Physiological Changes Associated with Bacterial Assimilation of Synthetic Polymer
Fusako KAWAI*a, Shogo ENOKIBARAb, Rie HIROTAc, Takashi UEDAc, and Kazuyoshi KAWAHARAd
a Research Institute for Bioresouorces, Okayama University, 2-20-1 Chuo, Kurashiki 710, Japan
b Department of Biology, Kobe University of Commerce, 8-2-1 Gakuen-Nishimachi, Nishi- Ku, Kobe 651-21, Japan
c Faculty of Nutrition, Kobe-Gakuin University, 518 Arise, Igawadani-cho, Nishi-ku, Kobe 651-21, Japan
d Shirokane, Minato-ku, Tokyo 108, Japan
Polyethylene glycol (PEG) is a xenobiotic polymer which is soluble in water and organic solvents. Although some PEGs have bigger molecular sizes than those allowed for the hydrophilic transport into cells via porins they were suggested to be intracellularly degraded. The study of physiological changes of bacterial membranes associated with bacterial assimilation of PEG promises to provide us with new information about the transport system of synthetic polymers and the adaptation of bacteria to a xenobiotic polymer. All the PEG 4000 and 20,000-utilizing bacteria which we have isolated were identified as Sphingomonas species, suggesting that specific membrane structures of the genus might be associated with the incorporation of the polymer.
S. terrae, S. macrogoltabidus 103, Sphingomonas sp. K1 and N6 clearly showed the changes of cellular surface, size and composition associated with growth carbons. S. macrogoltabidus 203 did not show the changes with carbon sources and thought to be a mutant. The increment of sphingolipids in the outer membranes seemed to solve PEG faster and the wrinkled surface area caused by decreased membrane proteins seemed to increase the adsorption of PEG onto cells. PEG is possibly incorporated into cells by a hydrophobic pathway derived from the hydrophobicity of the membranes.
