Abstract:
Free-living nitrogen fixing bacteria is a group of bacteria that can fix
nitrogen from the atmosphere and change it into ammonium without the help of
other organisms. These bacteria have been known to be resistance to various
metals. Iron (Fe) is a micro-nutrient needed by plants for their growth and
development. However, the high level of iron can lead to toxicity to others living
things. This research aimed to know the resistance of these bacteria to iron so they
could be used as bioremediation and biofertilizer agent. Thirteen free-living
nitrogen fixing bacteria were NR 10, NR 12, NR 15, NR 18, NR 19, NR 22, NR
24, NR 27, NR 28, NR 30, NR 31, R 41 and R 47. Each bacteria was grown on
Nitrogen Free Bromothymolblue (NFB) medium with various iron concentrations
(200, 300, 400, 500, 700, 900 and 1000 ppm). The growth of these bacteria was
analyzed descriptively by observing their colony growth on streak quadrant line
and the color-change of the medium. Three bacterial isolates that grew well in
1000 ppm concentration were NR 27, NR 28, and NR 31.
