Respiratory Kinetics of Marine Bacteria Exposed to Decreasing Oxygen Concentrations
Respiratory Kinetics of Marine Bacteria Exposed to Decreasing Oxygen Concentrations
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DOI：
10.1128/aem.03669-15
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发表时间：
2016-03-01
影响因子：
4.4
通讯作者：
Revsbech, Niels Peter
中科院分区：
文献类型：
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作者：
Gong, Xianzhe;Garcia-Robledo, Emilio;Revsbech, Niels Peter
在有氧呼吸过程中，微生物通过使用不同类型的末端氧化酶消耗氧气（O-2），这些末端氧化酶对O-2具有广泛的亲和力。这些酶的O-2的Km值已被确定为在3至200 nmol/L（-1）的范围内。在这项研究中，我们研究了4种海洋细菌（Dinoroseophyshikiensis，Roseophyshikificans，Idiomarina loihiensis和Marinoroseophydaepoensis）在暴露于O-2浓度降低的过程中的有氧呼吸动力学的发展的时间过程。所有四个物种的基因组都有高亲和力和低亲和力末端氧化酶的基因。细菌的呼吸速率通过使用极其灵敏的光学痕量O-2传感器（范围，1至1，000纳摩尔升（-1））来测量。当暴露于亚微摩尔O-2浓度时，四个分离物中的三个显示出30至60 nmol L（-1）的表观Km值，但是当每个细胞的呼吸速率降低并且细胞大小由于饥饿而减小时，观察到的Km值降低至10 nmol L（-1）以下。第四个分离物在饥饿期间没有达到每个细胞的低呼吸速率，并且在整个实验中表现出约20 nmol/L（-1）的表观Km值。结果清楚地表明，不仅酶动力学可能会限制O-2的摄取，但也可能是个别细胞的扩散限制，这种扩散限制是最明显的高呼吸速率。由于有机碳的限制，细胞尺寸因饥饿而减小，从而更有效的扩散吸收也可能有助于降低表观Km值。
During aerobic respiration, microorganisms consume oxygen (O-2) through the use of different types of terminal oxidases which have a wide range of affinities for O-2. The Km values for O-2 of these enzymes have been determined to be in the range of 3 to 200 nmol liter(-1). In this study, we examined the time course of development of aerobic respiratory kinetics of four marine bacterial species (Dinoroseobacter shibae, Roseobacter denitrificans, Idiomarina loihiensis, and Marinobacter daepoensis) during exposure to decreasing O-2 concentrations. The genomes of all four species have genes for both high-affinity and low-affinity terminal oxidases. The respiration rate of the bacteria was measured by the use of extremely sensitive optical trace O-2 sensors (range, 1 to 1,000 nmol liter(-1)). Three of the four isolates exhibited apparent Km values of 30 to 60 nmol liter(-1) when exposed to submicromolar O-2 concentrations, but a decrease to values below 10 nmol liter(-1) was observed when the respiration rate per cell was lowered and the cell size was decreased due to starvation. The fourth isolate did not reach a low respiration rate per cell during starvation and exhibited apparent Km values of about 20 nmol liter(-1) throughout the experiment. The results clearly demonstrate not only that enzyme kinetics may limit O-2 uptake but also that even individual cells may be diffusion limited and that this diffusion limitation is the most pronounced at high respiration rates. A decrease in cell size by starvation, due to limiting organic carbon, and thereby more efficient diffusion uptake may also contribute to lower apparent Km values.