College of Marine Studies, and School of Life and Health Sciences, University of Delaware, 19711, Newark, Delaware.
Microb Ecol. 1980 Jun;6(2):161-71. doi: 10.1007/BF02010555.
The effects of several fixed nitrogen compounds on acetylene reduction activity (nitrogen fixation) of surface sediments from a Delaware salt marsh were studied. Ammonia addition caused little decrease in activity early in the summer but resulted in a considerable decrease (85-95%) in activity late in the summer and early in the fall. Nitrate caused a near complete suppression of activity at all times. Other compounds such as glutamate, urea, and yeast extract caused a slight increase in activity in tallSpartina sediments and caused more than a 2.5-fold increase in shortSpartina sediments. There was a lag period (1-2 days) before the commencement of in vitro acetylene reduction activity during the spring and early summer, but this lag period was not present in the late summer. The addition of chloramphenicol to samples from a shortSpartina zone caused decreases in activity similar to those obtained with ammonia, whereas chlorate amendments yielded results which, when compared on an electron basis, were comparable to those obtained with nitrate. These results indicated that the observed lag period may be the result of a physiological response to the in situ levels of ammonia and/or nitrate. It is suggested here that in situ nitrogenase activity may be controlled by two processes: (a) repression and derepression of nitrogenase synthesis mediated by the levels of ammonia, and (b) competition for reducing power (electrons) and energy (ATP) between the processes of nitrate reduction and nitrogen fixation.
几种固定氮化合物对特拉华盐沼表层沉积物乙炔还原活性（固氮）的影响进行了研究。氨的添加在夏季早期几乎没有降低活性，但在夏季后期和秋季早期导致活性显著降低（85-95%）。硝酸盐在任何时候都几乎完全抑制了活性。其他化合物，如谷氨酸、尿素和酵母提取物，在高盐沼沉积物中略微增加了活性，并使短盐沼沉积物的活性增加了 2.5 倍以上。在春季和初夏，体外乙炔还原活性开始前有一个滞后期（1-2 天），但在夏末不存在滞后期。向短盐沼区样本中添加氯霉素会导致活性下降，类似于添加氨的情况，而添加氯酸盐的结果则与添加硝酸盐的结果相比，在电子基础上是可比的。这些结果表明，观察到的滞后期可能是对原位氨和/或硝酸盐水平的生理反应的结果。这里提出的观点是，原位固氮酶活性可能受到两个过程的控制：（a）由氨水平介导的固氮酶合成的抑制和去抑制，以及（b）硝酸盐还原和固氮之间的竞争还原力（电子）和能量（ATP）。
