Annika Gillis

Publications (2)7.44 Total impact

• Article: Atomic force microscopy: a powerful tool for studying bacterial swarming motility.

  Annika Gillis, Vincent Dupres, Jacques Mahillon, Yves F Dufrêne
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  ABSTRACT: Swarming motility is a fascinating phenomenon by which some bacteria use flagella to move over solid surfaces. Understanding the molecular mechanisms underlying swarming motility requires studying the factors that induce and control flagella expression in swarming cells. Traditionally, flagella are observed by optical or electron microscopy, but none of these techniques combine versatility and easiness, with quantitative and high-resolution information. We report an atomic force microscopy (AFM)-based approach for the fast imaging of bacterial phenotypes (cell shape, flagella expression) in swarming motility studies. Cells from the gram-positive bacterium Bacillus thuringiensis sv. israelensis were inoculated on energy-rich media containing increasing agar concentrations. Following swarming assays (2 days), the cell morphology and the amount of flagella were directly observed by AFM imaging in air. Consistent with the macroscopic swarming behavior, cells harvested from the rim of colonies spreading on soft agar were hyperflagellated, elongated and arranged in chains. Increasing the agar concentration led to much lower amounts of flagella and to shorter rod-shaped cells, a finding consistent with the slower swarming motility of the cells. Cells taken from colony centers on soft and hard agar surfaces were generally non-flagellated, rod-shaped, rarely arranged in chains, and exhibited lysis and sporulation. This study shows that AFM imaging can readily discriminate between swarming and non-swarming cells, and quantify their morphological details, thus offering an important tool to study the dynamics of bacterial populations.
  Micron 02/2012; 43(12):1304-11. · 1.53 Impact Factor
• Source

  Available from: Vincent Dupres

  Article: Nanoscale imaging of Bacillus thuringiensis flagella using atomic force microscopy.

  Annika Gillis, Vincent Dupres, Guillaume Delestrait, Jacques Mahillon, Yves F Dufrêne
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  ABSTRACT: Because bacterial flagella play essential roles in various processes (motility, adhesion, host interactions, secretion), studying their expression in relation to function is an important challenge. Here, we use atomic force microscopy (AFM) to gain insight into the nanoscale surface properties of two wild-type and four mutant strains of Bacillus thuringiensis exhibiting various levels of flagellation. We show that, unlike AFM in liquid, AFM in air is a simple and reliable approach to observe the morphological details of the bacteria, and to quantify the density and dimensions of their flagella. We found that the amount of flagella expressed by the six strains, as observed at the nanoscale, correlates with their microscopic swarming motility. These observations provide novel information on flagella expression in gram-positive bacteria and demonstrate the power of AFM in genetic studies for the fast assessment of the phenotypic characteristics of bacterial strains altered in cell surface appendages.
  Nanoscale 12/2011; 4(5):1585-91. · 5.91 Impact Factor