Characterization of the Adhesive Holdfast of Marine and Freshwater Caulobacters

SummaryIn legume nitrogen-fixing symbioses, rhizobial nod genes are obligatory for initiating infection thread formation and root nodule development. Here we show that the common nod genes, nodD1ABC, whose products synthesize core Nod factor, a chitin-like oligomer, are also required for the establishment of the three-dimensional architecture of the biofilm of Sinorhizobium meliloti. Common nod gene mutants form a biofilm that is a monolayer. Moreover, adding Nod Factor antibody to S. meliloti cells inhibits biofilm formation, while chitinase treatment disrupts pre-formed biofilms. These results attest to the involvement of core Nod factor in rhizobial biofilm establishment. However, luteolin, the plant-derived inducer of S. meliloti's nod genes, is not required for mature biofilm formation, although biofilm establishment is enhanced in the presence of this flavonoid inducer. Because biofilm formation is plant-inducerindependent and because all nodulating rhizobia, both alpha-and beta-proteobacteria have common nod genes, the role of core Nod factor in biofilm formation is likely to be an ancestral and evolutionarily conserved function of these genes.

Section: Discussionmentioning

confidence: 99%

Rhizobium common nod genes are required for biofilm formation

Fujishige

Lum

Hoff³

et al. 2007

“…We compared YB3079 to the podJ transposon mutant YB2863. Wild-type Caulobacter are known to bind to polystyrene and to the lectin wheat germ agglutinin (WGA) (Merker and Smit, 1988). Table 1 and Fig.…”

Section: Cells Express Multiple Forms Of Podjmentioning

confidence: 99%

The Caulobacter crescentus polar organelle development protein PodJ is differentially localized and is required for polar targeting of the PleC development regulator

Hinz

Larson

Smith

et al. 2003

104

181

Summary Regulation of polar development and cell division inCaulobacter crescentus relies on the dynamic localization of several proteins to cell poles at specific stages of the cell cycle. The p olar o rganelle d evelopment protein, PodJ, is required for the synthesis of the adhesive holdfast and pili. Here we show the cell cycle localization of PodJ and describe a novel role for this protein in controlling the dynamic localization of the developmental regulator PleC. In swarmer cells, a short form of PodJ is localized at the flagellated pole. Upon differentiation of the swarmer cell into a stalked cell, full length PodJ is synthesized and localizes to the pole opposite the stalk. In late predivisional cells, full length PodJ is processed into a short form which remains localized at the flagellar pole after cell division and is degraded during swarmer to stalked cell differentiation. Polar localization of the developmental regulator PleC requires the presence of PodJ. In contrast, the polar localization of PodJ is not dependent on the presence of PleC. These results indicate that PodJ is an important determinant for the localization of a major regulator of cell differentiation. Thus, PodJ acts directly or indirectly to target PleC to the incipient swarmer pole, to establish the cellular asymmetry that leads to the synthesis of holdfasts and pili at their proper subcellular location.

“…The fluorescent lectin-binding assay was used to visualize the holdfast by fluorescence microscopy using wheat germ agglutinin conjugated to fluorescein (Molecular Probes) (Merker and Smit, 1988;Janakiraman and Brun, 1999). Epifluorescence photomicroscopy was performed on a Nikon Eclipse E800 light microscope equipped with a Nikon B-2E FITC filter cube for FITC and a 100 ¥ plan Apo oil objective (NA 1.4).…”

Section: Detection Of the Holdfast With Fluorescein-labelled Lectinmentioning

confidence: 99%

“…The exact composition of the holdfast is not known; however, lectin binding studies have established that polysaccharides are part of the binding components of the holdfast. Binding and competition experiments with wheat germ agglutinin (WGA) lectin have indicated that the holdfast contains N -acetylglucosamine (GlcNAc) oligomers (Merker and Smit, 1988;Ong et al ., 1990). Treatment of cells with chitinase or lysozyme, enzymes that cleave oligomers of GlcNAc, disrupted rosettes, indicating that the integrity of the GlcNAc is required for holdfast binding (Merker and Smit, 1988).…”

Section: Introductionmentioning

confidence: 99%

“…Binding and competition experiments with wheat germ agglutinin (WGA) lectin have indicated that the holdfast contains N -acetylglucosamine (GlcNAc) oligomers (Merker and Smit, 1988;Ong et al ., 1990). Treatment of cells with chitinase or lysozyme, enzymes that cleave oligomers of GlcNAc, disrupted rosettes, indicating that the integrity of the GlcNAc is required for holdfast binding (Merker and Smit, 1988). The mechanisms by which the GlcNAc and other presumed components of the holdfast are precisely secreted at one pole of the cell and tightly attached to the tip of the stalk are unknown.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The HfaB and HfaD adhesion proteins of Caulobacter crescentus are localized in the stalk

Cole

Hardy

Bodenmiller

et al. 2003

SummaryThe differentiating bacterium Caulobacter crescentus produces two different cell types at each cell division, a motile swarmer cell and an adhesive stalked cell. The stalked cell harbours a stalk, a thin cylindrical extension of the cell surface. The tip of the stalk is decorated with a holdfast, an adhesive organelle composed at least in part of polysaccharides. The synthesis of the stalk and holdfast occur at the same pole during swarmer cell differentiation. Mutations in the hfaABDC gene cluster had been shown to disrupt the attachment of the holdfast to the tip of the stalk, but the role of individual genes was unknown. We used lacZ fusions of various DNA fragments from the hfaABDC region to show that these genes form an operon. In order to analyse the relative contribution of the different genes to holdfast attachment, mutations were constructed for each gene. hfaC was not required for holdfast attachment or binding to surfaces. The hfaA and hfaD mutants shed some holdfast material into the surrounding medium and were partially deficient in binding to surfaces. Unlike hfaA and hfaB mutants, hfaD mutants were still able to form rosettes efficiently. Cells with insertions in hfaB were unable to bind to surfaces, and lectin binding studies indicated that the hfaB mutants had the strongest holdfast shedding phenotype. We determined that HfaB and HfaD are membrane-associated proteins and that HfaB is a lipoprotein. Purification of stalks and cell bodies indicated that both HfaB and HfaD are enriched in the stalk as compared to the cell body. These results suggest that HfaB and HfaD, and probably HfaA, serve to anchor the holdfast to the tip of the stalk.