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Chen X, Wang M, Luo L, Liu X, An L, Nie Y, Wu XL. The evolution of autonomy from two cooperative specialists in fluctuating environments. Proc Natl Acad Sci U S A 2024; 121:e2317182121. [PMID: 39172793 DOI: 10.1073/pnas.2317182121] [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: 10/04/2023] [Accepted: 07/24/2024] [Indexed: 08/24/2024] Open
Abstract
From microbes to humans, organisms perform numerous tasks for their survival, including food acquisition, migration, and reproduction. A complex biological task can be performed by either an autonomous organism or by cooperation among several specialized organisms. However, it remains unclear how autonomy and cooperation evolutionarily switch. Specifically, it remains unclear whether and how cooperative specialists can repair deleted genes through direct genetic exchange, thereby regaining metabolic autonomy. Here, we address this question by experimentally evolving a mutualistic microbial consortium composed of two specialists that cooperatively degrade naphthalene. We observed that autonomous genotypes capable of performing the entire naphthalene degradation pathway evolved from two cooperative specialists and dominated the community. This evolutionary transition was driven by the horizontal gene transfer (HGT) between the two specialists. However, this evolution was exclusively observed in the fluctuating environment alternately supplied with naphthalene and pyruvate, where mutualism and competition between the two specialists alternated. The naphthalene-supplied environment exerted selective pressure that favors the expansion of autonomous genotypes. The pyruvate-supplied environment promoted the coexistence and cell density of the cooperative specialists, thereby increasing the likelihood of HGT. Using a mathematical model, we quantitatively demonstrate that environmental fluctuations facilitate the evolution of autonomy through HGT when the relative growth rate and carrying capacity of the cooperative specialists allow enhanced coexistence and higher cell density in the competitive environment. Together, our results demonstrate that cooperative specialists can repair deleted genes through a direct genetic exchange under specific conditions, thereby regaining metabolic autonomy.
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Affiliation(s)
- Xiaoli Chen
- College of Engineering, Peking University, Beijing 100871, China
- Institute of Ocean Research, Peking University, Beijing 100871, China
| | - Miaoxiao Wang
- Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
- Department of Environmental Microbiology, Eawag, Dübendorf, Switzerland
| | - Laipeng Luo
- College of Engineering, Peking University, Beijing 100871, China
| | - Xiaonan Liu
- College of Engineering, Peking University, Beijing 100871, China
| | - Liyun An
- College of Architecture and Environment, Sichuan University, Chengdu 610000, China
| | - Yong Nie
- College of Engineering, Peking University, Beijing 100871, China
| | - Xiao-Lei Wu
- College of Engineering, Peking University, Beijing 100871, China
- Institute of Ocean Research, Peking University, Beijing 100871, China
- Institute of Ecology, Peking University, Beijing 100871, China
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2
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Ilyas M, Purkait D, Atmakuri K. Genomic islands and their role in fitness traits of two key sepsis-causing bacterial pathogens. Brief Funct Genomics 2024; 23:55-68. [PMID: 36528816 DOI: 10.1093/bfgp/elac051] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/03/2022] [Accepted: 11/11/2022] [Indexed: 01/21/2024] Open
Abstract
To survive and establish a niche for themselves, bacteria constantly evolve. Toward that, they not only insert point mutations and promote illegitimate recombinations within their genomes but also insert pieces of 'foreign' deoxyribonucleic acid, which are commonly referred to as 'genomic islands' (GEIs). The GEIs come in several forms, structures and types, often providing a fitness advantage to the harboring bacterium. In pathogenic bacteria, some GEIs may enhance virulence, thus altering disease burden, morbidity and mortality. Hence, delineating (i) the GEIs framework, (ii) their encoded functions, (iii) the triggers that help them move, (iv) the mechanisms they exploit to move among bacteria and (v) identification of their natural reservoirs will aid in superior tackling of several bacterial diseases, including sepsis. Given the vast array of comparative genomics data, in this short review, we provide an overview of the GEIs, their types and the compositions therein, especially highlighting GEIs harbored by two important pathogens, viz. Acinetobacter baumannii and Klebsiella pneumoniae, which prominently trigger sepsis in low- and middle-income countries. Our efforts help shed some light on the challenges these pathogens pose when equipped with GEIs. We hope that this review will provoke intense research into understanding GEIs, the cues that drive their mobility across bacteria and the ways and means to prevent their transfer, especially across pathogenic bacteria.
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Affiliation(s)
- Mohd Ilyas
- Bacterial Pathogenesis Lab, Infection and Immunity Group, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana 121001, India
| | - Dyuti Purkait
- Bacterial Pathogenesis Lab, Infection and Immunity Group, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana 121001, India
| | - Krishnamohan Atmakuri
- Bacterial Pathogenesis Lab, Infection and Immunity Group, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana 121001, India
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3
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Chan YF, Chen YH, Yu SP, Chen HJ, Nozawa Y, Tang SL. Reciprocal transplant experiment reveals multiple factors influencing changes in coral microbial communities across climate zones. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 907:167929. [PMID: 37863230 DOI: 10.1016/j.scitotenv.2023.167929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Revised: 10/12/2023] [Accepted: 10/17/2023] [Indexed: 10/22/2023]
Abstract
Previous studies have demonstrated the influence of external factors (environmental factors and the coral host factors) on the community structure of coral-associated bacteria. However, the internal factors, e.g. the interaction within the bacterial community or bacteria itself, have often been overlooked in studies of the coral microbiome. Hence, we performed a reciprocal transplant of corals between two different climate zones to examine the resultant alterations in coral-associated bacterial communities. The findings highlight the significance of environmental factors, host selection, and highly resilient bacteria in shaping the coral microbial composition. The results support that coral species consistently harbor specific predominant bacterial groups influenced by host selection, while locations display unique bacterial taxa due to environmental variations. The transplantation of corals into new environments leads to a gradual shift in the bacterial community, from initially resembling that of the native location to eventually resembling that of the transplanted location, emphasizing the crucial role of bacterial community composition for coral survival under changing ambient conditions. Furthermore, highly resilient bacteria that persisted throughout the reciprocal transplant experiment demonstrated their adaptability to environmental and host changes, suggesting the presence of robust adaptation or resistance mechanisms in bacterial communities. Genetic adaptations within the prevalent bacterial group, Endozoicomonas, were also observed, suggesting variations in resilience and adaptation capabilities among different phylotypes. This study highlights the need to conduct further investigations into the coral-associated bacteria themselves, as they may hold some key insights into understanding the dynamics of coral-associated microbial communities. These data also highlight some key species of coral-associated bacteria which could benefit coral in response to alterations in ambient environment.
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Affiliation(s)
- Ya-Fan Chan
- Department of Microbiology, Soochow University, Taipei 111, Taiwan
| | - Yu-Hsiang Chen
- Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Sheng-Ping Yu
- Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Hsing-Ju Chen
- Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Yoko Nozawa
- Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Sen-Lin Tang
- Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan; Taiwan's Ocean Genome Center, National Taiwan Ocean University, Keelung, Taiwan.
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4
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Sezmis AL, Woods LC, Peleg AY, McDonald MJ. Horizontal Gene Transfer, Fitness Costs and Mobility Shape the Spread of Antibiotic Resistance Genes into Experimental Populations of Acinetobacter Baylyi. Mol Biol Evol 2023; 40:7036842. [PMID: 36788632 PMCID: PMC9985319 DOI: 10.1093/molbev/msad028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/17/2022] [Accepted: 01/27/2023] [Indexed: 02/16/2023] Open
Abstract
Horizontal gene transfer (HGT) is important for microbial evolution, but how evolutionary forces shape the frequencies of horizontally transferred genetic variants in the absence of strong selection remains an open question. In this study, we evolve laboratory populations of Acinetobacter baylyi (ADP1) with HGT from two clinically relevant strains of multidrug-resistant Acinetobacter baumannii (AB5075 and A9844). We find that DNA can cross the species barrier, even without strong selection, and despite substantial DNA sequence divergence between the two species. Our results confirm previous findings that HGT can drive the spread of antibiotic resistance genes (ARGs) without selection for that antibiotic, but not for all of the resistance genes present in the donor genome. We quantify the costs and benefits of horizontally transferred variants and use whole population sequencing to track the spread of ARGs from HGT donors into antibiotic-sensitive recipients. We find that even though most ARGs are taken up by populations of A. baylyi, the long-term fate of an individual gene depends both on its fitness cost and on the type of genetic element that carries the gene. Interestingly, we also found that an integron, but not its host plasmid, is able to spread in A. baylyi populations despite its strong deleterious effect. Altogether, our results show how HGT provides an evolutionary advantage to evolving populations by facilitating the spread of non-selected genetic variation including costly ARGs.
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Affiliation(s)
- Aysha L Sezmis
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia
| | - Laura C Woods
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia
| | - Anton Y Peleg
- Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia.,Infection Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Clayton, Victoria, Australia.,Centre to Impact AMR, Monash University, Clayton, Victoria, Australia
| | - Michael J McDonald
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia.,Centre to Impact AMR, Monash University, Clayton, Victoria, Australia
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Sloan DB, Warren JM, Williams AM, Kuster SA, Forsythe ES. Incompatibility and Interchangeability in Molecular Evolution. Genome Biol Evol 2023; 15:evac184. [PMID: 36583227 PMCID: PMC9839398 DOI: 10.1093/gbe/evac184] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 12/20/2022] [Accepted: 12/22/2022] [Indexed: 12/31/2022] Open
Abstract
There is remarkable variation in the rate at which genetic incompatibilities in molecular interactions accumulate. In some cases, minor changes-even single-nucleotide substitutions-create major incompatibilities when hybridization forces new variants to function in a novel genetic background from an isolated population. In other cases, genes or even entire functional pathways can be horizontally transferred between anciently divergent evolutionary lineages that span the tree of life with little evidence of incompatibilities. In this review, we explore whether there are general principles that can explain why certain genes are prone to incompatibilities while others maintain interchangeability. We summarize evidence pointing to four genetic features that may contribute to greater resistance to functional replacement: (1) function in multisubunit enzyme complexes and protein-protein interactions, (2) sensitivity to changes in gene dosage, (3) rapid rate of sequence evolution, and (4) overall importance to cell viability, which creates sensitivity to small perturbations in molecular function. We discuss the relative levels of support for these different hypotheses and lay out future directions that may help explain the striking contrasts in patterns of incompatibility and interchangeability throughout the history of molecular evolution.
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Affiliation(s)
- Daniel B Sloan
- Department of Biology, Colorado State University, Fort Collins, Colorado
| | - Jessica M Warren
- Center for Mechanisms of Evolution, Biodesign Institute and School of Life Sciences, Arizona State University, Tempe, Arizona
| | - Alissa M Williams
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee
| | - Shady A Kuster
- Department of Biology, Colorado State University, Fort Collins, Colorado
| | - Evan S Forsythe
- Department of Biology, Colorado State University, Fort Collins, Colorado
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6
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Distribution of fitness effects of cross-species transformation reveals potential for fast adaptive evolution. THE ISME JOURNAL 2023; 17:130-139. [PMID: 36224268 PMCID: PMC9751276 DOI: 10.1038/s41396-022-01325-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 09/14/2022] [Accepted: 09/20/2022] [Indexed: 12/15/2022]
Abstract
Bacterial transformation, a common mechanism of horizontal gene transfer, can speed up adaptive evolution. How its costs and benefits depend on the growth environment is poorly understood. Here, we characterize the distributions of fitness effects (DFE) of transformation in different conditions and test whether they predict in which condition transformation is beneficial. To determine the DFEs, we generate hybrid libraries between the recipient Bacillus subtilis and different donor species and measure the selection coefficient of each hybrid strain. In complex medium, the donor Bacillus vallismortis confers larger fitness effects than the more closely related donor Bacillus spizizenii. For both donors, the DFEs show strong effect beneficial transfers, indicating potential for fast adaptive evolution. While some transfers of B. vallismortis DNA show pleiotropic effects, various transfers are beneficial only under a single growth condition, indicating that the recipient can benefit from a variety of donor genes to adapt to varying growth conditions. We scrutinize the predictive value of the DFEs by laboratory evolution under different growth conditions and show that the DFEs correctly predict the condition at which transformation confers a benefit. We conclude that transformation has a strong potential for speeding up adaptation to varying environments by profiting from a gene pool shared between closely related species.
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7
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Prevalence and concentration of Campylobacter in faeces of dairy cows: A systematic review and meta-analysis. PLoS One 2022; 17:e0276018. [PMID: 36240215 PMCID: PMC9565387 DOI: 10.1371/journal.pone.0276018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 09/28/2022] [Indexed: 11/26/2022] Open
Abstract
The consumption of raw milk from dairy cows has caused multiple food-borne outbreaks of campylobacteriosis in the European Union (EU) since 2011. Cross-contamination of raw milk through faeces is an important vehicle for transmission of Campylobacter to consumers. This systematic review and meta-analysis, aimed to summarize data on the prevalence and concentration of Campylobacter in faeces of dairy cows. Suitable scientific articles published up to July 2021 were identified through a systematic literature search and subjected to screening and quality assessment. Fifty-three out of 1338 identified studies were eligible for data extraction and 44 were further eligible for meta-analysis. The pooled prevalence was calculated in two different meta-analytic models: a simple model based on one average prevalence estimate per study and a multilevel meta-analytic model that included all prevalence outcomes reported in each study (including different subgroups of e.g. health status and age of dairy cows). The results of the two models were significantly different with a pooled prevalence estimate of 29%, 95% CI [23-36%] and 51%, 95% CI [44-57%], respectively. The effect of sub-groups on prevalence were analyzed with a multilevel mixed-effect model which showed a significant effect of the faecal collection methods and Campylobacter species on the prevalence. A meta-analysis on concentration data could not be performed due to the limited availability of data. This systematic review highlights important data gaps and limitations in current studies and variation of prevalence outcomes between available studies. The included studies used a variety of methods for sampling, data collection and analysis of Campylobacter that added uncertainty to the pooled prevalence estimates. Nevertheless, the performed meta-analysis improved our understanding of Campylobacter prevalence in faeces of dairy cows and is considered a valuable basis for the further development of quantitative microbiological risk assessment models for Campylobacter in (raw) milk and food products thereof.
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8
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Martins Morasi R, Zimbardi da Silva A, Thais Alves Dantas S, Faganello C, Cristina Bastos Juliano L, Lúcia Mores Rall V, Ribeiro Tiba-Casas M, Pantoja JC, Ferreira Amarante A, Cristina Cirone Silva N. Overview of antimicrobial resistance and virulence factors in Salmonella spp. isolated in the last two decades from chicken in Brazil. Food Res Int 2022; 162:111955. [DOI: 10.1016/j.foodres.2022.111955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 07/29/2022] [Accepted: 09/16/2022] [Indexed: 11/29/2022]
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9
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Valcz G, Újvári B, Buzás EI, Krenács T, Spisák S, Kittel Á, Tulassay Z, Igaz P, Takács I, Molnár B. Small extracellular vesicle DNA-mediated horizontal gene transfer as a driving force for tumor evolution: Facts and riddles. Front Oncol 2022; 12:945376. [PMID: 36003770 PMCID: PMC9393732 DOI: 10.3389/fonc.2022.945376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 07/06/2022] [Indexed: 11/13/2022] Open
Abstract
The basis of the conventional gene-centric view on tumor evolution is that vertically inherited mutations largely define the properties of tumor cells. In recent years, however, accumulating evidence shows that both the tumor cells and their microenvironment may acquire external, non-vertically inherited genetic properties via horizontal gene transfer (HGT), particularly through small extracellular vesicles (sEVs). Many phases of sEV-mediated HGT have been described, such as DNA packaging into small vesicles, their release, uptake by recipient cells, and incorporation of sEV-DNA into the recipient genome to modify the phenotype and properties of cells. Recent techniques in sEV separation, genome sequencing and editing, as well as the identification of new secretion mechanisms, shed light on a number of additional details of this phenomenon. Here, we discuss the key features of this form of gene transfer and make an attempt to draw relevant conclusions on the contribution of HGT to tumor evolution.
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Affiliation(s)
- Gábor Valcz
- MTA-SE Molecular Medicine Research Group, Eötvös Loránd Research Network, Budapest, Hungary
- *Correspondence: Gábor Valcz,
| | - Beáta Újvári
- School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University, Waurn Ponds, VIC, Australia
| | - Edit I. Buzás
- Department of Genetics, Cell- and Immunobiology, Semmelweis University, Budapest, Hungary
- ELKH-SE Immune-Proteogenomics Extracellular Vesicle Research Group, Semmelweis University, Budapest, Hungary
- HCEMM-SU Extracellular Vesicle Research Group, Semmelweis University, Budapest, Hungary
| | - Tibor Krenács
- 1st Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary
| | - Sándor Spisák
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Ágnes Kittel
- Institute of Experimental Medicine, Eötvös Loránd Research Network, Budapest, Hungary
| | - Zsolt Tulassay
- MTA-SE Molecular Medicine Research Group, Eötvös Loránd Research Network, Budapest, Hungary
| | - Péter Igaz
- MTA-SE Molecular Medicine Research Group, Eötvös Loránd Research Network, Budapest, Hungary
- Department of Internal Medicine and Oncology, Semmelweis University, Budapest, Hungary
- Department of Endocrinology, Semmelweis University, Budapest, Hungary
| | - István Takács
- Department of Internal Medicine and Oncology, Semmelweis University, Budapest, Hungary
| | - Béla Molnár
- MTA-SE Molecular Medicine Research Group, Eötvös Loránd Research Network, Budapest, Hungary
- Department of Internal Medicine and Oncology, Semmelweis University, Budapest, Hungary
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Recombination resolves the cost of horizontal gene transfer in experimental populations of Helicobacter pylori. Proc Natl Acad Sci U S A 2022; 119:e2119010119. [PMID: 35298339 PMCID: PMC8944584 DOI: 10.1073/pnas.2119010119] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Horizontal gene transfer (HGT)—the transfer of DNA between lineages—is responsible for a large proportion of the genetic variation that contributes to evolution in microbial populations. While HGT can bring beneficial genetic innovation, the transfer of DNA from other species or strains can also have deleterious effects. In this study, we evolve populations of the bacteria Helicobacter pylori and use DNA sequencing to identify over 40,000 genetic variants transferred by HGT. We measure the cost of many of these and find that both strongly beneficial mutations and deleterious mutations are genetic variants transferred by natural transformation. Importantly, we also show how recombination that separates linked beneficial and deleterious mutations resolves the cost of HGT. Horizontal gene transfer (HGT) is important for microbial evolution, yet we know little about the fitness effects and dynamics of horizontally transferred genetic variants. In this study, we evolve laboratory populations of Helicobacter pylori, which take up DNA from their environment by natural transformation, and measure the fitness effects of thousands of transferred genetic variants. We find that natural transformation increases the rate of adaptation but comes at the cost of significant genetic load. We show that this cost is circumvented by recombination, which increases the efficiency of selection by decoupling deleterious and beneficial genetic variants. Our results show that adaptation with HGT, pervasive in natural microbial populations, is shaped by a combination of selection, recombination, and genetic drift not accounted for in existing models of evolution.
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11
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Riederer JM, Tiso S, van Eldijk TJ, Weissing FJ. Capturing the facets of evolvability in a mechanistic framework. Trends Ecol Evol 2022; 37:430-439. [DOI: 10.1016/j.tree.2022.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/13/2022] [Accepted: 01/18/2022] [Indexed: 10/19/2022]
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12
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"Take It or Leave It"-Factors Regulating Competence Development and DNA Uptake in Campylobacter jejuni. Int J Mol Sci 2021; 22:ijms221810169. [PMID: 34576332 PMCID: PMC8468864 DOI: 10.3390/ijms221810169] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 09/14/2021] [Accepted: 09/15/2021] [Indexed: 11/21/2022] Open
Abstract
Campylobacter jejuni has a large adaptive potential due to enormous genetic exchange. Factors regulating natural transformation in this food-borne pathogen are largely unknown but of interest for the application of sustained reduction strategies in the food-processing industry. Using a single cell DNA uptake assay, we visualized that recognition of methylated C. jejuni DNA was essential for the first step of DNA uptake into a DNase resistant state. Transformation rates using a resistance marker correlated with the fraction of competent bacteria, harboring one to maximally four locations of active DNA uptake, not necessarily being located at the cell pole. Competence developed with rising pH between 6.5 and 7.5 under microaerobic conditions and was nearly insensitive towards growth temperatures between 32 °C and 42 °C, CO2 concentrations ranging from 0 to 50% and growth rates. However, competence development was abolished at pH 5 or under aerobic stress conditions, in which the bacteria ceased growth but fully survived. The DNA uptake machinery in competent bacteria shut down at slightly acidic pH and was reversibly switched on upon neutralization. It was dependent on the proton motive force and, in contrast to competence development, slightly enhanced under aerobic conditions. The results suggest that natural transformation in C. jejuni occurs in the neutral and microaerobic intestinal environment for enhanced genetic diversity and pre-adaption before host switch. In addition, highly competent bacteria might be shed into the environment, still able to acquire genetic material for increased survival.
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Abstract
Horizontal gene transfer (HGT) is an important factor in bacterial evolution that can act across species boundaries. Yet, we know little about rate and genomic targets of cross-lineage gene transfer and about its effects on the recipient organism's physiology and fitness. Here, we address these questions in a parallel evolution experiment with two Bacillus subtilis lineages of 7% sequence divergence. We observe rapid evolution of hybrid organisms: gene transfer swaps ∼12% of the core genome in just 200 generations, and 60% of core genes are replaced in at least one population. By genomics, transcriptomics, fitness assays, and statistical modeling, we show that transfer generates adaptive evolution and functional alterations in hybrids. Specifically, our experiments reveal a strong, repeatable fitness increase of evolved populations in the stationary growth phase. By genomic analysis of the transfer statistics across replicate populations, we infer that selection on HGT has a broad genetic basis: 40% of the observed transfers are adaptive. At the level of functional gene networks, we find signatures of negative, positive, and epistatic selection, consistent with hybrid incompatibilities and adaptive evolution of network functions. Our results suggest that gene transfer navigates a complex cross-lineage fitness landscape, bridging epistatic barriers along multiple high-fitness paths.
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Bombaywala S, Mandpe A, Paliya S, Kumar S. Antibiotic resistance in the environment: a critical insight on its occurrence, fate, and eco-toxicity. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:24889-24916. [PMID: 33765260 DOI: 10.1007/s11356-021-13143-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 02/22/2021] [Indexed: 06/12/2023]
Abstract
The overuse, misuse, and underuse of antibiotics tend to increase the antibiotic burden in the environment resulting into the evolution in microbial community to possess resistance that renders antibiotics ineffective against them. The current review recapitulates the present state of knowledge about the occurrence and fate of antibiotics in various environmental matrices. Also, the prevalence of antibiotic-resistant bacteria/antibiotic-resistant genes (ARB/ARGs) in various biological and non-biological systems, eco-toxicity of antibiotics on non-target organisms, and remediation methods for antibiotics and ARB/ARGs removal were critically reviewed. Furthermore, a comparison of various technologies for their efficiency to eliminate antibiotic residues and ARB/ARGs is made. The study identified gaps in the investigation of toxic effects of low concentration of antibiotics and the mixture of multiple antibiotics on non-target organisms. The study of antibiotics' phytotoxicity and toxicity towards sediment and soil-dwelling organisms are also recognized as a knowledge gap. The review also details policies implemented across the globe to fight against antibiotic resistance, and the scarcity of data on lab to land transferred remediation technology was identified. The present study entails a critical review of literature providing guidelines for the articulation of policies for prudent use of antibiotics, limits on the amount of antibiotics in pharmaceutical formulations, and regular surveillance in the Indian context.
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Affiliation(s)
- Sakina Bombaywala
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 2010 02, India
- CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nehru Marg, Nagpur, 4400 20, India
| | - Ashootosh Mandpe
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 2010 02, India
- CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nehru Marg, Nagpur, 4400 20, India
| | - Sonam Paliya
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 2010 02, India
- CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nehru Marg, Nagpur, 4400 20, India
| | - Sunil Kumar
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 2010 02, India.
- CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nehru Marg, Nagpur, 4400 20, India.
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15
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Horizontal gene transfer potentiates adaptation by reducing selective constraints on the spread of genetic variation. Proc Natl Acad Sci U S A 2020; 117:26868-26875. [PMID: 33055207 DOI: 10.1073/pnas.2005331117] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Horizontal gene transfer (HGT) confers the rapid acquisition of novel traits and is pervasive throughout microbial evolution. Despite the central role of HGT, the evolutionary forces that drive the dynamics of HGT alleles in evolving populations are poorly understood. Here, we show that HGT alters the evolutionary dynamics of genetic variation, so that deleterious genetic variants, including antibiotic resistance genes, can establish in populations without selection. We evolve antibiotic-sensitive populations of the human pathogen Helicobacter pylori in an environment without antibiotic but with HGT from an antibiotic-resistant isolate of H. pylori We find that HGT increases the rate of adaptation, with most horizontally transferred genetic variants establishing at a low frequency in the population. When challenged with antibiotic, this low-level variation potentiates adaptation, with HGT populations flourishing in conditions where nonpotentiated populations go extinct. By extending previous models of evolution under HGT, we evaluated the conditions for the establishment and spread of HGT-acquired alleles into recipient populations. We then used our model to estimate parameters of HGT and selection from our experimental evolution data. Together, our findings show how HGT can act as an evolutionary force that facilitates the spread of nonselected genetic variation and expands the adaptive potential of microbial populations.
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Slomka S, Françoise I, Hornung G, Asraf O, Biniashvili T, Pilpel Y, Dahan O. Experimental Evolution of Bacillus subtilis Reveals the Evolutionary Dynamics of Horizontal Gene Transfer and Suggests Adaptive and Neutral Effects. Genetics 2020; 216:543-558. [PMID: 32847815 PMCID: PMC7536860 DOI: 10.1534/genetics.120.303401] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 08/16/2020] [Indexed: 12/18/2022] Open
Abstract
Tracing evolutionary processes that lead to fixation of genomic variation in wild bacterial populations is a prime challenge in molecular evolution. In particular, the relative contribution of horizontal gene transfer (HGT) vs.de novo mutations during adaptation to a new environment is poorly understood. To gain a better understanding of the dynamics of HGT and its effect on adaptation, we subjected several populations of competent Bacillus subtilis to a serial dilution evolution on a high-salt-containing medium, either with or without foreign DNA from diverse pre-adapted or naturally salt tolerant species. Following 504 generations of evolution, all populations improved growth yield on the medium. Sequencing of evolved populations revealed extensive acquisition of foreign DNA from close Bacillus donors but not from more remote donors. HGT occurred in bursts, whereby a single bacterial cell appears to have acquired dozens of fragments at once. In the largest burst, close to 2% of the genome has been replaced by HGT. Acquired segments tend to be clustered in integration hotspots. Other than HGT, genomes also acquired spontaneous mutations. Many of these mutations occurred within, and seem to alter, the sequence of flagellar proteins. Finally, we show that, while some HGT fragments could be neutral, others are adaptive and accelerate evolution.
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Affiliation(s)
- Shai Slomka
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Itamar Françoise
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Gil Hornung
- The Nancy and Stephen Grand Israel National Center for Personalized Medicine, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Omer Asraf
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tammy Biniashvili
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yitzhak Pilpel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Orna Dahan
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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17
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Guirimand G, Kulagina N, Papon N, Hasunuma T, Courdavault V. Innovative Tools and Strategies for Optimizing Yeast Cell Factories. Trends Biotechnol 2020; 39:488-504. [PMID: 33008642 DOI: 10.1016/j.tibtech.2020.08.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 08/24/2020] [Accepted: 08/27/2020] [Indexed: 12/13/2022]
Abstract
Metabolic engineering (ME) aims to develop efficient microbial cell factories that can produce a wide variety of valuable compounds, ideally at the highest yield and from various feedstocks. We summarize recent developments in ME methods for tailoring different yeast cell factories (YCFs). In particular, we highlight the most timely and cutting-edge molecular tools and strategies for biosynthetic pathway optimization (including genome-editing tools), combinatorial transcriptional and post-transcriptional engineering (cis/trans regulators), dynamic control of metabolic fluxes (e.g., rewiring of primary metabolism), and spatial reconfiguration of metabolic pathways. Finally, we discuss challenges and perspectives for adaptive laboratory evolution (ALE) of yeast to advance ME of microbial cell factories.
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Affiliation(s)
- Gregory Guirimand
- Graduate School of Sciences, Technology and Innovation, Kobe University, Kobe, Japan; Biomolécules et Biotechnologies Végétales (BBV), Équipe d'Accueil (EA) 2106, Université de Tours, Tours, France
| | - Natalja Kulagina
- Biomolécules et Biotechnologies Végétales (BBV), Équipe d'Accueil (EA) 2106, Université de Tours, Tours, France
| | - Nicolas Papon
- Groupe d'Etude des Interactions Hôte-Pathogène (GEIHP), EA 3142, Université Angers and Université Brest, Structure Féderative de Recherche (SFR) 4208 Interactions Cellulaires et Applications Thérapeutiques (ICAT), Angers, France
| | - Tomohisa Hasunuma
- Graduate School of Sciences, Technology and Innovation, Kobe University, Kobe, Japan; Engineering Biology Research Center, Kobe University, Kobe, Japan.
| | - Vincent Courdavault
- Biomolécules et Biotechnologies Végétales (BBV), Équipe d'Accueil (EA) 2106, Université de Tours, Tours, France.
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18
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French KE, Zhou Z, Terry N. Horizontal 'gene drives' harness indigenous bacteria for bioremediation. Sci Rep 2020; 10:15091. [PMID: 32934307 PMCID: PMC7492276 DOI: 10.1038/s41598-020-72138-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 08/24/2020] [Indexed: 01/21/2023] Open
Abstract
Engineering bacteria to clean-up oil spills is rapidly advancing but faces regulatory hurdles and environmental concerns. Here, we develop a new technology to harness indigenous soil microbial communities for bioremediation by flooding local populations with catabolic genes for petroleum hydrocarbon degradation. Overexpressing three enzymes (almA, xylE, p450cam) in Escherichia coli led to degradation of 60-99% of target hydrocarbon substrates. Mating experiments, fluorescence microscopy and TEM revealed indigenous bacteria could obtain these vectors from E. coli through several mechanisms of horizontal gene transfer (HGT), including conjugation and cytoplasmic exchange through nanotubes. Inoculating petroleum-polluted sediments with E. coli carrying the vector pSF-OXB15-p450camfusion showed that the E. coli cells died after five days but a variety of bacteria received and carried the vector for over 60 days after inoculation. Within 60 days, the total petroleum hydrocarbon content of the polluted soil was reduced by 46%. Pilot experiments show that vectors only persist in indigenous populations when under selection pressure, disappearing when this carbon source is removed. This approach to remediation could prime indigenous bacteria for degrading pollutants while providing minimal ecosystem disturbance.
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Affiliation(s)
- Katherine E French
- Department of Plant and Microbial Biology, University of California Berkeley, Koshland Hall, Berkeley, CA, 94720, USA.
| | - Zhongrui Zhou
- QB3, University of California Berkeley, Stanley Hall, Berkeley, CA, 94720, USA
| | - Norman Terry
- Department of Plant and Microbial Biology, University of California Berkeley, Koshland Hall, Berkeley, CA, 94720, USA
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19
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The complex phylogenetic relationships of a 4mC/6mA DNA methyltransferase in prokaryotes. Mol Phylogenet Evol 2020; 149:106837. [PMID: 32304827 DOI: 10.1016/j.ympev.2020.106837] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 01/30/2020] [Accepted: 04/09/2020] [Indexed: 01/04/2023]
Abstract
DNA methyltransferases are proteins that modify DNA via attachment of methyl groups to nucleobases and are ubiquitous across the bacterial, archaeal, and eukaryotic domains of life. Here, we investigated the complex evolutionary history of the large and consequential 4mC/6mA DNA methyltransferase protein family using phylogenetic reconstruction of amino acid sequences. We present a well-supported phylogeny of this family based on systematic sampling of taxa across superphyla of bacteria and archaea. We compared the phylogeny to a current representation of the species tree of life and found that the 4mC/6mA methyltransferase family has a strikingly complex evolutionary history that likely began sometime after the last universal common ancestor of life diverged into the bacterial and archaeal lineages and probably involved many horizontal gene transfers within and between domains. Despite the complexity of its evolutionary history, we inferred that only one significant shift in molecular evolutionary rate characterizes the diversification of this protein family.
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20
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Quistad SD, Doulcier G, Rainey PB. Experimental manipulation of selfish genetic elements links genes to microbial community function. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190681. [PMID: 32200751 PMCID: PMC7133536 DOI: 10.1098/rstb.2019.0681] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Microbial communities underpin the Earth's biological and geochemical processes, but their complexity hampers understanding. Motivated by the challenge of diversity and the need to forge ways of capturing dynamical behaviour connecting genes to function, biologically independent experimental communities comprising hundreds of microbial genera were established from garden compost and propagated on nitrogen-limited minimal medium with cellulose (paper) as sole carbon source. After 1 year of bi-weekly transfer, communities retained hundreds of genera. To connect genes to function, we used a simple experimental manipulation that involved the periodic collection of selfish genetic elements (SGEs) from separate communities, followed by pooling and redistribution across communities. The treatment was predicted to promote amplification and dissemination of SGEs and thus horizontal gene transfer. Confirmation came from comparative metagenomics, which showed the substantive movement of ecologically significant genes whose dynamic across space and time could be followed. Enrichment of genes implicated in nitrogen metabolism, and particularly ammonification, prompted biochemical assays that revealed a measurable impact on community function. Our simple experimental strategy offers a conceptually new approach for unravelling dynamical processes affecting microbial community function. This article is part of the theme issue ‘Conceptual challenges in microbial community ecology’.
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Affiliation(s)
- Steven D Quistad
- Laboratoire de Génétique de l'Evolution, Chemistry, Biology and Innovation (CBI) UMR8231, ESPCI Paris, CNRS, PSL Research University, 10 rue Vauquelin, Paris, France
| | - Guilhem Doulcier
- Laboratoire de Génétique de l'Evolution, Chemistry, Biology and Innovation (CBI) UMR8231, ESPCI Paris, CNRS, PSL Research University, 10 rue Vauquelin, Paris, France
| | - Paul B Rainey
- Laboratoire de Génétique de l'Evolution, Chemistry, Biology and Innovation (CBI) UMR8231, ESPCI Paris, CNRS, PSL Research University, 10 rue Vauquelin, Paris, France.,Department of Microbial Population Biology, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany
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21
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Sandberg TE, Salazar MJ, Weng LL, Palsson BO, Feist AM. The emergence of adaptive laboratory evolution as an efficient tool for biological discovery and industrial biotechnology. Metab Eng 2019; 56:1-16. [PMID: 31401242 DOI: 10.1016/j.ymben.2019.08.004] [Citation(s) in RCA: 254] [Impact Index Per Article: 50.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 08/01/2019] [Accepted: 08/05/2019] [Indexed: 12/21/2022]
Abstract
Harnessing the process of natural selection to obtain and understand new microbial phenotypes has become increasingly possible due to advances in culturing techniques, DNA sequencing, bioinformatics, and genetic engineering. Accordingly, Adaptive Laboratory Evolution (ALE) experiments represent a powerful approach both to investigate the evolutionary forces influencing strain phenotypes, performance, and stability, and to acquire production strains that contain beneficial mutations. In this review, we summarize and categorize the applications of ALE to various aspects of microbial physiology pertinent to industrial bioproduction by collecting case studies that highlight the multitude of ways in which evolution can facilitate the strain construction process. Further, we discuss principles that inform experimental design, complementary approaches such as computational modeling that help maximize utility, and the future of ALE as an efficient strain design and build tool driven by growing adoption and improvements in automation.
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Affiliation(s)
- Troy E Sandberg
- Department of Bioengineering, University of California, San Diego, CA, 92093, USA
| | - Michael J Salazar
- Department of Bioengineering, University of California, San Diego, CA, 92093, USA
| | - Liam L Weng
- Department of Bioengineering, University of California, San Diego, CA, 92093, USA
| | - Bernhard O Palsson
- Department of Bioengineering, University of California, San Diego, CA, 92093, USA; Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Lyngby, Denmark
| | - Adam M Feist
- Department of Bioengineering, University of California, San Diego, CA, 92093, USA; Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Lyngby, Denmark.
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22
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Kumar M, Jaiswal S, Sodhi KK, Shree P, Singh DK, Agrawal PK, Shukla P. Antibiotics bioremediation: Perspectives on its ecotoxicity and resistance. ENVIRONMENT INTERNATIONAL 2019; 124:448-461. [PMID: 30684803 DOI: 10.1016/j.envint.2018.12.065] [Citation(s) in RCA: 248] [Impact Index Per Article: 49.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/02/2018] [Accepted: 12/31/2018] [Indexed: 05/28/2023]
Abstract
Antibiotic is one of the most significant discoveries and have brought a revolution in the field of medicine for human therapy. In addition to the medical uses, antibiotics have broad applications in agriculture and animal husbandry. In developing nations, antibiotics use have helped to increase the life expectancy by lowering the deaths due to bacterial infections, but the risks associated with antibiotics pollution is largely affecting people. Since antibiotics are released partially degraded and undegraded into environment creating antibiotic pollution, and its bioremediation is a challenging task. In the present review, we have discussed the primary antibiotic sources like hospitals, dairy, and agriculture causing antibiotic pollution and their innovative detection methods. The strong commitment towards the resistance prevention and participation, nations through strict policies and their implementations now come to fight against the antibiotic resistance under WHO. The review also deciphers the bacterial evolution based strategies to overcome the effects of antibiotics, so the antibiotic degradation and elimination from the environment and its health benefits. The present review focuses on the environmental sources of antibiotics, it's possible degradation mechanisms, health effects, and bacterial antibiotics resistance mechanisms.
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Affiliation(s)
- Mohit Kumar
- Soil Microbial Ecology and Environmental Toxicology Laboratory, Department of Zoology, University of Delhi, Delhi 110007, India
| | - Shweta Jaiswal
- Enzyme Technology and Protein Bioinformatics Laboratory, Department of Microbiology, Maharshi Dayanand University, Rohtak 124001, Haryana, India
| | - Kushneet Kaur Sodhi
- Soil Microbial Ecology and Environmental Toxicology Laboratory, Department of Zoology, University of Delhi, Delhi 110007, India
| | - Pallee Shree
- Soil Microbial Ecology and Environmental Toxicology Laboratory, Department of Zoology, University of Delhi, Delhi 110007, India
| | - Dileep Kumar Singh
- Soil Microbial Ecology and Environmental Toxicology Laboratory, Department of Zoology, University of Delhi, Delhi 110007, India
| | - Pawan Kumar Agrawal
- National Agriculture Science Fund, Krishi Anusandhan Bhavan-I, Indian Agricultural Research Institute, Delhi 110012, India
| | - Pratyoosh Shukla
- Enzyme Technology and Protein Bioinformatics Laboratory, Department of Microbiology, Maharshi Dayanand University, Rohtak 124001, Haryana, India.
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23
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Ocaña-Pallarès E, Najle SR, Scazzocchio C, Ruiz-Trillo I. Reticulate evolution in eukaryotes: Origin and evolution of the nitrate assimilation pathway. PLoS Genet 2019; 15:e1007986. [PMID: 30789903 PMCID: PMC6400420 DOI: 10.1371/journal.pgen.1007986] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 03/05/2019] [Accepted: 01/25/2019] [Indexed: 01/17/2023] Open
Abstract
Genes and genomes can evolve through interchanging genetic material, this leading to reticular evolutionary patterns. However, the importance of reticulate evolution in eukaryotes, and in particular of horizontal gene transfer (HGT), remains controversial. Given that metabolic pathways with taxonomically-patchy distributions can be indicative of HGT events, the eukaryotic nitrate assimilation pathway is an ideal object of investigation, as previous results revealed a patchy distribution and suggested that the nitrate assimilation cluster of dikaryotic fungi (Opisthokonta) could have been originated and transferred from a lineage leading to Oomycota (Stramenopiles). We studied the origin and evolution of this pathway through both multi-scale bioinformatic and experimental approaches. Our taxon-rich genomic screening shows that nitrate assimilation is present in more lineages than previously reported, although being restricted to autotrophs and osmotrophs. The phylogenies indicate a pervasive role of HGT, with three bacterial transfers contributing to the pathway origin, and at least seven well-supported transfers between eukaryotes. In particular, we propose a distinct and more complex HGT path between Opisthokonta and Stramenopiles than the one previously suggested, involving at least two transfers of a nitrate assimilation gene cluster. We also found that gene fusion played an essential role in this evolutionary history, underlying the origin of the canonical eukaryotic nitrate reductase, and of a chimeric nitrate reductase in Ichthyosporea (Opisthokonta). We show that the ichthyosporean pathway, including this novel nitrate reductase, is physiologically active and transcriptionally co-regulated, responding to different nitrogen sources; similarly to distant eukaryotes with independent HGT-acquisitions of the pathway. This indicates that this pattern of transcriptional control evolved convergently in eukaryotes, favoring the proper integration of the pathway in the metabolic landscape. Our results highlight the importance of reticulate evolution in eukaryotes, by showing the crucial contribution of HGT and gene fusion in the evolutionary history of the nitrate assimilation pathway. One of the most relevant findings in evolution was that lineages, either genes or genomes, can evolve through interchanging genetic material. For example, exon shuffling can lead to genes with complete novel functions, and genomes can acquire novel functionalities by means of horizontal gene transfer (HGT). Whereas HGT is known to be an important driver of metabolic remodelling and ecological adaptations in Bacteria, its importance and prevalence in eukaryotes remains controversial. We show that HGT played a major role in the origin and evolution of the eukaryotic nitrate assimilation pathway, with several bacteria-to-eukaryote and eukaryote-to-eukaryote transfers promoting the acquisition of this ecologically-relevant pathway to autotrophs and to distinct groups of osmotrophs. Moreover, we also show that gene fusion was important in this evolutionary history, underlying the origin of the canonical eukaryotic nitrate reductase, but also of a non-canonical nitrate reductase that we describe in Ichthyosporea, a poorly-characterized eukaryotic group that includes many parasitic species. In conclusion, our results highlight the importance of reticulate evolution in eukaryotes, by showing the contribution of HGT and gene fusion in the evolutionary history of the nitrate assimilation pathway.
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Affiliation(s)
- Eduard Ocaña-Pallarès
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Catalonia, Spain
- * E-mail: (EOP); (IRT)
| | - Sebastián R. Najle
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Catalonia, Spain
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda s/n, Rosario S2000FHQ, Argentina
| | - Claudio Scazzocchio
- Department of Microbiology, Imperial College, London, United Kingdom
- Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Iñaki Ruiz-Trillo
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Catalonia, Spain
- Departament de Genètica, Microbiologia i Estadística, Facultat de Biologia, Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona (UB), Barcelona, Catalonia, Spain
- ICREA, Barcelona, Catalonia, Spain
- * E-mail: (EOP); (IRT)
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