Effect of organic solvents on solvent-tolerant <i style="">Aeromonas <strong>hydrophila</strong> </i>IBB_Po8 and <i style="">Pseudomonas aeruginosa </i>IBB_Po10

Abstract

Alkanes (<i style="">n</i>-hexane, <i style="">n</i>-heptane) with logarithm of partition coefficient between <i>n</i>-octanol and water (log <i>P_OW</i>) 3.86 to 4.39 were less toxic to <i style="">Aeromonas </i><strong><i style="">hydrophila</i></strong><i style=""> </i>IBB_Po8 and <i style="">Pseudomonas aeruginosa </i>IBB_Po10 as compared to aromatics (toluene, styrene, xylene isomers, ethylbenzene &amp; propylbenzene) with log <i style="">P_OW</i>2.64 to 3.69. The toxicity of 0.5% (v/v) second phase of organic solvents to these bacteria could be predictable on the basis of the solvents’ log <i>P_OW</i>. The tolerance, viability, adhesion and β-galactosidase activity of <i style="">A. </i><strong><i style="">hydrophila</i></strong><i style=""> </i>IBB_Po8 and <i style="">P. aeruginosa </i>IBB_Po10 cells in the presence of 0.5% (v/v) organic solvents varied significantly. The results indicated that <i style="">A. </i><strong><i style="">hydrophila</i></strong><i style=""> </i>IBB_Po8 was more susceptible to organic solvents than <i style="">P. aeruginosa </i>IBB_Po10, whereas both the bacterial strains harbour plasmids. <i style="">A. </i><strong><i style="">hydrophila</i></strong><i style=""> </i>IBB_Po8 did not posses hydrophobe/amphiphile efflux 1 (HAE1) transporter genes, while<i style=""> P. aeruginosa </i>IBB_Po10 did posses these genes. The adaptation mechanisms (modification of cell hydrophobicity, induction of β-galactosidase activity and changes in the membrane’s lipid and protein content) of bacterial cells, underlying solvent tolerance, in <i style="">A. </i><strong><i style="">hydrophila</i></strong><i style=""> </i>IBB_Po8 and <i style="">P. aeruginosa </i>IBB_Po10 showed a complex response to the presence of 0.5% (v/v) organic solvents in the culture medium. Bacterial strains able to survive in the presence of organic solvents could be used in two-phase biotransformation systems with whole cells for adequate bioremediation of heavily contaminated sites and could be&nbsp; a source for new solvent-stable enzymes with different applications.