were designed to measure the absolute abundances of the major PR types. Spatial and depth profiles showed that PR-containing bacteria were abundant throughout the photic zone, comprising up to 45% of total bacteria. Although their abundance varied greatly with location and depth, Alphaproteobacteria predominated in the PR community in all water masses, with SAR11 as the major PR type. Low nutrient concentrations rather than light were the environmental drivers that best explained the abundance and distribution of arctic PR types. Together, our data suggests that PR-based phototrophy could be the major phototrophic prokaryotic process during the Arctic Ocean summer.
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Affiliation(s)
- Dominique Boeuf
- CNRS, Station Biologique, UMR 7144 Adaptation and Diversité en Milieu MarinRoscoff, France; Sorbonne Universités - UPMC Université Paris 06, Station Biologique, UMR 7144 Adaptation and Diversité en Milieu MarinRoscoff, France
| | - Raphaël Lami
- CNRS, USR 3579, Laboratoire de Biodiversité et Biotechnologies MicrobiennesBanyuls-sur-Mer, France; Sorbonne Universités - UPMC Université Paris 06, USR 3579, Observatoire OcéanologiqueBanyuls-sur-Mer, France
| | - Emelyne Cunnington
- CNRS, Station Biologique, UMR 7144 Adaptation and Diversité en Milieu MarinRoscoff, France; Sorbonne Universités - UPMC Université Paris 06, Station Biologique, UMR 7144 Adaptation and Diversité en Milieu MarinRoscoff, France
| | - Christian Jeanthon
- CNRS, Station Biologique, UMR 7144 Adaptation and Diversité en Milieu MarinRoscoff, France; Sorbonne Universités - UPMC Université Paris 06, Station Biologique, UMR 7144 Adaptation and Diversité en Milieu MarinRoscoff, France
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Pinhassi J, DeLong EF, Béjà O, González JM, Pedrós-Alió C. Marine Bacterial and Archaeal Ion-Pumping Rhodopsins: Genetic Diversity, Physiology, and Ecology. Microbiol Mol Biol Rev 2016; 80:929-54. [PMID: 27630250 DOI: 10.1128/MMBR.00003-16] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The recognition of a new family of rhodopsins in marine planktonic bacteria, proton-pumping proteorhodopsin, expanded the known phylogenetic range, environmental distribution, and sequence diversity of retinylidene photoproteins. At the time of this discovery, microbial ion-pumping rhodopsins were known solely in haloarchaea inhabiting extreme hypersaline environments. Shortly thereafter, proteorhodopsins and other light-activated energy-generating rhodopsins were recognized to be widespread among marine bacteria. The ubiquity of marine rhodopsin photosystems now challenges prior understanding of the nature and contributions of "heterotrophic" bacteria to biogeochemical carbon cycling and energy fluxes. Subsequent investigations have focused on the biophysics and biochemistry of these novel microbial rhodopsins, their distribution across the tree of life, evolutionary trajectories, and functional expression in nature. Later discoveries included the identification of proteorhodopsin genes in all three domains of life, the spectral tuning of rhodopsin variants to wavelengths prevailing in the sea, variable light-activated ion-pumping specificities among bacterial rhodopsin variants, and the widespread lateral gene transfer of biosynthetic genes for bacterial rhodopsins and their associated photopigments. Heterologous expression experiments with marine rhodopsin genes (and associated retinal chromophore genes) provided early evidence that light energy harvested by rhodopsins could be harnessed to provide biochemical energy. Importantly, some studies with native marine bacteria show that rhodopsin-containing bacteria use light to enhance growth or promote survival during starvation. We infer from the distribution of rhodopsin genes in diverse genomic contexts that different marine bacteria probably use rhodopsins to support light-dependent fitness strategies somewhere between these two extremes.
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Affiliation(s)
- Shin Haruta
- Graduate School of Science and Engineering, Tokyo Metropolitan University
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18
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Chen Q, van der Steen JB, Dekker HL, Ganapathy S, de Grip WJ, Hellingwerf KJ. Expression of holo-proteorhodopsin in Synechocystis sp. PCC 6803. Metab Eng 2016; 35:83-94. [PMID: 26869136 DOI: 10.1016/j.ymben.2016.02.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 01/11/2016] [Accepted: 02/01/2016] [Indexed: 01/15/2023]
Abstract
Retinal-based photosynthesis may contribute to the free energy conversion needed for growth of an organism carrying out oxygenic photosynthesis, like a cyanobacterium. After optimization, this may even enhance the overall efficiency of phototrophic growth of such organisms in sustainability applications. As a first step towards this, we here report on functional expression of the archetype proteorhodopsin in Synechocystis sp. PCC 6803. Upon use of the moderate-strength psbA2 promoter, holo-proteorhodopsin is expressed in this cyanobacterium, at a level of up to 10(5) molecules per cell, presumably in a hexameric quaternary structure, and with approximately equal distribution (on a protein-content basis) over the thylakoid and the cytoplasmic membrane fraction. These results also demonstrate that Synechocystis sp. PCC 6803 has the capacity to synthesize all-trans-retinal. Expressing a substantial amount of a heterologous opsin membrane protein causes a substantial growth retardation Synechocystis, as is clear from a strain expressing PROPS, a non-pumping mutant derivative of proteorhodopsin. Relative to this latter strain, proteorhodopsin expression, however, measurably stimulates its growth.
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Affiliation(s)
- Que Chen
- Molecular Microbial Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Jeroen B van der Steen
- Molecular Microbial Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Henk L Dekker
- Mass Spectrometry of Biomacromolecules, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Srividya Ganapathy
- Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | - Willem J de Grip
- Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | - Klaas J Hellingwerf
- Molecular Microbial Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
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19
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Courties A, Riedel T, Rapaport A, Lebaron P, Suzuki MT. Light-driven increase in carbon yield is linked to maintenance in the proteorhodopsin-containing Photobacterium angustum S14. Front Microbiol 2015. [PMID: 26217320 PMCID: PMC4498439 DOI: 10.3389/fmicb.2015.00688] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [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: 11/13/2022] Open
Abstract
A type of photoheterotrophic bacteria contain a transmembrane light-driven proton pump called proteorhodopsins (PRs). Due to the prevalence of these organisms in the upper water column of the World's Ocean, and their potential for light-driven ATP generation, they have been suggested to significantly influence energy and matter flows in the biosphere. To date, evidence for the significance of the light-driven metabolism of PR-containing prokaryotes has been obtained by comparing growth in batch culture, under light versus dark conditions, and it appears that responses to light are linked to unfavorable conditions, which so far have not been well parameterized. We studied light responses to carbon yields of the PR-containing Photobacterium angustum S14 using continuous culture conditions and light-dark cycles. We observed significant effects of light-dark cycles compared to dark controls, as well as significant differences between samples after 12 h illumination versus 12 h darkness. However, these effects were only observed under higher cell counts and lower pH associated with higher substrate concentrations. Under these substrate levels Pirt's maintenance coefficient was higher when compared to lower substrate dark controls, and decreased under light-dark cycles. It appears that light responses by P. angustum S14 are induced by the energetic status of the cells rather than by low substrate concentrations.
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Affiliation(s)
- Alicia Courties
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique , Banyuls-sur-Mer, France
| | - Thomas Riedel
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique , Banyuls-sur-Mer, France
| | - Alain Rapaport
- INRA-Supagro, UMR MISTEA , Montpellier, France ; INRA-INRIA, MODEMIC Team , Sophia Antipolis, France
| | - Philippe Lebaron
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), Observatoire Océanologique , Banyuls-sur-Mer, France
| | - Marcelino T Suzuki
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), Observatoire Océanologique , Banyuls-sur-Mer, France
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20
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Shi X, Li L, Guo C, Lin X, Li M, Lin S. Rhodopsin gene expression regulated by the light dark cycle, light spectrum and light intensity in the dinoflagellate Prorocentrum. Front Microbiol 2015; 6:555. [PMID: 26082770 PMCID: PMC4451421 DOI: 10.3389/fmicb.2015.00555] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [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: 03/03/2015] [Accepted: 05/20/2015] [Indexed: 12/13/2022] Open
Abstract
The proton pump rhodopsin is widely found in marine bacteria and archaea, where it functions to capture light energy and convert it to ATP. While found in several lineages of dinoflagellates, this gene has not been studied in Prorocentrales species and whether it functionally tunes to light spectra and intensities as in bacteria remains unclear. Here we identified and characterized this gene in the bloom-forming Prorocentrum donghaiense. It is a 7-helix transmembrane polypeptide containing conserved domains and critical amino acid residues of PPR. This gene is phylogenetically affiliated to the xanthorhodopsin clade, but seems to have a distinct evolutionary origin. Quantitative reverse transcription PCR showed that in regular cultures, the transcript abundance of the gene exhibited a clear diel pattern, high abundance in the light period and low in the dark. The same diel pattern was observed for protein abundance with a Western blot using specific antiserum. The rhythm was dampened when the cultures were shifted to continuous dark or light condition, suggesting that this gene is not under circadian clock control. Rhodopsin transcript and protein abundances varied with light intensity, both being highest at a moderate illumination level. Furthermore, the expression of this gene responded to different light spectra, with slightly higher transcript abundance under green than blue light, and lowest abundance under red light. Transformed Escherichia coli over-expressing this rhodopsin gene also exhibited an absorption maximum in the blue–green region with slightly higher absorption in the green. These rhodopsin-promoting light conditions are similar to the relatively turbid marine habitat where the species forms blooms, suggesting that this gene may function to compensate for the light-limited photosynthesis in the dim environment.
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Affiliation(s)
- Xinguo Shi
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University Xiamen, China ; College of the Environment and Ecology, Xiamen University Xiamen, China
| | - Ling Li
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University Xiamen, China
| | - Chentao Guo
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University Xiamen, China
| | - Xin Lin
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University Xiamen, China
| | - Meizhen Li
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University Xiamen, China
| | - Senjie Lin
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University Xiamen, China ; Department of Marine Sciences, University of Connecticut Groton, CT, USA
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21
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Lever MA, Rogers KL, Lloyd KG, Overmann J, Schink B, Thauer RK, Hoehler TM, Jørgensen BB. Life under extreme energy limitation: a synthesis of laboratory- and field-based investigations. FEMS Microbiol Rev 2015; 39:688-728. [PMID: 25994609 DOI: 10.1093/femsre/fuv020] [Citation(s) in RCA: 174] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/25/2015] [Indexed: 11/13/2022] Open
Abstract
The ability of microorganisms to withstand long periods with extremely low energy input has gained increasing scientific attention in recent years. Starvation experiments in the laboratory have shown that a phylogenetically wide range of microorganisms evolve fitness-enhancing genetic traits within weeks of incubation under low-energy stress. Studies on natural environments that are cut off from new energy supplies over geologic time scales, such as deeply buried sediments, suggest that similar adaptations might mediate survival under energy limitation in the environment. Yet, the extent to which laboratory-based evidence of starvation survival in pure or mixed cultures can be extrapolated to sustained microbial ecosystems in nature remains unclear. In this review, we discuss past investigations on microbial energy requirements and adaptations to energy limitation, identify gaps in our current knowledge, and outline possible future foci of research on life under extreme energy limitation.
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Affiliation(s)
- Mark A Lever
- Center for Geomicrobiology, Institute of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
| | - Karyn L Rogers
- Rensselaer Polytechnic Institute, Earth and Environmental Sciences, Jonsson-Rowland Science Center, 1W19, 110 8th Street, Troy, NY 12180, USA
| | - Karen G Lloyd
- Department of Microbiology, University of Tennessee at Knoxville, M409 Walters Life Sciences, Knoxville, TN 37996-0845, USA
| | - Jörg Overmann
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Inhoffenstraße 7B, D-38124 Braunschweig, Germany
| | - Bernhard Schink
- Microbial Ecology, Department of Biology, University of Konstanz, P.O. Box 55 60, D-78457 Konstanz, Germany
| | - Rudolf K Thauer
- Max Planck Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Straße, D-35043 Marburg, Germany
| | - Tori M Hoehler
- NASA Ames Research Center, Mail Stop 239-4, Moffett Field, CA 94035-1000, USA
| | - Bo Barker Jørgensen
- Center for Geomicrobiology, Institute of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
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22
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Nguyen D, Maranger R, Balagué V, Coll-Lladó M, Lovejoy C, Pedrós-Alió C. Winter diversity and expression of proteorhodopsin genes in a polar ocean. ISME J 2015; 9:1835-45. [PMID: 25700336 DOI: 10.1038/ismej.2015.1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Revised: 12/09/2014] [Accepted: 12/12/2014] [Indexed: 12/25/2022]
Abstract
Mixotrophy is a valuable functional trait used by microbes when environmental conditions vary broadly or resources are limited. In the sunlit waters of the ocean, photoheterotrophy, a form of mixotrophy, is often mediated by proteorhodopsin (PR), a seven helices transmembrane protein binding the retinal chromophore. Altogether, they allow bacteria to capture photic energy for sensory and proton gradient formation cell functions. The seasonal occurrence and diversity of the gene coding for PR in cold oligotrophic polar oceans is not known and PR expression has not yet been reported. Here we show that PR is widely distributed among bacterial taxa, and that PR expression decreased markedly during the winter months in the Arctic Ocean. Gammaproteobacteria-like PR sequences were always dominant. However, within the second most common affiliation, there was a transition from Flavobacteria-like PR in early winter to Alphaproteobacteria-like PR in late winter. The phylogenetic shifts followed carbon dynamics, where patterns in expression were consistent with community succession, as identified by DNA community fingerprinting. Although genes for PR were always present, the trend in decreasing transcripts from January to February suggested reduced functional utility of PR during winter. Under winter darkness, sustained expression suggests that PR may continue to be useful for non-ATP forming functions, such as environmental sensing or small solute transport. The persistence of PR expression in winter among some bacterial groups may offer a competitive advantage, where its multifunctionality enhances microbial survival under harsh polar conditions.
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Affiliation(s)
- Dan Nguyen
- Groupe de Recherche Interuniversitaire en Limnologie et en Environnement Aquatique (GRIL), Département de sciences biologiques, Université de Montréal, Montréal, Québec, Canada
| | - Roxane Maranger
- Groupe de Recherche Interuniversitaire en Limnologie et en Environnement Aquatique (GRIL), Département de sciences biologiques, Université de Montréal, Montréal, Québec, Canada
| | - Vanessa Balagué
- Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta, Barcelona, Spain
| | - Montserrat Coll-Lladó
- Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta, Barcelona, Spain
| | - Connie Lovejoy
- Département de biologie, Québec-Océan, Institut de biologie intégrative et des systèmes (IBIS), Université Laval, Pavillon Charles-Eugène-Marchand, Québec, Québec, Canada
| | - Carlos Pedrós-Alió
- Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta, Barcelona, Spain
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Xing P, Hahnke RL, Unfried F, Markert S, Huang S, Barbeyron T, Harder J, Becher D, Schweder T, Glöckner FO, Amann RI, Teeling H. Niches of two polysaccharide-degrading Polaribacter isolates from the North Sea during a spring diatom bloom. ISME J 2015; 9:1410-22. [PMID: 25478683 DOI: 10.1038/ismej.2014.225] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 10/06/2014] [Accepted: 10/23/2014] [Indexed: 11/08/2022]
Abstract
Members of the flavobacterial genus Polaribacter thrive in response to North Sea spring phytoplankton blooms. We analyzed two respective Polaribacter species by whole genome sequencing, comparative genomics, substrate tests and proteomics. Both can degrade algal polysaccharides but occupy distinct niches. The liquid culture isolate Polaribacter sp. strain Hel1_33_49 has a 3.0-Mbp genome with an overall peptidase:CAZyme ratio of 1.37, four putative polysaccharide utilization loci (PULs) and features proteorhodopsin, whereas the agar plate isolate Polaribacter sp. strain Hel1_85 has a 3.9-Mbp genome with an even peptidase:CAZyme ratio, eight PULs, a mannitol dehydrogenase for decomposing algal mannitol-capped polysaccharides but no proteorhodopsin. Unlike other sequenced Polaribacter species, both isolates have larger sulfatase-rich PULs, supporting earlier assumptions that Polaribacter take part in the decomposition of sulfated polysaccharides. Both strains grow on algal laminarin and the sulfated polysaccharide chondroitin sulfate. For strain Hel1_33_49, we identified by proteomics (i) a laminarin-induced PUL, (ii) chondroitin sulfate-induced CAZymes and (iii) a chondroitin-induced operon that likely enables chondroitin sulfate recognition. These and other data suggest that strain Hel1_33_49 is a planktonic flavobacterium feeding on proteins and a small subset of algal polysaccharides, while the more versatile strain Hel1_85 can decompose a broader spectrum of polysaccharides and likely associates with algae.
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Palovaara J, Akram N, Baltar F, Bunse C, Forsberg J, Pedrós-Alió C, González JM, Pinhassi J. Stimulation of growth by proteorhodopsin phototrophy involves regulation of central metabolic pathways in marine planktonic bacteria. Proc Natl Acad Sci U S A 2014; 111:E3650-8. [PMID: 25136122 DOI: 10.1073/pnas.1402617111] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Proteorhodopsin (PR) is present in half of surface ocean bacterioplankton, where its light-driven proton pumping provides energy to cells. Indeed, PR promotes growth or survival in different bacteria. However, the metabolic pathways mediating the light responses remain unknown. We analyzed growth of the PR-containing Dokdonia sp. MED134 (where light-stimulated growth had been found) in seawater with low concentrations of mixed [yeast extract and peptone (YEP)] or single (alanine, Ala) carbon compounds as models for rich and poor environments. We discovered changes in gene expression revealing a tightly regulated shift in central metabolic pathways between light and dark conditions. Bacteria showed relatively stronger light responses in Ala compared with YEP. Notably, carbon acquisition pathways shifted toward anaplerotic CO2 fixation in the light, contributing 31 ± 8% and 24 ± 6% of the carbon incorporated into biomass in Ala and YEP, respectively. Thus, MED134 was a facultative double mixotroph, i.e., photo- and chemotrophic for its energy source and using both bicarbonate and organic matter as carbon sources. Unexpectedly, relative expression of the glyoxylate shunt genes (isocitrate lyase and malate synthase) was >300-fold higher in the light--but only in Ala--contributing a more efficient use of carbon from organic compounds. We explored these findings in metagenomes and metatranscriptomes and observed similar prevalence of the glyoxylate shunt compared with PR genes and highest expression of the isocitrate lyase gene coinciding with highest solar irradiance. Thus, regulatory interactions between dissolved organic carbon quality and central metabolic pathways critically determine the fitness of surface ocean bacteria engaging in PR phototrophy.
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Jimenez-Infante F, Ngugi DK, Alam I, Rashid M, Baalawi W, Kamau AA, Bajic VB, Stingl U. Genomic differentiation among two strains of the PS1 clade isolated from geographically separated marine habitats. FEMS Microbiol Ecol 2014; 89:181-97. [PMID: 24785133 DOI: 10.1111/1574-6941.12348] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 03/20/2014] [Accepted: 04/12/2014] [Indexed: 12/18/2022] Open
Abstract
Using dilution-to-extinction cultivation, we isolated a strain affiliated with the PS1 clade from surface waters of the Red Sea. Strain RS24 represents the second isolate of this group of marine Alphaproteobacteria after IMCC14465 that was isolated from the East (Japan) Sea. The PS1 clade is a sister group to the OCS116 clade, together forming a putatively novel order closely related to Rhizobiales. While most genomic features and most of the genetic content are conserved between RS24 and IMCC14465, their average nucleotide identity (ANI) is < 81%, suggesting two distinct species of the PS1 clade. Next to encoding two different variants of proteorhodopsin genes, they also harbor several unique genomic islands that contain genes related to degradation of aromatic compounds in IMCC14465 and in polymer degradation in RS24, possibly reflecting the physicochemical differences in the environment they were isolated from. No clear differences in abundance of the genomic content of either strain could be found in fragment recruitment analyses using different metagenomic datasets, in which both genomes were detectable albeit as minor part of the communities. The comparative genomic analysis of both isolates of the PS1 clade and the fragment recruitment analysis provide first insights into the ecology of this group.
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Affiliation(s)
- Francy Jimenez-Infante
- Red Sea Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
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26
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Luo H, Moran MA. Assembly-free metagenomic analysis reveals new metabolic capabilities in surface ocean bacterioplankton. Environ Microbiol Rep 2013; 5:686-696. [PMID: 24115619 DOI: 10.1111/1758-2229.12068] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 04/21/2013] [Indexed: 06/02/2023]
Abstract
Uncovering the metabolic capabilities of microbes is key to understanding global energy flux and nutrient transformations. Since the vast majority of environmental microorganisms are uncultured, metagenomics has become an important tool to genotype the microbial community. This study uses a recently developed computational method to confidently assign metagenomic reads to microbial clades without the requirement of metagenome assembly by comparing the evolutionary pattern of nucleotide sequences at non-synonymous sites between metagenomic and orthologous reference genes. We found evidence for new, ecologically relevant metabolic pathways in several lineages of surface ocean bacterioplankton using the Global Ocean Survey (GOS) metagenomic data, including assimilatory sulfate reduction and alkaline phosphatase capabilities in the alphaproteobacterial SAR11 clade, and proteorhodopsin-like genes in the cyanobacterial genus Prochlorococcus. These findings raise new hypotheses about microbial roles in energy flux and organic matter transformation in the ocean.
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Affiliation(s)
- Haiwei Luo
- Department of Marine Sciences, University of Georgia, Athens, GA, 30602, USA
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Feng S, Powell SM, Wilson R, Bowman JP. Light-stimulated growth of proteorhodopsin-bearing sea-ice psychrophile Psychroflexus torquis is salinity dependent. ISME J 2013; 7:2206-13. [PMID: 23788334 DOI: 10.1038/ismej.2013.97] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 03/15/2013] [Accepted: 05/16/2013] [Indexed: 12/27/2022]
Abstract
Proteorhodopsins (PRs) are commonly found in marine prokaryotes and allow microbes to use light as an energy source. In recent studies, it was reported that PR stimulates growth and survival under nutrient-limited conditions. In this study, we tested the effect of nutrient and salinity stress on the extremely psychrophilic sea-ice bacterial species Psychroflexus torquis, which possesses PR. We demonstrated for the first time that light-stimulated growth occurs under conditions of salinity stress rather than nutrient limitation and that elevated salinity is related to increased growth yields, PR levels and associated proton-pumping activity. PR abundance in P. torquis also is post-transcriptionally regulated by both light and salinity and thus could represent an adaptation to its sea-ice habitat. Our findings extend the existing paradigm that light provides an energy source for marine prokaryotes under stress conditions other than nutrient limitation.
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