Is gas-discharge plasma a new solution to the old problem of biofilm inactivation?
Conventional disinfection and sterilization methods are often ineffective with biofilms, which are ubiquitous, hard-to-destroy microbial communities embedded in a matrix mostly composed of exopolysaccharides. The use of gas-discharge plasmas represents an alternative method, since plasmas contain a mixture of charged particles, chemically reactive species and UV radiation, whose decontamination potential for free-living, planktonic micro-organisms is well established. In this study, biofilms were produced using Chromobacterium violaceum, a Gram-negative bacterium present in soil and water and used in this study as a model organism. Biofilms were subjected to an atmospheric pressure plasma jet for different exposure times. Our results show that 99.6 % of culturable cells are inactivated after a 5 min treatment. The survivor curve shows double-slope kinetics with a rapid initial decline in c.f.u. ml(-1) followed by a much slower decline with D values that are longer than those for the inactivation of planktonic organisms, suggesting a more complex inactivation mechanism for biofilms. DNA and ATP determinations together with atomic force microscopy and fluorescence microscopy show that non-culturable cells are still alive after short plasma exposure times. These results indicate the potential of plasma for biofilm inactivation and suggest that cells go through a sequential set of physiological and morphological changes before inactivation.
Joaquin
Jonathan C
JC
Biological Sciences Department, California State Polytechnic University, 3801 W. Temple Avenue, Pomona, CA 91768, USA.
Kwan
Calvin
C
Biological Sciences Department, California State Polytechnic University, 3801 W. Temple Avenue, Pomona, CA 91768, USA.
Abramzon
Nina
N
Center for Macromolecular Modeling and Materials Design (CM3D), California State Polytechnic University, 3801 W. Temple Avenue, Pomona, CA 91768, USA.|Physics Department, California State Polytechnic University, 3801 W. Temple Avenue, Pomona, CA 91768, USA.
Vandervoort
Kurt
K
Physics Department, California State Polytechnic University, 3801 W. Temple Avenue, Pomona, CA 91768, USA.
Brelles-Mariño
Graciela
G
Biological Sciences Department, California State Polytechnic University, 3801 W. Temple Avenue, Pomona, CA 91768, USA.
D018441:Biofilms; D002861:Chromobacterium / Q000187:drug effects / Q000254:growth & development*; D004269:DNA, Bacterial / Q000032:analysis; D005740:Gases / Q000494:pharmacology*; D050296:Microbial Viability; D018625:Microscopy, Atomic Force; D008856:Microscopy, Fluorescence; D013242:Sterilization / Q000379:methods*
D004269:DNA, Bacterial; D005740:Gases