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Hernandez AR, Parker E, Babar M, Banerjee A, Ding S, Simley A, Buford TW. Microbiome-driven alterations in metabolic pathways and impaired cognition in aged female TgF344-AD rats. AGING BRAIN 2024; 5:100119. [PMID: 38881651 PMCID: PMC11179252 DOI: 10.1016/j.nbas.2024.100119] [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: 01/15/2024] [Revised: 05/09/2024] [Accepted: 05/28/2024] [Indexed: 06/18/2024] Open
Abstract
Alzheimer's disease (AD) not only affects cognition and neuropathology, but several other facets capable of negatively impacting quality of life and potentially driving impairments, including altered gut microbiome (GMB) composition and metabolism. Aged (20 + mo) female TgF344-AD and wildtype rats were cognitively characterized on several tasks incorporating several cognitive domains, including task acquisition, object recognition memory, anxiety-like behaviors, and spatial navigation. Additionally, metabolic phenotyping, GMB sequencing throughout the intestinal tract (duodenum, jejunum, ileum, colon, and feces), neuropathological burden assessment and marker gene functional abundance predictions (PICRUSt2) were conducted. TgF344-AD rats demonstrated significant cognitive impairment in multiple domains, as well as regionally specific GMB dysbiosis. Relationships between peripheral factors were investigated using Canonical Correspondence Analysis (CCA), revealing correlations between GMB changes and both cognitive and metabolic factors. Moreover, communities of gut microbes contributing to essential metabolic pathways were significantly altered in TgF344-AD rats. These data indicate dysbiosis may affect cognitive outcomes in AD through alterations in metabolism-related enzymatic pathways that are necessary for proper brain function. Moreover, these changes were mostly observed in intestinal segments required for carbohydrate digestion, not fecal samples. These data support the targeting of intestinal and microbiome health for the treatment of AD.
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Affiliation(s)
- Abbi R Hernandez
- Department of Medicine, Division of Geriatrics, Gerontology & Palliative Care, University of Alabama at Birmingham, Birmingham, AL 35205, USA
| | - Erik Parker
- Department of Epidemiology and Biostatistics, School of Public Health, Indiana University-Bloomington, Bloomington, IN 47405, USA
| | - Maham Babar
- Department of Medicine, Division of Geriatrics, Gerontology & Palliative Care, University of Alabama at Birmingham, Birmingham, AL 35205, USA
| | - Anisha Banerjee
- Department of Medicine, Division of Geriatrics, Gerontology & Palliative Care, University of Alabama at Birmingham, Birmingham, AL 35205, USA
| | - Sarah Ding
- Department of Medicine, Division of Geriatrics, Gerontology & Palliative Care, University of Alabama at Birmingham, Birmingham, AL 35205, USA
| | - Alexis Simley
- Department of Medicine, Division of Geriatrics, Gerontology & Palliative Care, University of Alabama at Birmingham, Birmingham, AL 35205, USA
| | - Thomas W Buford
- Department of Medicine, Division of Geriatrics, Gerontology & Palliative Care, University of Alabama at Birmingham, Birmingham, AL 35205, USA
- Birmingham/Atlanta VA GRECC, Birmingham VA Medical Center, Birmingham, AL 35244, USA
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Coskun ÖK, Gomez-Saez GV, Beren M, Özcan D, Günay SD, Elkin V, Hoşgörmez H, Einsiedl F, Eisenreich W, Orsi WD. Quantifying genome-specific carbon fixation in a 750-meter deep subsurface hydrothermal microbial community. FEMS Microbiol Ecol 2024; 100:fiae062. [PMID: 38632042 DOI: 10.1093/femsec/fiae062] [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: 11/13/2023] [Revised: 02/16/2024] [Accepted: 04/16/2024] [Indexed: 04/19/2024] Open
Abstract
Dissolved inorganic carbon has been hypothesized to stimulate microbial chemoautotrophic activity as a biological sink in the carbon cycle of deep subsurface environments. Here, we tested this hypothesis using quantitative DNA stable isotope probing of metagenome-assembled genomes (MAGs) at multiple 13C-labeled bicarbonate concentrations in hydrothermal fluids from a 750-m deep subsurface aquifer in the Biga Peninsula (Turkey). The diversity of microbial populations assimilating 13C-labeled bicarbonate was significantly different at higher bicarbonate concentrations, and could be linked to four separate carbon-fixation pathways encoded within 13C-labeled MAGs. Microbial populations encoding the Calvin-Benson-Bassham cycle had the highest contribution to carbon fixation across all bicarbonate concentrations tested, spanning 1-10 mM. However, out of all the active carbon-fixation pathways detected, MAGs affiliated with the phylum Aquificae encoding the reverse tricarboxylic acid (rTCA) pathway were the only microbial populations that exhibited an increased 13C-bicarbonate assimilation under increasing bicarbonate concentrations. Our study provides the first experimental data supporting predictions that increased bicarbonate concentrations may promote chemoautotrophy via the rTCA cycle and its biological sink for deep subsurface inorganic carbon.
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Affiliation(s)
- Ömer K Coskun
- Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Richard-Wagner Straße 10, 80333 Munich, Germany
| | - Gonzalo V Gomez-Saez
- Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Richard-Wagner Straße 10, 80333 Munich, Germany
- GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner Straße 10, 80333 Munich, Germany
| | - Murat Beren
- Department of Geological Engineering, Istanbul University - Cerrahpasa, Büyükçekmece Campus, Block G, Floor 5, Istanbul, Turkey
| | - Doğacan Özcan
- Department of Geological Engineering, Istanbul University - Cerrahpasa, Büyükçekmece Campus, Block G, Floor 5, Istanbul, Turkey
| | - Suna D Günay
- Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Richard-Wagner Straße 10, 80333 Munich, Germany
| | - Viktor Elkin
- Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Richard-Wagner Straße 10, 80333 Munich, Germany
| | - Hakan Hoşgörmez
- Department of Geological Engineering, Istanbul University - Cerrahpasa, Büyükçekmece Campus, Block G, Floor 5, Istanbul, Turkey
| | - Florian Einsiedl
- Chair of Hydrogeology, School of Engineering and Design, Technical University Munich, Arcisstraße 21, 80333 Munich, Germany
| | - Wolfgang Eisenreich
- Lehrstuhl für Biochemie, Department Chemie, Technische Universität München, Lichtenbergstraße, 85748 Garching, Germany
| | - William D Orsi
- Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Richard-Wagner Straße 10, 80333 Munich, Germany
- GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner Straße 10, 80333 Munich, Germany
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Barnett SE, Buckley DH. Metagenomic stable isotope probing reveals bacteriophage participation in soil carbon cycling. Environ Microbiol 2023; 25:1785-1795. [PMID: 37139849 DOI: 10.1111/1462-2920.16395] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 04/25/2023] [Indexed: 05/05/2023]
Abstract
Soil viruses are important components of the carbon (C) cycle, yet we still know little about viral ecology in soils. We added diverse 13 C-labelled carbon sources to soil and we used metagenomic-SIP to detect 13 C assimilation by viruses and their putative bacterial hosts. These data allowed us to link a 13 C-labelled bacteriophage to its 13 C-labelled Streptomyces putative host, and we used qPCR to track the dynamics of the putative host and phage in response to C inputs. Following C addition, putative host numbers increased rapidly for 3 days, and then more gradually, reaching maximal abundance on Day 6. Viral abundance and virus:host ratio increased dramatically over 6 days, and remained high thereafter (8.42 ± 2.94). From Days 6 to 30, virus:host ratio remained high, while putative host numbers declined more than 50%. Putative host populations were 13 C-labelled on Days 3-30, while 13 C-labelling of phage was detected on Days 14 and 30. This dynamic suggests rapid growth and 13 C-labelling of the host fueled by new C inputs, followed by extensive host mortality driven by phage lysis. These findings indicate that the viral shunt promotes microbial turnover in soil following new C inputs, thereby altering microbial community dynamics, and facilitating soil organic matter production.
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Affiliation(s)
- Samuel E Barnett
- Soil and Crop Sciences Section, School of Integrative Plant Science, Cornell University, Ithaca, New York, USA
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Daniel H Buckley
- Soil and Crop Sciences Section, School of Integrative Plant Science, Cornell University, Ithaca, New York, USA
- Department of Microbiology, Cornell University, Ithaca, New York, USA
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Wassan JT, Wang H, Zheng H. Developing a New Phylogeny-Driven Random Forest Model for Functional Metagenomics. IEEE Trans Nanobioscience 2023; 22:763-770. [PMID: 37279136 DOI: 10.1109/tnb.2023.3283462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Metagenomics is an unobtrusive science linking microbial genes to biological functions or environmental states. Classifying microbial genes into their functional repertoire is an important task in the downstream analysis of Metagenomic studies. The task involves Machine Learning (ML) based supervised methods to achieve good classification performance. Random Forest (RF) has been applied rigorously to microbial gene abundance profiles, mapping them to functional phenotypes. The current research targets tuning RF by the evolutionary ancestry of microbial phylogeny, developing a Phylogeny-RF model for functional classification of metagenomes. This method facilitates capturing the effects of phylogenetic relatedness in an ML classifier itself rather than just applying a supervised classifier over the raw abundances of microbial genes. The idea is rooted in the fact that closely related microbes by phylogeny are highly correlated and tend to have similar genetic and phenotypic traits. Such microbes behave similarly; and hence tend to be selected together, or one of these could be dropped from the analysis, to improve the ML process. The proposed Phylogeny-RF algorithm has been compared with state-of-the-art classification methods including RF and the phylogeny-aware methods of MetaPhyl and PhILR, using three real-world 16S rRNA metagenomic datasets. It has been observed that the proposed method not only achieved significantly better performance than the traditional RF model but also performed better than the other phylogeny-driven benchmarks (p < 0.05). For example, Phylogeny-RF attained a highest AUC of 0.949 and Kappa of 0.891 over soil microbiomes in comparison to other benchmarks.
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Vyshenska D, Sampara P, Singh K, Tomatsu A, Kauffman WB, Nuccio EE, Blazewicz SJ, Pett-Ridge J, Louie KB, Varghese N, Kellom M, Clum A, Riley R, Roux S, Eloe-Fadrosh EA, Ziels RM, Malmstrom RR. A standardized quantitative analysis strategy for stable isotope probing metagenomics. mSystems 2023; 8:e0128022. [PMID: 37377419 PMCID: PMC10469821 DOI: 10.1128/msystems.01280-22] [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: 12/19/2022] [Accepted: 04/19/2023] [Indexed: 06/29/2023] Open
Abstract
Stable isotope probing (SIP) facilitates culture-independent identification of active microbial populations within complex ecosystems through isotopic enrichment of nucleic acids. Many DNA-SIP studies rely on 16S rRNA gene sequences to identify active taxa, but connecting these sequences to specific bacterial genomes is often challenging. Here, we describe a standardized laboratory and analysis framework to quantify isotopic enrichment on a per-genome basis using shotgun metagenomics instead of 16S rRNA gene sequencing. To develop this framework, we explored various sample processing and analysis approaches using a designed microbiome where the identity of labeled genomes and their level of isotopic enrichment were experimentally controlled. With this ground truth dataset, we empirically assessed the accuracy of different analytical models for identifying active taxa and examined how sequencing depth impacts the detection of isotopically labeled genomes. We also demonstrate that using synthetic DNA internal standards to measure absolute genome abundances in SIP density fractions improves estimates of isotopic enrichment. In addition, our study illustrates the utility of internal standards to reveal anomalies in sample handling that could negatively impact SIP metagenomic analyses if left undetected. Finally, we present SIPmg, an R package to facilitate the estimation of absolute abundances and perform statistical analyses for identifying labeled genomes within SIP metagenomic data. This experimentally validated analysis framework strengthens the foundation of DNA-SIP metagenomics as a tool for accurately measuring the in situ activity of environmental microbial populations and assessing their genomic potential. IMPORTANCE Answering the questions, "who is eating what?" and "who is active?" within complex microbial communities is paramount for our ability to model, predict, and modulate microbiomes for improved human and planetary health. These questions can be pursued using stable isotope probing to track the incorporation of labeled compounds into cellular DNA during microbial growth. However, with traditional stable isotope methods, it is challenging to establish links between an active microorganism's taxonomic identity and genome composition while providing quantitative estimates of the microorganism's isotope incorporation rate. Here, we report an experimental and analytical workflow that lays the foundation for improved detection of metabolically active microorganisms and better quantitative estimates of genome-resolved isotope incorporation, which can be used to further refine ecosystem-scale models for carbon and nutrient fluxes within microbiomes.
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Affiliation(s)
- Dariia Vyshenska
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Pranav Sampara
- Department of Civil Engineering, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Kanwar Singh
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Andy Tomatsu
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - W. Berkeley Kauffman
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Erin E. Nuccio
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Steven J. Blazewicz
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Jennifer Pett-Ridge
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
- Life & Environmental Sciences Department, University of California Merced, Merced, California, USA
| | - Katherine B. Louie
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Neha Varghese
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Matthew Kellom
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Alicia Clum
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Robert Riley
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Simon Roux
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Emiley A. Eloe-Fadrosh
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Ryan M. Ziels
- Department of Civil Engineering, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Rex R. Malmstrom
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
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Wei W, Wong CC, Jia Z, Liu W, Liu C, Ji F, Pan Y, Wang F, Wang G, Zhao L, Chu ESH, Zhang X, Sung JJY, Yu J. Parabacteroides distasonis uses dietary inulin to suppress NASH via its metabolite pentadecanoic acid. Nat Microbiol 2023; 8:1534-1548. [PMID: 37386075 PMCID: PMC10390331 DOI: 10.1038/s41564-023-01418-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/26/2023] [Indexed: 07/01/2023]
Abstract
Non-alcoholic steatohepatitis (NASH) is the severe form of non-alcoholic fatty liver disease, and is characterized by liver inflammation and fat accumulation. Dietary interventions, such as fibre, have been shown to alleviate this metabolic disorder in mice via the gut microbiota. Here, we investigated the mechanistic role of the gut microbiota in ameliorating NASH via dietary fibre in mice. Soluble fibre inulin was found to be more effective than insoluble fibre cellulose to suppress NASH progression in mice, as shown by reduced hepatic steatosis, necro-inflammation, ballooning and fibrosis. We employed stable isotope probing to trace the incorporation of 13C-inulin into gut bacterial genomes and metabolites during NASH progression. Shotgun metagenome sequencing revealed that the commensal Parabacteroides distasonis was enriched by 13C-inulin. Integration of 13C-inulin metagenomes and metabolomes suggested that P. distasonis used inulin to produce pentadecanoic acid, an odd-chain fatty acid, which was confirmed in vitro and in germ-free mice. P. distasonis or pentadecanoic acid was protective against NASH in mice. Mechanistically, inulin, P. distasonis or pentadecanoic acid restored gut barrier function in NASH models, which reduced serum lipopolysaccharide and liver pro-inflammatory cytokine expression. Overall this shows that gut microbiota members can use dietary fibre to generate beneficial metabolites to suppress metabolic disease.
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Affiliation(s)
- Wenchao Wei
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Chi Chun Wong
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Zhongjun Jia
- State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
- Institute of Soil Science, Chinese Academy of Science, Nanjing, China
| | - Weixin Liu
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Changan Liu
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Fenfen Ji
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Yasi Pan
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Feixue Wang
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Guoping Wang
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Liuyang Zhao
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Eagle S H Chu
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Xiang Zhang
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Joseph J Y Sung
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Jun Yu
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China.
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Jin Y, Lu Y. Syntrophic Propionate Oxidation: One of the Rate-Limiting Steps of Organic Matter Decomposition in Anoxic Environments. Appl Environ Microbiol 2023; 89:e0038423. [PMID: 37097179 PMCID: PMC10231205 DOI: 10.1128/aem.00384-23] [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] [Indexed: 04/26/2023] Open
Abstract
Syntrophic propionate oxidation is one of the rate-limiting steps during anaerobic decomposition of organic matter in anoxic environments. Syntrophic propionate-oxidizing bacteria (SPOB) are members of the "rare biosphere" living at the edge of the thermodynamic limit in most natural habitats. Hitherto, only 10 bacterial species capable of syntrophic propionate oxidization have been identified. SPOB employ different metabolisms for propionate oxidation (e.g., methylmalonyl-CoA pathway and C6 dismutation pathway) and show diverse life strategies (e.g., obligately and facultatively syntrophic lifestyle). The flavin-based electron bifurcation/confurcation (FBEB/C) systems have been proposed to help solve the thermodynamic dilemma during the formation of the low-potential products H2 and formate. Molecular ecological approaches, such as DNA stable isotope probing (DNA-SIP) and metagenomics, have been used to detect SPOB in natural environments. Furthermore, the biogeographical pattern of SPOB has been recently described in paddy soils. A comprehensive understanding of SPOB is essential for better predicting and managing organic matter decomposition and carbon cycling in anoxic environments. In this review, we described the critical role of syntrophic propionate oxidation in anaerobic decomposition of organic matter, phylogenetic and metabolic diversity, life strategies and ecophysiology, composition of syntrophic partners, and pattern of biogeographic distribution of SPOB in natural environments. We ended up with a few perspectives for future research.
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Affiliation(s)
- Yidan Jin
- College of Urban and Environmental Sciences, Peking University, Beijing, China
| | - Yahai Lu
- College of Urban and Environmental Sciences, Peking University, Beijing, China
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Vera-Gargallo B, Hernández M, Dumont MG, Ventosa A. Thrive or survive: prokaryotic life in hypersaline soils. ENVIRONMENTAL MICROBIOME 2023; 18:17. [PMID: 36915176 PMCID: PMC10012753 DOI: 10.1186/s40793-023-00475-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 02/24/2023] [Indexed: 06/18/2023]
Abstract
BACKGROUND Soil services are central to life on the planet, with microorganisms as their main drivers. Thus, the evaluation of soil quality requires an understanding of the principles and factors governing microbial dynamics within it. High salt content is a constraint for life affecting more than 900 million hectares of land, a number predicted to rise at an alarming rate due to changing climate. Nevertheless, little is known about how microbial life unfolds in these habitats. In this study, DNA stable-isotope probing (DNA-SIP) with 18O-water was used to determine for the first time the taxa able to grow in hypersaline soil samples (ECe = 97.02 dS/m). We further evaluated the role of light on prokaryotes growth in this habitat. RESULTS We detected growth of both archaea and bacteria, with taxon-specific growth patterns providing insights into the drivers of success in saline soils. Phylotypes related to extreme halophiles, including haloarchaea and Salinibacter, which share an energetically efficient mechanism for salt adaptation (salt-in strategy), dominated the active community. Bacteria related to moderately halophilic and halotolerant taxa, such as Staphylococcus, Aliifodinibius, Bradymonadales or Chitinophagales also grew during the incubations, but they incorporated less heavy isotope. Light did not stimulate prokaryotic photosynthesis but instead restricted the growth of most bacteria and reduced the diversity of archaea that grew. CONCLUSIONS The results of this study suggest that life in saline soils is energetically expensive and that soil heterogeneity and traits such as exopolysaccharide production or predation may support growth in hypersaline soils. The contribution of phototrophy to supporting the heterotrophic community in saline soils remains unclear. This study paves the way toward a more comprehensive understanding of the functioning of these environments, which is fundamental to their management. Furthermore, it illustrates the potential of further research in saline soils to deepen our understanding of the effect of salinity on microbial communities.
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Affiliation(s)
- Blanca Vera-Gargallo
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, 41012, Sevilla, Spain
- School of Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Marcela Hernández
- School of Biological Sciences, Norwich Research Park, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Marc G Dumont
- School of Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - Antonio Ventosa
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, 41012, Sevilla, Spain.
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9
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Jameson E, Taubert M, Angel R, Coyotzi S, Chen Y, Eyice Ö, Schäfer H, Murrell JC, Neufeld JD, Dumont MG. DNA-, RNA-, and Protein-Based Stable-Isotope Probing for High-Throughput Biomarker Analysis of Active Microorganisms. Methods Mol Biol 2023; 2555:261-282. [PMID: 36306091 DOI: 10.1007/978-1-0716-2795-2_17] [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] [Indexed: 06/16/2023]
Abstract
Stable-isotope probing (SIP) enables researchers to target active populations within complex microbial communities, which is achieved by providing growth substrates enriched in heavy isotopes, usually in the form of 13C, 18O, or 15N. After growth on the substrate and subsequent extraction of microbial biomarkers, typically nucleic acids or proteins, the SIP technique is used for the recovery and analysis of isotope-labelled biomarkers from active microbial populations. In the years following the initial development of DNA- and RNA-based SIP, it was common practice to characterize labelled populations by targeted gene analysis. Such approaches usually involved fingerprint-based analyses or sequencing clone libraries containing 16S rRNA genes or functional marker gene amplicons. Although molecular fingerprinting remains a valuable approach for rapid confirmation of isotope labelling, recent advances in sequencing technology mean that it is possible to obtain affordable and comprehensive amplicon profiles, or even metagenomes and metatranscriptomes from SIP experiments. Not only can the abundance of microbial groups be inferred from metagenomes, but researchers can bin, assemble, and explore individual genomes to build hypotheses about the metabolic capabilities of labelled microorganisms. Analysis of labelled mRNA is a more recent advance that can provide independent metatranscriptome-based analysis of active microorganisms. The power of metatranscriptomics is that mRNA abundance often correlates closely with the corresponding activity of encoded enzymes, thus providing insight into microbial metabolism at the time of sampling. Together, these advances have improved the sensitivity of SIP methods and allowed using labelled substrates at environmentally relevant concentrations. Particularly as methods improve and costs continue to drop, we expect that the integration of SIP with multiple omics-based methods will become prevalent components of microbial ecology studies, leading to further breakthroughs in our understanding of novel microbial populations and elucidation of the metabolic function of complex microbial communities. In this chapter, we provide protocols for obtaining labelled DNA, RNA, and proteins that can be used for downstream omics-based analyses.
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Affiliation(s)
- Eleanor Jameson
- School of Life Sciences, University of Warwick, Coventry, UK
| | - Martin Taubert
- Aquatic Geochemistry, Institute of Biodiversity, Friedrich Schiller University, Jena, Germany
| | - Roey Angel
- Soil & Water Research Infrastructure and Institute of Soil Biology, Biology Centre CAS, České Budějovice, Czechia
| | - Sara Coyotzi
- Department of Biology, University of Waterloo, Waterloo, Canada
| | - Yin Chen
- School of Life Sciences, University of Warwick, Coventry, UK
| | - Özge Eyice
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Hendrik Schäfer
- School of Life Sciences, University of Warwick, Coventry, UK
| | - J Colin Murrell
- School of Environmental Sciences, University of East Anglia, Norwich, UK
| | - Josh D Neufeld
- Department of Biology, University of Waterloo, Waterloo, Canada
| | - Marc G Dumont
- School of Biological Sciences, University of Southampton, Southampton, UK.
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Barnett SE, Youngblut ND, Buckley DH. Bacterial community dynamics explain carbon mineralization and assimilation in soils of different land-use history. Environ Microbiol 2022; 24:5230-5247. [PMID: 35920035 DOI: 10.1111/1462-2920.16146] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 07/16/2022] [Accepted: 07/20/2022] [Indexed: 11/30/2022]
Abstract
Soil dwelling microorganisms are key players in the terrestrial carbon cycle, driving both the degradation and stabilization of soil organic matter. Bacterial community structure and function vary with respect to land-use, yet the ecological drivers of this variation remain poorly described and difficult to predict. We conducted a multi-substrate DNA-stable isotope probing experiment across cropland, old-field, and forest habitats to link carbon mineralization dynamics with the dynamics of bacterial growth and carbon assimilation. We tracked the movement of 13 C derived from five distinct carbon sources as it was assimilated into bacterial DNA over time. We show that carbon mineralization, community composition, and carbon assimilation dynamics all differed with respect to land-use. We also show that microbial community dynamics affect carbon assimilation dynamics and are associated with soil DNA content. Soil DNA yield is easy to measure and may be useful in predicting microbial community dynamics linked to soil carbon cycling. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Samuel E Barnett
- School of Integrative Plant Science, Cornell University, Ithaca, NY, USA
| | - Nicholas D Youngblut
- Department of Microbiome Science, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Daniel H Buckley
- School of Integrative Plant Science, Cornell University, Ithaca, NY, USA
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11
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Barnett SE, Youngblut ND, Koechli CN, Buckley DH. Multisubstrate DNA stable isotope probing reveals guild structure of bacteria that mediate soil carbon cycling. Proc Natl Acad Sci U S A 2021; 118:e2115292118. [PMID: 34799453 PMCID: PMC8617410 DOI: 10.1073/pnas.2115292118] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 10/10/2021] [Indexed: 11/18/2022] Open
Abstract
Soil microorganisms determine the fate of soil organic matter (SOM), and their activities compose a major component of the global carbon (C) cycle. We employed a multisubstrate, DNA-stable isotope probing experiment to track bacterial assimilation of C derived from distinct sources that varied in bioavailability. This approach allowed us to measure microbial contributions to SOM processing by measuring the C assimilation dynamics of diverse microorganisms as they interacted within soil. We identified and tracked 1,286 bacterial taxa that assimilated 13C in an agricultural soil over a period of 48 d. Overall 13C-assimilation dynamics of bacterial taxa, defined by the source and timing of the 13C they assimilated, exhibited low phylogenetic conservation. We identified bacterial guilds composed of taxa that had similar 13C assimilation dynamics. We show that C-source bioavailability explained significant variation in both C mineralization dynamics and guild structure, and that the growth dynamics of bacterial guilds differed significantly in response to C addition. We also demonstrate that the guild structure explains significant variation in the biogeographical distribution of bacteria at continental and global scales. These results suggest that an understanding of in situ growth dynamics is essential for understanding microbial contributions to soil C cycling. We interpret these findings in the context of bacterial life history strategies and their relationship to terrestrial C cycling.
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Affiliation(s)
- Samuel E Barnett
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14853
| | - Nicholas D Youngblut
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14853
- Department of Microbiome Science, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Chantal N Koechli
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14853
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA 19104
| | - Daniel H Buckley
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14853;
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12
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Thomas F, Le Duff N, Wu TD, Cébron A, Uroz S, Riera P, Leroux C, Tanguy G, Legeay E, Guerquin-Kern JL. Isotopic tracing reveals single-cell assimilation of a macroalgal polysaccharide by a few marine Flavobacteria and Gammaproteobacteria. THE ISME JOURNAL 2021; 15:3062-3075. [PMID: 33953365 PMCID: PMC8443679 DOI: 10.1038/s41396-021-00987-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 03/25/2021] [Accepted: 04/09/2021] [Indexed: 02/03/2023]
Abstract
Algal polysaccharides constitute a diverse and abundant reservoir of organic matter for marine heterotrophic bacteria, central to the oceanic carbon cycle. We investigated the uptake of alginate, a major brown macroalgal polysaccharide, by microbial communities from kelp-dominated coastal habitats. Congruent with cell growth and rapid substrate utilization, alginate amendments induced a decrease in bacterial diversity and a marked compositional shift towards copiotrophic bacteria. We traced 13C derived from alginate into specific bacterial incorporators and quantified the uptake activity at the single-cell level, using halogen in situ hybridization coupled to nanoscale secondary ion mass spectrometry (HISH-SIMS) and DNA stable isotope probing (DNA-SIP). Cell-specific alginate uptake was observed for Gammaproteobacteria and Flavobacteriales, with carbon assimilation rates ranging from 0.14 to 27.50 fg C µm-3 h-1. DNA-SIP revealed that only a few initially rare Flavobacteriaceae and Alteromonadales taxa incorporated 13C from alginate into their biomass, accounting for most of the carbon assimilation based on bulk isotopic measurements. Functional screening of metagenomic libraries gave insights into the genes of alginolytic Alteromonadales active in situ. These results highlight the high degree of niche specialization in heterotrophic communities and help constraining the quantitative role of polysaccharide-degrading bacteria in coastal ecosystems.
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Affiliation(s)
- François Thomas
- Sorbonne Université, CNRS, Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), Roscoff, France.
| | - Nolwen Le Duff
- Sorbonne Université, CNRS, Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), Roscoff, France
| | - Ting-Di Wu
- Institut Curie, Université Paris-Saclay, Paris, France
- Université Paris-Saclay, INSERM US43, CNRS UMS2016, Multimodal Imaging Center, Orsay, France
| | | | - Stéphane Uroz
- Université de Lorraine, INRAE, UMR1136 « Interactions Arbres-Microorganismes », Champenoux, France
| | - Pascal Riera
- Sorbonne Université, CNRS, UMR7144, Station Biologique de Roscoff (SBR), Roscoff, France
| | - Cédric Leroux
- CNRS, Sorbonne Université, FR2424, Metabomer, Station Biologique de Roscoff, Roscoff, France
| | - Gwenn Tanguy
- CNRS, Sorbonne Université, FR2424, Genomer, Station Biologique de Roscoff, Roscoff, France
| | - Erwan Legeay
- CNRS, Sorbonne Université, FR2424, Genomer, Station Biologique de Roscoff, Roscoff, France
| | - Jean-Luc Guerquin-Kern
- Institut Curie, Université Paris-Saclay, Paris, France
- Université Paris-Saclay, INSERM US43, CNRS UMS2016, Multimodal Imaging Center, Orsay, France
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13
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Conover AE, Morando M, Zhao Y, Semones J, Hutchins DA, Webb EA. Alphaproteobacteria facilitate Trichodesmium community trimethylamine utilization. Environ Microbiol 2021; 23:6798-6810. [PMID: 34519133 DOI: 10.1111/1462-2920.15773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 08/26/2021] [Accepted: 09/09/2021] [Indexed: 11/28/2022]
Abstract
In the surface waters of the warm oligotrophic ocean, filaments and aggregated colonies of the nitrogen (N)-fixing cyanobacterium Trichodesmium create microscale nutrient-rich oases. These hotspots fuel primary productivity and harbour a diverse consortium of heterotrophs. Interactions with associated microbiota can affect the physiology of Trichodesmium, often in ways that have been predicted to support its growth. Recently, it was found that trimethylamine (TMA), a globally abundant organic N compound, inhibits N2 fixation in cultures of Trichodesmium without impairing growth rate, suggesting that Trichodesmium can use TMA as an alternate N source. In this study, 15 N-TMA DNA stable isotope probing (SIP) of a Trichodesmium enrichment was employed to further investigate TMA metabolism and determine whether TMA-N is incorporated directly or secondarily via cross-feeding facilitated by microbial associates. Herein, we identify two members of the marine Roseobacter clade (MRC) of Alphaproteobacteria as the likely metabolizers of TMA and provide genomic evidence that they converted TMA into a more readily available form of N, e.g., ammonium (NH4 + ), which was subsequently used by Trichodesmium and the rest of the community. The results implicate microbiome-mediated carbon (C) and N transformations in modulating N2 fixation and thus highlight the involvement of host-associated heterotrophs in global biogeochemical cycling.
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Affiliation(s)
- Asa E Conover
- Department of Marine and Environmental Biology, University of Southern California, CA, USA
| | - Michael Morando
- Department of Marine and Environmental Biology, University of Southern California, CA, USA
| | - Yiming Zhao
- Department of Marine and Environmental Biology, University of Southern California, CA, USA
| | - Jacob Semones
- Department of Marine and Environmental Biology, University of Southern California, CA, USA
| | - David A Hutchins
- Department of Marine and Environmental Biology, University of Southern California, CA, USA
| | - Eric A Webb
- Department of Marine and Environmental Biology, University of Southern California, CA, USA
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14
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Coskun ÖK, Vuillemin A, Schubotz F, Klein F, Sichel SE, Eisenreich W, Orsi WD. Quantifying the effects of hydrogen on carbon assimilation in a seafloor microbial community associated with ultramafic rocks. ISME JOURNAL 2021; 16:257-271. [PMID: 34312482 PMCID: PMC8692406 DOI: 10.1038/s41396-021-01066-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 07/05/2021] [Accepted: 07/09/2021] [Indexed: 11/09/2022]
Abstract
Thermodynamic models predict that H2 is energetically favorable for seafloor microbial life, but how H2 affects anabolic processes in seafloor-associated communities is poorly understood. Here, we used quantitative 13C DNA stable isotope probing (qSIP) to quantify the effect of H2 on carbon assimilation by microbial taxa synthesizing 13C-labeled DNA that are associated with partially serpentinized peridotite rocks from the equatorial Mid-Atlantic Ridge. The rock-hosted seafloor community was an order of magnitude more diverse compared to the seawater community directly above the rocks. With added H2, peridotite-associated taxa increased assimilation of 13C-bicarbonate and 13C-acetate into 16S rRNA genes of operational taxonomic units by 146% (±29%) and 55% (±34%), respectively, which correlated with enrichment of H2-oxidizing NiFe-hydrogenases encoded in peridotite-associated metagenomes. The effect of H2 on anabolism was phylogenetically organized, with taxa affiliated with Atribacteria, Nitrospira, and Thaumarchaeota exhibiting the most significant increases in 13C-substrate assimilation in the presence of H2. In SIP incubations with added H2, an order of magnitude higher number of peridotite rock-associated taxa assimilated 13C-bicarbonate, 13C-acetate, and 13C-formate compared to taxa that were not associated with peridotites. Collectively, these findings indicate that the unique geochemical nature of the peridotite-hosted ecosystem has selected for H2-metabolizing, rock-associated taxa that can increase anabolism under high H2 concentrations. Because ultramafic rocks are widespread in slow-, and ultraslow-spreading oceanic lithosphere, continental margins, and subduction zones where H2 is formed in copious amounts, the link between H2 and carbon assimilation demonstrated here may be widespread within these geological settings.
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Affiliation(s)
- Ömer K Coskun
- Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany
| | - Aurèle Vuillemin
- Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany.,GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Potsdam, Germany
| | - Florence Schubotz
- MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Frieder Klein
- Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Susanna E Sichel
- Departamento de Geologia e Geofísica/LAGEMAR-Universidade Federal Fluminense-Brazil, Niterói, RJ, Brazil
| | - Wolfgang Eisenreich
- Department of Chemistry, Bavarian NMR Center-Structural Membrane Biochemistry, Technische Universität München, Garching, Germany
| | - William D Orsi
- Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany. .,GeoBio-CenterLMU, Ludwig-Maximilians-Universität München, Munich, Germany.
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15
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Suominen S, van Vliet DM, Sánchez-Andrea I, van der Meer MTJ, Sinninghe Damsté JS, Villanueva L. Organic Matter Type Defines the Composition of Active Microbial Communities Originating From Anoxic Baltic Sea Sediments. Front Microbiol 2021; 12:628301. [PMID: 34025597 PMCID: PMC8131844 DOI: 10.3389/fmicb.2021.628301] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 04/06/2021] [Indexed: 11/13/2022] Open
Abstract
Carbon cycling in anoxic marine sediments is dependent on uncultured microbial communities. Niches of heterotrophic microorganisms are defined by organic matter (OM) type and the different phases in OM degradation. We investigated how OM type defines microbial communities originating from organic-rich, anoxic sediments from the Baltic Sea. We compared changes in the sediment microbial community, after incubation with different stable isotope labeled OM types [i.e., particulate algal organic matter (PAOM), protein, and acetate], by using DNA stable isotope probing (DNA-SIP). Incorporation of 13C and/or 15N label was predominantly detected in members of the phyla Planctomycetes and Chloroflexi, which also formed the majority (>50%) of the original sediment community. While these phylum-level lineages incorporated label from all OM types, phylogenetic analyses revealed a niche separation at the order level. Members of the MSBL9 (Planctomycetes), the Anaerolineales (Chloroflexi), and the class Bathyarchaeota, were identified as initial degraders of carbohydrate-rich OM, while other uncultured orders, like the CCM11a and Phycisphaerales (Planctomycetes), Dehalococcoidia, and JG30-KF-CM66 (Chloroflexi), incorporated label also from protein and acetate. Our study highlights the importance of initial fermentation of complex carbon pools in shaping anoxic sediment microbial communities and reveals niche specialization at the order level for the most important initial degraders in anoxic sediments.
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Affiliation(s)
- Saara Suominen
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, Netherlands
| | - Daan M. van Vliet
- Wageningen Food and Biobased Research (WFBR), Bornse Weilanden 9, Wageningen, Netherlands
- Laboratory of Microbiology, Wageningen University, Wageningen, Netherlands
| | | | - Marcel T. J. van der Meer
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, Netherlands
| | - Jaap S. Sinninghe Damsté
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, Netherlands
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Laura Villanueva
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, Netherlands
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
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16
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Competitive Exclusion and Metabolic Dependency among Microorganisms Structure the Cellulose Economy of an Agricultural Soil. mBio 2021; 12:mBio.03099-20. [PMID: 33402535 PMCID: PMC8545098 DOI: 10.1128/mbio.03099-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microorganisms that degrade cellulose utilize extracellular reactions that yield free by-products which can promote interactions with noncellulolytic organisms. We hypothesized that these interactions determine the ecological and physiological traits governing the fate of cellulosic carbon (C) in soil. We performed comparative genomics with genome bins from a shotgun metagenomic-stable isotope probing experiment to characterize the attributes of cellulolytic and noncellulolytic taxa accessing 13C from cellulose. We hypothesized that cellulolytic taxa would exhibit competitive traits that limit access, while noncellulolytic taxa would display greater metabolic dependency, such as signatures of adaptive gene loss. We tested our hypotheses by evaluating genomic traits indicative of competitive exclusion or metabolic dependency, such as antibiotic production, growth rate, surface attachment, biomass degrading potential, and auxotrophy. The most 13C-enriched taxa were cellulolytic Cellvibrio (Gammaproteobacteria) and Chaetomium (Ascomycota), which exhibited a strategy of self-sufficiency (prototrophy), rapid growth, and competitive exclusion via antibiotic production. Auxotrophy was more prevalent in cellulolytic Actinobacteria than in cellulolytic Proteobacteria, demonstrating differences in dependency among cellulose degraders. Noncellulolytic taxa that accessed 13C from cellulose (Planctomycetales, Verrucomicrobia, and Vampirovibrionales) were also more dependent, as indicated by patterns of auxotrophy and 13C labeling (i.e., partial labeling or labeling at later stages). Major 13C-labeled cellulolytic microbes (e.g., Sorangium, Actinomycetales, Rhizobiales, and Caulobacteraceae) possessed adaptations for surface colonization (e.g., gliding motility, hyphae, attachment structures) signifying the importance of surface ecology in decomposing particulate organic matter. Our results demonstrated that access to cellulosic C was accompanied by ecological trade-offs characterized by differing degrees of metabolic dependency and competitive exclusion.
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17
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Kapili BJ, Barnett SE, Buckley DH, Dekas AE. Evidence for phylogenetically and catabolically diverse active diazotrophs in deep-sea sediment. ISME JOURNAL 2020; 14:971-983. [PMID: 31907368 PMCID: PMC7082343 DOI: 10.1038/s41396-019-0584-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 12/16/2019] [Accepted: 12/19/2019] [Indexed: 12/18/2022]
Abstract
Diazotrophic microorganisms regulate marine productivity by alleviating nitrogen limitation. However, we know little about the identity and activity of diazotrophs in deep-sea sediments, a habitat covering nearly two-thirds of the planet. Here, we identify candidate diazotrophs from Pacific Ocean sediments collected at 2893 m water depth using 15N-DNA stable isotope probing and a novel pipeline for nifH sequence analysis. Together, these approaches detect an unexpectedly diverse assemblage of active diazotrophs, including members of the Acidobacteria, Firmicutes, Nitrospirae, Gammaproteobacteria, and Deltaproteobacteria. Deltaproteobacteria, predominately members of the Desulfobacterales and Desulfuromonadales, are the most abundant diazotrophs detected, and display the most microdiversity of associated nifH sequences. Some of the detected lineages, including those within the Acidobacteria, have not previously been shown to fix nitrogen. The diazotrophs appear catabolically diverse, with the potential for using oxygen, nitrogen, iron, sulfur, and carbon as terminal electron acceptors. Therefore, benthic diazotrophy may persist throughout a range of geochemical conditions and provide a stable source of fixed nitrogen over geologic timescales. Our results suggest that nitrogen-fixing communities in deep-sea sediments are phylogenetically and catabolically diverse, and open a new line of inquiry into the ecology and biogeochemical impacts of deep-sea microorganisms.
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Affiliation(s)
- Bennett J Kapili
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA.
| | - Samuel E Barnett
- School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA
| | - Daniel H Buckley
- School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA
| | - Anne E Dekas
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA.
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18
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Metabolic activity analyses demonstrate that Lokiarchaeon exhibits homoacetogenesis in sulfidic marine sediments. Nat Microbiol 2019; 5:248-255. [PMID: 31873205 DOI: 10.1038/s41564-019-0630-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 11/04/2019] [Indexed: 01/09/2023]
Abstract
The genomes of the Asgard superphylum of Archaea hold clues pertaining to the nature of the host cell that acquired the mitochondrion at the origin of eukaryotes1-4. Representatives of the Asgard candidate phylum Candidatus Lokiarchaeota (Lokiarchaeon) have the capacity for acetogenesis and fermentation5-7, but how their metabolic activity responds to environmental conditions is poorly understood. Here, we show that in anoxic Namibian shelf sediments, Lokiarchaeon gene expression levels are higher than those of bacterial phyla and increase with depth below the seafloor. Lokiarchaeon gene expression was significantly different across a hypoxic-sulfidic redox gradient, whereby genes involved in growth, fermentation and H2-dependent carbon fixation had the highest expression under the most reducing (sulfidic) conditions. Quantitative stable isotope probing revealed that anaerobic utilization of CO2 and diatomaceous extracellular polymeric substances by Lokiarchaeon was higher than the bacterial average, consistent with higher expression of Lokiarchaeon genes, including those involved in transport and fermentation of sugars and amino acids. The quantitative stable isotope probing and gene expression data demonstrate homoacetogenic activity of Candidatus Lokiarchaeota, whereby fermentative H2 production from organic substrates is coupled with the Wood-Ljungdahl carbon fixation pathway8. The high energetic efficiency provided by homoacetogenesis8 helps to explain the elevated metabolic activity of Lokiarchaeon in this anoxic, energy-limited setting.
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19
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Quantifying population-specific growth in benthic bacterial communities under low oxygen using H 218O. ISME JOURNAL 2019; 13:1546-1559. [PMID: 30783213 PMCID: PMC6776007 DOI: 10.1038/s41396-019-0373-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 01/26/2019] [Accepted: 01/31/2019] [Indexed: 01/09/2023]
Abstract
The benthos in estuarine environments often experiences periods of regularly occurring hypoxic and anoxic conditions, dramatically impacting biogeochemical cycles. How oxygen depletion affects the growth of specific uncultivated microbial populations within these diverse benthic communities, however, remains poorly understood. Here, we applied H218O quantitative stable isotope probing (qSIP) in order to quantify the growth of diverse, uncultured bacterial populations in response to low oxygen concentrations in estuarine sediments. Over the course of 7- and 28-day incubations with redox conditions spanning from hypoxia to euxinia (sulfidic), 18O labeling of bacterial populations exhibited different patterns consistent with micro-aerophilic, anaerobic, facultative anaerobic, and aerotolerant anaerobic growth. 18O-labeled populations displaying anaerobic growth had a significantly non-random phylogenetic distribution, exhibited by numerous clades currently lacking cultured representatives within the Planctomycetes, Actinobacteria, Latescibacteria, Verrucomicrobia, and Acidobacteria. Genes encoding the beta-subunit of the dissimilatory sulfate reductase (dsrB) became 18O labeled only during euxinic conditions. Sequencing of these 18O-labeled dsrB genes showed that Acidobacteria were the dominant group of growing sulfate-reducing bacteria, highlighting their importance for sulfur cycling in estuarine sediments. Our findings provide the first experimental constraints on the redox conditions underlying increased growth in several groups of "microbial dark matter", validating hypotheses put forth by earlier metagenomic studies.
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20
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Angel R. Experimental Setup and Data Analysis Considerations for DNA- and RNA-SIP Experiments in the Omics Era. Methods Mol Biol 2019; 2046:1-15. [PMID: 31407292 DOI: 10.1007/978-1-4939-9721-3_1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Careful and thoughtful experimental design is crucial to the success of any SIP experiment. This chapter discusses the essential aspects of designing a SIP experiment, focusing primarily on DNA- and RNA-SIP. The design aspects discussed here begin with considerations for carrying out the incubation, such as, the effect of choosing different stable isotopes and target biomolecules, to what degree should a labeled substrate be enriched, what concentration to use, and how long should the incubation take. Then tips and pitfalls in the technical execution of SIP are listed, including how much nucleic acids should be loaded, how many fractions to collect, and what centrifuge rotor to use. Lastly, a brief overview of the current methods for analyzing SIP data is presented, focusing on high-throughput amplicon sequencing, together with a discussion on how the choice of analysis method might affect the experimental design.
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Affiliation(s)
- Roey Angel
- Soil and Water Research Infrastructure and Institute of Soil Biology, Biology Centre CAS, České Budějovice, Czech Republic.
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21
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Barnett SE, Youngblut ND, Buckley DH. Data Analysis for DNA Stable Isotope Probing Experiments Using Multiple Window High-Resolution SIP. Methods Mol Biol 2019; 2046:109-128. [PMID: 31407300 DOI: 10.1007/978-1-4939-9721-3_9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
DNA stable isotope probing (DNA-SIP) allows for the identification of microbes that assimilate isotopically labeled substrates into DNA. Here we describe the analysis of sequencing data using the multiple window high-resolution DNA-SIP method (MW-HR-SIP). MW-HR-SIP has improved accuracy over other methods and is easily implemented on the statistical platform R. We also discuss key experimental parameters to consider when designing DNA-SIP experiments and how these parameters affect accuracy of analysis.
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Affiliation(s)
- Samuel E Barnett
- School of Integrative Plant Science, Cornell University, Ithaca, NY, USA
| | - Nicholas D Youngblut
- Department of Microbiome Science, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Daniel H Buckley
- School of Integrative Plant Science, Cornell University, Ithaca, NY, USA.
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22
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Linking Uncultivated Microbial Populations and Benthic Carbon Turnover by Using Quantitative Stable Isotope Probing. Appl Environ Microbiol 2018; 84:AEM.01083-18. [PMID: 29980553 PMCID: PMC6122004 DOI: 10.1128/aem.01083-18] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Accepted: 06/28/2018] [Indexed: 11/20/2022] Open
Abstract
Little is known about the ecological role of uncultivated microbial populations in carbon turnover in benthic environments. To better understand this, we used quantitative stable isotope probing (qSIP) to quantify the abundance of diverse, specific groups of uncultivated bacteria and archaea involved in autotrophy and heterotrophy in a benthic lacustrine habitat. Our results provide quantitative evidence for active heterotrophic and autotrophic metabolism of several poorly understood microbial groups, thus demonstrating their relevance for carbon turnover in benthic settings. Archaeal ammonia oxidizers were significant drivers of in situ “dark” primary production supporting the growth of heterotrophic bacteria. These findings expand our understanding of the microbial populations within benthic food webs and the role of uncultivated microbes in benthic carbon turnover. Benthic environments harbor highly diverse and complex microbial communities that control carbon fluxes, but the role of specific uncultivated microbial groups in organic matter turnover is poorly understood. In this study, quantitative DNA stable isotope probing (DNA-qSIP) was used for the first time to link uncultivated populations of bacteria and archaea to carbon turnover in lacustrine surface sediments. After 1-week incubations in the dark with [13C]bicarbonate, DNA-qSIP showed that ammonia-oxidizing archaea (AOA) were the dominant active chemolithoautotrophs involved in the production of new organic matter. Natural 13C-labeled organic matter was then obtained by incubating sediments in the dark for 2.5 months with [13C]bicarbonate, followed by extraction and concentration of high-molecular-weight (HMW) (>50-kDa) organic matter. qSIP showed that the labeled organic matter was turned over within 1 week by 823 microbial populations (operational taxonomic units [OTUs]) affiliated primarily with heterotrophic Proteobacteria, Chloroflexi, Verrucomicrobia, and Bacteroidetes. However, several OTUs affiliated with the candidate microbial taxa Latescibacteria, Omnitrophica, Aminicentantes, Cloacimonates, AC1, Bathyarchaeota, and Woesearchaeota, groups known only from genomic signatures, also contributed to biomass turnover. Of these 823 labeled OTUs, 52% (primarily affiliated with Proteobacteria) also became labeled in 1-week incubations with [13C]bicarbonate, indicating that they turned over carbon faster than OTUs that were labeled only in incubations with 13C-labeled HMW organic matter. These taxa consisted primarily of uncultivated populations within the Firmicutes, Bacteroidetes, Verrucomicrobia, and Chloroflexi, highlighting their ecological importance. Our study helps define the role of several poorly understood, uncultivated microbial groups in the turnover of benthic carbon derived from “dark” primary production. IMPORTANCE Little is known about the ecological role of uncultivated microbial populations in carbon turnover in benthic environments. To better understand this, we used quantitative stable isotope probing (qSIP) to quantify the abundance of diverse, specific groups of uncultivated bacteria and archaea involved in autotrophy and heterotrophy in a benthic lacustrine habitat. Our results provide quantitative evidence for active heterotrophic and autotrophic metabolism of several poorly understood microbial groups, thus demonstrating their relevance for carbon turnover in benthic settings. Archaeal ammonia oxidizers were significant drivers of in situ “dark” primary production supporting the growth of heterotrophic bacteria. These findings expand our understanding of the microbial populations within benthic food webs and the role of uncultivated microbes in benthic carbon turnover.
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Wilhelm RC. Following the terrestrial tracks of Caulobacter - redefining the ecology of a reputed aquatic oligotroph. ISME JOURNAL 2018; 12:3025-3037. [PMID: 30108303 DOI: 10.1038/s41396-018-0257-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 06/22/2018] [Accepted: 07/24/2018] [Indexed: 11/09/2022]
Abstract
For the past 60 years Caulobacter spp. have been commonly attributed an aquatic and oligotrophic lifestyle yet are not uncommon in nutrient-rich or soil environments. This study evaluates the environmental and ecological associations of Caulobacter to reconcile past evidence, largely limited to culturing and microscopy, with currently available metagenomic and genomic data. The distribution of Caulobacter species and their characteristic adhesion-conferring genes, holdfast (hfaAB), were determined using collections of 10,641 16S rRNA gene libraries (196 studies) and 2625 shotgun metagenomes (190 studies) from a range of terrestrial and aquatic environments. Evidence for ecotypic variation was tested in 26 genomes sourced from soil, rhizosphere, plant, groundwater, and water. Caulobacter were, on average, fourfold more relatively abundant in soil than in aquatic environments, and abundant in decomposing wood, compost, and particulate matter (in air and water). Caulobacter holdfast genes were 35-fold more abundant in soils than aquatic environments. Ecotypic differences between soil and aquatic Caulobacter were evident in the environmental associations of several species and differences in genome size and content among isolates. However, most abundant species were common to both environments, suggesting populations exist in a continuum that was evident in the re-analysis of studies on the temporal dynamics of, and sources of bacterioplankton to, lakes and rivers. This study provides a new perspective on the ecological profile of Caulobacter, demonstrating that members of this genus are predominantly soil-borne, possess an overlooked role in plant matter decomposition and a dependency on water-mediated dispersal.
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Affiliation(s)
- Roland C Wilhelm
- School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA.
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Egert M, Weis S, Schnell S. RNA-based stable isotope probing (RNA-SIP) to unravel intestinal host-microbe interactions. Methods 2018; 149:25-30. [PMID: 29857194 DOI: 10.1016/j.ymeth.2018.05.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/23/2018] [Accepted: 05/25/2018] [Indexed: 12/15/2022] Open
Abstract
The RNA-SIP technology, introduced into molecular microbial ecology in 2002, is an elegant technique to link the structure and function of complex microbial communities, i.e. to identify microbial key-players involved in distinct degradation and assimilation processes under in-situ conditions. Due to its dependence of microbial RNA, this technique is particularly suited for environments with high numbers of very active, i.e. significantly RNA-expressing, bacteria. So far, it was mainly used in environmental studies using microbiotas from soil or water habitats. Here we outline and summarize our application of RNA-SIP for the identification of bacteria involved in the degradation and assimilation of prebiotic carbohydrates in intestinal samples of human and animal origin. Following an isotope label from a prebiotic substrate into the RNA of distinct bacterial taxa will help to better understand the functionality of these medically and economically important nutrients in an intestinal environment.
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Affiliation(s)
- Markus Egert
- Faculty of Medical and Life Sciences, Institute of Precision Medicine, Microbiology and Hygiene Group, Furtwangen University, Villingen-Schwenningen, Germany.
| | - Severin Weis
- Faculty of Medical and Life Sciences, Institute of Precision Medicine, Microbiology and Hygiene Group, Furtwangen University, Villingen-Schwenningen, Germany; Institute of Applied Microbiology, Research Center for BioSystems, Land Use, and Nutrition (IFZ), Justus-Liebig-University Giessen, Germany
| | - Sylvia Schnell
- Institute of Applied Microbiology, Research Center for BioSystems, Land Use, and Nutrition (IFZ), Justus-Liebig-University Giessen, Germany
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