Lasko D R, Schwerdel C, Bailey J E, Sauer U
Institute of Biotechnology, ETH Zürich, Switzerland.
Biotechnol Prog. 1997 Sep-Oct;13(5):519-23. doi: 10.1021/bp970075f.
Many metabolic byproducts have toxic effects on bacteria, and acetic acid is an excellent model for such molecules. The negative effects of acetate, which include decreased growth rates and specific productivities, appear for Escherichia coli at acetate concentrations lower than 5 g/L. Acetic acid bacteria, however, are naturally resistant to the detrimental effects of acetate in their surroundings; they remain active at acetate levels well over 40 g/L. This study investigated the response to acetate challenges by the naturally acetate-resistant bacteria Acetobacter aceti and Gluconobacter suboxydans to learn more about possible mechanisms of tolerance to otherwise toxic low molecular weight metabolites. Growth studies showed that the resistant bacteria grow more slowly in the presence of acetate but are not slowed nearly so much as is E. coli. In addition, two-dimensional gel electrophoresis (2DE) was applied to study the relative protein patterns of acetate-resistant bacteria during growth in the presence and absence of acetate. In each organism, growth in acetate-containing medium led to elevated levels of many stress response proteins. 2DE analysis of heat-shocked cultures was used to determine which were nonspecific. Elimination of those proteins that were also amplified following heat shock left only eight proteins, here designated acetate-specific stress proteins (Asps), which are overexpressed specifically in response to acetate. Three of these, AspA, AspB, and AspC, appear to be analogous in the two bacterial strains studied, based on their apparent pIs and molecular weights.
许多代谢副产物对细菌具有毒性作用，乙酸就是这类分子的一个典型例子。乙酸盐的负面影响包括生长速率和比生产率降低，对于大肠杆菌而言，当乙酸盐浓度低于5 g/L时就会出现这些影响。然而，醋酸菌对其周围环境中的乙酸盐的有害影响具有天然抗性；它们在乙酸盐水平远超过40 g/L时仍保持活性。本研究调查了天然耐乙酸盐细菌醋酸杆菌和氧化葡萄糖杆菌对乙酸盐挑战的反应，以更多地了解对原本有毒的低分子量代谢物的耐受机制。生长研究表明，抗性细菌在乙酸盐存在的情况下生长较慢，但不像大肠杆菌那样受到很大影响。此外，二维凝胶电泳（2DE）被用于研究抗性细菌在有乙酸盐和无乙酸盐存在下生长期间的相对蛋白质模式。在每种生物体中，在含乙酸盐的培养基中生长导致许多应激反应蛋白水平升高。对热休克培养物进行2DE分析以确定哪些是非特异性的。去除那些在热休克后也被扩增的蛋白质后，只剩下8种蛋白质，这里称为乙酸盐特异性应激蛋白（Asps），它们是专门针对乙酸盐而过度表达的。基于它们的表观pI和分子量，其中三种，即AspA、AspB和AspC，在研究的两种细菌菌株中似乎是类似的。
