Hachicho Nancy, Birnbaum Astrid, Heipieper Hermann J
Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, 04318, Leipzig, Germany.
AMB Express. 2017 Dec;7(1):62. doi: 10.1186/s13568-017-0371-8. Epub 2017 Mar 15.
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.
已知浮游细胞和在表面生长的细胞（或作为菌落生物膜生长的细胞）在生长行为、细胞生理学、基因表达和应激耐受性方面存在显著差异。为了比较不同生长形式的应激行为，使用充分研究的模式生物恶臭假单胞菌mt-2进行了浮游生长的振荡培养和菌落生长的琼脂平板培养。将细胞暴露于氯化钠以引起渗透胁迫，这是细菌在土壤中生长时必须应对的一种主要环境应激源。与琼脂平板上生长的细胞在0.5M氯化钠时完全抑制生长相比，浮游细胞在0.7M氯化钠时更具耐受性。以水接触角测量的细胞表面疏水性，琼脂平板上生长的细胞（92°）显著高于浮游细胞（40°），并且在氯化钠存在下增加。琼脂平板上生长的细胞还显示出膜脂肪酸饱和度显著更高，且在氯化钠存在下增加。这些结果表明，浮游细菌和菌落生长的细菌在面对渗透胁迫时表现出不同的反应，这表明耐受性和适应机制取决于环境条件以及初始生理状态。
