Abundance and Spatial Distribution of Aerobic Anoxygenic Phototrophic Bacteria in Tama River, Japan

• Main Authors: Yuki Sato-Takabe, Setsuko Hirose, Tomoyuki Hori, Satoshi Hanada
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Water
• Subjects: aerobic anoxygenic phototrophic bacteria; river; bacteriochlorophyll
• Online Access: https://www.mdpi.com/2073-4441/12/1/150

Aerobic anoxygenic phototrophic bacteria (AAnPB) are widely distributed and regarded as key players driving the carbon cycle in surface water of global oceans, coastal and estuary areas and in other freshwater environments (e.g., ponds and lakes). However, the abundance and spatial distribution of AAnPB in rivers is much less well-known. Here we investigated the variation of the absolute cell abundances of the total bacteria, AAnPB and cyanobacteria, at four different sites in Tama River, Japan, and the spatial distribution (i.e., free-living or particle-attached existence form) of AAnPB at two out of the four sites using infra-red epifluorescence microscopy. Free-living cell abundances for the total bacteria, AAnPB and cyanobacteria were 1.6−3 × 10⁵, 1.5−4.4 × 10⁴ and <3.2 × 10⁴ cells mL^−1, respectively. The free-living AAnPB accounted for 6.1%−19.6% of the total bacterial abundance in the river. The peaks of the AAnPB and cyanobacteria abundances were found at the same site, suggesting that the AAnPB could potentially coexist with cyanobacteria. Meanwhile, the particle-attached AAnPB were observed at the two sites of the river, accounting for 52.2% of the total bacteria abundance in the particle. Our results showed the existence and aggregation form of AAnPB in the riverine environment.