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Sengupta S, Azad RK. Leveraging comparative genomics to uncover alien genes in bacterial genomes. Microb Genom 2023; 9:mgen000939. [PMID: 36748570 PMCID: PMC9973850 DOI: 10.1099/mgen.0.000939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
A significant challenge in bacterial genomics is to catalogue genes acquired through the evolutionary process of horizontal gene transfer (HGT). Both comparative genomics and sequence composition-based methods have often been invoked to quantify horizontally acquired genes in bacterial genomes. Comparative genomics methods rely on completely sequenced genomes and therefore the confidence in their predictions increases as the databases become more enriched in completely sequenced genomes. Recent developments including in microbial genome sequencing call for reassessment of alien genes based on information-rich resources currently available. We revisited the comparative genomics approach and developed a new algorithm for alien gene detection. Our algorithm compared favourably with the existing comparative genomics-based methods and is capable of detecting both recent and ancient transfers. It can be used as a standalone tool or in concert with other complementary algorithms for comprehensively cataloguing alien genes in bacterial genomes.
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Affiliation(s)
- Soham Sengupta
- Department of Biological Sciences and BioDiscovery Institute, University of North Texas, Denton, Texas, 76203, USA
| | - Rajeev K Azad
- Department of Biological Sciences and BioDiscovery Institute, University of North Texas, Denton, Texas, 76203, USA.,Department of Mathematics, University of North Texas, Denton, Texas, 76203, USA
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Burks DJ, Azad RK. Mapping Strengths and Weaknesses of Different Clustering Approaches to Deciphering Bacterial Chimerism. OMICS : A JOURNAL OF INTEGRATIVE BIOLOGY 2022; 26:422-439. [PMID: 35925817 DOI: 10.1089/omi.2022.0062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Bacterial genomes are chimeras of DNA of different ancestries. Deconstructing chimeric genomes is central to understanding the evolutionary trajectories of their disparate components and thus the organisms as a whole in the light of their evolutionary contexts. Of specific interest is to delineate and quantify native (vertically inherited) and alien (horizontally acquired) components of bacterial genomes and also specify genomic fractions that represent different donor sources. An agglomerative clustering procedure that prioritizes grouping of proximal similar genomic segments has previously been invoked for this purpose in conjunction with a recursive segmentation procedure. Surprisingly, however, the relative strengths and weaknesses of different clustering approaches to deciphering bacterial chimerism have not yet been investigated, despite the need to robustly interpret tens of thousands of completely sequenced bacterial genomes and nearly complete genome assemblies available in the public databases. To bridge this knowledge gap and develop more robust approaches, we assessed different clustering methods, including segment order based (proximal) clustering, hierarchical clustering, affinity propagation clustering, and a novel network clustering approach on chimeric genomes modeled after bacterial genomes representing a broad spectrum of compositional complexity. Although segment order-based clustering and network clustering compared favorably with the other approaches in discriminating between native and alien DNA at genome optimized settings, network clustering did consistently better than other methods at parametric settings optimized on all test genomes together. Segment order-based clustering and hierarchical clustering outperformed other methods in alien DNA identification while preserving donor identity in the genomes. Our study highlights the strengths and weaknesses of different approaches and suggests how this can be leveraged to achieve a more robust deconstruction of bacterial chimerism.
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Affiliation(s)
- David J Burks
- Department of Biological Sciences, BioDiscovery Institute, University of North Texas, Denton, Texas, USA
| | - Rajeev K Azad
- Department of Biological Sciences, BioDiscovery Institute, University of North Texas, Denton, Texas, USA
- Department of Mathematics, University of North Texas, Denton, Texas, USA
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Pandey RS, Azad RK. A Protocol for Horizontally Acquired Metabolic Gene Detection in Algae. Methods Mol Biol 2022; 2396:61-69. [PMID: 34786676 DOI: 10.1007/978-1-0716-1822-6_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Horizontal gene transfer (HGT) or lateral gene transfer (LGT), the exchange of genetic materials among organisms by means of other than parent-to-offspring (vertical) inheritance, plays a major role in prokaryotic genome evolution, facilitating adaptation of prokaryotes to changes in the environment. Phylogenetic methods have been frequently invoked to catalog horizontally acquired genes; however, these methods are often constrained by the paucity of sequenced genomes of close relatives (and even distant relatives) for a robust analysis and reliable inference. In this chapter, we describe a HGT quantification protocol that exploits the complementary strengths of the integrative segmentation and clustering method and the comparative genomics approach to identify foreign genes. Users can use this pipeline in combination with phylogenetic tree reconstruction to identify foreign genes that are supported by multiple lines of evidence, that is, atypical composition, atypical distribution in close relatives, and aberrant phylogenetic pattern.
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Affiliation(s)
- Ravi S Pandey
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Rajeev K Azad
- Department of Biological Sciences and BioDiscovery Institute, University of North Texas, Denton, TX, USA.
- Department of Mathematics, University of North Texas, Denton, TX, USA.
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The Xanthomonas RaxH-RaxR Two-Component Regulatory System Is Orthologous to the Zinc-Responsive Pseudomonas ColS-ColR System. Microorganisms 2021; 9:microorganisms9071458. [PMID: 34361895 PMCID: PMC8306577 DOI: 10.3390/microorganisms9071458] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 06/30/2021] [Accepted: 07/02/2021] [Indexed: 01/08/2023] Open
Abstract
Genome sequence comparisons to infer likely gene functions require accurate ortholog assignments. In Pseudomonas spp., the sensor-regulator ColS-ColR two-component regulatory system responds to zinc and other metals to control certain membrane-related functions, including lipid A remodeling. In Xanthomonas spp., three different two-component regulatory systems, RaxH-RaxR, VgrS-VgrR, and DetS-DetR, have been denoted as ColS-ColR in several different genome annotations and publications. To clarify these assignments, we compared the sensor periplasmic domain sequences and found that those from Pseudomonas ColS and Xanthomonas RaxH share a similar size as well as the location of a Glu-X-X-Glu metal ion-binding motif. Furthermore, we determined that three genes adjacent to raxRH are predicted to encode enzymes that remodel the lipid A component of lipopolysaccharide. The modifications catalyzed by lipid A phosphoethanolamine transferase (EptA) and lipid A 1-phosphatase (LpxE) previously were detected in lipid A from multiple Xanthomonas spp. The third gene encodes a predicted lipid A glycosyl transferase (ArnT). Together, these results indicate that the Xanthomonas RaxH-RaxR system is orthologous to the Pseudomonas ColS-ColR system that regulates lipid A remodeling. To avoid future confusion, we recommend that the terms ColS and ColR no longer be applied to Xanthomonas spp., and that the Vgr, Rax, and Det designations be used instead.
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Godde JS, Baichoo S, Mungloo-Dilmohamud Z, Jaufeerally-Fakim Y. Comparison of genomic islands in cyanobacteria: Evidence of bacteriophage-mediated horizontal gene transfer from eukaryotes. Microbiol Res 2018; 211:31-46. [DOI: 10.1016/j.micres.2018.03.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 02/11/2018] [Accepted: 03/17/2018] [Indexed: 12/21/2022]
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Akita T, Takuno S, Innan H. Coalescent framework for prokaryotes undergoing interspecific homologous recombination. Heredity (Edinb) 2018; 120:474-484. [PMID: 29358726 PMCID: PMC5889408 DOI: 10.1038/s41437-017-0034-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 10/04/2017] [Accepted: 10/23/2017] [Indexed: 12/11/2022] Open
Abstract
Coalescent process for prokaryote species is theoretically considered. Prokaryotes undergo homologous recombination with individuals of the same species (intraspecific recombination) and with individuals of other species (interspecific recombination). This work particularly focuses on interspecific recombination because intraspecific recombination has been well incorporated in coalescent framework. We present a simulation framework for generating SNP (single-nucleotide polymorphism) patterns that allows external DNA integration into host genome from other species. Using this simulation tool, msPro, we observed that the joint processes of intra- and interspecific recombination generate complex SNP patterns. The direct effect of interspecific recombination includes increased polymorphism. Because interspecific recombination is very rare in nature, it generates regions with exceptionally high polymorphism. Following interspecific recombination, intraspecific recombination cuts the integrated external DNA into small fragments, generating a complex SNP pattern that appears as if external DNA was integrated multiple times. The insight gained from our work using the msPro simulator will be useful for understanding and evaluating the relative contributions of intra- and interspecific recombination events in generating complex SNP patters in prokaryotes.
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Affiliation(s)
- Tetsuya Akita
- Graduate University for Advanced Studies, Hayama, Kanagawa, 240-0193, Japan
- National Research Institute of Far Seas Fisheries, Fisheries Research Agency, Yokohama, Kanagawa, 236-8648, Japan
| | - Shohei Takuno
- Graduate University for Advanced Studies, Hayama, Kanagawa, 240-0193, Japan
| | - Hideki Innan
- Graduate University for Advanced Studies, Hayama, Kanagawa, 240-0193, Japan.
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Darby CA, Stolzer M, Ropp PJ, Barker D, Durand D. Xenolog classification. Bioinformatics 2017; 33:640-649. [PMID: 27998934 PMCID: PMC5860392 DOI: 10.1093/bioinformatics/btw686] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 10/26/2016] [Indexed: 01/31/2023] Open
Abstract
Motivation Orthology analysis is a fundamental tool in comparative genomics. Sophisticated methods have been developed to distinguish between orthologs and paralogs and to classify paralogs into subtypes depending on the duplication mechanism and timing, relative to speciation. However, no comparable framework exists for xenologs: gene pairs whose history, since their divergence, includes a horizontal transfer. Further, the diversity of gene pairs that meet this broad definition calls for classification of xenologs with similar properties into subtypes. Results We present a xenolog classification that uses phylogenetic reconciliation to assign each pair of genes to a class based on the event responsible for their divergence and the historical association between genes and species. Our classes distinguish between genes related through transfer alone and genes related through duplication and transfer. Further, they separate closely-related genes in distantly-related species from distantly-related genes in closely-related species. We present formal rules that assign gene pairs to specific xenolog classes, given a reconciled gene tree with an arbitrary number of duplications and transfers. These xenology classification rules have been implemented in software and tested on a collection of ∼13 000 prokaryotic gene families. In addition, we present a case study demonstrating the connection between xenolog classification and gene function prediction. Availability and Implementation The xenolog classification rules have been implemented in N otung 2.9, a freely available phylogenetic reconciliation software package. http://www.cs.cmu.edu/~durand/Notung . Gene trees are available at http://dx.doi.org/10.7488/ds/1503 . Contact durand@cmu.edu. Supplementary information Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Charlotte A Darby
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Maureen Stolzer
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Patrick J Ropp
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Daniel Barker
- School of Biology, University of St. Andrews, St. Andrews, Fife KY16 9TH, UK
| | - Dannie Durand
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.,Department of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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Pandey RS, Saxena G, Bhattacharya D, Qiu H, Azad RK. Using complementary approaches to identify trans-domain nuclear gene transfers in the extremophile Galdieria sulphuraria (Rhodophyta). JOURNAL OF PHYCOLOGY 2017; 53:7-11. [PMID: 27704560 DOI: 10.1111/jpy.12466] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/05/2016] [Indexed: 06/06/2023]
Abstract
Identification of horizontal gene transfers (HGTs) has primarily relied on phylogenetic tree based methods, which require a rich sampling of sequenced genomes to ensure a reliable inference. Because the success of phylogenetic approaches depends on the breadth and depth of the database, researchers usually apply stringent filters to detect only the most likely gene transfers in the genomes of interest. One such study focused on a highly conservative estimate of trans-domain gene transfers in the extremophile eukaryote, Galdieria sulphuraria (Galdieri) Merola (Rhodophyta), by applying multiple filters in their phylogenetic pipeline. This led to the identification of 75 inter-domain acquisitions from Bacteria or Archaea. Because of the evolutionary, ecological, and potential biotechnological significance of foreign genes in algae, alternative approaches and pipelines complementing phylogenetics are needed for a more comprehensive assessment of HGT. We present here a novel pipeline that uncovered 17 novel foreign genes of prokaryotic origin in G. sulphuraria, results that are supported by multiple lines of evidence including composition-based, comparative data, and phylogenetics. These genes encode a variety of potentially adaptive functions, from metabolite transport to DNA repair.
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Affiliation(s)
- Ravi S Pandey
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
| | - Garima Saxena
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
| | - Debashish Bhattacharya
- Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, New Jersey, USA
| | - Huan Qiu
- Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, New Jersey, USA
| | - Rajeev K Azad
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
- Department of Mathematics, University of North Texas, Denton, Texas, USA
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Wang GH, Sun BF, Xiong TL, Wang YK, Murfin KE, Xiao JH, Huang DW. Bacteriophage WO Can Mediate Horizontal Gene Transfer in Endosymbiotic Wolbachia Genomes. Front Microbiol 2016; 7:1867. [PMID: 27965627 PMCID: PMC5126046 DOI: 10.3389/fmicb.2016.01867] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/07/2016] [Indexed: 11/26/2022] Open
Abstract
Phage-mediated horizontal gene transfer (HGT) is common in free-living bacteria, and many transferred genes can play a significant role in their new bacterial hosts. However, there are few reports concerning phage-mediated HGT in endosymbionts (obligate intracellular bacteria within animal or plant hosts), such as Wolbachia. The Wolbachia-infecting temperate phage WO can actively shift among Wolbachia genomes and has the potential to mediate HGT between Wolbachia strains. In the present study, we extend previous findings by validating that the phage WO can mediate transfer of non-phage genes. To do so, we utilized bioinformatic, phylogenetic, and molecular analyses based on all sequenced Wolbachia and phage WO genomes. Our results show that the phage WO can mediate HGT between Wolbachia strains, regardless of whether the transferred genes originate from Wolbachia or other unrelated bacteria.
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Affiliation(s)
- Guan H Wang
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of SciencesBeijing, China; University of Chinese Academy of SciencesBeijing, China
| | - Bao F Sun
- Disease Genomics and Individualized Medicine Laboratory, Beijing Institute of Genomics, Chinese Academy of Sciences Beijing, China
| | - Tuan L Xiong
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of SciencesBeijing, China; University of Chinese Academy of SciencesBeijing, China
| | - Yan K Wang
- College of Life Sciences, Hebei University Baoding, China
| | - Kristen E Murfin
- Section of Infectious Diseases, Yale University School of Medicine New Haven, CT, USA
| | - Jin H Xiao
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences Beijing, China
| | - Da W Huang
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of SciencesBeijing, China; College of Life Sciences, Hebei UniversityBaoding, China
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Identification of horizontally transferred genes in the genus Colletotrichum reveals a steady tempo of bacterial to fungal gene transfer. BMC Genomics 2015; 16:2. [PMID: 25555398 PMCID: PMC4320630 DOI: 10.1186/1471-2164-16-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 12/08/2014] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Horizontal gene transfer (HGT) is the stable transmission of genetic material between organisms by means other than vertical inheritance. HGT has an important role in the evolution of prokaryotes but is relatively rare in eukaryotes. HGT has been shown to contribute to virulence in eukaryotic pathogens. We studied the importance of HGT in plant pathogenic fungi by identifying horizontally transferred genes in the genomes of three members of the genus Colletotrichum. RESULTS We identified eleven HGT events from bacteria into members of the genus Colletotrichum or their ancestors. The HGT events include genes involved in amino acid, lipid and sugar metabolism as well as lytic enzymes. Additionally, the putative minimal dates of transference were calculated using a time calibrated phylogenetic tree. This analysis reveals a constant flux of genes from bacteria to fungi throughout the evolution of subphylum Pezizomycotina. CONCLUSIONS Genes that are typically transferred by HGT are those that are constantly subject to gene duplication and gene loss. The functions of some of these genes suggest roles in niche adaptation and virulence. We found no evidence of a burst of HGT events coinciding with major geological events. In contrast, HGT appears to be a constant, albeit rare phenomenon in the Pezizomycotina, occurring at a steady rate during their evolution.
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Ettensohn CA. Horizontal transfer of themsp130gene supported the evolution of metazoan biomineralization. Evol Dev 2014; 16:139-48. [DOI: 10.1111/ede.12074] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Charles A. Ettensohn
- Department of Biological Sciences; Carnegie Mellon University; 4400 Fifth Avenue Pittsburgh PA 15213 USA
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Davolos D, Pietrangeli B. A molecular study on bacterial resistance to arsenic-toxicity in surface and underground waters of Latium (Italy). ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2013; 96:1-9. [PMID: 23870163 DOI: 10.1016/j.ecoenv.2013.05.039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 05/09/2013] [Accepted: 05/13/2013] [Indexed: 05/08/2023]
Abstract
Latium, a region in central Italy, is known for its extensive volcanic areas that make a significant contribution to the arsenic (As) contamination of freshwater environments, even though some degree of As water pollution may be caused by human activities. The information available on indigenous As-resistant prokaryotes in aquatic environments of Latium is, however, still limited. In this study, we describe new bacteria that are resistant to arsenic toxicity and were isolated from the surface waters of Lake Vico and the Sacco River, two groundwater systems in Latium, as well as from bottled natural mineral water from the same region. The 16S rRNA gene sequence analysis for the As-resistant strains in lake and river waters points to a prevalence of β- and γ-Proteobacteria, while α-Proteobacteria, Firmicutes and Bacteroidetes are represented to a lesser extent. By contrast, solely γ-Proteobacteria were isolated from groundwater samples. The presence of Actinobacteria was documented exclusively in bottled mineral water. In addition, we conducted a DNA sequence-based study on the gene codifying arsB, an As(III) efflux membrane protein pump related to arsenic resistance, for all the As-resistant bacterial isolates. A phylogenetic analysis was carried out on the newly sequenced 16S rRNA genes and arsB in the present study as well as on an additional 16S rRNA/arsB dataset we obtained previously from Lake Albano, from the Tiber and from a well in Bassano Romano located in Latium (Davolos and Pietrangeli, 2011). Overall, the phylogenetic diversity of As-resistant bacteria in underground water was very limited if compared with lentic and lotic waters. Lastly, our molecular data support the hypothesis that the horizontal gene transfer of ars in As-containing freshwater environments is not limited to closely-related genomes, but also occurs between bacteria that are distant from an evolutionary viewpoint, thereby indicating that such genetic events may be considered a source of microbial resistance to arsenic-toxicity.
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Affiliation(s)
- Domenico Davolos
- INAIL-Research, Certification, Verification Area, Department of Productive Plants and Human Settlements (DIPIA), Via Urbana, 167, 00184 Rome, Italy.
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Abstract
Since the emergence of high-throughput genome sequencing platforms and more recently the next-generation platforms, the genome databases are growing at an astronomical rate. Tremendous efforts have been invested in recent years in understanding intriguing complexities beneath the vast ocean of genomic data. This is apparent in the spurt of computational methods for interpreting these data in the past few years. Genomic data interpretation is notoriously difficult, partly owing to the inherent heterogeneities appearing at different scales. Methods developed to interpret these data often suffer from their inability to adequately measure the underlying heterogeneities and thus lead to confounding results. Here, we present an information entropy-based approach that unravels the distinctive patterns underlying genomic data efficiently and thus is applicable in addressing a variety of biological problems. We show the robustness and consistency of the proposed methodology in addressing three different biological problems of significance—identification of alien DNAs in bacterial genomes, detection of structural variants in cancer cell lines and alignment-free genome comparison.
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Affiliation(s)
- Rajeev K Azad
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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