Nancy A. Fujishige

Loyola Marymount University

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Ann M. Hirsch

University of California, Los Angeles

Michelle R. Lum

Loyola Marymount University

Peter L. De Hoff

Salk Institute for Biological Studies

Neel N. Kapadia

Duke University

Cheryl A. Hackworth

University of California, Berkeley

Stephen Tran

University of California, San Diego

Laurence M. Brill

Sanford Burnham Prebys Medical Discovery Institute

William Villella

University of California, Los Angeles

P. van Rhijn

KU Leuven

Matt Nolan

Joint Genome Institute

Cooperative Institutions

University of California, Los Angeles

Joint Genome Institute

Lawrence Berkeley National Laboratory

University of California, Davis

Agricultural Research Organization

Lawrence Livermore National Laboratory

University of California System

Institute of Molecular and Cell Biology

Los Alamos National Laboratory

United States Department of Energy

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A feeling for the micro-organism: structure on a small scale. Biofilms on plant roots - eScholarship

Nancy A. Fujishige Neel N. Kapadia Ann M. Hirsch

Biofilms are structured communities of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface; they have clinical, industrial and environmental impacts. Biofilms that are established by bacteria on plants are found on the surfaces of roots, leaves, seeds and internal vascular tissues where the microbes live in commensal, mutualistic or parasitic/pathogenic associations with their host. The study of the structure of plant-associated biofilms has been considerably helped by the development of techniques using fluorescent markers coupled with confocal scanning laser microscopy as well as scanning electron microscopy. We review several of these techniques as well as some of the research that has dealt with plant-associated biofilms. Our investigations focus on biofilm formation in the early stages of the Rhizobium-legume symbiosis, in which Gram-negative rhizobia provide fixed nitrogen to a host legume, and in return, the legume provides carbon-containing molecules. Because root colonization is an important early step in the establishment of the nitrogen-fixing symbiosis, we looked at Sinorhizobium meliloti attachment and biofilm establishment on the roots of its legume hosts, Medicago sativa L. and Melilotus alba Desr. We also examined biofilm formation by Rhizobium leguminosarum bv. viciae on the roots of Arabidopsis thaliana ( L.) Heynh., a non-legume and non-host. Our ultimate goal is to characterize the rhizobial genes involved in aggregation and attachment to roots because several of these appear to be shared in biofilm formation and rhizobial entry of legume root cells. (c) 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 150, 79-88.

Sinorhizobium meliloti

Medicago truncatula

Rhizobium leguminosarum

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Microbial Encounters of a Symbiotic Kind: Attaching to Roots and Other Surfaces

Plant cell monographs (2008)

Ann M. Hirsch Michelle R. Lum Nancy A. Fujishige

Root hair

Rhizobium leguminosarum

Nod factor

10.1007/978-3-540-79405-9_6

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Citations (8)

Bacillus simplex—A Little Known PGPB with Anti-Fungal Activity—Alters Pea Legume Root Architecture and Nodule Morphology When Coinoculated with Rhizobium leguminosarum bv. viciae

Agronomy (2013)

Allison Schwartz Irma Ortiz Maskit Maymon Craig W. Herbold Nancy A. Fujishige

Two strains, 30N-5 and 30VD-1, identified as Bacillus simplex and B. subtilis, were isolated from the rhizospheres of two different plants, a Podocarpus and a palm, respectively, growing in the University of California, Los Angeles (UCLA) Mildred E. Mathias Botanical Garden. B. subtilis is a well-known plant-growth promoting bacterial species, but B. simplex is not. B. simplex 30N-5 was initially isolated on a nitrogen-free medium, but no evidence for nitrogen fixation was found. Nevertheless, pea plants inoculated with B. simplex showed a change in root architecture due to the emergence of more lateral roots. When Pisum sativum carrying a DR5::GUSA construct, an indicator for auxin response, was inoculated with either B. simplex 30N-5 or its symbiont Rhizobium leguminosarum bv. viciae 128C53, GUS expression in the roots was increased over the uninoculated controls. Moreover, when pea roots were coinoculated with either B. simplex 30N-5 or B. subtilis 30VD-1 and R. leguminosarum bv. viciae 128C53, the nodules were larger, clustered, and developed more highly branched vascular bundles. Besides producing siderophores and solubilizing phosphate, the two Bacillus spp., especially strain 30VD-1, exhibited anti-fungal activity towards Fusarium. Our data show that combining nodulating, nitrogen-fixing rhizobia with growth-promoting bacteria enhances plant development and strongly supports a coinoculation strategy to improve nitrogen fixation, increase biomass, and establish greater resistance to fungal disease.

Rhizobium leguminosarum

10.3390/agronomy3040595

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Citations (107)

Commensalisms

Elsevier eBooks (2008)

Ann M. Hirsch Nancy A. Fujishige

10.1016/b978-008045405-4.00643-1

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Citations (7)

Complete genome sequence of Micromonospora L5, a plant-growth regulating actinomycete, orginally isolated from Casuarina equisetifolia root nodules

Matt Nolan James Han Natalia Ivanova A. Pati Tanja Woyke

Casuarina equisetifolia

Casuarina

Sequence (biology)

Micromonospora

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Sugar-Binding Activity of Pea Lectin Enhances Heterologous Infection of Transgenic Alfalfa Plants by Rhizobium leguminosarum biovar viciae

PLANT PHYSIOLOGY (2001)

P. van Rhijn Nancy A. Fujishige Pyung Ok Lim Ann M. Hirsch

Abstract Transgenic alfalfa (Medicago sativa L. cv Regen) roots carrying genes encoding soybean lectin or pea (Pisum sativum) seed lectin (PSL) were inoculated withBradyrhizobium japonicum or Rhizobium leguminosarum bv viciae, respectively, and their responses were compared with those of comparably inoculated control plants. We found that nodule-like structures formed on alfalfa roots only when the rhizobial strains produced Nod factor from the alfalfa-nodulating strain, Sinorhizobium meliloti. Uninfected nodule-like structures developed on the soybean lectin-transgenic plant roots at very low inoculum concentrations, but bona fide infection threads were not detected even when B. japonicum produced the appropriate S. melilotiNod factor. In contrast, the PSL-transgenic plants were not only well nodulated but also exhibited infection thread formation in response toR. leguminosarum bv viciae, but only when the bacteria expressed the complete set of S. meliloti nod genes. A few nodules from the PSL-transgenic plant roots were even found to be colonized by R. leguminosarum bvviciae expressing S. meliloti nod genes, but the plants were yellow and senescent, indicating that nitrogen fixation did not take place. Exopolysaccharide appears to be absolutely required for both nodule development and infection thread formation because neither occurred in PSL-transgenic plant roots following inoculation with an Exo− R. leguminosarumbv viciae strain that produced S. meliloti Nod factor.

Rhizobium leguminosarum

Nod factor

10.1104/pp.126.1.133

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Citations (93)

Dg93, a Nodule-Abundant mRNA of Datisca glomerata with Homology to a Soybean Early Nodulin Gene

PLANT PHYSIOLOGY (2000)

Patricia A. Okubara Nancy A. Fujishige Ann M. Hirsch Alison M. Berry

Abstract We have isolated a 590-bp full-length cDNA clone designatedDg93, an mRNA that is highly expressed in symbiotic root nodules of the actinorhizal host Datisca glomerata. Dg93mRNA encodes a deduced polypeptide of 105 amino acids with significant identity (74%) to the soybean (Glycine max) early nodulin (ENOD) gene GmENOD93 (Kouchi and Hata, 1993).Dg93 mRNA is abundant in nodules at 4 weeks post inoculation, the earliest time assayed, and steady-state mRNA levels remain elevated 11 weeks after inoculation. Spatial patterns ofDg93 mRNA expression are complex, with transcript accumulation in the nodule lobe meristem, early infection zone, periderm, and cells of the vascular cylinder, but not in the surrounding uninfected cortical cells. Dg93 is encoded by a small gene family in D. glomerata. To our knowledge, this is the first report of a gene from an actinorhizal host that is expressed in the nodule meristem and that shares sequence homology with an early nodulin gene from a legume.

Frankia

Actinorhizal plant

Homology

clone (Java method)

10.1104/pp.122.4.1073

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Citations (22)

Microbial Encounters of a Symbiotic Kind: Attaching to Roots and Other Surfaces

Plant cell monographs (2008)

Ann M. Hirsch Michelle R. Lum Nancy A. Fujishige

Root hair

Rhizobium leguminosarum

Nod factor

10.1007/7089_2008_6

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Citations (0)

Investigations of Rhizobium biofilm formation

FEMS Microbiology Ecology (2006)

Nancy A. Fujishige Neel N. Kapadia Peter L. De Hoff Ann M. Hirsch

The development of nitrogen-fixing nodules of the Rhizobium-legume symbiosis, especially the early stages of root hair deformation and curling, infection thread formation, and nodule initiation, has been well studied from a genetic standpoint. In contrast, the factors important for the colonization of surfaces by rhizobia, including roots–an important prerequisite for nodule formation–have not been as thoroughly investigated. We developed conditions for analyzing the ability of two fast-growing rhizobia, Sinorhizobium meliloti and Rhizobium leguminosarum bv. viciae, to produce biofilms on abiotic surfaces such as glass, plastic microtiter plates, sand and soil as a prelude to characterizing the genes important for aggregation and attachment. Factors involved in adherence to abiotic surfaces are likely to be used in rhizobial attachment to legume root cells. In this report, we show that S. meliloti exopolysaccharide-deficient mutants as well as exopolysaccharide overproducers exhibit reduced biofilm phenotypes that show parallels with their nodulation abilities. We also investigated two flagella-less S. meliloti mutants and found them to have reduced biofilming capabilities. To investigate whether there was a symbiotic phenotype, we tested one of the Fla− mutants on two different S. meliloti hosts, alfalfa and white sweetclover, and found that nodule formation was significantly delayed on the latter.

10.1111/j.1574-6941.2005.00044.x

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Citations (251)

Complete Genome Sequence of Micromonospora Strain L5, a Potential Plant-Growth-Regulating Actinomycete, Originally Isolated from Casuarina equisetifolia Root Nodules

Genome Announcements (2013)

Ann M. Hirsch J.I. Merchan Alvarado David Bruce Olga Chertkov Peter L. De Hoff

ABSTRACT Micromonospora species live in diverse environments and exhibit a broad range of functions, including antibiotic production, biocontrol, and degradation of complex polysaccharides. To learn more about these versatile actinomycetes, we sequenced the genome of strain L5, originally isolated from root nodules of an actinorhizal plant growing in Mexico.

Casuarina equisetifolia

Casuarina

Strain (injury)

10.1128/genomea.00759-13

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Citations (18)