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Adaptative Response of Shewanella Putrefaciens and Pseudomonas Aeruginosa to Toxic Organic Solvents

ABSTRACT Organic solvents are compounds with high toxicity for the bacterial cells, and, as a result of their partition in lipid bilayer, they produce considerable modifications in the structure and functions of the membranes. Two bacterial strains, Shewanella putrefaciens IBBCt4 and Pseudomonas aeruginosa IBBCt5 which are tolerant to organic solvents (alkanes, aromatics) were isolated from Constanta harbor. Alkanes (i.e., n-hexane, n-decane) with logarithm of partition coefficient between n-octanol and water mixture (log POW) between 3.86 and 5.98, were less toxic for Shewanella putrefaciens IBBCt4 and Pseudomonas aeruginosa IBBCt5, compared to aromatics (i.e., toluene, styrene, xylene isomers, ethylbenzene, propylbenzene) with log POWbetween 2.64 and 3.69. Cell tolerance, cells viability, adhesion and β-galactosidase activity of Shewanella putrefaciens IBBCt4and Pseudomonas aeruginosa IBBCt5 in the presence of 1% (v/v) organic solvents (alkanes, aromatics) depends not only on their physicochemical properties, but also on the specific response of the cells, and the cellular response is not the same for these two Gamma-Proteobacteria. The lipolytic and proteolitic enzymes were produced in higher quantity by Pseudomonas aeruginosa IBBCt5 cells in the presence of 1% (v/v) organic solvents, compared with the enzymes produced by Shewanella putrefaciens IBBCt4. The results indicated that Pseudomonas aeruginosa IBBC5 is more tolerant to organic solvents than Shewanella putrefaciens IBBct4, although both bacterial strains posses HAE1 transporter genes and harbor plasmids.