1
|
Lanclos VC, Rasmussen AN, Kojima CY, Cheng C, Henson MW, Faircloth BC, Francis CA, Thrash JC. Ecophysiology and genomics of the brackish water adapted SAR11 subclade IIIa. THE ISME JOURNAL 2023; 17:620-629. [PMID: 36739346 PMCID: PMC10030771 DOI: 10.1038/s41396-023-01376-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 01/06/2023] [Accepted: 01/20/2023] [Indexed: 02/05/2023]
Abstract
The Order Pelagibacterales (SAR11) is the most abundant group of heterotrophic bacterioplankton in global oceans and comprises multiple subclades with unique spatiotemporal distributions. Subclade IIIa is the primary SAR11 group in brackish waters and shares a common ancestor with the dominant freshwater IIIb (LD12) subclade. Despite its dominance in brackish environments, subclade IIIa lacks systematic genomic or ecological studies. Here, we combine closed genomes from new IIIa isolates, new IIIa MAGS from San Francisco Bay (SFB), and 460 highly complete publicly available SAR11 genomes for the most comprehensive pangenomic study of subclade IIIa to date. Subclade IIIa represents a taxonomic family containing three genera (denoted as subgroups IIIa.1, IIIa.2, and IIIa.3) that had distinct ecological distributions related to salinity. The expansion of taxon selection within subclade IIIa also established previously noted metabolic differentiation in subclade IIIa compared to other SAR11 subclades such as glycine/serine prototrophy, mosaic glyoxylate shunt presence, and polyhydroxyalkanoate synthesis potential. Our analysis further shows metabolic flexibility among subgroups within IIIa. Additionally, we find that subclade IIIa.3 bridges the marine and freshwater clades based on its potential for compatible solute transport, iron utilization, and bicarbonate management potential. Pure culture experimentation validated differential salinity ranges in IIIa.1 and IIIa.3 and provided detailed IIIa cell size and volume data. This study is an important step forward for understanding the genomic, ecological, and physiological differentiation of subclade IIIa and the overall evolutionary history of SAR11.
Collapse
Affiliation(s)
- V Celeste Lanclos
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Anna N Rasmussen
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
| | - Conner Y Kojima
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Chuankai Cheng
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Michael W Henson
- Department of Geophysical Sciences, University of Chicago, Chicago, IL, 60637, USA
| | - Brant C Faircloth
- Department of Biological Sciences and Museum of Natural Science, Louisiana State University, Baton Rouge, LA, 70803, USA
| | | | - J Cameron Thrash
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
| |
Collapse
|
2
|
Oren A. Candidatus List No. 4: Lists of names of prokaryotic Candidatus taxa. Int J Syst Evol Microbiol 2022; 72. [PMID: 36748458 DOI: 10.1099/ijsem.0.005545] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Affiliation(s)
- Aharon Oren
- The Institute of Life Sciences, The Hebrew University of Jerusalem, The Edmond J. Safra Campus, 9190401 Jerusalem, Israel
| |
Collapse
|
3
|
RRAP: RPKM Recruitment Analysis Pipeline. Microbiol Resour Announc 2022; 11:e0064422. [PMID: 35993706 PMCID: PMC9476942 DOI: 10.1128/mra.00644-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
A common method for quantifying microbial abundances in situ is through metagenomic read recruitment to genomes and normalizing read counts as reads per kilobase (of genome) per million (bases of recruited sequences) (RPKM). We created RRAP (RPKM Recruitment Analysis Pipeline), a wrapper that automates this process using Bowtie2 and SAMtools.
Collapse
|
4
|
Phylogenomics of SAR116 Clade Reveals Two Subclades with Different Evolutionary Trajectories and an Important Role in the Ocean Sulfur Cycle. mSystems 2021; 6:e0094421. [PMID: 34609172 PMCID: PMC8547437 DOI: 10.1128/msystems.00944-21] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The SAR116 clade within the class Alphaproteobacteria represents one of the most abundant groups of heterotrophic bacteria inhabiting the surface of the ocean. The small number of cultured representatives of SAR116 (only two to date) is a major bottleneck that has prevented an in-depth study at the genomic level to understand the relationship between genome diversity and its role in the marine environment. In this study, we use all publicly available genomes to provide a genomic overview of the phylogeny, metabolism, and biogeography within the SAR116 clade. This increased genomic diversity has led to the discovery of two subclades that, despite coexisting in the same environment, display different properties in their genomic makeup. One represents a novel subclade for which no pure cultures have been isolated and is composed mainly of single-amplified genomes (SAGs). Genomes within this subclade showed convergent evolutionary trajectories with more streamlined features, such as low GC content (ca. 30%), short intergenic spacers (<22 bp), and strong purifying selection (low ratio of nonsynonymous to synonymous polymorphisms [dN/dS]). Besides, they were more abundant in metagenomic databases recruiting at the deep chlorophyll maximum. Less abundant and restricted to the upper photic layers of the global ocean, the other subclade of SAR116, enriched in metagenome-assembled genomes (MAGs), included the only two pure cultures. Genomic analysis suggested that both clades have a significant role in the sulfur cycle with differences in the way both clades can metabolize dimethylsulfoniopropionate (DMSP). IMPORTANCE The SAR116 clade of Alphaproteobacteria is a ubiquitous group of heterotrophic bacteria inhabiting the surface of the ocean, but the information about their ecology and population genomic diversity is scarce due to the difficulty of getting pure culture isolates. The combination of single-cell genomics and metagenomics has become an alternative approach to study these kinds of microbes. Our results expand the understanding of the genomic diversity, distribution, and lifestyles within this clade and provide evidence of different evolutionary trajectories in the genomic makeup of the two subclades that could serve to illustrate how evolutionary pressure can drive different adaptations to the same environment. Therefore, the SAR116 clade represents an ideal model organism for the study of the evolutionary streamlining of genomes in microbes that have relatively close relatedness to each other.
Collapse
|