Article

Motility and Chemotaxis in Agrobacterium tumefaciens Surface Attachment and Biofilm Formation

Department of Biology, Indiana University, 1001 E. 3rd St., Jordan Hall 142, Bloomington, IN 47405-1847, USA.
Journal of bacteriology (Impact Factor: 2.81). 12/2007; 189(22):8005-14. DOI: 10.1128/JB.00566-07
Source: PubMed

ABSTRACT

Bacterial motility mechanisms, including swimming, swarming, and twitching, are known to have important roles in biofilm formation, including colonization and the subsequent expansion into mature structured surface communities. Directed motility requires chemotaxis functions that are conserved among many bacterial species. The biofilm-forming plant pathogen Agrobacterium tumefaciens drives swimming motility by utilizing a small group of flagella localized to a single pole or the subpolar region of the cell. There is no evidence for twitching or swarming motility in A. tumefaciens. Site-specific deletion mutations that resulted in either aflagellate, flagellated but nonmotile, or flagellated but nonchemotactic A. tumefaciens derivatives were examined for biofilm formation under static and flowing conditions. Nonmotile mutants were significantly deficient in biofilm formation under static conditions. Under flowing conditions, however, the aflagellate mutant rapidly formed aberrantly dense, tall biofilms. In contrast, a nonmotile mutant with unpowered flagella was clearly debilitated for biofilm formation relative to the wild type. A nontumbling chemotaxis mutant was only weakly affected with regard to biofilm formation under nonflowing conditions but was notably compromised in flow, generating less adherent biomass than the wild type, with a more dispersed cellular arrangement. Extragenic suppressor mutants of the chemotaxis-impaired, straight-swimming phenotype were readily isolated from motility agar plates. These mutants regained tumbling at a frequency similar to that of the wild type. Despite this phenotype, biofilm formation by the suppressor mutants in static cultures was significantly deficient. Under flowing conditions, a representative suppressor mutant manifested a phenotype similar to yet distinct from that of its nonchemotactic parent.

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    • "Chemotaxis is also relevant for plant pathogens. Chemotaxis is needed for the soil-borne plant pathogens Agrobacterium tumefa- ciens[41,42]and Ralstonia solanacearum[43,44]to find the correct host plant roots in their soil environments. Similarly, the plant leaf pathogen Pseudomonas syringae uses flagellar motility and chemotaxis for successful formation of infections on leaf surfaces[45]. "
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    • "In addition, many microbial taxa have evolved the ability to sense chemical gradients towards favorable conditions, moving towards gradients of attractants and away from gradients of repellents (Taylor and Stocker 2012; Stocker 2012). Cell motility (e.g., flagellum or chemotaxis mediated) was recognized to be linked to surface attachment and subsequent biofilm formation due to the increase in collision frequency (Morisaki et al. 1999; Merritt et al. 2007; Lemon et al. 2007). Nevertheless, understanding of the underlying mechanisms of disinfection-driven microbial attachment through cell motility regulation remains elusive. "
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    • "These microbial biofilms form on natural and man-made surfaces and interfaces and play important roles in various health and environmental issues (Hall-Stoodley et al. 2004 ). Previous experimental studies have indicated the significance of bacterial motility mechanisms in the colonization process and the subsequent biofilm formation (O'Toole and Kolter 1998; Pratt and Kolter 1998; Watnick and Kolter 1999; Lemon et al. 2007; Merritt et al. 2007; Kim et al. 2008 ; Houry et al. 2010). In particular, flagellar mediated swimming is crucial in approaching the surface and initiating the adhesion process (Tuson and Weibel 2013) and pili-mediated motility highly promotes the surface exploration (Burrows 2012). "
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