16S rRNA genes of bacterioplankton community: a field sample
All microeukaryotes larger than 0.8 m were excluded through 0.8-m Isopore membrane filters (Millipore, Massachusetts, USA).Then 0.3-m  Isopore membrane filters were used to collected bacterioplankton. Filters were then transferred into autoclaved cryopreservation tubes and fully immersed by adding 1 mL Ambion RNAlater to the filters. The entire cryopreservation tube was rapidly frozen in liquid nitrogen. After complete freezing, the tubes were transferred to a refrigerator at -80 for storage until RNA was extracted. The V4V5 region of the 16S rRNA gene was amplified by PCR using the primers 515F/926R (Parada et al. 2016).