Diel variations in frequency of dividing cells and abundance of aerobic anoxygenic phototrophic bacteria in a coral reef system of the South China Sea

Abstract

With the ability of photoheterotrophic metabolism, aerobic anoxygenic phototrophic (AAP) bacteria are an important bacterial group in the marine microbial community. We investigated the diel variations of AAP bacteria in the coral reef water of the South China Sea, and report, for the first time, the frequency of dividing cells (FDC) of AAP bacteria. Our results showed that AAP bacte- rial abundance ranged from 1.54 × 10 4 ± 3.21 × 10 2 to 3.59 × 10 4 ± 3.04 × 10 3 cells ml -1 . The diel pat- tern of AAP bacterial abundance had 2 peak values, one at night around 21:00 h and the other in the daytime at around 9:00 h. Tidal current and light were the primary factors controlling the diel varia- tions of AAP bacteria in this area during our study period. FDC values in AAP and total bacteria were both higher during the night than during the day. The FDC values in AAP bacteria (3.53 ± 1.09 to 9.43 ± 0.80%) were significantly higher than those in total bacteria (1.06 ± 0.06 to 3.14 ± 1.38%), indicat- ing higher growth rate of AAP bacteria than total bacteria in the study area.