Membrane fatty acids adaptive profile in the simultaneous presence of arsenic and toluene in <Emphasis Type="Italic">Bacillus</Emphasis> sp. ORAs2 and <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. ORAs5 strains |
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Authors: | Milva Pepi Hermann J Heipieper Janett Fischer Marcella Ruta Margherita Volterrani Silvano E Focardi |
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Institution: | (1) Department of Environmental Sciences, University of Siena, Via P.A. Mattioli, 4, 53100 Siena, Italy;(2) Department of Bioremediation, UFZ-Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany |
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Abstract: | Bacillus sp. ORAs2 and Pseudomonas sp. ORAs5, two arsenic-resistant bacterial strains previously isolated from sediments of the Orbetello Lagoon, Italy, were
tested for their adaptation to mixed contaminants on the level of membrane fatty acid composition. The two bacterial strains
were characterized by high levels of arsenic resistance, and Pseudomonas sp. ORAs5 was also shown to be solvent-tolerant. The bacterial strains were exposed to mixtures of two toxic compounds: arsenic
at fixed concentrations and toluene in variable amounts or, alternatively, toluene at constant values along with arsenic added
at variable concentrations. Both strains react to the contaminants by changing the composition of their membrane fatty acids.
Bacillus sp. strain ORAs2 showed a correlation between growth rate decreases and fatty acids degree of saturation increases in both
cases, although pointedly in the presence of 1, 2, and 3 mM of toluene and different additions of arsenic, counteracting membranes
fluidity induced by toxic compounds. In Pseudomonas sp. ORAs5, adaptive changes in membrane composition was observed both in terms of increases in the degree of saturation and
in the trans/cis ratio of unsaturated fatty acids in the presence of varying toluene and constant arsenic concentrations, whereas only minor
changes occurred with increasing arsenic and constant toluene concentrations. Thus, on the level of membrane composition,
Bacillus sp. ORAs2 showed a higher potential for adaptation to the presence of mixed pollutants, suggesting its probable suitability
for bioremediation purposes. |
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Keywords: | Bacillus Pseudomonas Fatty acids Membrane fluidity Homeoviscous adaptation cis/trans isomerization Orbetello Lagoon |
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