Alvarez Héctor M, Silva Roxana A, Cesari Ana C, Zamit Ana L, Peressutti Silvia R, Reichelt Rudolf, Keller Ulrike, Malkus Ursula, Rasch Christiane, Maskow Thomas, Mayer Frank, Steinbüchel Alexander
Departamento de Bioquímica, Facultad de Ciencias Naturales, Universidad Nacional de la Patagonia San Juan Bosco, (9000) Comodoro Rivadavia, Argentina.
FEMS Microbiol Ecol. 2004 Nov 1;50(2):75-86. doi: 10.1016/j.femsec.2004.06.002.
Rhodococcus opacus PD630 was investigated for physiological and morphological changes under water stress challenge. Gluconate- and hexadecane-grown cells were extremely resistant to these conditions, and survival accounted for up to 300 and 400 days; respectively, when they were subjected to slow air-drying. Results of this study suggest that strain PD630 has specific mechanisms to withstand water stress. Water-stressed cells were sensitive to the application of ethanol, high temperatures and oxidative stress, whereas they exhibited cross-protection solely against osmotic stress during the first hours of application. Results indicate that the resistance programme for water stress in R. opacus PD630 includes the following physiological and morphological changes, among others: (1) energetic adjustments with drastic reduction of the metabolic activity ( approximately 39% decrease during the first 24 h and about 90% after 190 days under dehydration), (2) endogenous metabolism using intracellular triacylglycerols for generating energy and precursors, (3) biosynthesis of different osmolytes such as trehalose, ectoine and hydroxyectoine, which may achieve a water balance through osmotic adjustment and may explain the overlap between water and osmotic stress, (4) adjustments of the cell-wall through the turnover of mycolic acid species, as preliminary experiments revealed no evident changes in the thickness of the cell envelope, (5) formation of short fragmenting-cells as probable resistance forms, (6) production of an extracellular slime covering the surface of colonies, which probably regulates internal and external changes in water potential, and (7) formation of compact masses of cells. This contributes to understanding the water stress resistance processes in the soil bacterium R. opacus PD630.
研究了食油红球菌PD630在水分胁迫挑战下的生理和形态变化。以葡萄糖酸盐和十六烷为生长底物的细胞对这些条件具有极强的抗性，在缓慢风干的情况下，其存活时间分别可达300天和400天。本研究结果表明，菌株PD630具有耐受水分胁迫的特定机制。水分胁迫下的细胞对乙醇、高温和氧化胁迫敏感，而在胁迫处理的最初几个小时内，它们仅表现出对渗透胁迫的交叉保护作用。结果表明，食油红球菌PD630中水分胁迫的抗性程序包括以下生理和形态变化等：（1）能量调整，代谢活性急剧降低（脱水条件下，最初24小时内约降低39%，190天后约降低90%）；（2）利用细胞内三酰甘油进行内源性代谢以产生能量和前体；（3）生物合成不同的渗透保护剂，如海藻糖、四氢嘧啶和羟基四氢嘧啶，它们可通过渗透调节实现水平衡，这可能解释了水分胁迫和渗透胁迫之间的重叠；（4）通过分枝菌酸种类的更新来调整细胞壁，初步实验表明细胞包膜厚度没有明显变化；（5）形成短的碎片化细胞作为可能的抗性形式；（6）产生覆盖菌落表面的细胞外黏液，这可能调节水势的内部和外部变化；（7）形成紧密的细胞团块。这有助于理解土壤细菌食油红球菌PD630中的水分胁迫抗性过程。
