S D Cox1, J L Markham. 1. School of Science and Primary Industries, Charles Darwin University, Darwin, Australia. sean.cox@cdu.edu.au
Abstract
AIMS: To examine the causes for variations in sensitivity and intrinsic tolerance of Pseudomonas aeruginosa to plant volatile compounds. METHODS AND RESULTS: Minimum inhibitory concentrations were determined for a selection of volatile phytochemicals against P. aeruginosa using a microdilution assay. Effects on growth were also assessed in 100-ml broth cultures. The two strains of P. aeruginosa included in the study exhibited intrinsic tolerance to all compounds, with the exception of carvacrol and trans-cinnamaldehyde. The protonophore carbonyl cyanide m-chlorophenylhydrazone increased P. aeruginosa sensitivity to all compounds except trans-cinnamaldehyde, implicating an ATP-dependent efflux mechanism in the observed tolerance. Outer membrane integrity following treatment with test compounds was assessed by measuring sensitization to detergents. Only carvacrol caused damage to the outer membrane of P. aeruginosa. CONCLUSIONS: The intrinsic tolerance of P. aeruginosa strains to plant volatile compounds is associated with an active efflux mechanism and the barrier function of the outer membrane. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings offer an explanation for the intrinsic tolerance to plant volatile compounds exhibited by P. aeruginosa. The study also confirms that the outer membrane-permeabilizing action of carvacrol, previously reported for the gram-negative bacteria Escherichia coli and Salmonella, extends to monoterpene-tolerant strains of P. aeruginosa.
AIMS: To examine the causes for variations in sensitivity and intrinsic tolerance of Pseudomonas aeruginosa to plant volatile compounds. METHODS AND RESULTS: Minimum inhibitory concentrations were determined for a selection of volatile phytochemicals against P. aeruginosa using a microdilution assay. Effects on growth were also assessed in 100-ml broth cultures. The two strains of P. aeruginosa included in the study exhibited intrinsic tolerance to all compounds, with the exception of carvacrol and trans-cinnamaldehyde. The protonophore carbonyl cyanide m-chlorophenylhydrazone increased P. aeruginosa sensitivity to all compounds except trans-cinnamaldehyde, implicating an ATP-dependent efflux mechanism in the observed tolerance. Outer membrane integrity following treatment with test compounds was assessed by measuring sensitization to detergents. Only carvacrol caused damage to the outer membrane of P. aeruginosa. CONCLUSIONS: The intrinsic tolerance of P. aeruginosa strains to plant volatile compounds is associated with an active efflux mechanism and the barrier function of the outer membrane. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings offer an explanation for the intrinsic tolerance to plant volatile compounds exhibited by P. aeruginosa. The study also confirms that the outer membrane-permeabilizing action of carvacrol, previously reported for the gram-negative bacteria Escherichia coli and Salmonella, extends to monoterpene-tolerant strains of P. aeruginosa.
Authors: Chelsea J Papadopoulos; Christine F Carson; Barbara J Chang; Thomas V Riley Journal: Appl Environ Microbiol Date: 2008-01-11 Impact factor: 4.792
Authors: Thiago A F Ferro; Jéssica M M Araújo; Bruna L Dos Santos Pinto; Jéssica S Dos Santos; Eliene B Souza; Bruna L R da Silva; Valderlane L P Colares; Tânia M G Novais; Clovis M B Filho; Carsten Struve; João B Calixto; Valério Monteiro-Neto; Luís C N da Silva; Elizabeth S Fernandes Journal: Front Microbiol Date: 2016-12-21 Impact factor: 5.640
Authors: Ruth Schmidt; Desalegn W Etalo; Victor de Jager; Saskia Gerards; Hans Zweers; Wietse de Boer; Paolina Garbeva Journal: Front Microbiol Date: 2016-01-05 Impact factor: 5.640