Use of Purple Non-Sulfur Photosynthetic Bacteria (Rhodobacter sphaeroides) in Promoting Ciliated Protozoa Growth

Photosynthetic bacterium (PSB) was isolated from sediment samples of Yamagawa Bay, Kagoshima, Japan. Phylogenetic analysis results of PSB isolate were closely related to Rhodobacter sphaeroides, purple non-sulfur photosynthetic bacteria (PNSB). Pink-colored smooth edges of single bacterial colonies were observed after 3-5 days of incubation period on Basic I medium agar plates. Rhodobacter sphaeroides microscopic examination showed a short rod cell (1-2 mu m length) with round ends. Sediment and water samples used for ciliates cultivation were collected from Kuwano-ura Bay, Koshiki Island, Japan. Ciliates were cultivated using fish meal with radish leaves medium (MI), with sediment into MI (MII) and algae media (MIII). The use of the algae media (MIII) in cultivation mixture produced the highest total number of ciliates. Big size ciliates were identified as Euplotes minuta and Cyclidium varibonneti, while small size was identified as Micrometopion nutans, based on PCR-DGGE. When ciliates were cultured with the PSB isolate, Rhodobacter sphaeroides as a feed, ciliates grow to 2,081 individual ml(-1) 72 hrs later. These findings indicate that PNSB can be used to promote ciliates growth.