title: Heavy metal resistance of biofilm and planktonic Pseudomonas aeruginosa.
abstract: A study was undertaken to examine the effects of the heavy metals copper, lead, and zinc on biofilm and planktonic Pseudomonas aeruginosa. A rotating-disk biofilm reactor was used to generate biofilm and free-swimming cultures to test their relative levels of resistance to heavy metals. It was determined that biofilms were anywhere from 2 to 600 times more resistant to heavy metal stress than free-swimming cells. When planktonic cells at different stages of growth were examined, it was found that logarithmically growing cells were more resistant to copper and lead stress than stationary-phase cells. However, biofilms were observed to be more resistant to heavy metals than either stationary-phase or logarithmically growing planktonic cells. Microscopy was used to evaluate the effect of copper stress on a mature P. aeruginosa biofilm. The exterior of the biofilm was preferentially killed after exposure to elevated concentrations of copper, and the majority of living cells were near the substratum. A potential explanation for this is that the extracellular polymeric substances that encase a biofilm may be responsible for protecting cells from heavy metal stress by binding the heavy metals and retarding their diffusion within the biofilm.
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Gail M
authors.initials: GM
authors.lastname: Teitzel
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Parsek
mesh_terms: D000818:Animals; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D003300:Copper / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D019216:Metals, Heavy / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010933:Plankton / Q000187:drug effects* / Q000254:growth & development; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development
chemical_list: D019216:Metals, Heavy; D003300:Copper