[Identification and characterization of a hypothermia nitrite bacterium Pseudomonas tolaasii Y-11]

Denitrifying bacteria play an important role in the biological nitrogen removal process. However, there are few studies about hypothermia nitrite denitrifying bacteria. We isolated a hypothermia and aerobic nitrite-denitrifying bacterium (named as Y-11) from the long-term flooded paddy soil. Aims of this paper were to clarify the phylogeny and denitrifying characteristics of strain Y-11.

Morphological observation, specific phospholipid fatty acid and 16S rRNA analysis were employed to identify strain Y-11. Denitrification characteristics of strain Y-11, such as temperature, shaking speed, initial pH and carbon source were investigated by using shaking culture in Erlenmeyer flask.

Strain Y-11 with high removal efficiency of nitrite and total nitrogen was identified as Pseudomonas tolaasii. The optimum conditions of Y-11 effectively removing nitrite nitrogen and total nitrogen were: initial pH7.0; 15 degrees C; shaking speed 200 r/min; inoculum size 1.5 x 10(8) CFU per 100 mL medium; sodium acetate as carbon source; and nitrite nitrogen 10 mg/L. Strain Y-11 can remove nitrite nitrogen and total nitrogen up to 100% and 61.28% within 48 h.

Strain Y-11 was identified as Pseudomonas tolaasii with its potential nitrite polluted water treatment during early winter and late spring.