title: Membrane eicosapentaenoic acid is involved in the hydrophobicity of bacterial cells and affects the entry of hydrophilic and hydrophobic compounds.
abstract: Eicosapentaenoic acid (EPA)-producing Shewanella marinintestina IK-1 (IK-1) and its EPA-deficient mutant IK-1Delta8 (IK-1Delta8) were grown on microtitre plates at 20 degrees C in a nutrient medium that contained various types of growth inhibitors. The minimal inhibitory concentrations of hydrogen peroxide and tert-butyl hydroxyl peroxide were 100 microM and 1 mM, respectively, for IK-1 and 10 and 100 microM, respectively, for IK-1Delta8. IK-1 was much more resistant than IK-1Delta8 to the four water-soluble antibiotics (ampicillin sodium, kanamycin sulphate, streptomycin sulphate, and tetracycline hydrochloride) tested. In contrast, IK-1 was less resistant than IK-1Delta8 to two hydrophobic uncouplers: carbonyl cyanide m-chloro phenylhydrazone (CCCP) and N,N'-dicyclohexylcarbodiimide (DCCD). The hydrophobicity of the IK-1 and IK-1Delta8 cells grown at 20 degrees C was determined using the bacterial adhesion to hydrocarbon method. EPA-containing ( approximately 10% of total fatty acids) IK-1 cells were more hydrophobic than their counterparts with no EPA. These results suggest that the high hydrophobicity of IK-1 cells can be attributed to the presence of membrane EPA, which shields the entry of hydrophilic membrane-diffusible compounds, and that hydrophobic compounds such as CCCP and DCCD diffuse more effectively in the membranes of IK-1, where they can fulfil their inhibitory activities, than in the membranes of IK-1Delta8.
authors.affiliation: Hokkaido University, Sapporo, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Nishida
authors.forename: Ryuji
authors.initials: R
authors.lastname: Hori
authors.forename: Naoki
authors.initials: N
authors.lastname: Morita
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Okuyama
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology; D001692:Biological Transport; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D015118:Eicosapentaenoic Acid / Q000032:analysis*; D057927:Hydrophobic and Hydrophilic Interactions; D008826:Microbial Sensitivity Tests; D020592:Shewanella / Q000737:chemistry / Q000254:growth & development / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D015118:Eicosapentaenoic Acid