title: Mining the phytomicrobiome to understand how bacterial coinoculations enhance plant growth.
abstract: In previous work, we showed that coinoculating Rhizobium leguminosarum bv. viciae 128C53 and Bacillus simplex 30N-5 onto Pisum sativum L. roots resulted in better nodulation and increased plant growth. We now expand this research to include another alpha-rhizobial species as well as a beta-rhizobium, Burkholderia tuberum STM678. We first determined whether the rhizobia were compatible with B. simplex 30N-5 by cross-streaking experiments, and then Medicago truncatula and Melilotus alba were coinoculated with B. simplex 30N-5 and Sinorhizobium (Ensifer) meliloti to determine the effects on plant growth. Similarly, B. simplex 30N-5 and Bu. tuberum STM678 were coinoculated onto Macroptilium atropurpureum. The exact mechanisms whereby coinoculation results in increased plant growth are incompletely understood, but the synthesis of phytohormones and siderophores, the improved solubilization of inorganic nutrients, and the production of antimicrobial compounds are likely possibilities. Because B. simplex 30N-5 is not widely recognized as a Plant Growth Promoting Bacterial (PGPB) species, after sequencing its genome, we searched for genes proposed to promote plant growth, and then compared these sequences with those from several well studied PGPB species. In addition to genes involved in phytohormone synthesis, we detected genes important for the production of volatiles, polyamines, and antimicrobial peptides as well as genes for such plant growth-promoting traits as phosphate solubilization and siderophore production. Experimental evidence is presented to show that some of these traits, such as polyamine synthesis, are functional in B. simplex 30N-5, whereas others, e.g., auxin production, are not.
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Maskit
authors.initials: M
authors.lastname: Maymon
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Pilar
authors.initials: P
authors.lastname: Martínez-Hidalgo
authors.affiliation: Bioinformatics, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Tran
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Tyler
authors.initials: T
authors.lastname: Ice
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Karena
authors.initials: K
authors.lastname: Craemer
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Teni
authors.initials: T
authors.lastname: Anbarchian
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Sung
authors.affiliation: Pasarow Mass Spectrometry Laboratory, Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Lin H
authors.initials: LH
authors.lastname: Hwang
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Minxia
authors.initials: M
authors.lastname: Chou
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Fujishige
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: William
authors.initials: W
authors.lastname: Villella
authors.affiliation: Biotechnology, Plants, and Microorganisms Biology, University of Montpellier II Montpellier, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Ventosa
authors.affiliation: Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH Braunschweig, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Sikorski
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Erin R
authors.initials: ER
authors.lastname: Sanders
authors.affiliation: Pasarow Mass Spectrometry Laboratory, Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles Los Angeles, CA, USA ; Molecular Biology Institute, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Kym F
authors.initials: KF
authors.lastname: Faull
authors.affiliation: Departments of Molecular, Cell, and Developmental Biology, University of California, Los Angeles Los Angeles, CA, USA ; Molecular Biology Institute, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Hirsch
keywords: Bacillus simplex; coinoculations; genome studies; legumes; rhizosphere