[Isolation and Nitrogen Removal Characteristics of Salt-tolerant Heterotrophic Nitrification and Aerobic Denitrification Bacteria Zobellella sp. B307].

A heterotrophic nitrification and aerobic denitrification strain, B307, was isolated from the sediment of Jiaozhou Bay. The strain was identified by 16S rRNA sequence analysis, and its optimization condition and salt-tolerance characteristics were studied by single factor experiment. The denitrification effect in single or mixed nitrogen sources was investigated under optimum conditions. The results allowed the strain to be identified as Zobellella sp., based on 16S rRNA sequence analysis. The best carbon source was sodium succinate, and the optimum C/N was 5, the optimal initial pH was 9, and the optimal temperature was 35-40℃ respectively. After 12 hours, the NH4+-N and the NO3--N removal efficiencies were 98.35% and 99.75% in a mixed nitrogen source system. The removal efficiencies for NH4+-N and NO3--N were 97.67% and 94.39% within 24 hours when salinity was 75 g·L-1. The strain has highly efficient heterotrophic nitrification-aerobic denitrification ability and strong salt tolerance, which demonstrated that the strain has potential for extensive application for nitrogen removal in high salt wastewater.

[Effect of Silver Nanoparticles on Denitrification and Functional Gene Abundances of Sediment in Dagu River Estuary and Northwest of Jiaozhou Bay].

The influence of silver nanoparticles (AgNPs) on the denitrification performance, enzyme activity, and functional gene relative abundances of sediment was investigated based on the methods of laboratory simulation incubation in the Dagu River estuary and bay area in the northwest of Jiaozhou Bay. The different dosages of AgNPs (i.e., 0, 135, and 1350 mg·L-1 in final concentration) was added to the incubation system containing surface sediments and in-situ bottom water. During six days' incubation, the concentrations of NO3- and NO2-, NO3-, and NO2- reductases activity, and relative abundances of narG and nirS genes were measured to explore the effects of AgNPs on denitrification and its mechanism. The results showed that AgNPs significantly inhibited NO3- and NO2- reductive capacity, NO3- and NO2- reductase activity, and narG and nirS gene relative abundances, which led to aggravated accumulation of NO2-. The inhibition of NO2- reductase was significantly greater than that of NO3- reductase, and the inhibition of the nirS gene was significantly higher than that of the narG gene. The inhibition of NO3- reduction was mainly ascribed to the inhibition of functional genes, but the inhibition of NO2- reduction was mainly due to the inhibition of reductase activity. The inhibition of NO3- and NO2- reductive capacity, NO3- reductase activity, and narG and nirS gene relative abundances in the northwest of Jiaozhou Bay was significantly higher than that in the Dagu River estuary.

Characteristics of two novel cold- and salt-tolerant ammonia-oxidizing bacteria from Liaohe Estuarine Wetland.

To achieve a better contaminant removal efficiency in a low-temperature and high-salt environment, two novel strains of cold- and salt-tolerant ammonia-oxidizing bacteria (AOB), i.e., Ochrobactrum sp. (HXN-1) and Aquamicrobium sp. (HXN-2), were isolated from the surface sediment of Liaohe Estuarine Wetland (LEW), China. The optimization of initial ammonia nitrogen concentration, pH, carbon-nitrogen ratio, and petroleum hydrocarbons (PHCs) to improve the ammonia-oxidation capacity of the two bacterial strains was studied. Both bacterial strains showed a high ammonia nitrogen removal rate of over 80% under a high salinity of 10‰. Even at a temperature as low as 15°C, HXN-1 and HXN-2 could achieve an ammonia nitrogen removal rate of 53% and 62%, respectively. The cold- and salt-tolerant AOB in this study demonstrated a high potential for ammonia nitrogen removal from LEW.