Impact of potent bioremediation enhancing plant extracts on Raoultella ornithinolytica properties.

Long-term contact of microorganisms with different compounds in the environment can cause significant changes in cell metabolism. Surfactants adsorption on cell surface or incorporation in the cell membrane, lead to their modification, which helps microorganisms adopt to the conditions of metabolic stress. The main objective of this study was to investigate the effects of three saponin-reach plant extracts from Hedera helix, Saponaria officinalis and Sapindus mucorossi on growth and adaptation of Raoultella ornithinolytica to high concentrations of these substances. For this purpose we investigated cell surface properties, membrane fatty acids and genetic changes of the microorganisms. The results revealed that prolonged exposure of the microorganisms to high concentrations of these surfactants can induce genetic changes of their genes. Moreover, the adaptation to contact with high concentrations of saponins was also associated with changes in composition of fatty acids responsible for the stabilisation of membrane structure and the increase in membrane permeability. The changes affected also the outer layer of cells. A significant increase (p < 0.05) in the cell surface hydrophobicity of tested strain was also observed. The cells after long-term contact with S. officinalis and S. mucorossi acquire properties that may be favourable in hydrophobic substances bioremediation.

Hydrocarbon-induced changes in proteins and fatty acids profiles of Raoultella ornithinolytica M03.

Microorganisms can support environmental restoration by biodegradation of hydrocarbons but the mechanism of this process has been not described in detail yet. We present the effect of benzene derivatives on Raoultella ornithinolytica M03 cell composition. Comparison of the cell response after short-term and long-term stress revealed significant differences in surface properties, fatty acid composition and proteins profile. R. ornithinolytica M03 after long-term stress was characterized by lower cell surface hydrophobicity and much higher inner membrane permeability. Also decrease in the content of branched and unsaturated fatty acids was observed. Cells after short- and long-term stress were characterized by analyses of changes related to thirty-nine proteins participating in various metabolic pathways. The presence of benzene derivatives resulted in modifications in the abundance of proteins involved in determination of cell shape and ability to ion transport, lipid biosynthesis, amino-acid biosynthesis, tRNA ligases, chaperone and TCA cycle proteins, gluconeogenesis, transcription and nucleotide synthesis. Uptake and transport associated proteins, cell properties and membrane stability were also found to differ in the cells after short- and long-term stress suggesting the use of different mechanisms for transport and biodegradation of benzene derivatives and modification of cell response depending on the length of exposure to the stressor. BIOLOGICAL SIGNIFICANCE: This is the first comprehensive study whose results may contribute to a better understanding of the changes occurring during short- and long-term contact with benzene derivatives. After long term stress R. ornithinolytica M03 was characterized by lower cell surface hydrophobicity and much higher inner membrane permeability and decrease in the content of branched and unsaturated fatty acids. We identified changes related to multiple proteins engaged in various metabolic pathways such as biogenesis of cell membrane/wall, amino-acid biosynthesis, nucleotide and protein synthesis, gluconeogenesis and tRNA ligases. Changes in proteins participating in uptake and transport associated proteins, cell properties and membrane stability indicate modifications in transport and biodegradation of benzene derivatives, connected with the length of exposure to the stressor. The provided results seem to constitute an important aspect of remediation techniques.