How do bacteria find the optimal concentration of oxygen
How do bacteria find the optimal concentration of oxygen
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DOI：
10.1016/0968-0004(83)90030-0
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发表时间：
1983-12
影响因子：
13.8
通讯作者：
B. L. Taylor
中科院分区：
文献类型：
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作者：
B. L. Taylor
好氧细菌通过利用它们的电子传输系统作为对氧气的积极行为反应(趋氧性)的传感器和不同的负趋气性的受体来避免氧气太少或氧气太多的双重危险。鼠伤寒沙门氏菌沿着氧气的梯度向上游，直到末端氧化酶(细胞色素o)被氧气饱和。如果细菌碰巧在坡度上游得太远，它们就会被高浓度的氧气排斥。正趋气性的机制与趋化性有很大的不同。对大多数化学物质的适应依赖于转导蛋白的甲基化，但对氧的适应独立于甲基化。微生物经常在土壤或死水等环境中发现，在这些环境中，氧气的可用性受到限制，而趋氧性提高了生存能力，这对氧气有很强的吸引力。即使氧气的初始浓度足以满足有氧代谢，细菌的指数增长和高效趋化也会导致氧气的耗尽。下面的示例说明了这一点。细菌趋化性是指细菌对潜在营养物质的吸引，以及对有害环境信号的化学物质的排斥。如果丝氨酸，一种强引诱剂，从颗粒扩散到Escherichia cob“或Sa/Mone//a鼠伤寒杆菌的培养物中，细菌将沿着丝氨酸的梯度向上游，并聚集在穗部周围。菌团中的细胞密度可达109个细菌/毫升，肉眼可见。细菌迅速氧化丝氨酸，直到氧气耗尽。从最近的空气/水界面扩散的氧气很可能不足以维持有氧代谢；例如，鼠伤寒沙门氏菌的培养(每毫升6×108个细胞)消耗氧气如此之快，以至于只有空气界面下第一毫米处的细菌是有氧的。如果没有有氧反应，聚集在丝氨酸颗粒周围的细菌将被困在丝氨酸梯度中，最终被剥夺有氧代谢的能量优势。空气趋化性刺激从低氧区域迁徙，
Aerobic bacteria avoid the twin dangers of too little oxygen or too much oxygen by utilizing their electron transport system as the sensor for a positive behavioral response to oxygen (aerotaxis) and a different receptor for negative aerotaxis. Salmonella typhimurium swims up a gradient of oxygen until the terminal oxidase (cytochrome o) is saturated by oxygen. If the bacteria happen to swim too far up the gradient they are repelled by the high oxygen concentrations. The mechanism of positive aerotaxis is quite different from chemotaxis. Adaptation to most chemicals is dependent on methylation of a transducer protein, but adaptation to oxygen is independent of methylation.Microorganisms are often found in an environment, such as soil or stagnant water, where the availability of oxygen is limited and survival is enhanced by aerotaxis, a strong attraction toward oxygen. Even if the initial concentration of oxygen is adequate for aerobic metabolism, the exponential growth and efficient chemotaxis of bacteria can result in depletion of oxygen. This is illustrated in the following example. Bacterial chemotaxis is the attraction of bacteria to potential nutrients, and repulsion by chemicals that signal a harmful environment~-5. If serine, a strong attractant, is diffusing from a particle into a culture of Escherichia cob" or Sa/mone//a typhimurium, the bacteria will swim up the gradient of serine and cluster around the panicle. The cell density in the cluster may reach 109 bacteria per ml and be visible to the naked eye. The bacteria rapidly oxidize the serine until the oxygen is depleted. Diffusion of oxygen from the nearest air/water interface is likely to be inadequate to maintain aerobic metabolism; for example, a culture of S. typhimurium (6 x 108 cells per ml) consumes oxygen so rapidly that only the bacteria in the first millimeter below the air interface are aerobic. Without an aerotactic response the bacteria clustered around the serine particle would become trapped in the serine gradient and eventually be deprived of the energetic advantage of aerobic metabolism. Aerotaxis stimulates migration away from a hypoxic region,