Fig. 3.

Abundance of AOA amoA, AOB amoA, AOB 16S rRNA genes in the sediments of the Pearl River Estuary. qPCR was performed with three replicates for each sample. For AOA amoA gene, qPCR was conducted using FailSafe™ PCR Premix F and 0.5× SYBR® Green I (Invitrogen, Eugene, USA). For AOB 16S rRNA and amoA genes, PCR was performed using iQ™ SYBR® Green Super Mix. The qPCR thermocycling steps were set as follows: 95°C for 4 min and 45 cycles at 95°C for 45 s, 55°C for 45 s, and 72°C for 45 s. After qPCR assay, the specificity of amplification was verified by melting curve analysis and checking with agarose gel electrophoresis