title: Weakening effect of cell permeabilizers on gram-negative bacteria causing biodeterioration.
abstract: Gram-negative bacteria play an important role in the formation and stabilization of biofilm structures on stone surfaces. Therefore, the control of growth of gram-negative bacteria offers a way to diminish biodeterioration of stone materials. The effect of potential permeabilizers on the outer membrane (OM) properties of gram-negative bacteria was investigated and further characterized. In addition, efficacy of the agents in enhancing the activity of a biocide (benzalkonium chloride) was assessed. EDTA, polyethylenimine (PEI), and succimer (meso-2,3-dimercaptosuccinic) were shown to be efficient permeabilizers of the members of Pseudomonas and Stenotrophomonas genera, as indicated by an increase in the uptake of a hydrophobic probe (1-N-phenylnaphthylamine) and sensitization to hydrophobic antibiotics. Visualization of Pseudomonas cells treated with EDTA or PEI by atomic force microscopy revealed damage in the outer membrane structure. PEI especially increased the surface area and bulges of the cells. Topographic images of EDTA-treated cells were compatible with events assigned for the effect of EDTA on outer membranes, i.e., release of lipopolysaccharide and disintegration of OM structure. In addition, the effect of EDTA treatment was visualized in phase-contrast images as large areas with varying hydrophilicity on cell surfaces. In liquid culture tests, EDTA and PEI supplementation enhanced the activity of benzalkonium chloride toward the target strains. Use of permeabilizers in biocide formulations would enable the use of decreased concentrations of the active biocide ingredient, thereby providing environmentally friendlier products.
authors.affiliation: Biotechnology, VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Espoo, Finland. Hanna-Leena.Alakomi@vtt.fi
authors.forename: H-L
authors.initials: HL
authors.lastname: Alakomi
authors.forename: A
authors.initials: A
authors.lastname: Paananen
authors.forename: M-L
authors.initials: ML
authors.lastname: Suihko
authors.forename: I M
authors.initials: IM
authors.lastname: Helander
authors.forename: M
authors.initials: M
authors.lastname: Saarela
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002119:Calcium Carbonate / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D002463:Cell Membrane Permeability / Q000187:drug effects*; D004492:Edetic Acid / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D018625:Microscopy, Atomic Force; D008969:Molecular Sequence Data; D011094:Polyethyleneimine / Q000494:pharmacology*; D011549:Pseudomonas / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D017422:Sequence Analysis, DNA; D012822:Silicon Dioxide / Q000378:metabolism; D020579:Sinorhizobium / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D020588:Stenotrophomonas / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D012822:Silicon Dioxide; D011094:Polyethyleneimine; D004492:Edetic Acid; D002119:Calcium Carbonate