Powell S J, Prosser J I
Department of Molecular and Cell Biology, University of Aberdeen, Marischal College, UK.
J Gen Microbiol. 1991 Aug;137(8):1923-9. doi: 10.1099/00221287-137-8-1923.
Nitrate production by Nitrosomonas europaea in inorganic liquid medium containing ammonium was limited by reduction in pH. In the presence of montmorillonite and vermiculite, expanding clays with high cation-exchange-capacity (CEC), nitrite yield was increased, ammonia oxidation continued at pH values below those which inhibited growth in the absence of clays and growth was biphasic. The first phase was similar to that in the absence of clays, while the second was characterized by a lower rate of nitrite production. Illite, a non-expanding clay with low CEC, had no significant effect on ammonia oxidation, while oxidation of ammonia-treated vermiculite (ATV) occurred with no significant change in the pH of the medium. ATV, montmorillonite and vermiculite, but not illite, protected cells from inhibition by nitrapyrin at concentrations inhibitory to cells growing in suspended culture. This protection was maintained in ATV homo-ionic to Al3+, but montmorillonite made homo-ionic to Al3+ did not provide protection from inhibition. Attachment of cells to clays with high CEC is therefore advantageous in providing exchange at the clay surface of NH+4 and H+ produced by ammonia oxidation, in reducing pH toxicity, and in protecting cells from inhibition.
欧洲亚硝化单胞菌在含有铵的无机液体培养基中产生硝酸盐受到pH值降低的限制。在蒙脱石和蛭石（具有高阳离子交换容量（CEC）的膨胀性黏土）存在的情况下，亚硝酸盐产量增加，在低于无黏土时抑制生长的pH值下氨氧化仍继续进行，且生长呈双相性。第一阶段与无黏土时相似，而第二阶段的特征是亚硝酸盐产生速率较低。伊利石是一种具有低CEC的非膨胀性黏土，对氨氧化没有显著影响，而氨处理蛭石（ATV）的氨氧化发生时培养基pH值无显著变化。ATV、蒙脱石和蛭石，但不是伊利石，在对悬浮培养中生长的细胞有抑制作用的浓度下能保护细胞免受硝吡啉的抑制。这种保护作用在与Al3+同离子的ATV中得以维持，但与Al3+同离子的蒙脱石则不能提供免受抑制的保护。因此，细胞附着于具有高CEC的黏土有利于在黏土表面进行氨氧化产生的NH+4和H+的交换，降低pH毒性，并保护细胞免受抑制。
