Extracellular DNA and Type IV pili mediate surface attachment by <Emphasis Type="Italic">Acidovorax</Emphasis><Emphasis Type="Italic">temperans</Emphasis> |
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Authors: | Björn D Heijstra Franz B Pichler Quanfeng Liang Razel G Blaza Susan J Turner |
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Institution: | (1) School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand |
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Abstract: | Extracellular DNA can play a structural role in the microbial environment. Here evidence is presented that an environmental
isolate of Acidovorax
temperans utilises extracellular DNA for intercellular and cell-surface attachment and that Type IV pili and electrostatic interactions
play a role in this interaction. Preliminary attempts to isolate and purify extracellular polysaccharides from A. temperans strain CB2 yielded significant amounts of DNA raising the question of whether this molecule was present as a structural component
in the extracellular matrix. The role of DNA in attachment was indicated by experiments in which the addition of DNase to
liquid medium inhibited the attachment of Acidovorax to glass wool. A Tn5 insertional mutant, lacking Type IV pili, was unable to initiate attachment. Addition of DNase caused rapid detachment of
bound cells, but no detachment occurred when proteinase, RNase or inactivated DNase were used. Addition of MgCl2 also caused significant detachment, supporting the possible mechanistic role of electrostatic interactions in the attachment
process. Although attachment was apparent in early to mid-log phase growth, surprisingly DNA was not detected in the culture
supernatant until late stationary phase and coincided with an appreciable loss of cell viability. This suggests that during
log-phase growth attachment is mediated by eDNA that is released in low quantities and/or is highly localised within the extracellular
matrix and also that stationary phase DNA release through widespread cell lysis may be a separate and unrelated event. |
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Keywords: | Biofilm Extracellular DNA Type IV pili Activated sludge |
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