| Abstrak/Abstract |
This research aims to isolate and identify autochtonous nitrifying bacteria
from tilapia pond in Sleman Yogyakarta Indonesia for future application in aquaculture
practices in the region. Bacteria were isolated using a nitrification medium. Bacterial
characterization was carried out by non-pathogenic test to tilapia (Oreochromis sp.), and
nitrification activity test in a single bacterial fermentation medium for 9 days. Bacterial
identification was carried out based on the colony and cell morphologies, biochemical
tests, and molecular analysis using the 16S rRNA and gyrB genes. A total of 15 isolates
of nitrifying bacteria were obtained. Four non-pathogenic isolates obtained the highest
nitrification activity on the sixth day of incubation, with nitrate production of 17.26-
21.54 ppm. Two selected bacteria, isolates A2 and A3, have colony morphology that is
milky white, smooth surface, circular shape, entire edge, and convex elevation. Both
bacteria are short rods, Gram-negative, non-motile, produce catalase, fermenting glucose,
sucrose, and lactose, and do not produce oxidase, ornithine decarboxylase, indole, and
H2S. Molecular analysis showed that the two isolates had the highest similarity (99.28%
and 99.34%) to Klebsiella spp. |
