紫色土硝化过程中氨氧化细菌和古菌对温度的响应

Responses of Ammonia Oxidizing Bacteria and Archaea to Different Temperatures during Nitrification Process in a Neutral Purple Soil

采用室内恒温培养法,探究4℃、15℃、28℃和40℃条件下中性紫色土硝化作用的差异及氨氧化细菌(AOB)和氨氧化古菌(AOA)对不同温度的响应模式。结果表明:28℃条件下硝化作用最强,净硝化率为3.40 mg N kg^(-1) d^(-1),40℃条件下硝化作用较弱,净硝化率为1.52 mg N kg^(-1) d^(-1),15℃条件下硝化作用发生延迟,净硝化率为2.40 mg N kg^(-1) d^(-1),4℃条件下硝化作用被抑制。28℃条件下的硝化动力学过程符合一级动力学模型(R2为0.996),15℃和40℃条件下的硝化动力学过程符合零级动力学模型(R2分别为0.969和0.984),说明15℃和40℃条件下限制硝化作用的因子可能是硝化微生物活性。AOB amoA基因拷贝数在28℃条件下达到最大,而AOA amoA基因拷贝数在40℃条件下达到最大。AOA和AOB amoA基因拷贝数在培养期间的变化表明AOB和AOA可能在中性紫色土硝化作用中共同发挥作用。在培养过程中,AOA与AOB amoA基因拷贝数之比在15℃和28℃条件下,由1 d时的7.38和8.92下降为28 d时的1.51和2.12,呈显著降低趋势(P <0.05);在40℃条件下,AOA与AOB amoA基因拷贝数之比在培养过程中呈先显著升高后降低的趋势(P <0.05)且显著高于4℃、15℃和28℃三个温度条件(P<0.05);而4℃条件下AOB和AOA amoA活性均受到抑制。相比于AOB,AOA可能更适应高温环境。

The laboratory incubation experiment was carried out to investigate the responses of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) to different temperatures (4 ℃, 15 ℃, 28 ℃ and 40 ℃) in a neutral purple soil. The results showed that the nitrification was the highest at 28 ℃, with a net nitrification rate of 3.40 mg N kg^-1 d^-1 . It was depressed at 40 ℃ (net nitrification rate of 1.52 mg N kg^-1 d^-1 ) and was delayed at 15 ℃ (net nitrification rate of 2.40 mg N kg^-1 d^-1 ), but was inhibited at 4 ℃. Nitrification process was best fitted with the first-order kinetic model at 28 ℃ (R 2 = 0.996), and with zero-order kinetic model at 15 ℃ and 40 ℃ (R 2 = 0.969 and 0.984, respectively), which indicated that microbial activity may be the limiting factor of nitrification at 15 ℃ and 40 ℃. The amoA gene copy numbers of AOB reached the maximum values at 28 ℃, however, those of AOA was the highest at 40 ℃. The change in amoA gene copy numbers of AOA and AOB during the incubation indicated that both AOB and AOA control the nitrification in this neutral purple soil. During the incubation, the ratio of the amoA gene copy numbers of AOA to those of AOB at 15 ℃ and 28 ℃ was 7.38 and 8.92, respectively at day 1, and it decreased to 1.51 and 2.12, respectively (P<0.05) at the end of incubation. This ratio at 40 ℃ significantly increased first (P < 0.05) and then decreased. And the ratio of the amoA gene copy numbers of AOA to those of AOB was significantly higher at 40 ℃ than that at 4 ℃, 15 ℃ and 28 ℃ (P < 0.05). The amoA activities of AOB and AOA at 4 ℃ were both inhibited. Compared to AOB, AOA may be more suitable to high temperature environment.