Regensburg 2010 – scientific programme
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BP: Fachverband Biologische Physik
BP 26: From Single-Molecule to Tissue Dynamics
BP 26.2: Talk
Thursday, March 25, 2010, 14:30–14:45, H43
Import of DNA by Helicobacter pylori is reversible by application of external force — •Stephanie Müller1,2, Kerstin Stingl1,2, Gerda Scheidgen-Kleyboldt2, Martin Clausen2, and Berenike Maier2 — 1equal contribution — 2Westfälische Wilhelms-Universität, Biological Department, 48149 Münster, Germany
Many bacterial species are capable of taking up and incorporating exogenous DNA in their genome. For the transport of DNA across the outer and inner membrane, the gram-negative gastric pathogen Helicobacter pylori uses a reverse type-IV-secretion-system, termed ComB. Besides this secretion-system related mechanism, further proteins are also involved in DNA uptake, among them the inner membrane channel ComEC. DNA-uptake experiments revealed that H. pylori cells posses multiple polar DNA-uptake complexes. In addition, knockout mutants in two motor proteins, ComB4 (an ATPase) and ComB6 (an inner membrane protein), and in the inner membrane channel ComEC were characterized revealing that the ComB-system and the inner membrane channel act at different steps of DNA uptake. The physical properties of the uptake motor were characterized in laser-trap experiments: Upon application of external force, previously imported DNA was extracted, revealing reversibility of the motor at 23pN external force. The average DNA import velocity was 2,2 kbp/sec. Taken all data together, a temporally uncoupled mechanism of DNA uptake is proposed: First the fast and reversible uptake across the outer membrane mediated by the ComB-system, and secondly the ComEC-dependent inner-membrane transport.