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Enav H, Paz I, Ley RE. Strain tracking in complex microbiomes using synteny analysis reveals per-species modes of evolution. Nat Biotechnol 2024:10.1038/s41587-024-02276-2. [PMID: 38898177 DOI: 10.1038/s41587-024-02276-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 05/10/2024] [Indexed: 06/21/2024]
Abstract
Microbial species diversify into strains through single-nucleotide mutations and structural changes, such as recombination, insertions and deletions. Most strain-comparison methods quantify differences in single-nucleotide polymorphisms (SNPs) and are insensitive to structural changes. However, recombination is an important driver of phenotypic diversification in many species, including human pathogens. We introduce SynTracker, a tool that compares microbial strains using genome synteny-the order of sequence blocks in homologous genomic regions-in pairs of metagenomic assemblies or genomes. Genome synteny is a rich source of genomic information untapped by current strain-comparison tools. SynTracker has low sensitivity to SNPs, has no database requirement and is robust to sequencing errors. It outperforms existing tools when tracking strains in metagenomic data and is particularly suited for phages, plasmids and other low-data contexts. Applied to single-species datasets and human gut metagenomes, SynTracker, combined with an SNP-based tool, detects strains enriched in either point mutations or structural changes, providing insights into microbial evolution in situ.
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Affiliation(s)
- Hagay Enav
- Department of Microbiome Science, Max Planck Institute for Biology, Tübingen, Germany
| | - Inbal Paz
- Department of Microbiome Science, Max Planck Institute for Biology, Tübingen, Germany
| | - Ruth E Ley
- Department of Microbiome Science, Max Planck Institute for Biology, Tübingen, Germany.
- Cluster of Excellence EXC 2124: Controlling Microbes to Fight Infections (CMFI), University of Tübingen, Tübingen, Germany.
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2
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Pšeničnik A, Slemc L, Avbelj M, Tome M, Šala M, Herron P, Shmatkov M, Petek M, Baebler Š, Mrak P, Hranueli D, Starčević A, Hunter IS, Petković H. Oxytetracycline hyper-production through targeted genome reduction of Streptomyces rimosus. mSystems 2024; 9:e0025024. [PMID: 38564716 PMCID: PMC11097637 DOI: 10.1128/msystems.00250-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 03/07/2024] [Indexed: 04/04/2024] Open
Abstract
Most biosynthetic gene clusters (BGC) encoding the synthesis of important microbial secondary metabolites, such as antibiotics, are either silent or poorly expressed; therefore, to ensure a strong pipeline of novel antibiotics, there is a need to develop rapid and efficient strain development approaches. This study uses comparative genome analysis to instruct rational strain improvement, using Streptomyces rimosus, the producer of the important antibiotic oxytetracycline (OTC) as a model system. Sequencing of the genomes of two industrial strains M4018 and R6-500, developed independently from a common ancestor, identified large DNA rearrangements located at the chromosome end. We evaluated the effect of these genome deletions on the parental S. rimosus Type Strain (ATCC 10970) genome where introduction of a 145 kb deletion close to the OTC BGC in the Type Strain resulted in massive OTC overproduction, achieving titers that were equivalent to M4018 and R6-500. Transcriptome data supported the hypothesis that the reason for such an increase in OTC biosynthesis was due to enhanced transcription of the OTC BGC and not due to enhanced substrate supply. We also observed changes in the expression of other cryptic BGCs; some metabolites, undetectable in ATCC 10970, were now produced at high titers. This study demonstrated for the first time that the main force behind BGC overexpression is genome rearrangement. This new approach demonstrates great potential to activate cryptic gene clusters of yet unexplored natural products of medical and industrial value.IMPORTANCEThere is a critical need to develop novel antibiotics to combat antimicrobial resistance. Streptomyces species are very rich source of antibiotics, typically encoding 20-60 biosynthetic gene clusters (BGCs). However, under laboratory conditions, most are either silent or poorly expressed so that their products are only detectable at nanogram quantities, which hampers drug development efforts. To address this subject, we used comparative genome analysis of industrial Streptomyces rimosus strains producing high titers of a broad spectrum antibiotic oxytetracycline (OTC), developed during decades of industrial strain improvement. Interestingly, large-scale chromosomal deletions were observed. Based on this information, we carried out targeted genome deletions in the native strain S. rimosus ATCC 10970, and we show that a targeted deletion in the vicinity of the OTC BGC significantly induced expression of the OTC BGC, as well as some other silent BGCs, thus suggesting that this approach may be a useful way to identify new natural products.
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Affiliation(s)
- Alen Pšeničnik
- Chair of Biotechnology, Microbiology and Food Safety, University of Ljubljana Biotechnical Faculty, Ljubljana, Slovenia
| | - Lucija Slemc
- Chair of Biotechnology, Microbiology and Food Safety, University of Ljubljana Biotechnical Faculty, Ljubljana, Slovenia
| | - Martina Avbelj
- Chair of Biotechnology, Microbiology and Food Safety, University of Ljubljana Biotechnical Faculty, Ljubljana, Slovenia
| | - Miha Tome
- Chair of Biotechnology, Microbiology and Food Safety, University of Ljubljana Biotechnical Faculty, Ljubljana, Slovenia
| | - Martin Šala
- National Institute of Chemistry, Ljubljana, Slovenia
| | - Paul Herron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Maksym Shmatkov
- Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia
- Educational and Scientific Institute of High Technologies, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
| | - Marko Petek
- Department of Biotechnology and Systems Biology, National Institute of Biology, Ljubljana, Slovenia
| | - Špela Baebler
- Department of Biotechnology and Systems Biology, National Institute of Biology, Ljubljana, Slovenia
| | - Peter Mrak
- Antiinfectives, Sandoz, Mengeš, Slovenia
| | - Daslav Hranueli
- Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia
| | - Antonio Starčević
- Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia
| | - Iain S. Hunter
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Hrvoje Petković
- Chair of Biotechnology, Microbiology and Food Safety, University of Ljubljana Biotechnical Faculty, Ljubljana, Slovenia
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3
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Genetic Diversity and Anti-Oxidative Potential of Streptomyces spp. Isolated from Unexplored Niches of Meghalaya, India. Curr Microbiol 2022; 79:379. [DOI: 10.1007/s00284-022-03088-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 10/11/2022] [Indexed: 11/06/2022]
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Hariharan J, Buckley DH. Elevational Gradients Impose Dispersal Limitation on Streptomyces. Front Microbiol 2022; 13:856263. [PMID: 35592003 PMCID: PMC9113539 DOI: 10.3389/fmicb.2022.856263] [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: 01/17/2022] [Accepted: 03/25/2022] [Indexed: 11/16/2022] Open
Abstract
Dispersal governs microbial biogeography, but the rates and mechanisms of dispersal remain poorly characterized for most microbial taxa. Dispersal limitation is driven by limits on dissemination and establishment, respectively. Elevation gradients create striking patterns of biogeography because they produce steep environmental gradients at small spatial scales, and these gradients offer a powerful tool to examine mechanisms of dispersal limitation. We focus on Streptomyces, a bacterial genus common to soil, by using a taxon-specific phylogenetic marker, the RNA polymerase-encoding rpoB gene. By targeting Streptomyces, we assess dispersal limitation at finer phylogenetic resolution than is possible using whole community analyses. We characterized Streptomyces diversity at local spatial scales (100 to 3,000 m) in two temperate forest sites located in the Adirondacks region of New York State: Woods Lake (<100 m elevation change), and Whiteface Mountain (>1,000 m elevation change). Beta diversity varied considerably at both locations, indicative of dispersal limitation acting at local spatial scales, but beta diversity was significantly higher at Whiteface Mountain. Beta diversity varied across elevation at Whiteface Mountain, being lowest at the mountain’s base. We show that Streptomyces taxa exhibit elevational preferences, and these preferences are phylogenetically conserved. These results indicate that habitat preferences influence Streptomyces biogeography and suggest that barriers to establishment structure Streptomyces communities at higher elevations. These data illustrate that Streptomyces biogeography is governed by dispersal limitation resulting from a complex mixture of stochastic and deterministic processes.
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Affiliation(s)
- Janani Hariharan
- School of Integrative Plant Science, Cornell University, Ithaca, NY, United States
| | - Daniel H Buckley
- School of Integrative Plant Science, Cornell University, Ithaca, NY, United States
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5
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Salazar-Hamm PS, Hathaway JJM, Winter AS, Caimi NA, Buecher DC, Valdez EW, Northup DE. Great diversity of KS α sequences from bat-associated microbiota suggests novel sources of uncharacterized natural products. FEMS MICROBES 2022; 3:xtac012. [PMID: 35573391 PMCID: PMC9097503 DOI: 10.1093/femsmc/xtac012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/10/2022] [Accepted: 04/13/2022] [Indexed: 11/17/2022] Open
Abstract
Polyketide synthases (PKSs) are multidomain enzymes in microorganisms that synthesize complex, bioactive molecules. PKS II systems are iterative, containing only a single representative of each domain: ketosynthase alpha (KS[Formula: see text]), ketosynthase beta and the acyl carrier protein. Any gene encoding for one of these domains is representative of an entire PKS II biosynthetic gene cluster (BGC). Bat skin surfaces represent an extreme environment prolific in Actinobacteria that may constitute a source for bioactive molecule discovery. KS[Formula: see text] sequences were obtained from culturable bacteria from bats in the southwestern United States. From 467 bat bacterial isolates, we detected 215 (46%) had KS[Formula: see text] sequences. Sequencing yielded 210 operational taxonomic units, and phylogenetic placement found 45 (21%) shared <85% homology to characterized metabolites. Additionally, 16 Actinobacteria genomes from the bat microbiome were analyzed for biosynthetic capacity. A range of 69-93% of the BGCs were novel suggesting the bat microbiome may contain valuable uncharacterized natural products. Documenting and characterizing these are important in understanding the susceptibility of bats to emerging infectious diseases, such as white-nose syndrome. Also noteworthy was the relationship between KS [Formula: see text] homology and total BGC novelty within each fully sequenced strain. We propose amplification and detection of KS[Formula: see text] could predict a strain's global biosynthetic capacity.
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Affiliation(s)
- Paris S Salazar-Hamm
- Department of Biology, University of New Mexico, Albuquerque, NM 87131-0001, USA
| | | | - Ara S Winter
- Department of Biology, University of New Mexico, Albuquerque, NM 87131-0001, USA
| | - Nicole A Caimi
- Department of Biology, University of New Mexico, Albuquerque, NM 87131-0001, USA
| | | | - Ernest W Valdez
- Department of Biology, University of New Mexico, Albuquerque, NM 87131-0001, USA
- U.S. Geological Survey, Fort Collins Science Center, Department of Biology, MSC03 2020, University of New Mexico, lbuquerque, NM 87131, USA
| | - Diana E Northup
- Department of Biology, University of New Mexico, Albuquerque, NM 87131-0001, USA
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6
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Hariharan J, Choudoir MJ, Diebold P, Panke-Buisse K, Buckley DH. Streptomyces apricus sp. nov., isolated from soil. Int J Syst Evol Microbiol 2022; 72. [DOI: 10.1099/ijsem.0.005178] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A novel
Streptomyces
strain, SUN51T, was isolated from soils sampled in Wisconsin, USA, as part of a
Streptomyces
biogeography survey. Genome sequencing revealed that this strain had less than 90 % average nucleotide identity (ANI) to type species of
Streptomyces
: SUN51T was most closely related to Streptomyces dioscori A217T (99.5 % 16S rRNA gene identity, 89.4 % ANI). Genome size was estimated at 8.81 Mb, and the genome DNA G+C content was 72 mol%. The strain possessed the cellular fatty acids anteiso-C15 : 0, iso-C16 : 0, 16 : 1 ω7c, anteiso-C17 : 0, iso-C14 : 0 and C16 : 0. The predominant menaquinones were MK-9 H4, MK-9 H6 and MK-9 H8. Strain SUN51T contained the polar lipids phosphatidic acid, phosphatidyl ethanolamine, phosphatidyl glycerol and diphosphatidyl glycerol. The cell wall contained ll-diaminopimelic acid. The strain could grow on a broad range of carbon sources and tolerate temperatures of up to 40 °C. The results of the polyphasic study confirmed that this isolate represents a novel species of the genus
Streptomyces
, for which the name Streptomyces apricus sp. nov. is proposed. The type strain of this species is SUN51T (=NRRL B-65543T=JCM 33736T).
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Affiliation(s)
- Janani Hariharan
- School of Integrative Plant Science, Cornell University, Ithaca, NY, USA
| | | | - Peter Diebold
- Department of Microbiology, Cornell University, Ithaca, NY, USA
| | - Kevin Panke-Buisse
- United States Department of Agriculture, Agricultural Research Service, Madison, WI, USA
| | - Daniel H. Buckley
- School of Integrative Plant Science, Cornell University, Ithaca, NY, USA
- Department of Microbiology, Cornell University, Ithaca, NY, USA
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Chevrette MG, Gavrilidou A, Mantri S, Selem-Mojica N, Ziemert N, Barona-Gómez F. The confluence of big data and evolutionary genome mining for the discovery of natural products. Nat Prod Rep 2021; 38:2024-2040. [PMID: 34787598 DOI: 10.1039/d1np00013f] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
This review covers literature between 2003-2021The development and application of genome mining tools has given rise to ever-growing genetic and chemical databases and propelled natural products research into the modern age of Big Data. Likewise, an explosion of evolutionary studies has unveiled genetic patterns of natural products biosynthesis and function that support Darwin's theory of natural selection and other theories of adaptation and diversification. In this review, we aim to highlight how Big Data and evolutionary thinking converge in the study of natural products, and how this has led to an emerging sub-discipline of evolutionary genome mining of natural products. First, we outline general principles to best utilize Big Data in natural products research, addressing key considerations needed to provide evolutionary context. We then highlight successful examples where Big Data and evolutionary analyses have been combined to provide bioinformatic resources and tools for the discovery of novel natural products and their biosynthetic enzymes. Rather than an exhaustive list of evolution-driven discoveries, we highlight examples where Big Data and evolutionary thinking have been embraced for the evolutionary genome mining of natural products. After reviewing the nascent history of this sub-discipline, we discuss the challenges and opportunities of genomic and metabolomic tools with evolutionary foundations and/or implications and provide a future outlook for this emerging and exciting field of natural product research.
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Affiliation(s)
- Marc G Chevrette
- Wisconsin Institute for Discovery, Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, USA
| | - Athina Gavrilidou
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), Interfaculty Institute for Biomedical Informatics (IBMI), University of Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.
| | - Shrikant Mantri
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), Interfaculty Institute for Biomedical Informatics (IBMI), University of Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany. .,Computational Biology Laboratory, National Agri-Food Biotechnology Institute (NABI), Mohali, Punjab, India
| | - Nelly Selem-Mojica
- Laboratorio de Evolución de la Diversidad Metabólica, Unidad de Genómica Avanzada (Langebio), Cinvestav-IPN, Irapuato, Guanajuato, Mexico.
| | - Nadine Ziemert
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), Interfaculty Institute for Biomedical Informatics (IBMI), University of Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.
| | - Francisco Barona-Gómez
- Laboratorio de Evolución de la Diversidad Metabólica, Unidad de Genómica Avanzada (Langebio), Cinvestav-IPN, Irapuato, Guanajuato, Mexico.
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8
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van Bergeijk DA, Terlouw BR, Medema MH, van Wezel GP. Ecology and genomics of Actinobacteria: new concepts for natural product discovery. Nat Rev Microbiol 2020; 18:546-558. [DOI: 10.1038/s41579-020-0379-y] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2020] [Indexed: 01/09/2023]
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9
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Belknap KC, Park CJ, Barth BM, Andam CP. Genome mining of biosynthetic and chemotherapeutic gene clusters in Streptomyces bacteria. Sci Rep 2020; 10:2003. [PMID: 32029878 PMCID: PMC7005152 DOI: 10.1038/s41598-020-58904-9] [Citation(s) in RCA: 109] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 01/22/2020] [Indexed: 01/05/2023] Open
Abstract
Streptomyces bacteria are known for their prolific production of secondary metabolites, many of which have been widely used in human medicine, agriculture and animal health. To guide the effective prioritization of specific biosynthetic gene clusters (BGCs) for drug development and targeting the most prolific producer strains, knowledge about phylogenetic relationships of Streptomyces species, genome-wide diversity and distribution patterns of BGCs is critical. We used genomic and phylogenetic methods to elucidate the diversity of major classes of BGCs in 1,110 publicly available Streptomyces genomes. Genome mining of Streptomyces reveals high diversity of BGCs and variable distribution patterns in the Streptomyces phylogeny, even among very closely related strains. The most common BGCs are non-ribosomal peptide synthetases, type 1 polyketide synthases, terpenes, and lantipeptides. We also found that numerous Streptomyces species harbor BGCs known to encode antitumor compounds. We observed that strains that are considered the same species can vary tremendously in the BGCs they carry, suggesting that strain-level genome sequencing can uncover high levels of BGC diversity and potentially useful derivatives of any one compound. These findings suggest that a strain-level strategy for exploring secondary metabolites for clinical use provides an alternative or complementary approach to discovering novel pharmaceutical compounds from microbes.
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Affiliation(s)
- Kaitlyn C Belknap
- University of New Hampshire, Department of Molecular, Cellular and Biomedical Sciences, Durham, NH, 03824, USA
| | - Cooper J Park
- University of New Hampshire, Department of Molecular, Cellular and Biomedical Sciences, Durham, NH, 03824, USA
| | - Brian M Barth
- University of New Hampshire, Department of Molecular, Cellular and Biomedical Sciences, Durham, NH, 03824, USA
| | - Cheryl P Andam
- University of New Hampshire, Department of Molecular, Cellular and Biomedical Sciences, Durham, NH, 03824, USA.
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10
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Population Genomics Insights into Adaptive Evolution and Ecological Differentiation in Streptomycetes. Appl Environ Microbiol 2019; 85:AEM.02555-18. [PMID: 30658977 DOI: 10.1128/aem.02555-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 01/14/2019] [Indexed: 12/20/2022] Open
Abstract
Deciphering the genomic variation that represents microevolutionary processes toward species divergence is key to understanding microbial speciation, which has long been under debate. Streptomycetes are filamentous bacteria that are ubiquitous in nature and the richest source of antibiotics; however, their speciation processes remain unknown. To tackle this issue, we performed a comprehensive population genomics analysis on Streptomyces albidoflavus residing in different habitats and with a worldwide distribution and identified and characterized the foundational changes within the species. We detected three well-defined phylogenomic clades, of which clades I and III mainly contained free-living (soil/marine) and insect-associated strains, respectively, and clade II had a mixed origin. By performing genome-wide association studies (GWAS), we identified a number of genetic variants associated with free-living or entomic (denoting or relating to insects) habitats in both the accessory and core genomes. These variants contributed collectively to the population structure and had annotated or confirmed functions that likely facilitate differential adaptation of the species. In addition, we detected higher levels of homologous recombination within each clade and in the free-living group than within the whole species and in the entomic group. A subset of the insect-associated strains (clade III) showed a relatively independent evolutionary trajectory with more symbiosis-favorable genes but little genetic interchange with the other lineages. Our results demonstrate that ecological adaptation promotes genetic differentiation in S. albidoflavus, suggesting a model of ecological speciation with gene flow in streptomycetes.IMPORTANCE Species are the fundamental units of ecology and evolution, and speciation leads to the astounding diversity of life on Earth. Studying speciation is thus of great significance to understand, protect, and exploit biodiversity, but it is a challenge in the microbial world. In this study, using population genomics, we placed Streptomyces albidoflavus strains in a spectrum of speciation and showed that the genetic differences between phylogenomic clusters evolved mainly by environmental selection and gene-specific sweeps. These findings highlight the role of ecology in structuring recombining bacterial species, making a step toward a deeper understanding of microbial speciation. Our results also raise concerns of an underrated microbial diversity at the intraspecies level, which can be utilized for mining of ecologically relevant natural products.
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Park CJ, Andam CP. Within-Species Genomic Variation and Variable Patterns of Recombination in the Tetracycline Producer Streptomyces rimosus. Front Microbiol 2019; 10:552. [PMID: 30949149 PMCID: PMC6437091 DOI: 10.3389/fmicb.2019.00552] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 03/04/2019] [Indexed: 01/09/2023] Open
Abstract
Streptomyces rimosus is best known as the primary source of the tetracycline class of antibiotics, most notably oxytetracycline, which have been widely used against many gram-positive and gram-negative pathogens and protozoan parasites. However, despite the medical and agricultural importance of S. rimosus, little is known of its evolutionary history and genome dynamics. In this study, we aim to elucidate the pan-genome characteristics and phylogenetic relationships of 32 S. rimosus genomes. The S. rimosus pan-genome contains more than 22,000 orthologous gene clusters, and approximately 8.8% of these genes constitutes the core genome. A large part of the accessory genome is composed of 9,646 strain-specific genes. S. rimosus exhibits an open pan-genome (decay parameter α = 0.83) and high gene diversity between strains (genomic fluidity φ = 0.12). We also observed strain-level variation in the distribution and abundance of biosynthetic gene clusters (BGCs) and that each individual S. rimosus genome has a unique repertoire of BGCs. Lastly, we observed variation in recombination, with some strains donating or receiving DNA more often than others, strains that tend to frequently recombine with specific partners, genes that often experience recombination more than others, and variable sizes of recombined DNA sequences. We conclude that the high levels of inter-strain genomic variation in S. rimosus is partly explained by differences in recombination among strains. These results have important implications on current efforts for natural drug discovery, the ecological role of strain-level variation in microbial populations, and addressing the fundamental question of why microbes have pan-genomes.
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Affiliation(s)
- Cooper J Park
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH, United States
| | - Cheryl P Andam
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH, United States
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12
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Wright ES, Baum DA. Exclusivity offers a sound yet practical species criterion for bacteria despite abundant gene flow. BMC Genomics 2018; 19:724. [PMID: 30285620 PMCID: PMC6171291 DOI: 10.1186/s12864-018-5099-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 09/21/2018] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND The question of whether bacterial species objectively exist has long divided microbiologists. A major source of contention stems from the fact that bacteria regularly engage in horizontal gene transfer (HGT), making it difficult to ascertain relatedness and draw boundaries between taxa. A natural way to define taxa is based on exclusivity of relatedness, which applies when members of a taxon are more closely related to each other than they are to any outsider. It is largely unknown whether exclusive bacterial taxa exist when averaging over the genome or are rare due to rampant hybridization. RESULTS Here, we analyze a collection of 701 genomes representing a wide variety of environmental isolates from the family Streptomycetaceae, whose members are competent at HGT. We find that the presence/absence of auxiliary genes in the pan-genome displays a hierarchical (tree-like) structure that correlates significantly with the genealogy of the core-genome. Moreover, we identified the existence of many exclusive taxa, although individual genes often contradict these taxa. These conclusions were supported by repeating the analysis on 1,586 genomes belonging to the genus Bacillus. However, despite confirming the existence of exclusive groups (taxa), we were unable to identify an objective threshold at which to assign the rank of species. CONCLUSIONS The existence of bacterial taxa is justified by considering average relatedness across the entire genome, as captured by exclusivity, but is rejected if one requires unanimous agreement of all parts of the genome. We propose using exclusivity to delimit taxa and conventional genome similarity thresholds to assign bacterial taxa to the species rank. This approach recognizes species that are phylogenetically meaningful, while also establishing some degree of comparability across species-ranked taxa in different bacterial clades.
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Affiliation(s)
- Erik S Wright
- Department of Biomedical Informatics, University of Pittsburgh, Pittsburgh, USA.
- Pittsburgh Center for Evolutionary Biology and Medicine, Pittsburgh, USA.
| | - David A Baum
- Department of Botany, University of Wisconsin-Madison, Madison, USA
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Phylogenetic conservatism of thermal traits explains dispersal limitation and genomic differentiation of Streptomyces sister-taxa. ISME JOURNAL 2018; 12:2176-2186. [PMID: 29880909 DOI: 10.1038/s41396-018-0180-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 03/22/2018] [Accepted: 03/26/2018] [Indexed: 12/28/2022]
Abstract
The latitudinal diversity gradient is a pattern of biogeography observed broadly in plants and animals but largely undocumented in terrestrial microbial systems. Although patterns of microbial biogeography across broad taxonomic scales have been described in a range of contexts, the mechanisms that generate biogeographic patterns between closely related taxa remain incompletely characterized. Adaptive processes are a major driver of microbial biogeography, but there is less understanding of how microbial biogeography and diversification are shaped by dispersal limitation and drift. We recently described a latitudinal diversity gradient of species richness and intraspecific genetic diversity in Streptomyces by using a geographically explicit culture collection. Within this geographically explicit culture collection, we have identified Streptomyces sister-taxa whose geographic distribution is delimited by latitude. These sister-taxa differ in geographic distribution, genomic diversity, and ecological traits despite having nearly identical SSU rRNA gene sequences. Comparative genomic analysis reveals genomic differentiation of these sister-taxa consistent with restricted gene flow across latitude. Furthermore, we show phylogenetic conservatism of thermal traits between the sister-taxa suggesting that thermal trait adaptation limits dispersal and gene flow across climate regimes as defined by latitude. Such phylogenetic conservatism of thermal traits is commonly associated with latitudinal diversity gradients for plants and animals. These data provide further support for the hypothesis that the Streptomyces latitudinal diversity gradient was formed as a result of historical demographic processes defined by dispersal limitation and driven by paleoclimate dynamics.
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14
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Liu Q, Xin YH, Zhou YG, Chen WX. Multilocus sequence analysis of homologous recombination and diversity in Arthrobacter sensu lato named species and glacier-inhabiting strains. Syst Appl Microbiol 2017; 41:23-29. [PMID: 29129356 DOI: 10.1016/j.syapm.2017.08.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 07/30/2017] [Accepted: 08/19/2017] [Indexed: 10/18/2022]
Abstract
Members of the bacterial genus Arthrobacter sensu lato are Gram-positive actinomycetes distributed worldwide and found in numerous environments including soil, water, glacier ice, and sewage. Homologous recombination is an important driving force in bacterial evolution, but its impact on Arthrobacter sensu lato evolution is poorly understood. We evaluated homologous recombination among 41 Arthrobacter sensu lato named species, using multilocus sequence analysis (MLSA). A high level of recombination was found, associated with strong diversification and a reticulate evolutionary pattern of Arthrobacter sensu lato. We also collected a total of 31 cold-adapted Arthrobacter sensu lato strains from two cold glaciers located in northwest China and two temperate glaciers in southwest China, and evaluated their diversity and population structure by MLSA. The glacier strains displayed high diversity, but rates of recombination among the four glacier groups were quite low, indicating that barriers to homologous recombination formed in the past among the populations on different glaciers. Our findings indicate that historical glaciation events shaped the contemporary distributions, taxonomic relationships, and phylogeographic patterns of Arthrobacter sensu lato species on glaciers.
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Affiliation(s)
- Qing Liu
- China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Yu-Hua Xin
- China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
| | - Yu-Guang Zhou
- China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Wen-Xin Chen
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
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15
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Millán-Aguiñaga N, Chavarria KL, Ugalde JA, Letzel AC, Rouse GW, Jensen PR. Phylogenomic Insight into Salinispora (Bacteria, Actinobacteria) Species Designations. Sci Rep 2017; 7:3564. [PMID: 28620214 PMCID: PMC5472633 DOI: 10.1038/s41598-017-02845-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 04/18/2017] [Indexed: 11/12/2022] Open
Abstract
Bacteria represent the most genetically diverse kingdom of life. While great progress has been made in describing this diversity, it remains difficult to identify the phylogenetic and ecological characteristics that delineate groups of bacteria that possess species-like properties. One major challenge associated with species delineations is that not all shared genes have the same evolutionary history, and thus the choice of loci can have a major impact on phylogenetic reconstruction. Sequencing the genomes of large numbers of closely related strains provides new opportunities to distinguish ancestral from acquired alleles and assess the effects of recombination on phylogenetic inference. Here we analyzed the genomes of 119 strains of the marine actinomycete genus Salinispora, which is currently comprised of three named species that share 99% 16S rRNA gene sequence identity. While 63% of the core genome showed evidence of recombination, this had no effect on species-level phylogenomic resolution. Recombination did however blur intra-species relationships and biogeographic resolution. The genome-wide average nucleotide identity provided a new perspective on Salinispora diversity, revealing as many as seven new species. Patterns of orthologous group distributions reveal a genetic basis to delineation the candidate taxa and insight into the levels of genetic cohesion associated with bacterial species.
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Affiliation(s)
- Natalie Millán-Aguiñaga
- Center for Marine Biotechnology and Biomedicine Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States.,Universidad Autónoma de Baja California. Facultad de Ciencias Marinas, Ensenada, Baja California, Mexico
| | - Krystle L Chavarria
- Center for Marine Biotechnology and Biomedicine Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States
| | - Juan A Ugalde
- Center for Marine Biotechnology and Biomedicine Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States.,Centro de Bioinformática y Biología Integrativa, Facultad de Ciencias Biológicas, Universidad Andrés Bella, Santiago, Chile
| | - Anne-Catrin Letzel
- Center for Marine Biotechnology and Biomedicine Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States
| | - Greg W Rouse
- Marine Biology Research Division Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States
| | - Paul R Jensen
- Center for Marine Biotechnology and Biomedicine Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States. .,Marine Biology Research Division Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States.
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16
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Genetic Stability and Evolution of the sigB Allele, Used for Listeria Sensu Stricto Subtyping and Phylogenetic Inference. Appl Environ Microbiol 2017; 83:AEM.00306-17. [PMID: 28389543 DOI: 10.1128/aem.00306-17] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 04/03/2017] [Indexed: 11/20/2022] Open
Abstract
Sequencing of single genes remains an important tool that allows the rapid classification of bacteria. Sequencing of a portion of sigB, which encodes a stress-responsive alternative sigma factor, has emerged as a commonly used molecular tool for the initial characterization of diverse Listeria isolates. In this study, evolutionary approaches were used to assess the validity of sigB allelic typing for Listeria For a data set of 4,280 isolates, sigB allelic typing showed a Simpson's index of diversity of 0.96. Analyses of 164 sigB allelic types (ATs) found among the 6 Listeriasensu stricto species, representing these 4,280 isolates, indicate that neither frequent homologous recombination nor positive selection significantly contributed to the evolution of sigB, confirming its genetic stability. The molecular clock test provided evidence for unequal evolution rates across clades; Listeria welshimeri displayed the lowest sigB diversity and was the only species in which sigB evolved in a clocklike manner, implying a unique natural history. Among the four L. monocytogenes lineages, sigB evolution followed a molecular clock only in lineage IV. Moreover, sigB displayed a significant negative Tajima D value in lineage II, suggesting a recent population bottleneck followed by lineage expansion. The absence of positive selection along with the violation of the molecular clock suggested a nearly neutral mechanism of Listeriasensu strictosigB evolution. While comparison with a whole-genome sequence-based phylogeny revealed that the sigB phylogeny did not correctly reflect the ancestry of L. monocytogenes lineage IV, the availability of a large sigB AT database allowed accurate species classification.IMPORTANCEsigB allelic typing has been widely used for species delineation and subtyping of Listeria However, an informative evaluation of this method from an evolutionary perspective was missing. Our data indicate that the genetic stability of sigB is affected by neither frequent homologous recombination nor positive selection, which supports that sigB allelic typing provides reliable subtyping and classification of Listeria sensu stricto strains. However, multigene data are required for accurate phylogeny reconstruction of Listeria This study thus contributes to a better understanding of the evolution of sigB and confirms the robustness of the sigB subtyping system for Listeria.
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17
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Choudoir MJ, Panke-Buisse K, Andam CP, Buckley DH. Genome Surfing As Driver of Microbial Genomic Diversity. Trends Microbiol 2017; 25:624-636. [PMID: 28283403 DOI: 10.1016/j.tim.2017.02.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/03/2017] [Accepted: 02/10/2017] [Indexed: 01/20/2023]
Abstract
Historical changes in population size, such as those caused by demographic range expansions, can produce nonadaptive changes in genomic diversity through mechanisms such as gene surfing. We propose that demographic range expansion of a microbial population capable of horizontal gene exchange can result in genome surfing, a mechanism that can cause widespread increase in the pan-genome frequency of genes acquired by horizontal gene exchange. We explain that patterns of genetic diversity within Streptomyces are consistent with genome surfing, and we describe several predictions for testing this hypothesis both in Streptomyces and in other microorganisms.
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Affiliation(s)
- Mallory J Choudoir
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14850 USA
| | - Kevin Panke-Buisse
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14850 USA
| | - Cheryl P Andam
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham NH 03824, USA
| | - Daniel H Buckley
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14850 USA.
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18
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Choudoir MJ, Doroghazi JR, Buckley DH. Latitude delineates patterns of biogeography in terrestrial Streptomyces. Environ Microbiol 2016; 18:4931-4945. [PMID: 27322415 DOI: 10.1111/1462-2920.13420] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 06/04/2016] [Indexed: 01/23/2023]
Abstract
The biogeography of Streptomyces was examined at regional spatial scales to identify factors that govern patterns of microbial diversity. Streptomyces are spore forming filamentous bacteria which are widespread in soil. Streptomyces strains were isolated from perennial grass habitats sampled across a spatial scale of more than 6000 km. Previous analysis of this geographically explicit culture collection provided evidence for a latitudinal diversity gradient in Streptomyces species. Here the hypothesis that this latitudinal diversity gradient is a result of evolutionary dynamics associated with historical demographic processes was evaluated. Historical demographic phenomena have genetic consequences that can be evaluated through analysis of population genetics. Population genetic approaches were applied to analyze population structure in six of the most numerically abundant and geographically widespread Streptomyces phylogroups from our culture collection. Streptomyces population structure varied at regional spatial scales, and allelic diversity correlated with geographic distance. In addition, allelic diversity and gene flow are partitioned by latitude. Finally, it was found that nucleotide diversity within phylogroups was negatively correlated with latitude. These results indicate that phylogroup diversification is constrained by dispersal limitation at regional spatial scales, and they are consistent with the hypothesis that historical demographic processes have influenced the contemporary biogeography of Streptomyces.
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Affiliation(s)
- Mallory J Choudoir
- School of Integrative Plant Sciences, Cornell University, Ithaca, NY, 14853, USA
| | - James R Doroghazi
- School of Integrative Plant Sciences, Cornell University, Ithaca, NY, 14853, USA
| | - Daniel H Buckley
- School of Integrative Plant Sciences, Cornell University, Ithaca, NY, 14853, USA
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