湖泊沉积物中氨氧化微生物的amoA基因数量

采用定量PCR方法测定了4个湖泊沉积物中氨氧化微生物的amoA基因数量,并分析了其与环境因子之间的关系. 结果表明:小南湖AOA(氨氧化古菌)和AOB(氨氧化细菌)的amoA基因数量最多,分别达2.1×104和2.8×103copies/g(以干质量计,下同)；梁子湖仅检测到了AOA amoA基因的存在,平均值为4.9×103copies/g. 东湖和汤逊湖的AOA amoA基因数量比较接近,约为3.0×103copies/g,然而AOB的amoA基因数量在这2个湖泊中仅分别为37和86copies/g；在这些采样点中,AOA的amoA基因数量是AOB的3~278倍. 统计分析发现,随着湖泊营养水平和间隙水中ρ(NH₄+)的上升,AOA和AOB的amoA基因数量均呈增加趋势,但ρ(NH₄+)增加对AOB的促进作用要大于AOA,导致AOA和AOB的amoA基因数量比值与间隙水中ρ(NH₄+)呈显著负相关. pH上升对2类氨氧化微生物的抑制作用则与ρ(NH₄+)增加对它们的促进作用相反. 沉积物中amoA基因数量与间隙水中ρ(NO₂-)无显著相关性,但与ρ(NO₃-)呈显著正相关. 由于ρ(NH₄+)与ρ(DO)之间呈显著负相关,因此认为ρ(DO)与氨氧化微生物amoA基因数量之间的显著负相关可能更多的是对ρ(NH₄+)与氨氧化微生物amoA基因数量之间紧密关系的一种间接反应. 

Abundance of amoA Genes of Ammonia Oxidizing Microorganisms in Lake Sediments

The abundance of amoA genes of ammonia oxidizing microorganisms in sediments from four lakes in central China was quantified using the quantitative polymerase chain reaction (qPCR), and their relationships with environmental factors were analyzed. The results showed that the number of amoA gene of ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) was the most abundant in the Lake Xiaonanhu, with average values of 2.1×104and 2.8×103copies/g in the dry sediment, respectively. In the Lake Liangzi, only AOA were detected. The average gene number was 4.9×103copies/g for dry sediment. The mean number of AOA amoA gene in the lakes of Donghu and Tangxun was about 3.0×103copies/g. The average number of AOB amoA gene, however, was only 37and 86copies/g for the two lakes respectively. At all sampling sites, the number of amoA gene of AOA was about 3-278times that of AOB. The statistical analysis showed that both gene abundances of AOA and AOB increased with the increasing ρ(NH₄+) (for AOA, R=0.646, P<0.01; AOB, R=0.903, P<0.01), but AOB were more favored by this increase, resulting in a significant negative relationship between the ratio of AOA/AOB and ρ(NH₄+) (R=-0.685, P<0.01). Compared to the more positive effects of increased ρ(NH₄+) on AOB over AOA, a reverse negative impact of increased pH on ammonia oxidizing microorganisms was found. The abundance of amoA gene in the sediments was significantly and positively correlated with ρ(NO₃-) in the pore water (for AOA, R=0.614, P<0.05; AOB, R=0.804, P<0.01). However, no significant relationship was found for ρ(NO₂-) (P>0.05). Since a significant and negative relationship was found between ρ(NH₄+) and ρ(DO) (R=-0.641, P<0.008), the negative relationship between the abundance of amoA genes and ρ(DO) (for AOA, R=-0.520, P<0.05; AOB, R=-0.647, P<0.05) might be an indirect reflection of the intense association of ρ(NH₄+) and the abundance of amoA genes.