Heterotrophic nitrification by a thermophilicBacillusspecies as influenced by different culture conditions

Abstract

The nitrification activity of a thermophilic heterotrophic bacterium, Bacillus MS30 isolated from a deep-sea hydrothermal vent, was studied under various growth conditions. Nitrification was estimated from the nitrogen balance calculations in the culture media. The results showed that this isolate actively nitrified in culture conditions similar to those prevailing in hydrothermal sites. Therefore, its ecological significance was considered. In standard aerobic conditions, MS30 produced nitrite from ammonia and acetate (1.13 mumol NO2-.mg-1 dry wt), but nitrate was never produced, and a low nitrite reduction was often observed. Higher nitrification activities were observed in defined optimal conditions (simple carbon substrate, 65 degrees C, pH 7.5, and 15 g sea salts.L-1). In addition, discrepancies between the optima for growth and nitrification were observed, showing the ability of MS30 to adapt to changing environmental conditions typical of hydrothermal sites.

Physiological and molecular biological characteristics of heterotrophic ammonia oxidation by Bacillus sp. LY

“…This shows that when the cells actively grow, the nitrogen will be converted to biomass nitrogen rather than NO x --N. A similar phenomenon has previously been described (Mével and Prieur 2000). That means that heterotrophic nitrifiers may give lower growth yields when actively nitrifying (Robertson and Kuenen 1988;Robertson et al 1989;Mével and Prieur 2000). In our culture, high cell growth may lead to oxygen depletion in the medium.…”

“…With all three COD Cr /TN ratios in our experiments, about 48.8-59.8% of N input was nitrified and almost 100% of the nitrification products were denitrified accordingly, which indicates that nitrification may be the speed limited step in this procedure. Moreover, until now, it is impossible to say whether the falling yield was due to the osmotic effect of the carbon source, sheer overload of the electron transport system, or something else, such as oxygen limitation (Mével and Prieur 2000), but the results clearly show that nitrification was inhibited by high substrate concentrations and was peaked in the poorest medium.…”

Simultaneous Heterotrophic Nitrification and Aerobic Denitrification by the Marine Origin Bacterium Pseudomonas sp. ADN-42

“…Nar was more sensitive to oxygen inhibition. Most aerobic denitrifying bacteria mainly reduced NO 3 -into NO 2 − by Nap [9,20]. According to the results of this experiment, it could be inferred that certain increase of DO may promote the growth of the strains and denitrification, and the continuous low DO may be better for denitrification.…”

Isolation and characterization of a heterotrophic nitrifier Proteus mirabilis strain V7 and its potential application in NH4 +-N removal

“…The remaining NH 4 + -N in the supernatant was determined after inoculation at 30°C for 64 h. Data are the means of three independent experiments and are presented as means±SE Proteus mirabilis strain V7 possessed a much lower NH 4 + -N removal efficiency in the seawater matrix. According to a previous study by Wehrfritz et al (1993), the coenzyme Q involved in NH 4 + oxidization acquired an electron through oxidization of the supplied reducing organic carbon source during the heterotrophic nitrification process, and thus the organic carbon source exerted effects not only on the growth state but also on the nitrification activity of heterotrophic nitrifiers (Mevel and Prieur 2000). Thus, the low nitrification efficiency of Proteus mirabilis strain V7 in the 2216E medium may be due to the oligotrophic characteristic of the medium.…”