Publication

Characterization of cell surface and extracellular matrix remodeling of Azospirillum brasilense chemotaxis-like 1 signal transduction pathway mutants by atomic force microscopy. Public

Amanda N. Edwards,Piro Siuti,Amber N. Bible,Gladys Alexandre,Scott T. Retterer,Mitchel J. Doktycz,Jennifer L. Morrell-Falvey 2011 January 01 FEMS Microbiol Lett. 2011 Jan;314(2):131-9. doi: 10.1111/j.1574-6968.2010.02156.x. Epub 2010 Nov 24.
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Abstract

To compete in complex microbial communities, bacteria must sense environmental changes and adjust cellular functions for optimal growth. Chemotaxis-like signal transduction pathways are implicated in the regulation of multiple behaviors in response to changes in the environment, including motility patterns, exopolysaccharide production, and cell-to-cell interactions. In Azospirillum brasilense, cell surface properties, including exopolysaccharide production, are thought to play a direct role in promoting flocculation. Recently, the Che1 chemotaxis-like pathway from A. brasilense was shown to modulate flocculation, suggesting an associated modulation of cell surface properties. Using atomic force microscopy, distinct changes in the surface morphology of flocculating A. brasilense Che1 mutant strains were detected. Whereas the wild-type strain produces a smooth mucosal extracellular matrix after 24 h, the flocculating Che1 mutant strains produce distinctive extracellular fibril structures. Further analyses using flocculation inhibition, lectin-binding assays, and comparison of lipopolysaccharides profiles suggest that the extracellular matrix differs between the cheA1 and the cheY1 mutants, despite an apparent similarity in the macroscopic floc structures. Collectively, these data indicate that disruption of the Che1 pathway is correlated with distinctive changes in the extracellular matrix, which likely result from changes in surface polysaccharides structure and/or composition.

Highlights


 Flocculating che1 mutants produce a fibrillar material during premature flocculation. (a) Nonflocculating wild-type Sp7 at 24 h; (b) flocculating wild-type Sp7 at 1 week; (c) flocculating mutant strain AB101 (ΔcheA1) at 24 h; (d) flocculating mutant strain AB102 (ΔcheY1) at 24 h. The white arrows point to the fibrillar material. All scale bars represent 200 nm.


AFM deflection images revealed a dissimilarity in the organization of flocs between the two mutant strains. (a) Wild-type Sp7 deflection; (b) AB101 (ΔcheA1) deflection; (c) AB102 (ΔcheY1) deflection; (d) 5 μm2 micrograph with a height cross-section measurement between wild-type cells; (e) between AB101 (ΔcheA1) cells; and (f) between AB102 (ΔcheY1) cells revealing a distinct extracellular material not observed for wild type or AB101 (ΔcheA1). Scale bars represent 5 μm.


The che1 mutants differentially bind lentil (LcH) and lima bean (LBL) lectins. (a,d) wild-type stained with LcH and Syto61; (b,e) AB101(ΔcheA1) stained with LcH and Syto61; (c,f)AB102(ΔcheY1) stained with LcH and Syto61; (g,j) wild-type stained with LBL and Syto61; (h,k) AB101(ΔcheA1) stained with LBL and Syto61; (i,l) AB102(ΔcheY1) stained with LBL and Syto61.

Citation

Edwards AN, Siuti P, Bible AN, Alexandre G, Retterer ST, Doktycz MJ, Morrell-Falvey JL. Characterization of cell surface and extracellular matrix remodeling of Azospirillum brasilense chemotaxis-like 1 signal transduction pathway mutants by atomic force microscopy. FEMS Microbiol Lett. 2011 Jan;314(2):131-9. doi: 10.1111/j.1574-6968.2010.02156.x. Epub 2010 Nov 24. PubMed PMID: 21105907.


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Comments

Final version published online 24 November 2010.