title: A Pseudomonas putida cardiolipin synthesis mutant exhibits increased sensitivity to drugs related to transport functionality.
abstract: Biological membranes have evolved different mechanisms to modify their composition in response to chemical stimuli in a process called 'homeoviscous adaptation'. Among these mechanisms, modifications in the ratio of saturated/unsaturated fatty acids and in cis/trans fatty acid isomers, cyclopropanation and changes in the phospholipids head group composition have been observed. To further understand the role of phospholipid head groups in solvent stress adaptation, we knocked out the cls (cardiolipin synthase) gene in Pseudomonas putida DOT-T1E. As expected, cls mutant membranes contained less cardiolipin than those of the wild-type strain. Although no significant growth rate defect was observed in the cls mutant compared with the wild-type strain, mutant cells were significantly smaller than the wild-type cells. The cls mutant was more sensitive to toluene shocks and to several antibiotics than the parental strain, suggesting either that the RND efflux pumps involved in the extrusion of these drugs were not working efficiently or that membrane permeability was altered in the mutant. Membranes of the cls mutant strain seemed to be more rigid than those of the parental strain, as observed by measurements of fluorescence polarization using the DPH probe, which intercalates into the membranes. Ethidium bromide is pumped out in Pseudomonas putida by at least one RND efflux pump involved in antibiotic and solvent resistance, and the higher rate of accumulation of ethidium bromide inside mutant cells indicated that functioning of the efflux pumps was compromised as a consequence of the alteration in phospholipid head group composition.
authors.affiliation: Consejo Superior de Investigaciones Científicas-Estación Experimental del Zaidín, Department of Environmental Protection, Profesor Albareda 1, E-18008 Granada, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Bernal
authors.forename: Jesús
authors.initials: J
authors.lastname: Muñoz-Rojas
authors.forename: Ana
authors.initials: A
authors.lastname: Hurtado
authors.forename: Juan L
authors.initials: JL
authors.lastname: Ramos
authors.forename: Ana
authors.initials: A
authors.lastname: Segura
mesh_terms: D002308:Cardiolipins / Q000187:drug effects* / Q000378:metabolism; D004996:Ethidium / Q000378:metabolism; D008560:Membrane Fluidity / Q000187:drug effects* / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000187:drug effects*; D008969:Molecular Sequence Data; D010539:Permeability; D016958:Pseudomonas putida / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D012997:Solvents / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D017855:Transferases (Other Substituted Phosphate Groups) / Q000235:genetics*
chemical_list: D002308:Cardiolipins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D012997:Solvents; D017855:Transferases (Other Substituted Phosphate Groups); C100091:cardiolipin synthetase; D004996:Ethidium