| Nitrous oxide(N2O)is a potent greenhouse gas with a 100-year scale warming potential 300 times that of carbon dioxide(CO2).Among them,the treatment of high salinity industrial wastewater is one of the sources of N2O generation.N2O is mainly produced in the aerobic section of wastewater treatment,because oxygen(O2)inhibits N2O reductase redulting in a denitrification product of N2O rather than N2.Therefore,the study of complete denitrifying bacteria under aerobic conditions is very important in terms of denitrification effect and N2O emission reduction.Our previous study has shown that Halomonas may play an important role in N2O reduction in high salinity wetland sediments by sequencing analysis.In this study,Halomonas sp.3H was isolated from wetland sediments,and its salt tolerance,heavy metal tolerance,preliminary denitrification potential and whole genome sequence were determined,and then aerobic denitrification and N2O removal under different salinity conditions were investigated under different salinity conditions.The main results are as follows:(1)A total of 11 strains of bacteria were isolated from Uliangsuhai sediments,of which 8 strains belonged to Proteobacteria(one of which belonged to the Halomonas)and 3 strains belonged to Firmicutes.Physiological and biochemical experiments of the isolate Halomonas sp.3H showed that the strain had alkali resistance( 6+,Co2+,Ni2+,Cu2+,As5+).(2)The results of whole genome sequencing analysis showed that the genome size of strain 3H contained one circular chromosome of 3900707 bp,a GC content of 68.3%.A total of 3505 genes were identified.In the genome annotation results,the bacterium has all the genes required for the complete denitrification process,including the assimilatory nitrate reductase encoding genes nas EFAD,the nitrate reductase encoding genes nar IJHGXLK,nitrite reductase enconding genes nir SBD,NO reductase encoding genes nor EDQBC and the N2O reductase encoding gene nos LYFDZR for reducing N2O to N2.In addition,strain 3H also has resistance genes for Cr6+?Co2+?Ni2+?Cu2+?As5+,indicating that this strain has the potential of complete denitrification genes in a complex environment.(3)Under aerobic conditions with different salinities(0% and 5%),the removal experiments of different nitrogen sources showed that the isolate 3H could completely remove 100 mg/L of ammonia nitrogen by assimilation under aerobic conditions without producing N2O.100 mg/L of nitrate nitrogen and nitrite nitrogen were removed by aerobic denitrification,and a large amount of N2O(36-42 mg/L)was produced.When Cu2+(400 ?g/L)were added,the removal effects of three nitrogen sources(ammonia nitrogen,nitrate nitrogen and nitrite nitrogen)were unchanged,but N2O was not generated.It shows that the strain 3H has Cu2+-dependent aerobic denitrification and N2O removal ability.(4)Under anaerobic conditions,the experimental results of the removal of different nitrogen sources with different salinities(0% and 5%)showed that the isolate 3H could not remove ammonia nitrogen under anaerobic conditions,but could remove 100 mg/L of nitrate and nitrite through denitrification,and produce a large amount of N2O(38 40 mg/L).After adding Cu(2+)400 ?g/L,all the N2O produced by denitrification and the added N2O can be completely removed.In conclusion,this study explored the denitrification of Halomonas sp.3H in extreme environments such as high salinity wastewater and excess nitrogen and the removal of the greenhouse gas N2 O,indicating that the isolate has good application potential and prospects. |
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