Effects of nitrite on ammonia-nitrogen removal and nitrite-nitrogen as well as photopigment biosynthesis of Marichromatium gracile YL28

Abstract:

[Objective] To understand the adaptability of Marichromatium gracile YL28 to nitrite environment. [Methods] When YL28 was grown with nitrite as the sole nitrogen source or with nitrite-ammonium as coexisting nitrogen sources, the removal efficiency of ammonium-nitrogen and nitrite-nitrogen, the effect of nitrite on bacterial growth and total amounts of photopigments including carotenoids and bacterio chlorophylls were studied by spectrophotometry. The effect of nitrite on compositions of carotenoid and bacteriochlorophyll was investigated by thin layer chromatography. [Results] Strain YL28 was capable of growing with nitrite as the sole nitrogen sources; mainly accumulated two BChl a intermediates (BChl aTHGG and BChl ap), bacterio pheophytin (BPhe) and four carotenoids (rhodopin, spirilloxanthin, anhydro rhodovibrin and lycopene). Bacterial growth and nitrite removal efficiency were decreased with increasing nitrite concentration, more than 200 mg/L of nitrite could be completely removed by strain YL28. When nitrite concentration reached to 25 mg/L, the total amounts of carotenoid and bacteriochlorophyll were decreased dramatically, whereas the relative contents of BChl ap (end product of BChl a biosynthesis), spirilloxanthin (end product of carotenoids biosynthesis) and Bphe increased. When YL28 was grown with nitrite-ammonium as coexisting nitrogen source, the tolerance of YL28 to nitrite and removal efficiency of nitrite by YL28 were significantly enhanced compared with nitrite as the sole nitrogen source, more than 300 mg/L of nitrite was completely eliminated by strain YL28. The inhibitory of nitrite on photopigment biosynthesis was alleviated, the total amounts of carotenoid and bacteriochlorophyll were enhanced, the changes in photopigment compositions were similar to those with nitrate as the sole nitrogen sources. [Conclusion] YL28 could remove nitrite. High concentration nitrite inhibited bacterial growth and photopigment biosynthesis, but the presence of ammonium together with nitrite could promote the tolerance of strain YL28 to nitrite. This work should be helpful to develop novel marine water cleaner for high efficient removal of nitrite.