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Azadnia A, Mikryukov V, Anslan S, Hagh-Doust N, Rahimlou S, Tamm H, Tedersoo L. Structure of plant-associated microeukaryotes in roots and leaves of aquatic and terrestrial plants revealed by blocking peptide-nucleic acid (PNA) amplification. FEMS Microbiol Ecol 2023; 99:fiad152. [PMID: 38012113 DOI: 10.1093/femsec/fiad152] [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: 07/30/2023] [Revised: 11/05/2023] [Accepted: 11/16/2023] [Indexed: 11/29/2023] Open
Abstract
Studies of plant-microbe interactions, including mutualistic, antagonistic, parasitic, or commensal microbes, have greatly benefited our understanding of ecosystem functioning. New molecular identification tools have increasingly revealed the association patterns between microorganisms and plants. Here, we integrated long-read PacBio single-molecule sequencing technology with a blocking protein-nucleic acid (PNA) approach to minimise plant amplicons in a survey of plant-eukaryotic microbe relationships in roots and leaves of different aquatic and terrestrial plants to determine patterns of organ, host, and habitat preferences. The PNA approach reduced the samples' relative amounts of plant reads and did not distort the fungal and other microeukaryotic composition. Our analyses revealed that the eukaryotic microbiomes associated with leaves and roots of aquatic plants exhibit a much larger proportion of non-fungal microorganisms than terrestrial plants, and leaf and root microbiomes are similar. Terrestrial plants had much stronger differentiation of leaf and root microbiomes and stronger partner specificity than aquatic plants.
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Affiliation(s)
- Avid Azadnia
- Department of Botany, Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, Tartu 50409, Estonia
| | - Vladimir Mikryukov
- Department of Botany, Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, Tartu 50409, Estonia
| | - Sten Anslan
- Department of Botany, Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, Tartu 50409, Estonia
- Mycology and Microbiology Center, University of Tartu, Tartu 50409, Estonia
| | - Niloufar Hagh-Doust
- Department of Botany, Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, Tartu 50409, Estonia
- Mycology and Microbiology Center, University of Tartu, Tartu 50409, Estonia
| | - Saleh Rahimlou
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Heidi Tamm
- Department of Botany, Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, Tartu 50409, Estonia
| | - Leho Tedersoo
- Department of Botany, Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, Tartu 50409, Estonia
- Mycology and Microbiology Center, University of Tartu, Tartu 50409, Estonia
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2
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Tan L, Zeng WA, Xiao Y, Li P, Gu S, Wu S, Zhai Z, Feng K, Deng Y, Hu Q. Fungi-Bacteria Associations in Wilt Diseased Rhizosphere and Endosphere by Interdomain Ecological Network Analysis. Front Microbiol 2021; 12:722626. [PMID: 34552573 PMCID: PMC8450586 DOI: 10.3389/fmicb.2021.722626] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 08/11/2021] [Indexed: 11/13/2022] Open
Abstract
In the plant rhizosphere and endosphere, some fungal and bacterial species regularly co-exist, however, our knowledge about their co-existence patterns is quite limited, especially during invasion by bacterial wilt pathogens. In this study, the fungal communities from soil to endophytic compartments were surveyed during an outbreak of tobacco wilt disease caused by Ralstonia solanacearum. It was found that the stem endophytic fungal community was significantly altered by pathogen invasion in terms of community diversity, structure, and composition. The associations among fungal species in the rhizosphere and endosphere infected by R. solanacearum showed more complex network structures than those of healthy plants. By integrating the bacterial dataset, associations between fungi and bacteria were inferred by Inter-Domain Ecological Network (IDEN) approach. It also revealed that infected samples, including both the rhizosphere and endosphere, had more complex interdomain networks than the corresponding healthy samples. Additionally, the bacterial wilt pathogenic Ralstonia members were identified as the keystone genus within the IDENs of both root and stem endophytic compartments. Ralstonia members was negatively correlated with the fungal genera Phoma, Gibberella, and Alternaria in infected roots, as well as Phoma, Gibberella, and Diaporthe in infected stems. This suggested that those endophytic fungi may play an important role in resisting the invasion of R. solanacearum.
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Affiliation(s)
- Lin Tan
- Hunan Agricultural University, Changsha, China
| | - Wei-Ai Zeng
- Changsha Tobacco Company of Hunan Province, Changsha, China
| | - Yansong Xiao
- Chenzhou Tobacco Company of Hunan Province, Chenzhou, China
| | - Pengfei Li
- Wenshan Tobacco Company of Yunnan Province, Wenshan, China
| | - Songsong Gu
- CAS Key Laboratory for Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,Institute for Marine Science and Technology, Shandong University, Qingdao, China
| | - Shaolong Wu
- Tobacco Company of Hunan Province, Changsha, China
| | | | - Kai Feng
- CAS Key Laboratory for Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Ye Deng
- CAS Key Laboratory for Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,Institute for Marine Science and Technology, Shandong University, Qingdao, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Qiulong Hu
- Hunan Agricultural University, Changsha, China
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3
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Janssen K, Low SL, Wang Y, Mu Q, Bierbaum G, Gee CT. Elucidating biofilm diversity on water lily leaves through 16S rRNA amplicon analysis: Comparison of four DNA extraction kits. APPLICATIONS IN PLANT SCIENCES 2021; 9:e11444. [PMID: 34504737 PMCID: PMC8419396 DOI: 10.1002/aps3.11444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
PREMISE Within a broader study on leaf fossilization in freshwater environments, a long-term study on the development and microbiome composition of biofilms on the foliage of aquatic plants has been initiated to understand how microbes and biofilms contribute to leaf decay and preservation. Here, water lily leaves are employed as a study model to investigate the relationship between bacterial microbiomes, biodegradation, and fossilization. We compare four DNA extraction kits to reduce biases in interpretation and to identify the most suitable kit for the extraction of DNA from bacteria associated with biofilms on decaying water lily leaves for 16S rRNA amplicon analysis. METHODS We extracted surface-associated DNA from Nymphaea leaves in early stages of decay at two water depth levels using four commercially available kits to identify the most suitable protocol for bacterial extraction, applying a mock microbial community standard to enable a reliable comparison of the kits. RESULTS Kit 4, the FastDNA Spin Kit for Soil, resulted in high DNA concentrations with better quality and yielded the most accurate depiction of the mock community. Comparison of the leaves at two water depths showed no significant differences in community composition. DISCUSSION The success of Kit 4 may be attributed to its use of bead beating with a homogenizer, which was more efficient in the lysis of Gram-positive bacteria than the manual vortexing protocols used by the other kits. Our results show that microbial composition on leaves during early decay remains comparable and may change only in later stages of decomposition.
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Affiliation(s)
- Kathrin Janssen
- Institute of Medical Microbiology, Immunology and Parasitology, University Clinic of Bonn, Rheinische Friedrich‐Wilhelms‐University Bonn, Venusberg‐Campus 153127BonnGermany
| | - Shook Ling Low
- Institute of Geosciences, Division of PaleontologyRheinische Friedrich‐Wilhelms‐University Bonn, Nussallee 853115BonnGermany
| | - Yan Wang
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of SciencesMengla666303China
| | - Qi‐Yong Mu
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of SciencesMengla666303China
| | - Gabriele Bierbaum
- Institute of Medical Microbiology, Immunology and Parasitology, University Clinic of Bonn, Rheinische Friedrich‐Wilhelms‐University Bonn, Venusberg‐Campus 153127BonnGermany
| | - Carole T. Gee
- Institute of Geosciences, Division of PaleontologyRheinische Friedrich‐Wilhelms‐University Bonn, Nussallee 853115BonnGermany
- Huntington Botanical Gardens1151 Oxford Road, San MarinoCalifornia91108USA
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4
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Lundberg DS, Pramoj Na Ayutthaya P, Strauß A, Shirsekar G, Lo WS, Lahaye T, Weigel D. Host-associated microbe PCR (hamPCR) enables convenient measurement of both microbial load and community composition. eLife 2021; 10:e66186. [PMID: 34292157 PMCID: PMC8387020 DOI: 10.7554/elife.66186] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 07/19/2021] [Indexed: 12/26/2022] Open
Abstract
The ratio of microbial population size relative to the amount of host tissue, or 'microbial load', is a fundamental metric of colonization and infection, but it cannot be directly deduced from microbial amplicon data such as 16S rRNA gene counts. Because existing methods to determine load, such as serial dilution plating, quantitative PCR, and whole metagenome sequencing add substantial cost and/or experimental burden, they are only rarely paired with amplicon sequencing. We introduce host-associated microbe PCR (hamPCR), a robust strategy to both quantify microbial load and describe interkingdom microbial community composition in a single amplicon library. We demonstrate its accuracy across multiple study systems, including nematodes and major crops, and further present a cost-saving technique to reduce host overrepresentation in the library prior to sequencing. Because hamPCR provides an accessible experimental solution to the well-known limitations and statistical challenges of compositional data, it has far-reaching potential in culture-independent microbiology.
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Affiliation(s)
- Derek S Lundberg
- Department of Molecular Biology, Max Planck Institute for Developmental BiologyTübingenGermany
| | | | - Annett Strauß
- Department of Evolutionary Biology, Max Planck Institute for Developmental BiologyTübingenGermany
| | - Gautam Shirsekar
- Department of Molecular Biology, Max Planck Institute for Developmental BiologyTübingenGermany
| | - Wen-Sui Lo
- ZMBP-General Genetics, University of TübingenTübingenGermany
| | - Thomas Lahaye
- ZMBP-General Genetics, University of TübingenTübingenGermany
| | - Detlef Weigel
- Department of Molecular Biology, Max Planck Institute for Developmental BiologyTübingenGermany
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5
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Characterizing Microbiomes via Sequencing of Marker Loci: Techniques To Improve Throughput, Account for Cross-Contamination, and Reduce Cost. mSystems 2021; 6:e0029421. [PMID: 34254828 PMCID: PMC8409480 DOI: 10.1128/msystems.00294-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
New approaches to characterizing microbiomes via high-throughput sequencing provide impressive gains in efficiency and cost reduction compared to approaches that were standard just a few years ago. However, the speed of method development has been such that staying abreast of the latest technological advances is challenging. Moreover, shifting laboratory protocols to include new methods can be expensive and time consuming. To facilitate adoption of new techniques, we provide a guide and review of recent advances that are relevant for single-locus sequence-based study of microbiomes—from extraction to library preparation—including a primer regarding the use of liquid-handling automation in small-scale academic settings. Additionally, we describe several amendments to published techniques to improve throughput, track contamination, and reduce cost. Notably, we suggest adding synthetic DNA molecules to each sample during nucleic acid extraction, thus providing a method of documenting incidences of cross-contamination. We also describe a dual-indexing scheme for Illumina sequencers that allows multiplexing of many thousands of samples with minimal PhiX input. Collectively, the techniques that we describe demonstrate that laboratory technology need not impose strict limitations on the scale of molecular microbial ecology studies. IMPORTANCE New methods to characterize microbiomes reduce technology-imposed limitations to study design, but many new approaches have not been widely adopted. Here, we present techniques to increase throughput and reduce contamination alongside a thorough review of current best practices.
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6
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Haro C, Anguita-Maeso M, Metsis M, Navas-Cortés JA, Landa BB. Evaluation of Established Methods for DNA Extraction and Primer Pairs Targeting 16S rRNA Gene for Bacterial Microbiota Profiling of Olive Xylem Sap. FRONTIERS IN PLANT SCIENCE 2021; 12:640829. [PMID: 33777075 PMCID: PMC7994608 DOI: 10.3389/fpls.2021.640829] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 02/08/2021] [Indexed: 06/12/2023]
Abstract
Next-generation sequencing has revolutionized our ability to investigate the microbiota composition of diverse and complex environments. However, a number of factors can affect the accuracy of microbial community assessment, such as the DNA extraction method, the hypervariable region of 16S rRNA gene targeted, or the PCR primers used for amplification. The aim of this study was to assess the influence of commercially available DNA extraction kits and different primer pairs to provide a non-biased vision of the composition of bacterial communities present in olive xylem sap. For that purpose, branches from "Picual" and "Arbequina" olive cultivars were used for xylem sap extraction using a Scholander chamber device. The DNA extraction protocol significantly affected xylem sap bacterial community assessment. That resulted in significant differences in alpha (Richness) and beta diversity (UniFrac distances) metrics among DNA extraction protocols, with the 12 DNA extraction kits evaluated being clustered in four groups behaving differently. Although the core number of taxa detected by all DNA extraction kits included four phyla, seven classes, 12 orders, 16 or 21 families, and 12 or 14 genera when using the Greengenes or Silva database for taxonomic assignment, respectively, some taxa, particularly those identified at low frequency, were detected by some DNA extraction kits only. The most accurate depiction of a bacterial mock community artificially inoculated on sap samples was generated when using the PowerPlant DNA extraction kit, the combination of 799F/1193R primers amplifying the hypervariable V5-V7 region, and the Silva 132 database for taxonomic assignment. The DESeq2 analysis displayed significant differences among genera abundance between the different PCR primer pairs tested. Thus, Enterobacter, Granulicatella, Prevotella, and Brevibacterium presented a significant higher abundance in all PCR protocols when compared with primer pair 799F/1193R, while the opposite was true for Pseudomonas and Pectobacterium. The methodological approach followed in this study can be useful to optimize plant-associated microbiome analysis, especially when exploring new plant niches. Some of the DNA extraction kits and PCR primers selected in this study will contribute to better characterize bacterial communities inhabiting the xylem sap of olives or other woody crop species.
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Affiliation(s)
- Carmen Haro
- Institute for Sustainable Agriculture, Spanish National Research Council (CSIC), Córdoba, Spain
| | - Manuel Anguita-Maeso
- Institute for Sustainable Agriculture, Spanish National Research Council (CSIC), Córdoba, Spain
| | | | - Juan A. Navas-Cortés
- Institute for Sustainable Agriculture, Spanish National Research Council (CSIC), Córdoba, Spain
| | - Blanca B. Landa
- Institute for Sustainable Agriculture, Spanish National Research Council (CSIC), Córdoba, Spain
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7
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Francioli D, Lentendu G, Lewin S, Kolb S. DNA Metabarcoding for the Characterization of Terrestrial Microbiota-Pitfalls and Solutions. Microorganisms 2021; 9:361. [PMID: 33673098 PMCID: PMC7918050 DOI: 10.3390/microorganisms9020361] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 02/04/2021] [Accepted: 02/09/2021] [Indexed: 02/06/2023] Open
Abstract
Soil-borne microbes are major ecological players in terrestrial environments since they cycle organic matter, channel nutrients across trophic levels and influence plant growth and health. Therefore, the identification, taxonomic characterization and determination of the ecological role of members of soil microbial communities have become major topics of interest. The development and continuous improvement of high-throughput sequencing platforms have further stimulated the study of complex microbiota in soils and plants. The most frequently used approach to study microbiota composition, diversity and dynamics is polymerase chain reaction (PCR), amplifying specific taxonomically informative gene markers with the subsequent sequencing of the amplicons. This methodological approach is called DNA metabarcoding. Over the last decade, DNA metabarcoding has rapidly emerged as a powerful and cost-effective method for the description of microbiota in environmental samples. However, this approach involves several processing steps, each of which might introduce significant biases that can considerably compromise the reliability of the metabarcoding output. The aim of this review is to provide state-of-the-art background knowledge needed to make appropriate decisions at each step of a DNA metabarcoding workflow, highlighting crucial steps that, if considered, ensures an accurate and standardized characterization of microbiota in environmental studies.
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Affiliation(s)
- Davide Francioli
- Microbial Biogeochemistry, Research Area Landscape Functioning, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Müncheberg, Germany; (S.L.); (S.K.)
| | - Guillaume Lentendu
- Laboratory of Soil Biodiversity, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland;
| | - Simon Lewin
- Microbial Biogeochemistry, Research Area Landscape Functioning, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Müncheberg, Germany; (S.L.); (S.K.)
| | - Steffen Kolb
- Microbial Biogeochemistry, Research Area Landscape Functioning, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Müncheberg, Germany; (S.L.); (S.K.)
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8
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Víquez‐R L, Fleischer R, Wilhelm K, Tschapka M, Sommer S. Jumping the green wall: The use of PNA-DNA clamps to enhance microbiome sampling depth in wildlife microbiome research. Ecol Evol 2020; 10:11779-11786. [PMID: 33145000 PMCID: PMC7593133 DOI: 10.1002/ece3.6814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/12/2020] [Accepted: 08/24/2020] [Indexed: 01/04/2023] Open
Abstract
As microbiome research moves away from model organisms to wildlife, new challenges for microbiome high-throughput sequencing arise caused by the variety of wildlife diets. High levels of contamination are commonly observed emanating from the host (mitochondria) or diet (chloroplast). Such high contamination levels affect the overall sequencing depth of wildlife samples thus decreasing statistical power and leading to poor performance in downstream analysis. We developed an amplification protocol utilizing PNA-DNA clamps to maximize the use of resources and to increase the sampling depth of true microbiome sequences in samples with high levels of plastid contamination. We chose two study organisms, a bat (Leptonyteris yerbabuenae) and a bird (Mimus parvulus), both relying on heavy plant-based diets that sometimes lead to traces of plant-based fecal material producing high contamination signals from chloroplasts and mitochondria. On average, our protocol yielded a 13-fold increase in bacterial sequence amplification compared with the standard protocol (Earth Microbiome Protocol) used in wildlife research. For both focal species, we were able to increase significantly the percentage of sequences available for downstream analyses after the filtering of plastids and mitochondria. Our study presents the first results obtained by using PNA-DNA clamps to block the PCR amplification of chloroplast and mitochondrial DNA from the diet in the gut microbiome of wildlife. The method involves a cost-effective molecular technique instead of the filtering out of unwanted sequencing reads. As 33% and 26% of birds and bats, respectively, have a plant-based diet, the tool that we present here will optimize the sequencing and analysis of wild microbiomes.
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Affiliation(s)
- Luis Víquez‐R
- Institute for Evolutionary Ecology and Conservation GenomicsUniversity of UlmUlmGermany
| | - Ramona Fleischer
- Institute for Evolutionary Ecology and Conservation GenomicsUniversity of UlmUlmGermany
| | - Kerstin Wilhelm
- Institute for Evolutionary Ecology and Conservation GenomicsUniversity of UlmUlmGermany
| | - Marco Tschapka
- Institute for Evolutionary Ecology and Conservation GenomicsUniversity of UlmUlmGermany
- Smithsonian Tropical Research InstituteBalboaPanama
| | - Simone Sommer
- Institute for Evolutionary Ecology and Conservation GenomicsUniversity of UlmUlmGermany
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9
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Alonso P, Blondin L, Gladieux P, Mahé F, Sanguin H, Ferdinand R, Filloux D, Desmarais E, Cerqueira F, Jin B, Huang H, He X, Morel JB, Martin DP, Roumagnac P, Vernière C. Heterogeneity of the rice microbial community of the Chinese centuries-old Honghe Hani rice terraces system. Environ Microbiol 2020; 22:3429-3445. [PMID: 32510843 PMCID: PMC7497281 DOI: 10.1111/1462-2920.15114] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 05/29/2020] [Accepted: 06/02/2020] [Indexed: 11/30/2022]
Abstract
The Honghe Hani rice terraces system (HHRTS) is a traditional rice cultivation system where Hani people cultivate remarkably diverse rice varieties. Recent introductions of modern rice varieties to the HHRTS have significantly increased the severity of rice diseases within the terraces. Here, we determine the impacts of these recent introductions on the composition of the rice-associated microbial communities. We confirm that the HHRTS contains a range of both traditional HHRTS landraces and introduced modern rice varieties and find differences between the microbial communities of these two groups. However, this introduction of modern rice varieties has not strongly impacted the overall diversity of the HHRTS rice microbial community. Furthermore, we find that the rice varieties (i.e. groups of closely related genotypes) have significantly structured the rice microbial community composition (accounting for 15%-22% of the variance) and that the core microbial community of HHRTS rice plants represents less than 3.3% of all the microbial taxa identified. Collectively, our study suggests a highly diverse HHRTS rice holobiont (host with its associated microbes) where the diversity of rice hosts mirrors the diversity of their microbial communities. Further studies will be needed to better determine how such changes might impact the sustainability of the HHRTS.
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Affiliation(s)
- Pascal Alonso
- CIRAD, BGPI, Montpellier, France.,BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France
| | - Laurence Blondin
- CIRAD, BGPI, Montpellier, France.,BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France
| | - Pierre Gladieux
- BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France.,INRA, BGPI, Montpellier, France
| | - Frédéric Mahé
- CIRAD, BGPI, Montpellier, France.,BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France
| | - Hervé Sanguin
- CIRAD, BGPI, Montpellier, France.,BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France
| | - Romain Ferdinand
- CIRAD, BGPI, Montpellier, France.,BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France
| | - Denis Filloux
- CIRAD, BGPI, Montpellier, France.,BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France
| | - Eric Desmarais
- ISEM, CNRS, University of Montpellier, IRD, EPHE, Montpellier, France
| | | | - Baihui Jin
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, 650201, China
| | - Huichuan Huang
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, 650201, China
| | - Xiahong He
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, 650201, China.,Southwest Forestry University, Kunming, China
| | - Jean-Benoit Morel
- BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France.,INRA, BGPI, Montpellier, France
| | - Darren P Martin
- Computational Biology Group, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, 4579, South Africa
| | - Philippe Roumagnac
- CIRAD, BGPI, Montpellier, France.,BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France
| | - Christian Vernière
- CIRAD, BGPI, Montpellier, France.,BGPI, INRAE, CIRAD, Institut Agro, Univ Montpellier, Montpellier, France
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10
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Song L, Xie K. Engineering CRISPR/Cas9 to mitigate abundant host contamination for 16S rRNA gene-based amplicon sequencing. MICROBIOME 2020; 8:80. [PMID: 32493511 PMCID: PMC7268715 DOI: 10.1186/s40168-020-00859-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 05/08/2020] [Indexed: 05/20/2023]
Abstract
BACKGROUND High-throughput sequencing of bacterial 16S rRNA gene (16S-seq) is a useful and common method for studying bacterial community structures. However, contamination of the 16S rRNA genes from the mitochondrion and plastid hinders the sensitive bacterial 16S-seq in plant microbiota profiling, especially for some plant species such as rice. To date, efficiently mitigating such host contamination without a bias is challenging in 16S rRNA gene-based amplicon sequencing. RESULTS We developed Cas-16S-seq method to reduce abundant host contamination for plant microbiota profiling. This method utilizes the Cas9 nuclease and specific guide RNA (gRNA) to cut 16S rRNA targets during library construction, thereby removing host contamination in 16S-seq. We used rice as an example to validate the feasibility and effectiveness of Cas-16S-seq. We established a bioinformatics pipeline to design gRNAs that specifically target rice 16S rRNA genes without bacterial 16S rRNA off-targets. We compared the effectiveness of Cas-16S-seq with that of the commonly used 16S-seq method for artificially mixed 16S rRNA gene communities, paddy soil, rice root, and phyllosphere samples. The results showed that Cas-16S-seq substantially reduces the fraction of rice 16S rRNA gene sequences from 63.2 to 2.9% in root samples and from 99.4 to 11.6% in phyllosphere samples on average. Consequently, Cas-16S-seq detected more bacterial species than the 16S-seq in plant samples. Importantly, when analyzing soil samples, Cas-16S-seq and 16S-seq showed almost identical bacterial communities, suggesting that Cas-16S-seq with host-specific gRNAs that we designed has no off-target in rice microbiota profiling. CONCLUSION Our Cas-16S-seq can efficiently remove abundant host contamination without a bias for 16S rRNA gene-based amplicon sequencing, thereby enabling deeper bacterial community profiling with a low cost and high flexibility. Thus, we anticipate that this method would be a useful tool for plant microbiomics. Video Abstract.
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Affiliation(s)
- Luyang Song
- National Key Laboratory of Crop Genetic Improvement and Hubei Key Laboratory of Plant Pathology, Huazhong Agricultural University, No.1 Shizishan Street, Hongshan District, Wuhan, 430070 China
| | - Kabin Xie
- National Key Laboratory of Crop Genetic Improvement and Hubei Key Laboratory of Plant Pathology, Huazhong Agricultural University, No.1 Shizishan Street, Hongshan District, Wuhan, 430070 China
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11
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Zhu D, Ding J, Yin Y, Ke X, O'Connor P, Zhu YG. Effects of Earthworms on the Microbiomes and Antibiotic Resistomes of Detritus Fauna and Phyllospheres. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:6000-6008. [PMID: 32352284 DOI: 10.1021/acs.est.9b04500] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Our understanding of the influences of animals on microbial communities and antibiotic resistance genes (ARGs) throughout the food web is limited, particularly in the soil ecosystem. We performed a microcosm experiment using the combination of 16S rRNA gene high-throughput sequencing and high-throughput qPCR to study the effects of earthworms on the microbiomes and resistomes of the phyllospheres and soil detritus fauna. A full factorial design was employed in this study, including two earthworm treatments (control and earthworm addition) and two soil treatments (control and manure amendment). Earthworms changed the bacterial composition of the soil detritus fauna and the phyllosphere by modifying the shared habitat. Earthworms also reduced the number and abundance of ARGs in the soil fauna and phyllosphere microbiomes by changing their microbial communities, suggesting that earthworms may be able to provide a sustainable and natural solution to address the ARG crisis in the soil ecosystem. This study provides a new understanding on the effects of soil animals on microbial communities, driving shifts in the resistome of other animals and the phyllosphere, by altering the shared soil habitat.
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Affiliation(s)
- Dong Zhu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Jing Ding
- School of Environmental and Material Engineering, Yantai University, 30 Qingquan Road, Yantai 264005, China
| | - Yue Yin
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Xin Ke
- Institute of Plant Physiology and Ecology, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Patrick O'Connor
- Centre for Global Food and Resources, University of Adelaide, Adelaide 5005, Australia
| | - Yong-Guan Zhu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, China
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12
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Benucci GMN, Burnard D, Shepherd LD, Bonito G, Munkacsi AB. Evidence for Co-evolutionary History of Early Diverging Lycopodiaceae Plants With Fungi. Front Microbiol 2020; 10:2944. [PMID: 32010072 PMCID: PMC6974469 DOI: 10.3389/fmicb.2019.02944] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 12/06/2019] [Indexed: 11/13/2022] Open
Abstract
Lycopods are tracheophytes in the Kingdom Plantae and represent one of the oldest lineages of living vascular plants. Symbiotic interactions between these plants with fungi and bacteria, including fine root endophytes in Endogonales, have been hypothesized to have helped early diverging plant lineages colonize land. However, attempts to study the lycopod rhizobiome in its natural environment are still limited. In this study, we used Illumina amplicon sequencing to characterize fungal and bacterial diversity in nine Lycopodiaceae (club moss) species collected in New Zealand. This was done with generic fungal ITS rDNA primers, as well as Endogonales- and arbuscular mycorrhizal fungi (AMF)-selective primer sets targeting the 18S rDNA, and generic bacterial primers targeting the V4 region of the 16S rDNA. We found that the Lycopodiaceae rhizobiome was comprised of an unexpected high frequency of Basidiomycota and Ascomycota coincident with a low abundance of Endogonales and Glomerales. The distribution and abundance of Endogonales varied with host lycopod, and included a novel taxon as well as a single operational taxonomic unit (OTU) that was detected across all plant species. The Lycopodiaceae species with the greatest number and also most unique OTUs was Phlegmariurus varius, while the plant species that shared the most fungal OTUs were Lycopodiella fastigiatum and Lycopodium scariosum. The bacterial OTU distribution was generally not consistent with fungal OTU distribution. For example, community dissimilarity analysis revealed strong concordance between the evolutionary histories of host plants with the fungal community but not with the bacterial community, indicating that Lycopodiaceae have evolved specific relationships with their fungal symbionts. Notably, nearly 16% of the ITS rDNA fungal diversity detected in the Lycopodiaceae rhizobiome remained poorly classified, indicating there is much plant-associated fungal diversity left to describe in New Zealand.
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Affiliation(s)
- Gian Maria Niccolò Benucci
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States
| | - Delaney Burnard
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Lara D Shepherd
- Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand
| | - Gregory Bonito
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States
| | - Andrew B Munkacsi
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
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Pfister CA, Altabet MA, Weigel BL. Kelp beds and their local effects on seawater chemistry, productivity, and microbial communities. Ecology 2019; 100:e02798. [PMID: 31233610 DOI: 10.1002/ecy.2798] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 04/11/2019] [Accepted: 05/28/2019] [Indexed: 11/10/2022]
Abstract
Kelp forests are known as key habitats for species diversity and macroalgal productivity; however, we know little about how these biogenic habitats interact with seawater chemistry and phototroph productivity in the water column. We examined kelp forest functions at three locales along the Olympic Peninsula of Washington state by quantifying carbonate chemistry, nutrient concentrations, phytoplankton productivity, and seawater microbial communities inside and outside of kelp beds dominated by the canopy kelp species Nereocystis luetkeana and Macrocystis pyrifera. Kelp beds locally increased the pH, oxygen, and aragonite saturation state of the seawater, but lowered seawater inorganic carbon content and total alkalinity. Although kelp beds depleted nitrate and phosphorus concentrations, ammonium and dissolved organic carbon (DOC) concentrations were enhanced. Kelp beds also decreased chlorophyll concentrations and carbon fixed by phytoplankton, although kelp carbon fixation more than compensated for any difference in phytoplankton production. Kelp beds entrained distinct microbial communities, with higher taxonomic and phylogenetic diversity compared to seawater outside of the kelp bed. Kelp forests thus had significant effects on seawater chemistry, productivity and the microbial assemblages in their proximity. Thereby, the diversity of pathways for carbon and nitrogen cycling was also enhanced. Overall, these observations suggest that the contribution of kelp forests to nearshore carbon and nitrogen cycling is greater than previously documented.
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Affiliation(s)
- Catherine A Pfister
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, 60637, USA
- Committee on Evolutionary Biology, University of Chicago, Chicago, Illinois, 60637, USA
| | - Mark A Altabet
- School of Marine Sciences, University of Massachusetts, Dartmouth, Massachusetts, 02744, USA
| | - Brooke L Weigel
- Committee on Evolutionary Biology, University of Chicago, Chicago, Illinois, 60637, USA
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Feng K, Zhang Y, He Z, Ning D, Deng Y. Interdomain ecological networks between plants and microbes. Mol Ecol Resour 2019; 19:1565-1577. [PMID: 31479575 DOI: 10.1111/1755-0998.13081] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 07/26/2019] [Accepted: 08/07/2019] [Indexed: 12/11/2022]
Abstract
While macroscopic interkingdom relationships have been intensively investigated in various ecosystems, the above-belowground ecology in natural ecosystems has been poorly understood, especially for the plant-microbe associations at a regional scale. In this study, we proposed a workflow to construct interdomain ecological networks (IDEN) between multiple plants and various microbes (bacteria and archaea in this study). Across 30 latitudinal forests in China, the regional IDEN showed particular topological features, including high connectance, nested structure, asymmetric specialization and modularity. Also, plant species exhibited strong preference to specific microbial groups, and the observed network was significantly different from randomly rewired networks. Network module analysis indicated that a majority of microbes associated with plants within modules rather than across modules, suggesting specialized associations between plants and microorganisms. Consistent plant-microbe associations were captured via IDENs constructed within individual forest locations, which reinforced the validity of IDEN analysis. In addition, the plant-forest link distribution showed the geographical distribution of plants had higher endemicity than that of microorganisms. With cautious experimental design and data processing, this study shows interdomain species associations between plants and microbes in natural forest ecosystems and provides new insights into our understanding of meta-communities across different domain species.
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Affiliation(s)
- Kai Feng
- CAS Key Laboratory for Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Yuguang Zhang
- Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Key Laboratory of Forest Ecology and Environment of State Forestry Administration, Beijing, China
| | - Zhili He
- Environmental Microbiomics Research Center, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, China
| | - Daliang Ning
- Institute for Environmental Genomics, Department of Microbiology and Plant Biology, School of Civil Engineering and Environmental Sciences, University of Oklahoma, Norman, OK, USA
| | - Ye Deng
- CAS Key Laboratory for Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
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15
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Scolari F, Casiraghi M, Bonizzoni M. Aedes spp. and Their Microbiota: A Review. Front Microbiol 2019; 10:2036. [PMID: 31551973 PMCID: PMC6738348 DOI: 10.3389/fmicb.2019.02036] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 08/19/2019] [Indexed: 12/21/2022] Open
Abstract
Aedes spp. are a major public health concern due to their ability to be efficient vectors of dengue, Chikungunya, Zika, and other arboviruses. With limited vaccines available and no effective therapeutic treatments against arboviruses, the control of Aedes spp. populations is currently the only strategy to prevent disease transmission. Host-associated microbes (i.e., microbiota) recently emerged as a promising field to be explored for novel environmentally friendly vector control strategies. In particular, gut microbiota is revealing its impact on multiple aspects of Aedes spp. biology, including vector competence, thus being a promising target for manipulation. Here we describe the technological advances, which are currently expanding our understanding of microbiota composition, abundance, variability, and function in the two main arboviral vectors, the mosquitoes Aedes aegypti and Aedes albopictus. Aedes spp. microbiota is described in light of its tight connections with the environment, with which mosquitoes interact during their various developmental stages. Unraveling the dynamic interactions among the ecology of the habitat, the mosquito and the microbiota have the potential to uncover novel physiological interdependencies and provide a novel perspective for mosquito control.
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Affiliation(s)
- Francesca Scolari
- Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
| | - Maurizio Casiraghi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
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The Origin, Succession, and Predicted Metabolism of Bacterial Communities Associated with Leaf Decomposition. mBio 2019; 10:mBio.01703-19. [PMID: 31481384 PMCID: PMC6722416 DOI: 10.1128/mbio.01703-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Community ecologists have traditionally treated individuals within a species as uniform, with individual-level biodiversity rarely considered as a regulator of community and ecosystem function. In our study system, we have documented clear evidence of within-species variation causing local ecosystem adaptation to fluxes across ecosystem boundaries. In this striking pattern of a “home-field advantage,” leaves from individual trees tend to decompose most rapidly when immediately adjacent to their parent tree. Here, we merge community ecology experiments with microbiome approaches to describe how bacterial communities adjust to within-species variation in leaves over spatial scales of less than a kilometer. The results show that bacterial community compositional changes facilitate rapid ecosystem responses to environmental change, effectively maintaining high rates of carbon and nutrient cycling through ecosystems. Intraspecific variation in plant nutrient and defensive traits can regulate ecosystem-level processes, such as decomposition and transformation of plant carbon and nutrients. Understanding the regulatory mechanisms of ecosystem functions at local scales may facilitate predictions of the resistance and resilience of these functions to change. We evaluated how riverine bacterial community assembly and predicted gene content corresponded to decomposition rates of green leaf inputs from red alder trees into rivers of Washington State, USA. Previously, we documented accelerated decomposition rates for leaves originating from trees growing adjacent to the site of decomposition versus more distant locales, suggesting that microbes have a “home-field advantage” in decomposing local leaves. Here, we identified repeatable stages of bacterial succession, each defined by dominant taxa with predicted gene content associated with metabolic pathways relevant to the leaf characteristics and course of decomposition. “Home” leaves contained bacterial communities with distinct functional capacities to degrade aromatic compounds. Given known spatial variation of alder aromatics, this finding helps explain locally accelerated decomposition. Bacterial decomposer communities adjust to intraspecific variation in leaves at spatial scales of less than a kilometer, providing a mechanism for rapid response to changes in resources such as range shifts among plant genotypes. Such rapid responses among bacterial communities in turn may maintain high rates of carbon and nutrient cycling through aquatic ecosystems.
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Gołębiewski M, Tretyn A. Generating amplicon reads for microbial community assessment with next‐generation sequencing. J Appl Microbiol 2019; 128:330-354. [DOI: 10.1111/jam.14380] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 07/03/2019] [Accepted: 07/05/2019] [Indexed: 12/12/2022]
Affiliation(s)
- M. Gołębiewski
- Plant Physiology and Biotechnology Nicolaus Copernicus University Toruń Poland
- Centre for Modern Interdisciplinary Technologies Nicolaus Copernicus University Toruń Poland
| | - A. Tretyn
- Plant Physiology and Biotechnology Nicolaus Copernicus University Toruń Poland
- Centre for Modern Interdisciplinary Technologies Nicolaus Copernicus University Toruń Poland
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18
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Weigel BL, Pfister CA. Successional Dynamics and Seascape-Level Patterns of Microbial Communities on the Canopy-Forming Kelps Nereocystis luetkeana and Macrocystis pyrifera. Front Microbiol 2019; 10:346. [PMID: 30863387 PMCID: PMC6399156 DOI: 10.3389/fmicb.2019.00346] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 02/08/2019] [Indexed: 11/23/2022] Open
Abstract
Canopy-forming kelps create underwater forests that are among the most productive marine ecosystems. On the Pacific coast of North America, two canopy-forming kelps with contrasting life histories co-occur; Macrocystis pyrifera, a perennial species, and Nereocystis luetkeana, an annual species. Kelp blade-associated microbes were sampled from 12 locations across a spatial gradient in Washington, United States, from the outer Pacific Coast to Puget Sound. Microbial communities were characterized using next-generation Illumina sequencing of 16S rRNA genes. At higher taxonomic levels (bacterial phylum and class), canopy-forming kelps hosted remarkably similar microbial communities, but at the amplicon sequence variant level, microbial communities on M. pyrifera and N. luetkeana were host-specific and distinct from free-living bacteria in the surrounding seawater. Microbial communities associated with blades of each kelp species displayed significant geographic variation. The microbiome of N. luetkeana changed along the spatial gradient and was significantly correlated to salinity, with outer Pacific coast sites enriched in Bacteroidetes (family Saprospiraceae) and Gammaproteobacteria (Granulosicoccus sp.), and southern Puget Sound sites enriched in Alphaproteobacteria (family Hyphomonadaceae). We also examined microbial community development and succession on meristematic and apical N. luetkeana blade tissues throughout the summer growing season on Tatoosh Island, WA. Across all dates, microbial communities were less diverse on younger, meristematic blade tissue compared to the older, apical tissues. In addition, phylogenetic relatedness among microbial taxa increased from meristematic to apical blade tissues, suggesting that the addition of microbial taxa to the community was a non-random process that selected for certain phylogenetic groups of microbes. Microbial communities on older, apical tissues displayed significant temporal variation throughout the summer and microbial taxa that were differentially abundant over time displayed clear patterns of community succession. Overall, we report that host species identity, geographic location, and blade tissue age shape the microbial communities on canopy-forming kelps.
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Affiliation(s)
- Brooke L Weigel
- Committee on Evolutionary Biology, University of Chicago, Chicago, IL, United States
| | - Catherine A Pfister
- Department of Ecology and Evolution, University of Chicago, Chicago, IL, United States
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19
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20
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Fitzpatrick CR, Lu-Irving P, Copeland J, Guttman DS, Wang PW, Baltrus DA, Dlugosch KM, Johnson MTJ. Chloroplast sequence variation and the efficacy of peptide nucleic acids for blocking host amplification in plant microbiome studies. MICROBIOME 2018; 6:144. [PMID: 30121081 PMCID: PMC6098832 DOI: 10.1186/s40168-018-0534-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 08/14/2018] [Indexed: 05/25/2023]
Abstract
BACKGROUND The ability to efficiently characterize microbial communities from host individuals can be limited by co-amplification of host organellar sequences (mitochondrial and/or plastid), which share a common ancestor and thus sequence similarity with extant bacterial lineages. One promising approach is the use of sequence-specific peptide nucleic acid (PNA) clamps, which bind to, and block amplification of, host-derived DNA. Universal PNA clamps have been proposed to block host plant-derived mitochondrial (mPNA) and plastid (pPNA) sequences at the V4 16S rRNA locus, but their efficacy across a wide range of host plant species has not been experimentally tested. RESULTS Using the universal PNA clamps, we amplified and sequenced root microbial communities from replicate individuals of 32 plant species with a most recent common ancestor inferred at 140 MYA. We found the average rate of host plastid contamination across plant species was 23%, however, particular lineages exhibited much higher rates (62-94%), with the highest levels of contamination occurring in the Asteraceae. We investigated chloroplast sequence variation at the V4 locus across 500 land plant species (Embryophyta) and found six lineages with mismatches between plastid and the universal pPNA sequence, including all species within the Asteraceae. Using a modified pPNA for the Asteraceae sequence, we found (1) host contamination in Asteraceae species was reduced from 65 to 23%; and (2) host contamination in non-Asteraceae species was increased from 12 to 69%. These results demonstrate that even single nucleotide mismatches can lead to drastic reductions in pPNA efficacy in blocking host amplification. Importantly, we found that pPNA type (universal or modified) had no effect on the detection of individual bacterial taxa, or estimates of within and between sample bacterial diversity, suggesting that our modification did not introduce bias against particular bacterial lineages. CONCLUSIONS When high similarity exists between host organellar DNA and PCR target sequences, PNA clamps are an important molecular tool to reduce host contamination during amplification. Here, we provide a validated framework to modify universal PNA clamps to accommodate host variation in organellar sequences.
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Affiliation(s)
- Connor R Fitzpatrick
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada.
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada.
| | - Patricia Lu-Irving
- Department of Ecology & Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA
| | - Julia Copeland
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - David S Guttman
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, ON, M5S 3B2, Canada
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Pauline W Wang
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, ON, M5S 3B2, Canada
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - David A Baltrus
- School of Plant Sciences, University of Arizona, Tucson, AZ, 85721, USA
| | - Katrina M Dlugosch
- Department of Ecology & Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA
| | - Marc T J Johnson
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
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