An Aquatic Bacterium That Lyses Cyanobacteria Associated with Off-Flavor of Channel Catfish (Ictalurus punctatus)

In laboratory studies a bacterium isolated from pond water lysed cells of selected cyanobacteria, including species of Anabaena and Oscillatoria. The bacterium was a Gram negative rod that produced yellow colonies when streaked on BG-11 medium supplemented with 6 g/liter tryptic soy broth and solidified with 1% agar. The DNA sequence for the 16S rRNA gene of the bacterium indicated a relationship to species of Xanthomonas, but the sequence homology of 95.58% indicated no definitive match for the genus. Shake-flask cultures of the bacterium produced approximately 3 × 109 plaque-forming units/ml of culture broth when grown in BG-11 medium plus 6 g/liter tryptic soy broth and assayed in lawns of Anabaena sp. (ATCC 27898). Seven days after the bacterium was inoculated to shake-flask cultures of algae and cyanobacteria, average reductions in chlorophyll a were 94 to 98% for Oscillatoria spp. (ATCC 29205, UTEX 1567, O. cf. chalybea (LA OC-1), UTEX 390, UTEX 1566), 77% for Lyngbya sp. (UTEX 386), and 13 to 98% for Anabaena spp. (ATCC 27892, ATCC 27893, ATCC 27898, ATCC 27211, UTEX 1609, and UTEX 377). No significant reductions in chlorophyll a were noted for Chlorella vulgaris (UTEX 26), Scenedesmus subspicatus (UTEX 2594), Selenastrum capricornutum (UTEX 1648), Microcystis aeruginosa (UTEX 2063), or Plectonema boryanum (ATCC 18200). The bacterium could be a potential microbial algicide for some cyanobacteria, particularly species of Anabaena and Oscillatoria that have been associated with off-flavor in commercially grown channel catfish, Ictalurus punctatus.