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Wei N, Hu C, Dittmann E, Song L, Gan N. The biological functions of microcystins. WATER RESEARCH 2024; 262:122119. [PMID: 39059200 DOI: 10.1016/j.watres.2024.122119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Revised: 07/16/2024] [Accepted: 07/17/2024] [Indexed: 07/28/2024]
Abstract
Microcystins are potent hepatotoxins predominantly produced by bloom-forming freshwater cyanobacteria (e.g., Microcystis, Planktothrix, Dolichospermum). Microcystin biosynthesis involves large multienzyme complexes and tailoring enzymes encoded by the mcy gene cluster. Mutation, recombination, and deletion events have shaped the mcy gene cluster in the course of evolution, resulting in a large diversity of microcystin congeners and the natural coexistence of toxic and non-toxic strains. The biological functions of microcystins and their association with algal bloom formation have been extensively investigated over the past decades. This review synthesizes recent advances in decoding the biological role of microcystins in carbon/nitrogen metabolism, antioxidation, colony formation, and cell-to-cell communication. Microcystins appear to adopt multifunctional roles in cyanobacteria that reflect the adaptive plasticity of toxic cyanobacteria to changing environments.
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Affiliation(s)
- Nian Wei
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
| | - Chenlin Hu
- College of Pharmacy, University of Houston, Houston, TX 77204, USA
| | - Elke Dittmann
- Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam-Golm, Germany
| | - Lirong Song
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Nanqin Gan
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
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2
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Hancock TL, Dahedl EK, Kratz MA, Urakawa H. The synchronicity of bloom-forming cyanobacteria transcription patterns and hydrogen peroxide dynamics. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 348:123812. [PMID: 38527584 DOI: 10.1016/j.envpol.2024.123812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 03/08/2024] [Accepted: 03/15/2024] [Indexed: 03/27/2024]
Abstract
Hydrogen peroxide is a reactive oxygen species (ROS) naturally occurring at low levels in aquatic environments and production varies widely across different ecosystems. Oxygenic photosynthesis generates hydrogen peroxide as a byproduct, of which some portion can be released to ambient water. However, few studies have examined hydrogen peroxide dynamics in relation to cyanobacterial harmful algal blooms (cHABs). A year-long investigation of algal succession and hydrogen peroxide dynamics was conducted at the Caloosahatchee River, Florida, USA. We aimed to identify potential biological mechanisms responsible for elevated hydrogen peroxide production during cHAB events through the exploration of the freshwater microbial metatranscriptome. Hydrogen peroxide concentrations were elevated from February to September of 2021 when cyanobacteria were active and abundant. We observed one Microcystis cHAB event in spring and one in winter. Both had distinct nutrient uptake and cyanotoxin gene expression patterns. While meaningful levels of microcystin were only detected during periods of elevated hydrogen peroxide, cyanopeptolin was by far the most expressed cyanotoxin during the spring bloom when hydrogen peroxide was at its yearly maxima. Gene expressions of five microbial enzymes (Rubisco, superoxide dismutase, cytochrome b559, pyruvate oxidase, and NADH dehydrogenase) positively correlated to hydrogen peroxide concentrations. Additionally, there was higher nitrogen-fixing gene (nifDKH) expression by filamentous cyanobacteria after the spring bloom but no secondary bloom formation occurred. Overall, elevated environmental hydrogen peroxide concentrations were linked to cyanobacterial dominance and greater expression of specific enzymes in the photosynthesis of cyanobacteria. This implicates cyanobacterial photosynthesis and growth results in increased hydrogen peroxide generation as reflected in measured environmental concentrations.
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Affiliation(s)
- Taylor L Hancock
- School of Geosciences, University of South Florida, Tampa, FL, 33620, USA; Department of Ecology and Environmental Studies, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - Elizabeth K Dahedl
- Department of Ecology and Environmental Studies, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - Michael A Kratz
- Department of Ecology and Environmental Studies, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - Hidetoshi Urakawa
- School of Geosciences, University of South Florida, Tampa, FL, 33620, USA; Department of Ecology and Environmental Studies, Florida Gulf Coast University, Fort Myers, Florida, USA.
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3
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Haavisto V, Landry Z, Pontrelli S. High-throughput profiling of metabolic responses to exogenous nutrients in Synechocystis sp. PCC 6803. mSystems 2024; 9:e0022724. [PMID: 38534128 PMCID: PMC11019784 DOI: 10.1128/msystems.00227-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 02/27/2024] [Indexed: 03/28/2024] Open
Abstract
Cyanobacteria fix carbon dioxide and release carbon-containing compounds into the wider ecosystem, yet they are sensitive to small metabolites that may impact their growth and physiology. Several cyanobacteria can grow mixotrophically, but we currently lack a molecular understanding of how specific nutrients may alter the compounds they release, limiting our knowledge of how environmental factors might impact primary producers and the ecosystems they support. In this study, we develop a high-throughput phytoplankton culturing platform and identify how the model cyanobacterium Synechocystis sp. PCC 6803 responds to nutrient supplementation. We assess growth responses to 32 nutrients at two concentrations, identifying 15 that are utilized mixotrophically. Seven nutrient sources significantly enhance growth, while 19 elicit negative growth responses at one or both concentrations. High-throughput exometabolomics indicates that oxidative stress limits Synechocystis' growth but may be alleviated by antioxidant metabolites. Furthermore, glucose and valine induce strong changes in metabolite exudation in a possible effort to correct pathway imbalances or maintain intracellular elemental ratios. This study sheds light on the flexibility and limits of cyanobacterial physiology and metabolism, as well as how primary production and trophic food webs may be modulated by exogenous nutrients.IMPORTANCECyanobacteria capture and release carbon compounds to fuel microbial food webs, yet we lack a comprehensive understanding of how external nutrients modify their behavior and what they produce. We developed a high throughput culturing platform to evaluate how the model cyanobacterium Synechocystis sp. PCC 6803 responds to a broad panel of externally supplied nutrients. We found that growth may be enhanced by metabolites that protect against oxidative stress, and growth and exudate profiles are altered by metabolites that interfere with central carbon metabolism and elemental ratios. This work contributes a holistic perspective of the versatile response of Synechocystis to externally supplied nutrients, which may alter carbon flux into the wider ecosystem.
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Affiliation(s)
- Vilhelmiina Haavisto
- Institute of Molecular Systems Biology, Department of Biology, ETH Zürich, Zürich, Switzerland
| | - Zachary Landry
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zürich, Zürich, Switzerland
| | - Sammy Pontrelli
- Institute of Molecular Systems Biology, Department of Biology, ETH Zürich, Zürich, Switzerland
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4
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Cai L, Li H, Deng J, Zhou R, Zeng Q. Biological interactions with Prochlorococcus: implications for the marine carbon cycle. Trends Microbiol 2024; 32:280-291. [PMID: 37722980 DOI: 10.1016/j.tim.2023.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 08/25/2023] [Accepted: 08/28/2023] [Indexed: 09/20/2023]
Abstract
The unicellular picocyanobacterium Prochlorococcus is the most abundant photoautotroph and contributes substantially to global CO2 fixation. In the vast euphotic zones of the open ocean, Prochlorococcus converts CO2 into organic compounds and supports diverse organisms, forming an intricate network of interactions that regulate the magnitude of carbon cycling and storage in the ocean. An understanding of the biological interactions with Prochlorococcus is critical for accurately estimating the contributions of Prochlorococcus and interacting organisms to the marine carbon cycle. This review synthesizes the primary production contributed by Prochlorococcus in the global ocean. We outline recent progress on the interactions of Prochlorococcus with heterotrophic bacteria, phages, and grazers that multifacetedly determine Prochlorococcus carbon production and fate. We discuss that climate change might affect the biological interactions with Prochlorococcus and thus the marine carbon cycle.
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Affiliation(s)
- Lanlan Cai
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Haofu Li
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China; HKUST Shenzhen-Hong Kong Collaborative Innovation Research Institute, Shenzhen, China
| | - Junwei Deng
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Ruiqian Zhou
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Qinglu Zeng
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China; HKUST Shenzhen-Hong Kong Collaborative Innovation Research Institute, Shenzhen, China; Center for Ocean Research in Hong Kong and Macau, The Hong Kong University of Science and Technology, Hong Kong, China.
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5
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Alonso-Sáez L, Palacio AS, Cabello AM, Robaina-Estévez S, González JM, Garczarek L, López-Urrutia Á. Transcriptional Mechanisms of Thermal Acclimation in Prochlorococcus. mBio 2023:e0342522. [PMID: 37052490 DOI: 10.1128/mbio.03425-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023] Open
Abstract
Low temperature limits the growth and the distribution of the key oceanic primary producer Prochlorococcus, which does not proliferate above a latitude of ca. 40°. Yet, the molecular basis of thermal acclimation in this cyanobacterium remains unexplored. We analyzed the transcriptional response of the Prochlorococcus marinus strain MIT9301 in long-term acclimations and in natural Prochlorococcus populations along a temperature range enabling its growth (17 to 30°C). MIT9301 upregulated mechanisms of the global stress response at the temperature minimum (17°C) but maintained the expression levels of genes involved in essential metabolic pathways (e.g., ATP synthesis and carbon fixation) along the whole thermal niche. Notably, the declining growth of MIT9301 from the optimum to the minimum temperature was coincident with a transcriptional suppression of the photosynthetic apparatus and a dampening of its circadian expression patterns, indicating a loss in their regulatory capacity under cold conditions. Under warm conditions, the cellular transcript inventory of MIT9301 was strongly streamlined, which may also induce regulatory imbalances due to stochasticity in gene expression. The daytime transcriptional suppression of photosynthetic genes at low temperature was also observed in metatranscriptomic reads mapping to MIT9301 across the global ocean, implying that this molecular mechanism may be associated with the restricted distribution of Prochlorococcus to temperate zones. IMPORTANCE Prochlorococcus is a major marine primary producer with a global impact on atmospheric CO2 fixation. This cyanobacterium is widely distributed across the temperate ocean, but virtually absent at latitudes above 40° for yet unknown reasons. Temperature has been suggested as a major limiting factor, but the exact mechanisms behind Prochlorococcus thermal growth restriction remain unexplored. This study brings us closer to understanding how Prochlorococcus functions under challenging temperature conditions, by focusing on its transcriptional response after long-term acclimation from its optimum to its thermal thresholds. Our results show that the drop in Prochlorococcus growth rate under cold conditions was paralleled by a transcriptional suppression of the photosynthetic machinery during daytime and a loss in the organism's regulatory capacity to maintain circadian expression patterns. Notably, warm temperature induced a marked shrinkage of the organism's cellular transcript inventory, which may also induce regulatory imbalances in the future functioning of this cyanobacterium.
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Affiliation(s)
- Laura Alonso-Sáez
- AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Antonio S Palacio
- AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Ana M Cabello
- AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | | | - José M González
- Department of Microbiology, University of La Laguna, La Laguna, Spain
| | - Laurence Garczarek
- Sorbonne Université, CNRS, UMR 7144 Adaptation and Diversity in the Marine Environment (AD2M), Station Biologique de Roscoff (SBR), Roscoff, France
| | - Ángel López-Urrutia
- Centro Oceanográfico de Gijón, Instituto Español de Oceanografía, IEO-CSIC, Gijón, Asturias, Spain
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6
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Phototroph-heterotroph interactions during growth and long-term starvation across Prochlorococcus and Alteromonas diversity. THE ISME JOURNAL 2023; 17:227-237. [PMID: 36335212 PMCID: PMC9860064 DOI: 10.1038/s41396-022-01330-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 10/02/2022] [Accepted: 10/05/2022] [Indexed: 11/08/2022]
Abstract
Due to their potential impact on ecosystems and biogeochemistry, microbial interactions, such as those between phytoplankton and bacteria, have been studied intensively using specific model organisms. Yet, to what extent interactions differ between closely related organisms, or how these interactions change over time, or culture conditions, remains unclear. Here, we characterize the interactions between five strains each of two globally abundant marine microorganisms, Prochlorococcus (phototroph) and Alteromonas (heterotroph), from the first encounter between individual strains and over more than a year of repeated cycles of exponential growth and long-term nitrogen starvation. Prochlorococcus-Alteromonas interactions had little effect on traditional growth parameters such as Prochlorococcus growth rate, maximal fluorescence, or lag phase, affecting primarily the dynamics of culture decline, which we interpret as representing cell mortality and lysis. The shape of the Prochlorococcus decline curve and the carrying capacity of the co-cultures were determined by the phototroph and not the heterotroph strains involved. Comparing various mathematical models of culture mortality suggests that Prochlorococcus death rate increases over time in mono-cultures but decreases in co-cultures, with cells potentially becoming more resistant to stress. Our results demonstrate intra-species differences in ecologically relevant co-culture outcomes. These include the recycling efficiency of N and whether the interactions are mutually synergistic or competitive. They also highlight the information-rich growth and death curves as a useful readout of the interaction phenotype.
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7
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Labban A, Shibl AA, Calleja ML, Hong PY, Morán XAG. Growth dynamics and transcriptional responses of a Red Sea Prochlorococcus strain to varying temperatures. Environ Microbiol 2022; 25:1007-1021. [PMID: 36567447 DOI: 10.1111/1462-2920.16326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 12/11/2022] [Indexed: 12/27/2022]
Abstract
Prochlorococcus play a crucial role in the ocean's biogeochemical cycling, but it remains controversial how they will respond to global warming. Here we assessed the response to temperature (22-30°C) of the growth dynamics and gene expression profiles of a Red Sea Prochlorococcus strain (RSP50) in a non-axenic culture. Both the specific growth rate (0.55-0.80 day-1 ) and cell size (0.04-0.07 μm3 ) of Prochlorococcus increased significantly with temperature. The primary production released extracellularly ranged from 20% to 34%, with humic-like fluorescent compounds increasing up to fivefold as Prochlorococcus reached its maximum abundance. At 30°C, genes involved in carbon fixation such as CsoS2 and CsoS3 and photosynthetic electron transport including PTOX were downregulated, suggesting a cellular homeostasis and energy saving mechanism response. In contrast, PTOX was found upregulated at 22°C and 24°C. Similar results were found for transaldolase, related to carbon metabolism, and citrate synthase, an important enzyme in the TCA cycle. Our data suggest that in spite of the currently warm temperatures of the Red Sea, Prochlorococcus can modulate its gene expression profiles to permit growth at temperatures lower than its optimum temperature (28°C) but is unable to cope with temperatures exceeding 30°C.
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Affiliation(s)
- Abbrar Labban
- Marine Science, Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia.,Environmental Science and Engineering, Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Ahmed A Shibl
- Genetic Heritage Group, Biology Program, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.,Public Health Research Center, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Maria Ll Calleja
- Climate Geochemistry Department, Max Plank Institute for Chemistry, Mainz, Germany
| | - Pei-Ying Hong
- Environmental Science and Engineering, Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Xosé Anxelu G Morán
- Marine Science, Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia.,Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía (IEO-CSIC), Gijón/Xixón, Spain
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8
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Wietz M, López-Pérez M, Sher D, Biller SJ, Rodriguez-Valera F. Microbe Profile: Alteromonas macleodii - a widespread, fast-responding, 'interactive' marine bacterium. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 36748580 DOI: 10.1099/mic.0.001236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Alteromonas macleodii is a marine heterotrophic bacterium with widespread distribution - from temperate to tropical oceans, and from surface to deep waters. Strains of A. macleodii exhibit considerable genomic and metabolic variability, and can grow rapidly on diverse organic compounds. A. macleodii is a model organism for the study of population genomics, physiological adaptations and microbial interactions, with individual genomes encoding diverse phenotypic traits influenced by recombination and horizontal gene transfer.
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Affiliation(s)
- Matthias Wietz
- Deep-Sea Ecology and Technology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.,Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Mario López-Pérez
- Evolutionary Genomics Group, División de Microbiología, Universidad Miguel Hernández, Alicante, Spain
| | - Daniel Sher
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
| | - Steven J Biller
- Department of Biological Sciences, Wellesley College, Wellesley, Massachusetts, USA
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9
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Heterotrophic Bacteria Dominate Catalase Expression during Microcystis Blooms. Appl Environ Microbiol 2022; 88:e0254421. [PMID: 35862723 PMCID: PMC9328184 DOI: 10.1128/aem.02544-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In the oligotrophic oceans, key autotrophs depend on "helper" bacteria to reduce oxidative stress from hydrogen peroxide (H2O2) in the extracellular environment. H2O2 is also a ubiquitous stressor in freshwaters, but the effects of H2O2 on autotrophs and their interactions with bacteria are less well understood in freshwaters. Naturally occurring H2O2 in freshwater systems is proposed to impact the proportion of microcystin-producing (toxic) and non-microcystin-producing (nontoxic) Microcystis in blooms, which influences toxin concentrations and human health impacts. However, how different strains of Microcystis respond to naturally occurring H2O2 concentrations and the microbes responsible for H2O2 decomposition in freshwater cyanobacterial blooms are unknown. To address these knowledge gaps, we used metagenomics and metatranscriptomics to track the presence and expression of genes for H2O2 decomposition by microbes during a cyanobacterial bloom in western Lake Erie in the summer of 2014. katG encodes the key enzyme for decomposing extracellular H2O2 but was absent in most Microcystis cells. katG transcript relative abundance was dominated by heterotrophic bacteria. In axenic Microcystis cultures, an H2O2 scavenger (pyruvate) significantly improved growth rates of one toxic strain while other toxic and nontoxic strains were unaffected. These results indicate that heterotrophic bacteria play a key role in H2O2 decomposition in Microcystis blooms and suggest that their activity may affect the fitness of some Microcystis strains and thus the strain composition of Microcystis blooms but not along a toxic versus nontoxic dichotomy. IMPORTANCE Cyanobacterial harmful algal blooms (CHABs) threaten freshwater ecosystems globally through the production of toxins. Toxin production by cyanobacterial species and strains during CHABs varies widely over time and space, but the ecological drivers of the succession of toxin-producing species remain unclear. Hydrogen peroxide (H2O2) is ubiquitous in natural waters, inhibits microbial growth, and may determine the relative proportions of Microcystis strains during blooms. However, the mechanisms and organismal interactions involved in H2O2 decomposition are unexplored in CHABs. This study shows that some strains of bloom-forming freshwater cyanobacteria benefit from detoxification of H2O2 by associated heterotrophic bacteria, which may impact bloom development.
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10
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Morris JJ, Rose AL, Lu Z. Reactive oxygen species in the world ocean and their impacts on marine ecosystems. Redox Biol 2022; 52:102285. [PMID: 35364435 PMCID: PMC8972015 DOI: 10.1016/j.redox.2022.102285] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 03/07/2022] [Accepted: 03/10/2022] [Indexed: 11/17/2022] Open
Abstract
Reactive oxygen species (ROS) are omnipresent in the ocean, originating from both biological (e.g., unbalanced metabolism or stress) and non-biological processes (e.g. photooxidation of colored dissolved organic matter). ROS can directly affect the growth of marine organisms, and can also influence marine biogeochemistry, thus indirectly impacting the availability of nutrients and food sources. Microbial communities and evolution are shaped by marine ROS, and in turn microorganisms influence steady-state ROS concentrations by acting as the predominant sink for marine ROS. Through their interactions with trace metals and organic matter, ROS can enhance microbial growth, but ROS can also attack biological macromolecules, causing extensive modifications with deleterious results. Several biogeochemically important taxa are vulnerable to very low ROS concentrations within the ranges measured in situ, including the globally distributed marine cyanobacterium Prochlorococcus and ammonia-oxidizing archaea of the phylum Thaumarchaeota. Finally, climate change may increase the amount of ROS in the ocean, especially in the most productive surface layers. In this review, we explore the sources of ROS and their roles in the oceans, how the dynamics of ROS might change in the future, and how this change might impact the ecology and chemistry of the future ocean.
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Affiliation(s)
- J Jeffrey Morris
- Department of Biology, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - Andrew L Rose
- Faculty of Science and Engineering, Southern Cross University, New South Wales, Australia
| | - Zhiying Lu
- Department of Biology, University of Alabama at Birmingham, Birmingham, AL, USA.
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11
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Mechanisms underlying interactions between two abundant oral commensal bacteria. THE ISME JOURNAL 2022; 16:948-957. [PMID: 34732850 PMCID: PMC8940909 DOI: 10.1038/s41396-021-01141-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 09/21/2021] [Accepted: 10/07/2021] [Indexed: 01/12/2023]
Abstract
Complex polymicrobial biofilm communities are abundant in nature particularly in the human oral cavity where their composition and fitness can affect health. While the study of these communities during disease is essential and prevalent, little is known about interactions within the healthy plaque community. Here we describe interactions between two of the most abundant species in this healthy microbiome, Haemophilus parainfluenzae and Streptococcus mitis. We discovered that H. parainfluenzae typically exists adjacent to mitis group streptococci in vivo with which it is also positively correlated based on microbiome data. By comparing in vitro coculture data to ex vivo microscopy we revealed that this co-occurrence is density dependent and further influenced by H2O2 production. We discovered that H. parainfluenzae utilizes a more redundant, multifactorial response to H2O2 than related microorganisms and that this system's integrity enhances streptococcal fitness. Our results indicate that mitis group streptococci are likely the in vivo source of NAD for H. parainfluenzae and also evoke patterns of carbon utilization in vitro for H. parainfluenzae similar to those observed in vivo. Our findings describe mechanistic interactions between two of the most abundant and prevalent members of healthy supragingival plaque that contribute to their in vivo survival.
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12
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Kearney SM, Coe A, Castro KG, Chisholm SW. Filter Plating Method for Rendering Picocyanobacteria Cultures Free of Heterotrophic Bacterial Contaminants and Clonal. Front Microbiol 2022; 13:821803. [PMID: 35250937 PMCID: PMC8888907 DOI: 10.3389/fmicb.2022.821803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 01/21/2022] [Indexed: 11/21/2022] Open
Abstract
Isolates of the marine picocyanobacteria, Prochlorococcus and Synechococcus, are often accompanied by diverse heterotrophic “contaminating” bacteria, which can act as confounding variables in otherwise controlled experiments. Traditional microbiological methods for eliminating contaminants, such as direct streak-plating, are often unsuccessful with this particular group of microorganisms. While they will grow in pour plates, colonies often remain contaminated with heterotrophic bacteria that can migrate through the soft agar. Additionally, axenic clones of picocyanobacteria can be recovered via dilution-to-extinction in liquid medium, but the efficiency of recovery is low, often requiring large numbers of 96-well plates. Here, we detail a simple and effective protocol for rendering cultures of Synechococcus and Prochlorococcus strains free of bacterial contaminants while at the same time yielding clonal isolates. We build on the fact that co-culture with specific heterotrophs—“helper heterotrophs”—is often necessary to grow colonies of picocyanobacteria from single cells in agar. Suspecting that direct physical contact between the helper and the picocyanobacterial cells was not necessary for the “helper effect,” we developed a protocol in which the helper cells are embedded in soft agar pour plates, a filter overlaid on the surface, and a picocyanobacterial culture is diluted and then spotted on top of the filter. With this approach, motile contaminants cannot swim to the colonies, and it is possible to obtain the expected number of colonies from a given input (i.e., a Poisson distribution of colonies with an expected value equal to the input number of cells), thus ensuring clonal colonies. Using this protocol, we rendered three strains of Synechococcus, two strains of Prochlorococcus, and 19 new strains of Synechococcus from coastal seawater clonal and free of heterotrophic bacteria. The simplicity of this approach should expand the repertoire of axenic picocyanobacterial strains available for controlled physiological experiments. It will also enable the study of microdiversity in populations of picocyanobacteria by facilitating large-scale isolation of picocyanobacterial clones from a single source, including direct isolation from natural seawater.
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Affiliation(s)
- Sean M Kearney
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Allison Coe
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Kurt G Castro
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Sallie W Chisholm
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
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13
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Prochlorococcus Exudate Stimulates Heterotrophic Bacterial Competition with Rival Phytoplankton for Available Nitrogen. mBio 2022; 13:e0257121. [PMID: 35012332 PMCID: PMC8749424 DOI: 10.1128/mbio.02571-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The marine cyanobacterium Prochlorococcus numerically dominates the phytoplankton community of the nutrient-limited open ocean, establishing itself as the most abundant photosynthetic organism on Earth. This ecological success has been attributed to lower cell quotas for limiting nutrients, superior resource acquisition, and other advantages associated with cell size reduction and genome streamlining. In this study, we tested the prediction that Prochlorococcus outcompetes its rivals for scarce nutrients and that this advantage leads to its numerical success in nutrient-limited waters. Strains of Prochlorococcus and its sister genus Synechococcus grew well in both mono- and cocultures when nutrients were replete. However, in nitrogen-limited medium, Prochlorococcus outgrew Synechococcus but only when heterotrophic bacteria were also present. In the nitrogen-limited medium, the heterotroph Alteromonas macleodii outcompeted Synechococcus for nitrogen but only if stimulated by the exudate released by Prochlorococcus or if a proxy organic carbon source was provided. Genetic analysis of Alteromonas suggested that it outcompetes Synechococcus for nitrate and/or nitrite, during which cocultured Prochlorococcus grows on ammonia or other available nitrogen species. We propose that Prochlorococcus can stimulate antagonism between heterotrophic bacteria and potential phytoplankton competitors through a metabolic cross-feeding interaction, and this stimulation could contribute to the numerical success of Prochlorococcus in nutrient-limited regions of the ocean. IMPORTANCE In nutrient-poor habitats, competition for limited resources is thought to select for organisms with an enhanced ability to scavenge nutrients and utilize them efficiently. Such adaptations characterize the cyanobacterium Prochlorococcus, the most abundant photosynthetic organism in the nutrient-limited open ocean. In this study, the competitive superiority of Prochlorococcus over a rival cyanobacterium, Synechococcus, was captured in laboratory culture. Critically, this outcome was achieved only when key aspects of the open ocean were simulated: a limited supply of nitrogen and the presence of heterotrophic bacteria. The results indicate that Prochlorococcus promotes its numerical dominance over Synechococcus by energizing the heterotroph's ability to outcompete Synechococcus for available nitrogen. This study demonstrates how interactions between trophic groups can influence interactions within trophic groups and how these interactions likely contribute to the success of the most abundant photosynthetic microorganism.
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Production of hydrogen peroxide in an intra-meander hyporheic zone at East River, Colorado. Sci Rep 2022; 12:712. [PMID: 35027569 PMCID: PMC8758664 DOI: 10.1038/s41598-021-04171-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 12/03/2021] [Indexed: 11/20/2022] Open
Abstract
The traditionally held assumption that photo-dependent processes are the predominant source of H2O2 in natural waters has been recently questioned by an increrasing body of evidence showing the ubiquitiousness of H2O2 in dark water bodies and in groundwater. In this study, we conducted field measurement of H2O2 in an intra-meander hyporheic zone and in surface water at East River, CO. On-site detection using a sensitive chemiluminescence method suggests H2O2 concentrations in groundwater ranging from 6 nM (at the most reduced region) to ~ 80 nM (in a locally oxygen-rich area) along the intra-meander transect with a maxima of 186 nM detected in the surface water in an early afternoon, lagging the maximum solar irradiance by ∼ 1.5 h. Our results suggest that the dark profile of H2O2 in the hyporheic zone is closely correlated to local redox gradients, indicating that interactions between various redox sensitive elements could play an essential role. Due to its transient nature, the widespread presence of H2O2 in the hyporheic zone indicates the existence of a sustained balance between H2O2 production and consumption, which potentially involves a relatively rapid succession of various biogeochemically important processes (such as organic matter turnover, metal cycling and contaminant mobilization). More importantly, this study confirmed the occurrence of reactive oxygen species at a subsurface redox transition zone and further support our understanding of redox boundaries on reactive oxygen species generation and as key locations of biogeochemical activity.
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15
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Han Y, Zhang M, Chen X, Zhai W, Tan E, Tang K. Transcriptomic evidences for microbial carbon and nitrogen cycles in the deoxygenated seawaters of Bohai Sea. ENVIRONMENT INTERNATIONAL 2022; 158:106889. [PMID: 34619534 DOI: 10.1016/j.envint.2021.106889] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Revised: 09/19/2021] [Accepted: 09/20/2021] [Indexed: 06/13/2023]
Abstract
Eutrophication-induced water deoxygenation occurs continually in coastal oceans, and alters community structure, metabolic processes, and the energy shunt, resulting in a major threat to the ecological environment. Seasonal deoxygenation events have occurred in the Bohai Sea (China), however, how these affect the functional activity of microorganisms remains unclear. Here, through the use of absolute quantification of 16S rRNA genes amplicon sequencing and metatranscriptomics approaches, we investigated the structure of the microbial community and the patterns of transcriptional activity in deoxygenated seawaters. The dominant phyla were Proteobacteria (average value, 1.4 × 106 copies ml-1), Cyanobacteria (3.7 × 105 copies ml-1), Bacteroidetes (2.7 × 105 copies ml-1), and the ammonia-oxidizing archaea Thaumarchaeota (1.9 × 105 copies ml-1). Among the various environmental factors, dissolved oxygen, pH and temperature displayed the most significant correlation with microbial community composition and functional activity. Metatranscriptomic data showed high transcriptional activity of Thaumarchaeota in the deoxygenated waters, with a significant increase in the expression of core genes representing ammonia oxidation, ammonia transport, and carbon fixation (3-hydroxypropionic acid/4-hydroxybutyric acid cycle) pathways. The transcripts of Cyanobacteria involved in photosynthesis and carbon fixation (Calvin-Benson-Bassham cycle) significantly decreased in low oxygen waters. Meanwhile, the transcripts for the ribulose bisphosphate carboxylase-encoding gene shifted from being assigned to photoautotrophic to chemoautotrophic organisms in surface and bottom waters, respectively. Moreover, the transcription profile indicated that heterotrophs play a critical role in transforming low-molecular-weight dissolved organic nitrogen. Elevated abundances of transcripts related to microbial antioxidant activity corresponded to an enhanced aerobic metabolism of Thaumarchaeota in the low oxygen seawater. In general, our transcriptional evidences showed a population increase of Thaumarchaeota, especially the coastal ecotype of ammonia oxidizers, in low oxygen aquatic environments, and indicated an enhanced contribution of chemolithoautotrophic carbon fixation to carbon flow.
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Affiliation(s)
- Yu Han
- State Key Laboratory of Marine Environmental Science, Fujian Key Laboratory of Marine Carbon Sequestration, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, Fujian, PR China
| | - Mu Zhang
- State Key Laboratory of Marine Environmental Science, Fujian Key Laboratory of Marine Carbon Sequestration, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, Fujian, PR China
| | - Xiaofeng Chen
- State Key Laboratory of Marine Environmental Science, Fujian Key Laboratory of Marine Carbon Sequestration, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, Fujian, PR China
| | - Weidong Zhai
- Institute of Marine Science and Technology, Shandong University, Qingdao 266000, Shandong, PR China
| | - Ehui Tan
- State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou 570228, Hainan, PR China
| | - Kai Tang
- State Key Laboratory of Marine Environmental Science, Fujian Key Laboratory of Marine Carbon Sequestration, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, Fujian, PR China.
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16
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Liu J, Chen J, Zuo K, Li H, Peng F, Ran Q, Wang R, Jiang Z, Song H. Chemically induced oxidative stress improved bacterial laccase-mediated degradation and detoxification of the synthetic dyes. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2021; 226:112823. [PMID: 34597843 DOI: 10.1016/j.ecoenv.2021.112823] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/15/2021] [Accepted: 09/21/2021] [Indexed: 06/13/2023]
Abstract
To alleviate the risk of textile effluent, the development of highly effective bioremediation strategies for synthetic dye removal is needed. Herein, we aimed to assess whether intensified bioactivity of Bacillus pumilus ZB1 by oxidative stress could improve the removal of textile dyes. Methyl methanesulfonate (MMS) induced oxidative stress significantly promoted laccase expression of B. pumilus ZB1. Both the level of hydrogen dioxide and superoxide anion showed a significant positive correlation with laccase activity (RSQ = 0.963 and 0.916, respectively) along with the change of MMS concentration. The regulation of laccase expression was closely related to oxidative stress. The overexpressed laccase in the supernatant improved the decolorization of synthetic dyes (16.43% for Congo Red, 54.05% for Crystal Violet, and 41.61% for Reactive Blue 4). Laccase was subsequently expressed in E. coli. Investigation of the potential of bacterial laccase in dye remediation using Congo Red showed that an effective degradation of azo dye could be achieved with laccase treatment. Laccase remediation alleviated the cytotoxicity of Congo Red to human hepatocytes. In silico study identified eight amino acid residues of laccase involved in binding with Congo Red. Overall, regulation of oxidative stress towards bacterium can be used as a promising approach for the improvement of bacterial bioactivity in synthetic dye remediation.
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Affiliation(s)
- Jiashu Liu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Industrial Biotechnology, School of Life Science, Hubei University, Wuhan 430062, PR China
| | - Jianhui Chen
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Industrial Biotechnology, School of Life Science, Hubei University, Wuhan 430062, PR China
| | - Kangjia Zuo
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Industrial Biotechnology, School of Life Science, Hubei University, Wuhan 430062, PR China
| | - Huanan Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Industrial Biotechnology, School of Life Science, Hubei University, Wuhan 430062, PR China
| | - Fang Peng
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, PR China
| | - Qiuping Ran
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Industrial Biotechnology, School of Life Science, Hubei University, Wuhan 430062, PR China
| | - Rui Wang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Industrial Biotechnology, School of Life Science, Hubei University, Wuhan 430062, PR China
| | - Zhengbing Jiang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Industrial Biotechnology, School of Life Science, Hubei University, Wuhan 430062, PR China
| | - Huiting Song
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei University, Wuhan 430062, PR China; Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, PR China.
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17
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Coe A, Biller SJ, Thomas E, Boulias K, Bliem C, Arellano A, Dooley K, Rasmussen AN, LeGault K, O'Keefe TJ, Stover S, Greer EL, Chisholm SW. Coping with darkness: The adaptive response of marine picocyanobacteria to repeated light energy deprivation. LIMNOLOGY AND OCEANOGRAPHY 2021; 66:3300-3312. [PMID: 34690365 PMCID: PMC8518828 DOI: 10.1002/lno.11880] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 03/22/2021] [Accepted: 05/29/2021] [Indexed: 06/13/2023]
Abstract
The picocyanobacteria Prochlorococcus and Synechococcus are found throughout the ocean's euphotic zone, where the daily light:dark cycle drives their physiology. Periodic deep mixing events can, however, move cells below this region, depriving them of light for extended periods of time. Here, we demonstrate that members of these genera can adapt to tolerate repeated periods of light energy deprivation. Strains kept in the dark for 3 d and then returned to the light initially required 18-26 d to resume growth, but after multiple rounds of dark exposure they began to regrow after only 1-2 d. This dark-tolerant phenotype was stable and heritable; some cultures retained the trait for over 132 generations even when grown in a standard 13:11 light:dark cycle. We found no genetic differences between the dark-tolerant and parental strains of Prochlorococcus NATL2A, indicating that an epigenetic change is likely responsible for the adaptation. To begin to explore this possibility, we asked whether DNA methylation-one potential mechanism mediating epigenetic inheritance in bacteria-occurs in Prochlorococcus. LC-MS/MS analysis showed that while DNA methylations, including 6 mA and 5 mC, are found in some other Prochlorococcus strains, there were no methylations detected in either the parental or dark-tolerant NATL2A strains. These findings suggest that Prochlorococcus utilizes a yet-to-be-determined epigenetic mechanism to adapt to the stress of extended light energy deprivation, and highlights phenotypic heterogeneity as an additional dimension of Prochlorococcus diversity.
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Affiliation(s)
- Allison Coe
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Steven J. Biller
- Department of Biological SciencesWellesley CollegeWellesleyMassachusettsUSA
| | - Elaina Thomas
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Konstantinos Boulias
- Division of Newborn MedicineBoston Children's HospitalBostonMassachusettsUSA
- Department of PediatricsHarvard Medical SchoolBostonMassachusettsUSA
| | - Christina Bliem
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Aldo Arellano
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Keven Dooley
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Anna N. Rasmussen
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Kristen LeGault
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Tyler J. O'Keefe
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Sarah Stover
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Eric L. Greer
- Division of Newborn MedicineBoston Children's HospitalBostonMassachusettsUSA
- Department of PediatricsHarvard Medical SchoolBostonMassachusettsUSA
| | - Sallie W. Chisholm
- Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
- Department of BiologyMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
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18
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Abstract
Microalgal cultures are often maintained in xenic conditions, i.e., with associated bacteria, and many studies indicate that these communities both are complex and have significant impacts on the physiology of the target photoautotroph. Here, we investigated the structure and stability of microbiomes associated with a diverse sampling of diatoms during long-term maintenance in serial batch culture. We found that, counter to our initial expectation, evenness diversity increased with time since cultivation, driven by a decrease in dominance by the most abundant taxa in each culture. We also found that the site from which and time at which a culture was initially collected had a stronger impact on microbiome structure than the diatom species; however, some bacterial taxa were commonly present in most cultures despite having widely geographically separated collection sites. Our results support the conclusion that stochastic initial conditions (i.e., the local microbial community at the collection site) are important for the long-term structure of these microbiomes, but deterministic forces such as negative frequency dependence and natural selection exerted by the diatom are also at work. IMPORTANCE Natural microbial communities are extremely complex, with many more species coexisting in the same place than there are different resources to support them. Understanding the forces that allow this high level of diversity has been a central focus of ecological and evolutionary theory for many decades. Here, we used stock cultures of diatoms, which were maintained for years in continuous growth alongside populations of bacteria, as proxies for natural communities. We show that the bacterial communities remained relatively stable for years, and there is evidence that ecological forces worked to stabilize coexistence instead of favoring competition and exclusion. We also show evidence that, despite some important regional differences in bacterial communities, there was a globally present core microbiome potentially selected for in these diatom cultures. Understanding interactions between bacteria and diatoms is important both for basic ecological science and for practical science, such as industrial biofuel production.
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19
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Roth Rosenberg D, Haber M, Goldford J, Lalzar M, Aharonovich D, Al-Ashhab A, Lehahn Y, Segrè D, Steindler L, Sher D. Particle-associated and free-living bacterial communities in an oligotrophic sea are affected by different environmental factors. Environ Microbiol 2021; 23:4295-4308. [PMID: 34036706 DOI: 10.1111/1462-2920.15611] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 05/23/2021] [Indexed: 12/20/2022]
Abstract
In the oceans and seas, environmental conditions change over multiple temporal and spatial scales. Here, we ask what factors affect the bacterial community structure across time, depth and size fraction during six seasonal cruises (2 years) in the ultra-oligotrophic Eastern Mediterranean Sea. The bacterial community varied most between size fractions (free-living (FL) vs. particle-associated), followed by depth and finally season. The FL community was taxonomically richer and more stable than the particle-associated (PA) one, which was characterized by recurrent 'blooms' of heterotrophic bacteria such as Alteromonas and Ralstonia. The heterotrophic FL and PA communities were also correlated with different environmental parameters: the FL population correlated with depth and phytoplankton, whereas PA bacteria were correlated primarily with the time of sampling. A significant part of the variability in community structure could, however, not be explained by the measured parameters. The metabolic potential of the PA community, predicted from 16S rRNA amplicon data using PICRUSt, was enriched in pathways associated with the degradation and utilization of biological macromolecules, as well as plastics, other petroleum products and herbicides. The FL community was enriched in predicted pathways for the metabolism of inositol phosphate, a potential phosphorus source, and of polycyclic aromatic hydrocarbons.
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Affiliation(s)
- Dalit Roth Rosenberg
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
| | - Markus Haber
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
| | | | - Maya Lalzar
- Bioinformatics Support Unit, University of Haifa, Haifa, Israel
| | - Dikla Aharonovich
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
| | - Ashraf Al-Ashhab
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel.,Microbial Metagenomics Division, Dead Sea and Arava Science Center, Masada, Israel
| | - Yoav Lehahn
- Department of Maritime Geosciences, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
| | - Daniel Segrè
- Bioinformatics Program, Boston University, Boston, MA, USA
| | - Laura Steindler
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
| | - Daniel Sher
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
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20
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Dick GJ, Duhaime MB, Evans JT, Errera RM, Godwin CM, Kharbush JJ, Nitschky HS, Powers MA, Vanderploeg HA, Schmidt KC, Smith DJ, Yancey CE, Zwiers CC, Denef VJ. The genetic and ecophysiological diversity of Microcystis. Environ Microbiol 2021; 23:7278-7313. [PMID: 34056822 DOI: 10.1111/1462-2920.15615] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 05/24/2021] [Accepted: 05/27/2021] [Indexed: 01/30/2023]
Abstract
Microcystis is a cyanobacterium that forms toxic blooms in freshwater ecosystems around the world. Biological variation among taxa within the genus is apparent through genetic and phenotypic differences between strains and via the spatial and temporal distribution of strains in the environment, and this fine-scale diversity exerts strong influence over bloom toxicity. Yet we do not know how varying traits of Microcystis strains govern their environmental distribution, the tradeoffs and links between these traits, or how they are encoded at the genomic level. Here we synthesize current knowledge on the importance of diversity within Microcystis and on the genes and traits that likely underpin ecological differentiation of taxa. We briefly review spatial and environmental patterns of Microcystis diversity in the field and genetic evidence for cohesive groups within Microcystis. We then compile data on strain-level diversity regarding growth responses to environmental conditions and explore evidence for variation of community interactions across Microcystis strains. Potential links and tradeoffs between traits are identified and discussed. The resulting picture, while incomplete, highlights key knowledge gaps that need to be filled to enable new models for predicting strain-level dynamics, which influence the development, toxicity and cosmopolitan nature of Microcystis blooms.
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Affiliation(s)
- Gregory J Dick
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA.,Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Melissa B Duhaime
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Jacob T Evans
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Reagan M Errera
- National Oceanographic and Atmospheric Administration Great Lakes Environmental Research Lab, Ann Arbor, MI, USA
| | - Casey M Godwin
- School for Environment and Sustainability, Cooperative Institute for Great Lakes Research, University of Michigan, Ann Arbor, MI, USA
| | - Jenan J Kharbush
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Helena S Nitschky
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - McKenzie A Powers
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Henry A Vanderploeg
- National Oceanographic and Atmospheric Administration Great Lakes Environmental Research Lab, Ann Arbor, MI, USA
| | - Kathryn C Schmidt
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Derek J Smith
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Colleen E Yancey
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Claire C Zwiers
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Vincent J Denef
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
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21
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Smith DJ, Tan JY, Powers MA, Lin XN, Davis TW, Dick GJ. Individual Microcystis colonies harbour distinct bacterial communities that differ by Microcystis oligotype and with time. Environ Microbiol 2021; 23:3020-3036. [PMID: 33830633 DOI: 10.1111/1462-2920.15514] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 03/11/2021] [Accepted: 04/06/2021] [Indexed: 12/31/2022]
Abstract
Interactions between bacteria and phytoplankton in the phycosphere have impacts at the scale of whole ecosystems, including the development of harmful algal blooms. The cyanobacterium Microcystis causes toxic blooms that threaten freshwater ecosystems and human health globally. Microcystis grows in colonies that harbour dense assemblages of other bacteria, yet the taxonomic composition of these phycosphere communities and the nature of their interactions with Microcystis are not well characterized. To identify the taxa and compositional variance within Microcystis phycosphere communities, we performed 16S rRNA V4 region amplicon sequencing on individual Microcystis colonies collected biweekly via high-throughput droplet encapsulation during a western Lake Erie cyanobacterial bloom. The Microcystis phycosphere communities were distinct from microbial communities in whole water and bulk phytoplankton seston in western Lake Erie but lacked 'core' taxa found across all colonies. However, dissimilarity in phycosphere community composition correlated with sampling date and the Microcystis 16S rRNA oligotype. Several taxa in the phycosphere were specific to and conserved with Microcystis of a single oligotype or sampling date. Together, this suggests that physiological differences between Microcystis strains, temporal changes in strain phenotypes, and the composition of seeding communities may impact community composition of the Microcystis phycosphere.
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Affiliation(s)
- Derek J Smith
- Department of Earth & Environmental Science, The University of Michigan, 1100 N. University Building, 1100 N. University Avenue, Ann Arbor, MI, 48109, USA
| | - James Y Tan
- Department of Chemical Engineering, The University of Michigan, NCRC, 2800 Plymouth Rd., Ann Abor, MI, 48109, USA
| | - McKenzie A Powers
- Department of Earth & Environmental Science, The University of Michigan, 1100 N. University Building, 1100 N. University Avenue, Ann Arbor, MI, 48109, USA
| | - Xiaoxia N Lin
- Department of Chemical Engineering, The University of Michigan, NCRC, 2800 Plymouth Rd., Ann Abor, MI, 48109, USA
| | - Timothy W Davis
- Department of Biological Sciences, Bowling Green State University, Life Sciences Building, Corner of N. College Dr and E. Merry Avenue, Bowling Green, OH, 43403, USA
| | - Gregory J Dick
- Department of Earth & Environmental Science, The University of Michigan, 1100 N. University Building, 1100 N. University Avenue, Ann Arbor, MI, 48109, USA
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22
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Dedman CJ, King AM, Christie-Oleza JA, Davies GL. Environmentally relevant concentrations of titanium dioxide nanoparticles pose negligible risk to marine microbes. ENVIRONMENTAL SCIENCE. NANO 2021; 8:1236-1255. [PMID: 34046180 PMCID: PMC8136324 DOI: 10.1039/d0en00883d] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 04/06/2021] [Indexed: 05/26/2023]
Abstract
Nano-sized titanium dioxide (nTiO2) represents the highest produced nanomaterial by mass worldwide and, due to its prevalent industrial and commercial use, it inevitably reaches the natural environment. Previous work has revealed a negative impact of nTiO2 upon marine phytoplankton growth, however, studies are typically carried out at concentrations far exceeding those measured and predicted to occur in the environment currently. Here, a series of experiments were carried out to assess the effects of both research-grade nTiO2 and nTiO2 extracted from consumer products upon the marine dominant cyanobacterium, Prochlorococcus, and natural marine communities at environmentally relevant and supra-environmental concentrations (i.e., 1 μg L-1 to 100 mg L-1). Cell declines observed in Prochlorococcus cultures were associated with the extensive aggregation behaviour of nTiO2 in saline media and the subsequent entrapment of microbial cells. Hence, higher concentrations of nTiO2 particles exerted a stronger decline of cyanobacterial populations. However, within natural oligotrophic seawater, cultures were able to recover over time as the nanoparticles aggregated out of solution after 72 h. Subsequent shotgun proteomic analysis of Prochlorococcus cultures exposed to environmentally relevant concentrations confirmed minimal molecular features of toxicity, suggesting that direct physical effects are responsible for short-term microbial population decline. In an additional experiment, the diversity and structure of natural marine microbial communities showed negligible variations when exposed to environmentally relevant nTiO2 concentrations (i.e., 25 μg L-1). As such, the environmental risk of nTiO2 towards marine microbial species appears low, however the potential for adverse effects in hotspots of contamination exists. In future, research must be extended to consider any effect of other components of nano-enabled product formulations upon nanomaterial fate and impact within the natural environment.
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Affiliation(s)
- Craig J Dedman
- School of Life Sciences, Gibbet Hill Campus, University of Warwick Coventry CV4 7AL UK
- Department of Chemistry, University of Warwick Gibbet Hill Coventry CV4 7EQ UK
| | - Aaron M King
- UCL Department of Chemistry, University College London 20 Gordon Street London WC1H 0AJ UK
| | - Joseph A Christie-Oleza
- School of Life Sciences, Gibbet Hill Campus, University of Warwick Coventry CV4 7AL UK
- Department of Biology, University of the Balearic Islands Ctra. Valldemossa, km 7.5 CP: 07122 Palma Spain
- IMEDEA (CSIC-UIB) CP: 07190 Esporles Spain
| | - Gemma-Louise Davies
- UCL Department of Chemistry, University College London 20 Gordon Street London WC1H 0AJ UK
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23
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Ofaim S, Sulheim S, Almaas E, Sher D, Segrè D. Dynamic Allocation of Carbon Storage and Nutrient-Dependent Exudation in a Revised Genome-Scale Model of Prochlorococcus. Front Genet 2021; 12:586293. [PMID: 33633777 PMCID: PMC7900632 DOI: 10.3389/fgene.2021.586293] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 01/14/2021] [Indexed: 12/02/2022] Open
Abstract
Microbial life in the oceans impacts the entire marine ecosystem, global biogeochemistry and climate. The marine cyanobacterium Prochlorococcus, an abundant component of this ecosystem, releases a significant fraction of the carbon fixed through photosynthesis, but the amount, timing and molecular composition of released carbon are still poorly understood. These depend on several factors, including nutrient availability, light intensity and glycogen storage. Here we combine multiple computational approaches to provide insight into carbon storage and exudation in Prochlorococcus. First, with the aid of a new algorithm for recursive filling of metabolic gaps (ReFill), and through substantial manual curation, we extended an existing genome-scale metabolic model of Prochlorococcus MED4. In this revised model (iSO595), we decoupled glycogen biosynthesis/degradation from growth, thus enabling dynamic allocation of carbon storage. In contrast to standard implementations of flux balance modeling, we made use of forced influx of carbon and light into the cell, to recapitulate overflow metabolism due to the decoupling of photosynthesis and carbon fixation from growth during nutrient limitation. By using random sampling in the ensuing flux space, we found that storage of glycogen or exudation of organic acids are favored when the growth is nitrogen limited, while exudation of amino acids becomes more likely when phosphate is the limiting resource. We next used COMETS to simulate day-night cycles and found that the model displays dynamic glycogen allocation and exudation of organic acids. The switch from photosynthesis and glycogen storage to glycogen depletion is associated with a redistribution of fluxes from the Entner–Doudoroff to the Pentose Phosphate pathway. Finally, we show that specific gene knockouts in iSO595 exhibit dynamic anomalies compatible with experimental observations, further demonstrating the value of this model as a tool to probe the metabolic dynamic of Prochlorococcus.
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Affiliation(s)
- Shany Ofaim
- Bioinformatics Program and Biological Design Center, Boston University, Boston, MA, United States.,Department of Marine Biology, University of Haifa, Haifa, Israel
| | - Snorre Sulheim
- Bioinformatics Program and Biological Design Center, Boston University, Boston, MA, United States.,Department of Biotechnology and Food Science, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.,Department of Biotechnology and Nanomedicine, SINTEF Industry, Trondheim, Norway
| | - Eivind Almaas
- Department of Biotechnology and Food Science, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.,K.G. Jebsen Center for Genetic Epidemiology, NTNU - Norwegian University of Science and Technology, Trondheim, Norway
| | - Daniel Sher
- Department of Marine Biology, University of Haifa, Haifa, Israel
| | - Daniel Segrè
- Bioinformatics Program and Biological Design Center, Boston University, Boston, MA, United States.,Department of Biomedical Engineering, Boston University, Boston, MA, United States.,Department of Physics, Boston University, Boston, MA, United States.,Department of Biology, Boston University, Boston, MA, United States
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Kearney SM, Thomas E, Coe A, Chisholm SW. Microbial diversity of co-occurring heterotrophs in cultures of marine picocyanobacteria. ENVIRONMENTAL MICROBIOME 2021; 16:1. [PMID: 33902739 PMCID: PMC8067657 DOI: 10.1186/s40793-020-00370-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 11/28/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND The cyanobacteria Prochlorococcus and Synechococcus are responsible for around 10% of global net primary productivity, serving as part of the foundation of marine food webs. Heterotrophic bacteria are often co-isolated with these picocyanobacteria in seawater enrichment cultures that contain no added organic carbon; heterotrophs grow on organic carbon supplied by the photolithoautotrophs. For examining the selective pressures shaping autotroph/heterotroph interactions, we have made use of unialgal enrichment cultures of Prochlorococcus and Synechococcus maintained for hundreds to thousands of generations in the lab. We examine the diversity of heterotrophs in 74 enrichment cultures of these picocyanobacteria obtained from diverse areas of the global oceans. RESULTS Heterotroph community composition differed between clades and ecotypes of the autotrophic 'hosts' but there was significant overlap in heterotroph community composition across these cultures. Collectively, the cultures were comprised of many shared taxa, even at the genus level. Yet, observed differences in community composition were associated with time since isolation, location, depth, and methods of isolation. The majority of heterotrophs in the cultures are rare in the global ocean, but enrichment conditions favor the opportunistic outgrowth of these rare bacteria. However, we found a few examples, such as bacteria in the family Rhodobacteraceae, of heterotrophs that were ubiquitous and abundant in cultures and in the global oceans. We found their abundance in the wild is also positively correlated with that of picocyanobacteria. CONCLUSIONS Particular conditions surrounding isolation have a persistent effect on long-term culture composition, likely from bottlenecking and selection that happen during the early stages of enrichment for the picocyanobacteria. We highlight the potential for examining ecologically relevant relationships by identifying patterns of distribution of culture-enriched organisms in the global oceans.
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Affiliation(s)
- Sean M. Kearney
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 15 Vassar St, Cambridge, MA 02139 USA
| | - Elaina Thomas
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 15 Vassar St, Cambridge, MA 02139 USA
| | - Allison Coe
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 15 Vassar St, Cambridge, MA 02139 USA
| | - Sallie W. Chisholm
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 15 Vassar St, Cambridge, MA 02139 USA
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25
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Co‐culture with
Synechococcus
facilitates growth of
Prochlorococcus
under ocean acidification conditions. Environ Microbiol 2020; 22:4876-4889. [DOI: 10.1111/1462-2920.15277] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 10/09/2020] [Accepted: 10/09/2020] [Indexed: 12/01/2022]
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26
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Prochlorococcus Cells Rely on Microbial Interactions Rather than on Chlorotic Resting Stages To Survive Long-Term Nutrient Starvation. mBio 2020; 11:mBio.01846-20. [PMID: 32788385 PMCID: PMC7439483 DOI: 10.1128/mbio.01846-20] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The ability of microorganisms to withstand long periods of nutrient starvation is key to their survival and success under highly fluctuating conditions that are common in nature. Therefore, one would expect this trait to be prevalent among organisms in the nutrient-poor open ocean. Here, we show that this is not the case for Prochlorococcus, a globally abundant and ecologically important marine cyanobacterium. Instead, Prochlorococcus relies on co-occurring heterotrophic bacteria to survive extended phases of nutrient and light starvation. Our results highlight the power of microbial interactions to drive major biogeochemical cycles in the ocean and elsewhere with consequences at the global scale. Many microorganisms produce resting cells with very low metabolic activity that allow them to survive phases of prolonged nutrient or energy stress. In cyanobacteria and some eukaryotic phytoplankton, the production of resting stages is accompanied by a loss of photosynthetic pigments, a process termed chlorosis. Here, we show that a chlorosis-like process occurs under multiple stress conditions in axenic laboratory cultures of Prochlorococcus, the dominant phytoplankton linage in large regions of the oligotrophic ocean and a global key player in ocean biogeochemical cycles. In Prochlorococcus strain MIT9313, chlorotic cells show reduced metabolic activity, measured as C and N uptake by Nanoscale secondary ion mass spectrometry (NanoSIMS). However, unlike many other cyanobacteria, chlorotic Prochlorococcus cells are not viable and do not regrow under axenic conditions when transferred to new media. Nevertheless, cocultures with a heterotrophic bacterium, Alteromonas macleodii HOT1A3, allowed Prochlorococcus to survive nutrient starvation for months. We propose that reliance on co-occurring heterotrophic bacteria, rather than the ability to survive extended starvation as resting cells, underlies the ecological success of Prochlorococcus.
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27
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Mena C, Reglero P, Balbín R, Martín M, Santiago R, Sintes E. Seasonal Niche Partitioning of Surface Temperate Open Ocean Prokaryotic Communities. Front Microbiol 2020; 11:1749. [PMID: 32849378 PMCID: PMC7399227 DOI: 10.3389/fmicb.2020.01749] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 07/03/2020] [Indexed: 12/20/2022] Open
Abstract
Surface microbial communities are exposed to seasonally changing environmental conditions, resulting in recurring patterns of community composition. However, knowledge on temporal dynamics of open ocean microbial communities remains scarce. Seasonal patterns and associations of taxa and oligotypes from surface and chlorophyll maximum layers in the western Mediterranean Sea were studied over a 2-year period. Summer stratification versus winter mixing governed not only the prokaryotic community composition and diversity but also the temporal dynamics and co-occurrence association networks of oligotypes. Flavobacteriales, Rhodobacterales, SAR11, SAR86, and Synechococcales oligotypes exhibited contrasting seasonal dynamics, and consequently, specific microbial assemblages and potential inter-oligotype connections characterized the different seasons. In addition, oligotypes composition and dynamics differed between surface and deep chlorophyll maximum (DCM) prokaryotic communities, indicating depth-related environmental gradients as a major factor affecting association networks between closely related taxa. Taken together, the seasonal and depth specialization of oligotypes suggest temporal dynamics of community composition and metabolism, influencing ecosystem function and global biogeochemical cycles. Moreover, our results indicate highly specific associations between microbes, pointing to keystone ecotypes and fine-tuning of the microbes realized niche.
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Affiliation(s)
- Catalina Mena
- Instituto Español de Oceanografía (IEO), Centre Oceanogràfic de les Balears, Ecosystem Oceanography Group (GRECO), Palma, Spain
| | - Patricia Reglero
- Instituto Español de Oceanografía (IEO), Centre Oceanogràfic de les Balears, Ecosystem Oceanography Group (GRECO), Palma, Spain
| | - Rosa Balbín
- Instituto Español de Oceanografía (IEO), Centre Oceanogràfic de les Balears, Ecosystem Oceanography Group (GRECO), Palma, Spain
| | - Melissa Martín
- Instituto Español de Oceanografía (IEO), Centre Oceanogràfic de les Balears, Ecosystem Oceanography Group (GRECO), Palma, Spain
| | - Rocío Santiago
- Instituto Español de Oceanografía (IEO), Centre Oceanogràfic de les Balears, Ecosystem Oceanography Group (GRECO), Palma, Spain
| | - Eva Sintes
- Instituto Español de Oceanografía (IEO), Centre Oceanogràfic de les Balears, Ecosystem Oceanography Group (GRECO), Palma, Spain
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28
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Xian WD, Salam N, Li MM, Zhou EM, Yin YR, Liu ZT, Ming YZ, Zhang XT, Wu G, Liu L, Xiao M, Jiang HC, Li WJ. Network-directed efficient isolation of previously uncultivated Chloroflexi and related bacteria in hot spring microbial mats. NPJ Biofilms Microbiomes 2020; 6:20. [PMID: 32350263 PMCID: PMC7190741 DOI: 10.1038/s41522-020-0131-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 04/07/2020] [Indexed: 12/16/2022] Open
Abstract
The perplexity of the complex multispecies community interactions is one of the many reasons why majority of the microorganisms are still uncultivated. We analyzed the entire co-occurrence networks between the OTUs of Tibet and Yunnan hot spring samples, and found that less abundant OTUs such as genus Tepidimonas (relative abundant <1%) had high-degree centricity (key nodes), while dominant OTUs particularly genus Chloroflexus (relative abundant, 13.9%) formed the peripheral vertexes. A preliminary growth-promotion assay determined that Tepidimonas sp. strain SYSU G00190W enhanced the growth of Chloroflexus sp. SYSU G00190R. Exploiting this result, an ameliorated isolation medium containing 10% spent-culture supernatant of Tepidimonas sp. strain SYSU G00190W was prepared for targeted isolation of Chloroflexi in the Tibet and Yunnan hot spring samples. 16S rRNA gene fingerprinting characterized majority of the colonies isolated from these media as previously uncultivated Chloroflexi, of which 36 are potential novel species (16S rRNA sequence identity <98.5%). Metabolomes studies indicated that the spent-culture supernatant comprises several low-molecular-weight organic substrates that can be utilized as potential nutrients for the growth of these bacteria. These findings suggested that limited knowledge on the interaction of microbes provide threshold to traditional isolation method.
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Affiliation(s)
- Wen-Dong Xian
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Nimaichand Salam
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Meng-Meng Li
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - En-Min Zhou
- School of Resource Environment and Earth Science, Yunnan Institute of Geography, Yunnan University, Kunming, 650091, China
| | - Yi-Rui Yin
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Ze-Tao Liu
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Yu-Zhen Ming
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Xiao-Tong Zhang
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Geng Wu
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, China
| | - Lan Liu
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Min Xiao
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Hong-Chen Jiang
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, China
| | - Wen-Jun Li
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Sciences and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, School of Ecology, Sun Yat-sen University, Guangzhou, 510275, China.
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29
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Zinser ER. The microbial contribution to reactive oxygen species dynamics in marine ecosystems. ENVIRONMENTAL MICROBIOLOGY REPORTS 2018; 10:412-427. [PMID: 29411545 DOI: 10.1111/1758-2229.12626] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/28/2018] [Indexed: 05/21/2023]
Abstract
This review surveys the current state of knowledge of the concentrations, sources and sinks of reactive oxygen species (ROS) in the ocean. Both abiotic and biotic factors contribute to ROS dynamics in seawater, and ROS can feature prominently in marine microbe-microbe interactions. The sun plays a key role in the production of ROS in the ocean, and consequently ROS concentrations are typically maximal in the sun-exposed surface. However, microbes can also contribute significantly to extracellular ROS. Production of superoxide is widespread within the microbial community, and may benefit the producers as antimicrobial agents or perhaps more generally, as a means of nutrient scavenging. Decomposition of hydrogen peroxide is a community-wide activity, though some members may play less significant roles in this process. The more reactive forms of ROS, singlet oxygen and the hydroxyl radical, may be less important as microbial stressors, as they tend to react with the chemicals in seawater before they can contact the cells. However, exceptions may exist for microbes attached to singlet oxygen-generating sinking particulate matter. Extracellular ROS thus plays an important role in the ecology of marine microbes, the full extent to which we are only beginning to appreciate.
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Affiliation(s)
- Erik R Zinser
- Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
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30
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Zinser ER. Cross-protection from hydrogen peroxide by helper microbes: the impacts on the cyanobacterium Prochlorococcus and other beneficiaries in marine communities. ENVIRONMENTAL MICROBIOLOGY REPORTS 2018; 10:399-411. [PMID: 29411546 DOI: 10.1111/1758-2229.12625] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/25/2018] [Accepted: 01/27/2017] [Indexed: 05/27/2023]
Abstract
Hydrogen peroxide (HOOH) is a reactive oxygen species, derived from molecular oxygen, that is capable of damaging microbial cells. Surprisingly, the HOOH defence systems of some aerobes in the oxygenated marine environments are critically depleted, relative to model aerobes. For instance, the gene encoding catalase is absent in the numerically dominant photosynthetic cyanobacterium, Prochlorococcus. Accordingly, Prochlorococcus is highly susceptible to HOOH when exposed as pure cultures. Pure cultures do not exist in the marine environment, however. Catalase-positive community members can remove HOOH from the seawater medium, thus lowering the threat to Prochlorococcus and any other member that likewise lacks their own catalase. This cross-protection may constitute a loosely defined symbiosis, whereby the catalase-positive helper cells may benefit through the acquisition of nutrients released by the beneficiaries such as Prochlorococcus. Other members of the community that may be helped by the catalase-positive cells may include some lineages of Synechococcus - the sister genus of Prochlorococcus - as well as some lineages of SAR11 and ammonia oxidizing archaea and bacteria. The co-occurrence of catalase-positive and -negative members suggests that cross-protection from HOOH-mediated oxidative stress may play an important role in the construction of the marine microbial community.
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Affiliation(s)
- Erik R Zinser
- Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
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31
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Heterotroph Interactions Alter Prochlorococcus Transcriptome Dynamics during Extended Periods of Darkness. mSystems 2018; 3:mSystems00040-18. [PMID: 29854954 PMCID: PMC5974335 DOI: 10.1128/msystems.00040-18] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/01/2018] [Indexed: 12/13/2022] Open
Abstract
Microbes evolve within complex ecological communities where biotic interactions impact both individual cells and the environment as a whole. Here we examine how cellular regulation in the marine cyanobacterium Prochlorococcus is influenced by a heterotrophic bacterium, Alteromonas macleodii, under different light conditions. We monitored the transcriptome of Prochlorococcus, grown either alone or in coculture, across a diel light:dark cycle and under the stress of extended darkness-a condition that cells would experience when mixed below the ocean's euphotic zone. More Prochlorococcus transcripts exhibited 24-h periodic oscillations in coculture than in pure culture, both over the normal diel cycle and after the shift to extended darkness. This demonstrates that biotic interactions, and not just light, can affect timing mechanisms in Prochlorococcus, which lacks a self-sustaining circadian oscillator. The transcriptomes of replicate pure cultures of Prochlorococcus lost their synchrony within 5 h of extended darkness and reflected changes in stress responses and metabolic functions consistent with growth cessation. In contrast, when grown with Alteromonas, replicate Prochlorococcus transcriptomes tracked each other for at least 13 h in the dark and showed signs of continued biosynthetic and metabolic activity. The transcriptome patterns suggest that the heterotroph may be providing energy or essential biosynthetic substrates to Prochlorococcus in the form of organic compounds, sustaining this autotroph when it is deprived of solar energy. Our findings reveal conditions where mixotrophic metabolism may benefit marine cyanobacteria and highlight new impacts of community interactions on basic Prochlorococcus cellular processes. IMPORTANCEProchlorococcus is the most abundant photosynthetic organism on the planet. These cells play a central role in the physiology of surrounding heterotrophs by supplying them with fixed organic carbon. It is becoming increasingly clear, however, that interactions with heterotrophs can affect autotrophs as well. Here we show that such interactions have a marked impact on the response of Prochlorococcus to the stress of extended periods of darkness, as reflected in transcriptional dynamics. These data suggest that diel transcriptional rhythms within Prochlorococcus, which are generally considered to be strictly under the control of light quantity, quality, and timing, can also be influenced by biotic interactions. Together, these findings provide new insights into the importance of microbial interactions on Prochlorococcus physiology and reveal conditions where heterotroph-derived compounds may support autotrophs-contrary to the canonical autotroph-to-heterotroph trophic paradigm.
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