Holert Johannes, Hahnke Sarah, Cypionka Heribert
Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg Carl-von-Ossietzky-Straße 9-11, D-26111 Oldenburg, Germany.
Environ Microbiol Rep. 2011 Feb;3(1):136-141. doi: 10.1111/j.1758-2229.2010.00199.x.
In the present study we have investigated the influence of light and anoxia on the energetic state of the aerobic anoxygenic phototroph (AAP) Dinoroseobacter shibae. Respiration, chemiosmotic proton translocation and the adenylate energy charge (AEC) of the cells were measured comparing light versus dark and oxic versus anoxic conditions. Light caused a decrease of the respiration rates of washed cells. This might be a substitution rather than a direct inhibitory effect, because both photosynthesis and respiration contribute to the proton-motive force. As known from other AAPs, light alone did not induce proton translocation if applied to anoxic cell suspensions. However, additions of small oxygen pulses to anoxic cell suspensions caused two times more proton translocation in the light than in the dark. The AEC of the cells was measured by means of a modified luciferin-luciferase method. Growing cells of D. shibae kept an AEC of 0.93, indicating that the adenylate pool was highly phosphorylated. After harvesting and storing the cells under anoxic conditions for 2 h, the AEC dropped to 0.12. However, the cells remained reactive. Upon addition of oxygen, the AEC increased to its original value within 40 s by the formation of about 12 mM of intracellular ATP. There were no differences whether this recovery experiment was carried out in the dark or in the light. We conclude that D. shibae is able to change its energetic state not only in response to the light regime but also during oxic-anoxic transitions. Both responses appear suited to save in situ organic substrates and endogenous electron donors, thus enhancing the role of photosynthetic energy conservation.
在本研究中，我们调查了光照和缺氧对需氧不产氧光合细菌（AAP）希氏玫瑰杆菌（Dinoroseobacter shibae）能量状态的影响。通过比较光照与黑暗以及有氧与缺氧条件，测量了细胞的呼吸作用、化学渗透质子转运和腺苷酸能量电荷（AEC）。光照导致洗涤后的细胞呼吸速率下降。这可能是一种替代而非直接抑制作用，因为光合作用和呼吸作用都对质子动力势有贡献。正如从其他AAP中所知，如果将光照应用于缺氧细胞悬液，仅光照不会诱导质子转运。然而，向缺氧细胞悬液中添加少量氧气脉冲后，光照下的质子转运量比黑暗中多两倍。通过改良的荧光素 - 荧光素酶方法测量细胞的AEC。希氏玫瑰杆菌的生长细胞保持AEC为0.93，表明腺苷酸库高度磷酸化。在缺氧条件下收获并储存细胞2小时后，AEC降至0.12。然而，细胞仍具有活性。加入氧气后，细胞内ATP形成约12 mM，AEC在40秒内恢复到其原始值。无论该恢复实验是在黑暗还是光照下进行，均无差异。我们得出结论，希氏玫瑰杆菌不仅能够响应光照条件改变其能量状态，而且在有氧 - 缺氧转变过程中也能如此。这两种反应似乎都适合节省原位有机底物和内源性电子供体，从而增强光合能量守恒的作用。
