1
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Novak JK, Gardner JG. Current models in bacterial hemicellulase-encoding gene regulation. Appl Microbiol Biotechnol 2024; 108:39. [PMID: 38175245 PMCID: PMC10766802 DOI: 10.1007/s00253-023-12977-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 12/06/2023] [Accepted: 12/07/2023] [Indexed: 01/05/2024]
Abstract
The discovery and characterization of bacterial carbohydrate-active enzymes is a fundamental component of biotechnology innovation, particularly for renewable fuels and chemicals; however, these studies have increasingly transitioned to exploring the complex regulation required for recalcitrant polysaccharide utilization. This pivot is largely due to the current need to engineer and optimize enzymes for maximal degradation in industrial or biomedical applications. Given the structural simplicity of a single cellulose polymer, and the relatively few enzyme classes required for complete bioconversion, the regulation of cellulases in bacteria has been thoroughly discussed in the literature. However, the diversity of hemicelluloses found in plant biomass and the multitude of carbohydrate-active enzymes required for their deconstruction has resulted in a less comprehensive understanding of bacterial hemicellulase-encoding gene regulation. Here we review the mechanisms of this process and common themes found in the transcriptomic response during plant biomass utilization. By comparing regulatory systems from both Gram-negative and Gram-positive bacteria, as well as drawing parallels to cellulase regulation, our goals are to highlight the shared and distinct features of bacterial hemicellulase-encoding gene regulation and provide a set of guiding questions to improve our understanding of bacterial lignocellulose utilization. KEY POINTS: • Canonical regulatory mechanisms for bacterial hemicellulase-encoding gene expression include hybrid two-component systems (HTCS), extracytoplasmic function (ECF)-σ/anti-σ systems, and carbon catabolite repression (CCR). • Current transcriptomic approaches are increasingly being used to identify hemicellulase-encoding gene regulatory patterns coupled with computational predictions for transcriptional regulators. • Future work should emphasize genetic approaches to improve systems biology tools available for model bacterial systems and emerging microbes with biotechnology potential. Specifically, optimization of Gram-positive systems will require integration of degradative and fermentative capabilities, while optimization of Gram-negative systems will require bolstering the potency of lignocellulolytic capabilities.
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Affiliation(s)
- Jessica K Novak
- Department of Biological Sciences, University of Maryland - Baltimore County, Baltimore, MD, USA
| | - Jeffrey G Gardner
- Department of Biological Sciences, University of Maryland - Baltimore County, Baltimore, MD, USA.
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2
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Li X, Cheng X, Xu J, Wu J, Chan LL, Cai Z, Zhou J. Dynamic patterns of carbohydrate metabolism genes in bacterioplankton during marine algal blooms. Microbiol Res 2024; 286:127785. [PMID: 38851011 DOI: 10.1016/j.micres.2024.127785] [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: 01/27/2024] [Revised: 05/01/2024] [Accepted: 05/25/2024] [Indexed: 06/10/2024]
Abstract
Carbohydrates play a pivotal role in nutrient recycling and regulation of algal-bacterial interactions. Despite their ecological significance, the intricate molecular mechanisms governing regulation of phycosphere carbohydrates by bacterial taxa linked with natural algal bloom have yet to be fully elucidated. Here, a comprehensive temporal metagenomic analysis was conducted to explore the carbohydrate-active enzyme (CAZyme) genes in two discrete algal bloom microorganisms (Gymnodinium catenatum and Phaeocystis globosa) across three distinct bloom stages: pre-bloom, peak bloom, and post-bloom. Elevated levels of extracellular carbohydrates, primarily rhamnose, galactose, glucose, and arabinose, were observed during the initial and post-peak stages. The prominent CAZyme families identified-glycoside hydrolases (GH) and carbohydrate-binding modules (CBMs)-were present in both algal bloom occurrences. In the G. catenatum bloom, GH23/24 and CBM13/14 were prevalent during the pre-bloom and peak bloom stages, whereas GH2/3/30 and CBM12/24 exhibited increased prevalence during the post-bloom phase. In contrast, the P. globosa bloom had a dominance of GH13/23 and CBM19 in the initial phase, and this was succeeded by GH3/19/24/30 and CBM54 in the later stages. This gene pool variation-observed distinctly in specific genera-highlighted the dynamic structural shifts in functional resources driven by temporal alterations in available substrates. Additionally, ecological linkage analysis underscored a correlation between carbohydrates (or their related genes) and phycospheric bacteria, hinting at a pattern of bottom-up control. These findings contribute to understanding of the dynamic nature of CAZymes, emphasizing the substantial influence of substrate availability on the metabolic capabilities of algal symbiotic bacteria, especially in terms of carbohydrates.
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Affiliation(s)
- Xinyang Li
- Marine Ecology and Human Factors Assessment Technical Innovation Center of Natural Resources Ministry, Tsinghua Shenzhen International Graduate School, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Key Laboratory of Advanced Technology for Marine Ecology, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China
| | - Xueyu Cheng
- Marine Ecology and Human Factors Assessment Technical Innovation Center of Natural Resources Ministry, Tsinghua Shenzhen International Graduate School, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Key Laboratory of Advanced Technology for Marine Ecology, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China
| | - Junjie Xu
- Marine Ecology and Human Factors Assessment Technical Innovation Center of Natural Resources Ministry, Tsinghua Shenzhen International Graduate School, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Key Laboratory of Advanced Technology for Marine Ecology, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China
| | - Jiajun Wu
- State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong, China
| | - Leo Lai Chan
- State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong, China
| | - Zhonghua Cai
- Marine Ecology and Human Factors Assessment Technical Innovation Center of Natural Resources Ministry, Tsinghua Shenzhen International Graduate School, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Key Laboratory of Advanced Technology for Marine Ecology, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China
| | - Jin Zhou
- Marine Ecology and Human Factors Assessment Technical Innovation Center of Natural Resources Ministry, Tsinghua Shenzhen International Graduate School, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China; Shenzhen Key Laboratory of Advanced Technology for Marine Ecology, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, Guangdong Province 518055, PR China.
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3
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Beidler I, Steinke N, Schulze T, Sidhu C, Bartosik D, Zühlke MK, Martin LT, Krull J, Dutschei T, Ferrero-Bordera B, Rielicke J, Kale V, Sura T, Trautwein-Schult A, Kirstein IV, Wiltshire KH, Teeling H, Becher D, Bengtsson MM, Hehemann JH, Bornscheuer UT, Amann RI, Schweder T. Alpha-glucans from bacterial necromass indicate an intra-population loop within the marine carbon cycle. Nat Commun 2024; 15:4048. [PMID: 38744821 PMCID: PMC11093988 DOI: 10.1038/s41467-024-48301-5] [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: 08/03/2023] [Accepted: 04/24/2024] [Indexed: 05/16/2024] Open
Abstract
Phytoplankton blooms provoke bacterioplankton blooms, from which bacterial biomass (necromass) is released via increased zooplankton grazing and viral lysis. While bacterial consumption of algal biomass during blooms is well-studied, little is known about the concurrent recycling of these substantial amounts of bacterial necromass. We demonstrate that bacterial biomass, such as bacterial alpha-glucan storage polysaccharides, generated from the consumption of algal organic matter, is reused and thus itself a major bacterial carbon source in vitro and during a diatom-dominated bloom. We highlight conserved enzymes and binding proteins of dominant bloom-responder clades that are presumably involved in the recycling of bacterial alpha-glucan by members of the bacterial community. We furthermore demonstrate that the corresponding protein machineries can be specifically induced by extracted alpha-glucan-rich bacterial polysaccharide extracts. This recycling of bacterial necromass likely constitutes a large-scale intra-population energy conservation mechanism that keeps substantial amounts of carbon in a dedicated part of the microbial loop.
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Affiliation(s)
- Irena Beidler
- Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, 17489, Greifswald, Germany
| | - Nicola Steinke
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany
- University of Bremen, Center for Marine Environmental Sciences, MARUM, 28359, Bremen, Germany
| | - Tim Schulze
- Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, 17489, Greifswald, Germany
| | - Chandni Sidhu
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany
| | - Daniel Bartosik
- Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, 17489, Greifswald, Germany
- Institute of Marine Biotechnology, 17489, Greifswald, Germany
| | - Marie-Katherin Zühlke
- Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, 17489, Greifswald, Germany
| | - Laura Torres Martin
- Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, 17489, Greifswald, Germany
| | - Joris Krull
- Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, 17489, Greifswald, Germany
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany
| | - Theresa Dutschei
- Biotechnology and Enzyme Catalysis, Institute of Biochemistry, University of Greifswald, 17489, Greifswald, Germany
| | - Borja Ferrero-Bordera
- Microbial Proteomics, Institute of Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Julia Rielicke
- Microbial Proteomics, Institute of Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Vaikhari Kale
- Microbial Proteomics, Institute of Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Thomas Sura
- Microbial Proteomics, Institute of Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Anke Trautwein-Schult
- Microbial Proteomics, Institute of Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Inga V Kirstein
- Alfred Wegener Institute for Polar and Marine Research, Biologische Anstalt Helgoland, 27483, Helgoland, Germany
| | - Karen H Wiltshire
- Alfred Wegener Institute for Polar and Marine Research, Biologische Anstalt Helgoland, 27483, Helgoland, Germany
| | - Hanno Teeling
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany
| | - Dörte Becher
- Microbial Proteomics, Institute of Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Mia Maria Bengtsson
- Microbial Physiology and Molecular Biology, Institute of Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Jan-Hendrik Hehemann
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany
- University of Bremen, Center for Marine Environmental Sciences, MARUM, 28359, Bremen, Germany
| | - Uwe T Bornscheuer
- Biotechnology and Enzyme Catalysis, Institute of Biochemistry, University of Greifswald, 17489, Greifswald, Germany
| | - Rudolf I Amann
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany
| | - Thomas Schweder
- Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, 17489, Greifswald, Germany.
- Institute of Marine Biotechnology, 17489, Greifswald, Germany.
- Alfred Wegener Institute for Polar and Marine Research, Biologische Anstalt Helgoland, 27483, Helgoland, Germany.
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Miksch S, Orellana LH, Oggerin de Orube M, Vidal-Melgosa S, Solanki V, Hehemann JH, Amann R, Knittel K. Taxonomic and functional stability overrules seasonality in polar benthic microbiomes. THE ISME JOURNAL 2024; 18:wrad005. [PMID: 38365229 PMCID: PMC10811738 DOI: 10.1093/ismejo/wrad005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 11/06/2023] [Accepted: 11/07/2023] [Indexed: 02/18/2024]
Abstract
Coastal shelf sediments are hot spots of organic matter mineralization. They receive up to 50% of primary production, which, in higher latitudes, is strongly seasonal. Polar and temperate benthic bacterial communities, however, show a stable composition based on comparative 16S rRNA gene sequencing despite different microbial activity levels. Here, we aimed to resolve this contradiction by identifying seasonal changes at the functional level, in particular with respect to algal polysaccharide degradation genes, by combining metagenomics, metatranscriptomics, and glycan analysis in sandy surface sediments from Isfjorden, Svalbard. Gene expressions of diverse carbohydrate-active enzymes changed between winter and spring. For example, β-1,3-glucosidases (e.g. GH30, GH17, GH16) degrading laminarin, an energy storage molecule of algae, were elevated in spring, while enzymes related to α-glucan degradation were expressed in both seasons with maxima in winter (e.g. GH63, GH13_18, and GH15). Also, the expression of GH23 involved in peptidoglycan degradation was prevalent, which is in line with recycling of bacterial biomass. Sugar extractions from bulk sediments were low in concentrations during winter but higher in spring samples, with glucose constituting the largest fraction of measured monosaccharides (84% ± 14%). In porewater, glycan concentrations were ~18-fold higher than in overlying seawater (1107 ± 484 vs. 62 ± 101 μg C l-1) and were depleted in glucose. Our data indicate that microbial communities in sandy sediments digest and transform labile parts of photosynthesis-derived particulate organic matter and likely release more stable, glucose-depleted residual glycans of unknown structures, quantities, and residence times into the ocean, thus modulating the glycan composition of marine coastal waters.
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Affiliation(s)
- Sebastian Miksch
- Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany
| | - Luis H Orellana
- Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany
| | - Monike Oggerin de Orube
- Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany
| | - Silvia Vidal-Melgosa
- Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany
- MARUM MPG Bridge Group Marine Glycobiology, Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Vipul Solanki
- Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany
| | - Jan-Hendrik Hehemann
- Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany
- MARUM MPG Bridge Group Marine Glycobiology, Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Rudolf Amann
- Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany
| | - Katrin Knittel
- Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany
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5
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Dutschei T, Beidler I, Bartosik D, Seeßelberg JM, Teune M, Bäumgen M, Ferreira SQ, Heldmann J, Nagel F, Krull J, Berndt L, Methling K, Hein M, Becher D, Langer P, Delcea M, Lalk M, Lammers M, Höhne M, Hehemann JH, Schweder T, Bornscheuer UT. Marine Bacteroidetes enzymatically digest xylans from terrestrial plants. Environ Microbiol 2023; 25:1713-1727. [PMID: 37121608 DOI: 10.1111/1462-2920.16390] [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: 09/23/2022] [Accepted: 04/18/2023] [Indexed: 05/02/2023]
Abstract
Marine Bacteroidetes that degrade polysaccharides contribute to carbon cycling in the ocean. Organic matter, including glycans from terrestrial plants, might enter the oceans through rivers. Whether marine bacteria degrade structurally related glycans from diverse sources including terrestrial plants and marine algae was previously unknown. We show that the marine bacterium Flavimarina sp. Hel_I_48 encodes two polysaccharide utilization loci (PULs) which degrade xylans from terrestrial plants and marine algae. Biochemical experiments revealed activity and specificity of the encoded xylanases and associated enzymes of these PULs. Proteomics indicated that these genomic regions respond to glucuronoxylans and arabinoxylans. Substrate specificities of key enzymes suggest dedicated metabolic pathways for xylan utilization. Some of the xylanases were active on different xylans with the conserved β-1,4-linked xylose main chain. Enzyme activity was consistent with growth curves showing Flavimarina sp. Hel_I_48 uses structurally different xylans. The observed abundance of related xylan-degrading enzyme repertoires in genomes of other marine Bacteroidetes indicates similar activities are common in the ocean. The here presented data show that certain marine bacteria are genetically and biochemically variable enough to access parts of structurally diverse xylans from terrestrial plants as well as from marine algal sources.
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Affiliation(s)
- Theresa Dutschei
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University Greifswald, Greifswald, Germany
| | - Irena Beidler
- Department of Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
| | - Daniel Bartosik
- Department of Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
- Institute of Marine Biotechnology e.V., Greifswald, Germany
| | - Julia-Maria Seeßelberg
- Department of Protein Biochemistry, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Michelle Teune
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University Greifswald, Greifswald, Germany
| | - Marcus Bäumgen
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University Greifswald, Greifswald, Germany
| | - Soraia Querido Ferreira
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University Greifswald, Greifswald, Germany
| | - Julia Heldmann
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University Greifswald, Greifswald, Germany
| | - Felix Nagel
- Department of Biophysical Chemistry, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Joris Krull
- Institute of Marine Biotechnology e.V., Greifswald, Germany
- Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Leona Berndt
- Department of Synthetic and Structural Biochemistry, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Karen Methling
- Department of Cellular Biochemistry and Metabolomics, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Martin Hein
- Department of Organic Chemistry, Institute of Chemistry, University of Rostock, Rostock, Germany
| | - Dörte Becher
- Department of Microbial Proteomics, Institute of Microbiology, University of Greifswald, Greifswald, Germany
| | - Peter Langer
- Department of Organic Chemistry, Institute of Chemistry, University of Rostock, Rostock, Germany
| | - Mihaela Delcea
- Department of Biophysical Chemistry, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Michael Lalk
- Department of Cellular Biochemistry and Metabolomics, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Michael Lammers
- Department of Synthetic and Structural Biochemistry, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Matthias Höhne
- Department of Protein Biochemistry, Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Jan-Hendrik Hehemann
- Institute of Marine Biotechnology e.V., Greifswald, Germany
- Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Thomas Schweder
- Department of Pharmaceutical Biotechnology, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
- Institute of Marine Biotechnology e.V., Greifswald, Germany
| | - Uwe T Bornscheuer
- Department of Biotechnology & Enzyme Catalysis, Institute of Biochemistry, University Greifswald, Greifswald, Germany
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6
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Zhu XY, Li Y, Xue CX, Lidbury IDEA, Todd JD, Lea-Smith DJ, Tian J, Zhang XH, Liu J. Deep-sea Bacteroidetes from the Mariana Trench specialize in hemicellulose and pectin degradation typically associated with terrestrial systems. MICROBIOME 2023; 11:175. [PMID: 37550707 PMCID: PMC10405439 DOI: 10.1186/s40168-023-01618-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 07/11/2023] [Indexed: 08/09/2023]
Abstract
BACKGROUND Hadal trenches (>6000 m) are the deepest oceanic regions on Earth and depocenters for organic materials. However, how these enigmatic microbial ecosystems are fueled is largely unknown, particularly the proportional importance of complex polysaccharides introduced through deposition from the photic surface waters above. In surface waters, Bacteroidetes are keystone taxa for the cycling of various algal-derived polysaccharides and the flux of carbon through the photic zone. However, their role in the hadal microbial loop is almost unknown. RESULTS Here, culture-dependent and culture-independent methods were used to study the potential of Bacteroidetes to catabolize diverse polysaccharides in Mariana Trench waters. Compared to surface waters, the bathypelagic (1000-4000 m) and hadal (6000-10,500 m) waters harbored distinct Bacteroidetes communities, with Mesoflavibacter being enriched at ≥ 4000 m and Bacteroides and Provotella being enriched at 10,400-10,500 m. Moreover, these deep-sea communities possessed distinct gene pools encoding for carbohydrate active enzymes (CAZymes), suggesting different polysaccharide sources are utilised in these two zones. Compared to surface counterparts, deep-sea Bacteroidetes showed significant enrichment of CAZyme genes frequently organized into polysaccharide utilization loci (PULs) targeting algal/plant cell wall polysaccharides (i.e., hemicellulose and pectin), that were previously considered an ecological trait associated with terrestrial Bacteroidetes only. Using a hadal Mesoflavibacter isolate (MTRN7), functional validation of this unique genetic potential was demonstrated. MTRN7 could utilize pectic arabinans, typically associated with land plants and phototrophic algae, as the carbon source under simulated deep-sea conditions. Interestingly, a PUL we demonstrate is likely horizontally acquired from coastal/land Bacteroidetes was activated during growth on arabinan and experimentally shown to encode enzymes that hydrolyze arabinan at depth. CONCLUSIONS Our study implies that hadal Bacteroidetes exploit polysaccharides poorly utilized by surface populations via an expanded CAZyme gene pool. We propose that sinking cell wall debris produced in the photic zone can serve as an important carbon source for hadal heterotrophs and play a role in shaping their communities and metabolism. Video Abstract.
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Affiliation(s)
- Xiao-Yu Zhu
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China
- Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao, 266273, China
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Yang Li
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China
- Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao, 266273, China
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Chun-Xu Xue
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China
- Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao, 266273, China
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Ian D E A Lidbury
- Molecular Microbiology: Biochemistry to Disease, School of Biosciences, The University of Sheffield, Sheffield, S10 2TN, UK
| | - Jonathan D Todd
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - David J Lea-Smith
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Jiwei Tian
- Key Laboratory of Physical Oceanography, Ministry of Education, Ocean University of China, Qingdao, 266100, China
| | - Xiao-Hua Zhang
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China
- Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao, 266273, China
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Jiwen Liu
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China.
- Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao, 266273, China.
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China.
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