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Utturkar SM, Cude WN, Robeson MS, Yang ZK, Klingeman DM, Land ML, Allman SL, Lu TYS, Brown SD, Schadt CW, Podar M, Doktycz MJ, Pelletier DA. Enrichment of Root Endophytic Bacteria from Populus deltoides and Single-Cell-Genomics Analysis. Appl Environ Microbiol 2016; 82:5698-708. [PMID: 27422831 PMCID: PMC5007785 DOI: 10.1128/aem.01285-16] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/07/2016] [Indexed: 12/11/2022] Open
Abstract
UNLABELLED Bacterial endophytes that colonize Populus trees contribute to nutrient acquisition, prime immunity responses, and directly or indirectly increase both above- and below-ground biomasses. Endophytes are embedded within plant material, so physical separation and isolation are difficult tasks. Application of culture-independent methods, such as metagenome or bacterial transcriptome sequencing, has been limited due to the predominance of DNA from the plant biomass. Here, we describe a modified differential and density gradient centrifugation-based protocol for the separation of endophytic bacteria from Populus roots. This protocol achieved substantial reduction in contaminating plant DNA, allowed enrichment of endophytic bacteria away from the plant material, and enabled single-cell genomics analysis. Four single-cell genomes were selected for whole-genome amplification based on their rarity in the microbiome (potentially uncultured taxa) as well as their inferred abilities to form associations with plants. Bioinformatics analyses, including assembly, contamination removal, and completeness estimation, were performed to obtain single-amplified genomes (SAGs) of organisms from the phyla Armatimonadetes, Verrucomicrobia, and Planctomycetes, which were unrepresented in our previous cultivation efforts. Comparative genomic analysis revealed unique characteristics of each SAG that could facilitate future cultivation efforts for these bacteria. IMPORTANCE Plant roots harbor a diverse collection of microbes that live within host tissues. To gain a comprehensive understanding of microbial adaptations to this endophytic lifestyle from strains that cannot be cultivated, it is necessary to separate bacterial cells from the predominance of plant tissue. This study provides a valuable approach for the separation and isolation of endophytic bacteria from plant root tissue. Isolated live bacteria provide material for microbiome sequencing, single-cell genomics, and analyses of genomes of uncultured bacteria to provide genomics information that will facilitate future cultivation attempts.
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Affiliation(s)
- Sagar M Utturkar
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee, USA
| | - W Nathan Cude
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Michael S Robeson
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Zamin K Yang
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Dawn M Klingeman
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Miriam L Land
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Steve L Allman
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Tse-Yuan S Lu
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Steven D Brown
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | | | - Mircea Podar
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Mitchel J Doktycz
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Dale A Pelletier
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
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Cude WN, Buchan A. Acyl-homoserine lactone-based quorum sensing in the Roseobacter clade: complex cell-to-cell communication controls multiple physiologies. Front Microbiol 2013; 4:336. [PMID: 24273537 PMCID: PMC3824088 DOI: 10.3389/fmicb.2013.00336] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 10/24/2013] [Indexed: 11/13/2022] Open
Abstract
Bacteria have been widely reported to use quorum sensing (QS) systems, which employ small diffusible metabolites to coordinate gene expression in a population density dependent manner. In Proteobacteria, the most commonly described QS signaling molecules are N-acyl-homoserine lactones (AHLs). Recent studies suggest that members of the abundant marine Roseobacter lineage possess AHL-based QS systems and are environmentally relevant models for relating QS to ecological success. As reviewed here, these studies suggest that the roles of QS in roseobacters are varied and complex. An analysis of the 43 publically available Roseobacter genomes shows conservation of QS protein sequences and overall gene topologies, providing support for the hypothesis that QS is a conserved and widespread trait in the clade.
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Affiliation(s)
| | - Alison Buchan
- Department of Microbiology, University of TennesseeKnoxville, TN, USA
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Cude WN, Mooney J, Tavanaei AA, Hadden MK, Frank AM, Gulvik CA, May AL, Buchan A. Production of the antimicrobial secondary metabolite indigoidine contributes to competitive surface colonization by the marine roseobacter Phaeobacter sp. strain Y4I. Appl Environ Microbiol 2012; 78:4771-80. [PMID: 22582055 PMCID: PMC3416362 DOI: 10.1128/aem.00297-12] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 04/25/2012] [Indexed: 11/20/2022] Open
Abstract
Members of the Roseobacter lineage of marine bacteria are prolific surface colonizers in marine coastal environments, and antimicrobial secondary metabolite production has been hypothesized to provide a competitive advantage to colonizing roseobacters. Here, we report that the roseobacter Phaeobacter sp. strain Y4I produces the blue pigment indigoidine via a nonribosomal peptide synthase (NRPS)-based biosynthetic pathway encoded by a novel series of genetically linked genes: igiBCDFE. A Tn5-based random mutagenesis library of Y4I showed a perfect correlation between indigoidine production by the Phaeobacter strain and inhibition of Vibrio fischeri on agar plates, revealing a previously unrecognized bioactivity of this molecule. In addition, igiD null mutants (igiD encoding the indigoidine NRPS) were more resistant to hydrogen peroxide, less motile, and faster to colonize an artificial surface than the wild-type strain. Collectively, these data provide evidence for pleiotropic effects of indigoidine production in this strain. Gene expression assays support phenotypic observations and demonstrate that igiD gene expression is upregulated during growth on surfaces. Furthermore, competitive cocultures of V. fischeri and Y4I show that the production of indigoidine by Y4I significantly inhibits colonization of V. fischeri on surfaces. This study is the first to characterize a secondary metabolite produced by an NRPS in roseobacters.
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Affiliation(s)
- W. Nathan Cude
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
| | - Jason Mooney
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
| | - Arash A. Tavanaei
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
| | - Mary K. Hadden
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
| | - Ashley M. Frank
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
| | | | - Amanda L. May
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee, USA
| | - Alison Buchan
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
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