title: Osmotic stress in colony and planktonic cells of Pseudomonas putida mt-2 revealed significant differences in adaptive response mechanisms.
abstract: Planktonic cells and those grown on surfaces (or as colony biofilm) are known to show significant differences regarding growth behavior, cell physiology, gene expression and stress tolerance. In order to compare stress behavior of different growth forms, shake cultures for planktonic growth and agar plate cultivation for colony growth, were carried out with the well investigated model organism, Pseudomonas putida mt-2. Cells were exposed to sodium chloride to cause osmotic stress as one main environmental stressor bacteria have to cope with when growing in soil. Planktonic cells were more tolerant with a complete inhibition of growth at 0.7 M NaCl, compared to 0.5 M for agar-grown cells. Cell surface hydrophobicity, measured as water contact angles, was significantly higher for agar-grown cells (92°) than for planktonic cells (40°), and increased in the presence of NaCl. Agar-grown cells also showed a significantly higher degree of saturation of membrane fatty acids that increased in the presence of NaCl. These results demonstrate that planktonic and colony grown bacteria show different responses when confronted with osmotic stress suggesting that the tolerance and adaptive mechanisms are dependent on the environmental conditions as well as the initial physiological state.
authors.affiliation: Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, 04318, Leipzig, Germany.
authors.forename: Nancy
authors.initials: N
authors.lastname: Hachicho
authors.affiliation: Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, 04318, Leipzig, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Birnbaum
authors.affiliation: Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, 04318, Leipzig, Germany. hermann.heipieper@ufz.de.
authors.forename: Hermann J
authors.initials: HJ
authors.lastname: Heipieper
keywords: Agar grown cells; Cell surface hydrophobicity; Membrane fatty acids; Osmotic stress; Planktonic cells; Pseudomonas putida; Stress response