Response of ammonia-oxidizing Bacteria and Archaea to long-term saline water irrigation in alluvial grey desert soils

Abstract

Soil nitrification via ammonia oxidation is a key ecosystem process in terrestrial environments, but little is known of how increasing irrigation of farmland soils with saline waters effects these processes. We investigated the effects of long-term irrigation with saline water on the abundances and community structures of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Irrigation with brackish or saline water increased soil salinity (EC 1:5 ) and NH 4 -n compared to irrigation with freshwater, while no 3 -n, potential nitrification rates (PNR) and amoA gene copy numbers of AOA and AOB decreased markedly under irrigation regimes with saline waters. Moreover, irrigation with brackish water lowered AOA/ AOB ratios. PNR was positively correlated with AOA and AOB amoA gene copy numbers across treatments. Saline and brackish water irrigation significantly increased the diversity of AOA, as noted by Shannon index values, while saline water irrigation markedly reduced AOB diversity. In addition, irrigation with brackish or fresh waters resulted in higher proportions of unclassified taxa in the AOB communities. However, irrigation with saline water led to higher proportions of unclassified taxa in the AoA communities along with the Candidatus Nitrosocaldus genus, as compared to soils irrigated with freshwater. AOA community structures were closely associated with soil salinity, NO 3 − n, and pH, while AOB communities were only significantly associated with NO 3 − N and pH. These results suggest that salinity was the dominant factor affecting the growth of ammonia-oxidizing microorganisms and community structure. These results can provide a scientific basis for further exploring the response mechanism of ammonia-oxidizing microorganisms and their roles in nitrogen transformation in alluvial grey desert soils of arid areas.index showed a significant (P < 0.001) opposite relationship. In addition, the SW treatment soils had a significantly lower AOB Shannon index (P = 0.002) compared to the FW soils, but a significantly higher Simpson index value (P = 0.003). The BW treatment did not have a significant effect on AOB diversity index. Scientific RepoRtS | (2020) 10:489 | https://doi.Scientific RepoRtS | (2020) 10:489 | https://doi.org/10.1038/s41598-019-57402-xwww.nature.com/scientificreports www.nature.com/scientificreports/ Nitrosomonadaceae and Nitrosopumilaceae were the two most dominant families in the dataset. The relative abundances of Nitrosomonadaceae were significantly greater in the FW treatment soils than in those of the BW and SW treatments (P < 0.001). However, no significant differences were observed for the relative abundances of Nitrosopumilaceae among the FW, BW, and SW treatment soils. Nitrosopumilus and Nitrosospira were the two most dominant genera in the sequencing datasets. The relative abundances of Nitrosospira were significantly higher in the FW treatment soils than in those of the BW and SW treatments (P < 0.001). However, no significant differences were observed for the relative abundances of Ni...

Saline and Alkaline Stresses Alter Soil Properties And Composition And Structure of Gene-Based Nitrifier And Denitrifier Communities In A Calcareous Desert Soil

“…The effects of salinity on the structure of AOB and AOA communities have been investigated in many previous studies [24][25]. Salinity signi cantly alters the structure of AOA and AOB communities in wetland soil [58].…”

“…Ammonia oxidation is dominated by AOA in acidic soils but by AOB in alkaline soils, because of the low survival of AOB at low pH [21][22][23]. In addition, previous studies found that copies of the amoA gene of AOB and AOA are negatively correlated with soil salinity [24][25].…”

“…An understanding of the effects of saline and alkaline stresses on the abundance of nitri ers and denitri ers is important, because nitri cation and denitri cation rates determine soil inorganic N concentrations, nitrate leaching, and the production of N 2 O [25,36,42]. An increase in soil salinity may shift microbial community structure and increase the predominance of saline or alkaline adapted microorganisms.…”

Response of Nitrifier and Denitrifier Abundance to Salinity Gradients in Agricultural Soils at the Yellow River Estuary

“…The differences in salt tolerance or range and the populations of nitrifiers diverged in different environments. Based on molecular studies, the abundance of AOA and AOB is reported to decrease with salinity [16]. In contrast, other studies found that AOA abundance and potential nitrification rates increased under moderate salinity (10-20 ppt), while AOB abundance was negatively or not correlated with salinity [15,21].…”

“…Several studies explored the response of nitrifiers and denitrifiers communities to salinity in mangrove sediments [12], coastal wetlands [13][14][15], and desert soils [16]. In some cases, it was found that salinity harmed nitrification [17].…”