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Gazitúa MC, Vik DR, Roux S, Gregory AC, Bolduc B, Widner B, Mulholland MR, Hallam SJ, Ulloa O, Sullivan MB. Potential virus-mediated nitrogen cycling in oxygen-depleted oceanic waters. THE ISME JOURNAL 2021; 15:981-998. [PMID: 33199808 PMCID: PMC8115048 DOI: 10.1038/s41396-020-00825-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 09/30/2020] [Accepted: 10/27/2020] [Indexed: 01/29/2023]
Abstract
Viruses play an important role in the ecology and biogeochemistry of marine ecosystems. Beyond mortality and gene transfer, viruses can reprogram microbial metabolism during infection by expressing auxiliary metabolic genes (AMGs) involved in photosynthesis, central carbon metabolism, and nutrient cycling. While previous studies have focused on AMG diversity in the sunlit and dark ocean, less is known about the role of viruses in shaping metabolic networks along redox gradients associated with marine oxygen minimum zones (OMZs). Here, we analyzed relatively quantitative viral metagenomic datasets that profiled the oxygen gradient across Eastern Tropical South Pacific (ETSP) OMZ waters, assessing whether OMZ viruses might impact nitrogen (N) cycling via AMGs. Identified viral genomes encoded six N-cycle AMGs associated with denitrification, nitrification, assimilatory nitrate reduction, and nitrite transport. The majority of these AMGs (80%) were identified in T4-like Myoviridae phages, predicted to infect Cyanobacteria and Proteobacteria, or in unclassified archaeal viruses predicted to infect Thaumarchaeota. Four AMGs were exclusive to anoxic waters and had distributions that paralleled homologous microbial genes. Together, these findings suggest viruses modulate N-cycling processes within the ETSP OMZ and may contribute to nitrogen loss throughout the global oceans thus providing a baseline for their inclusion in the ecosystem and geochemical models.
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Affiliation(s)
- M. Consuelo Gazitúa
- grid.261331.40000 0001 2285 7943Department of Microbiology, The Ohio State University, Columbus, OH 43210 USA ,Viromica Consulting, Santiago, Chile
| | - Dean R. Vik
- grid.261331.40000 0001 2285 7943Department of Microbiology, The Ohio State University, Columbus, OH 43210 USA
| | - Simon Roux
- grid.451309.a0000 0004 0449 479XDOE Joint Genome Institute, Berkeley, CA USA
| | - Ann C. Gregory
- grid.261331.40000 0001 2285 7943Department of Microbiology, The Ohio State University, Columbus, OH 43210 USA
| | - Benjamin Bolduc
- grid.261331.40000 0001 2285 7943Department of Microbiology, The Ohio State University, Columbus, OH 43210 USA
| | - Brittany Widner
- grid.261368.80000 0001 2164 3177Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA USA ,grid.56466.370000 0004 0504 7510Woods Hole Oceanographic Institution, Woods Hole, MA USA
| | - Margaret R. Mulholland
- grid.261368.80000 0001 2164 3177Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA USA
| | - Steven J. Hallam
- grid.17091.3e0000 0001 2288 9830Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC Canada
| | - Osvaldo Ulloa
- grid.5380.e0000 0001 2298 9663Departamento de Oceanografía & Instituto Milenio de Oceanografía, Universidad de Concepción, Concepción, Chile
| | - Matthew B. Sullivan
- grid.261331.40000 0001 2285 7943Department of Microbiology, The Ohio State University, Columbus, OH 43210 USA ,grid.261331.40000 0001 2285 7943Department of Civil, Environmental and Geodetic Engineering, The Ohio State University, Columbus, OH USA
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Spiro S. Nitrous oxide production and consumption: regulation of gene expression by gas-sensitive transcription factors. Philos Trans R Soc Lond B Biol Sci 2012; 367:1213-25. [PMID: 22451107 DOI: 10.1098/rstb.2011.0309] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Several biochemical mechanisms contribute to the biological generation of nitrous oxide (N(2)O). N(2)O generating enzymes include the respiratory nitric oxide (NO) reductase, an enzyme from the flavo-diiron family, and flavohaemoglobin. On the other hand, there is only one enzyme that is known to use N(2)O as a substrate, which is the respiratory N(2)O reductase typically found in bacteria capable of denitrification (the respiratory reduction of nitrate and nitrite to dinitrogen). This article will briefly review the properties of the enzymes that make and consume N(2)O, together with the accessory proteins that have roles in the assembly and maturation of those enzymes. The expression of the genes encoding the enzymes that produce and consume N(2)O is regulated by environmental signals (typically oxygen and NO) acting through regulatory proteins, which, either directly or indirectly, control the frequency of transcription initiation. The roles and mechanisms of these proteins, and the structures of the regulatory networks in which they participate will also be reviewed.
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Affiliation(s)
- Stephen Spiro
- Department of Molecular and Cell Biology, University of Texas at Dallas, Richardson, TX 75080, USA.
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Physiological roles for two periplasmic nitrate reductases in Rhodobacter sphaeroides 2.4.3 (ATCC 17025). J Bacteriol 2011; 193:6483-9. [PMID: 21949073 DOI: 10.1128/jb.05324-11] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The metabolically versatile purple bacterium Rhodobacter sphaeroides 2.4.3 is a denitrifier whose genome contains two periplasmic nitrate reductase-encoding gene clusters. This work demonstrates nonredundant physiological roles for these two enzymes. One cluster is expressed aerobically and repressed under low oxygen while the second is maximally expressed under low oxygen. Insertional inactivation of the aerobically expressed nitrate reductase eliminated aerobic nitrate reduction, but cells of this strain could still respire nitrate anaerobically. In contrast, when the anaerobic nitrate reductase was absent, aerobic nitrate reduction was detectable, but anaerobic nitrate reduction was impaired. The aerobic nitrate reductase was expressed but not utilized in liquid culture but was utilized during growth on solid medium. Growth on a variety of carbon sources, with the exception of malate, the most oxidized substrate used, resulted in nitrite production on solid medium. This is consistent with a role for the aerobic nitrate reductase in redox homeostasis. These results show that one of the nitrate reductases is specific for respiration and denitrification while the other likely plays a role in redox homeostasis during aerobic growth.
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Abstract
Denitrification is generally considered to occur under micro-oxic or anoxic conditions. With this in mind, the physiological function and regulation of several steps in the denitrification of model α-proteobacteria are compared in the present review. Expression of the periplasmic nitrate reductase is quite variable, with this enzyme being maximally expressed under oxic conditions in some bacteria, but under micro-oxic conditions in others. Expression of nitrite and NO reductases in most denitrifiers is more tightly controlled, with expression only occurring under micro-oxic conditions. A possible exception to this may be Roseobacter denitrificans, but the physiological role of these enzymes under oxic conditions is uncertain.
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