Environmental Factors Shape Sediment Anammox Bacterial Communities in Hypernutrified Jiaozhou Bay, China

Abstract

Bacterial anaerobic ammonium oxidation (anammox) is an important process in the marine nitrogen cycle. Because ongoing eutrophication of coastal bays contributes significantly to the formation of low-oxygen zones, monitoring of the anammox bacterial community offers a unique opportunity for assessment of anthropogenic perturbations in these environments. The current study used targeting of 16S rRNA and hzo genes to characterize the composition and structure of the anammox bacterial community in the sediments of the eutrophic Jiaozhou Bay, thereby unraveling their diversity, abundance, and distribution. Abundance and distribution of hzo genes revealed a greater taxonomic diversity in Jiaozhou Bay, including several novel clades of anammox bacteria. In contrast, the targeting of 16S rRNA genes verified the presence of only "Candidatus Scalindua," albeit with a high microdiversity. The genus "Ca. Scalindua" comprised the apparent majority of active sediment anammox bacteria. Multivariate statistical analyses indicated a heterogeneous distribution of the anammox bacterial assemblages in Jiaozhou Bay. Of all environmental parameters investigated, sediment organic C/organic N (OrgC/OrgN), nitrite concentration, and sediment median grain size were found to impact the composition, structure, and distribution of the sediment anammox bacterial community. Analysis of Pearson correlations between environmental factors and abundance of 16S rRNA and hzo genes as determined by fluorescent real-time PCR suggests that the local nitrite concentration is the key regulator of the abundance of anammox bacteria in Jiaozhou Bay sediments.

Bacterial composition and spatiotemporal variation in sediments of Jiaozhou Bay, China

“…Interestingly, nearly all studies on the microbial communities in Jiaozhou Bay sediment indicated that the bacterial assemblage in the D1 station was the most distinct from other stations (Dang et al 2009b(Dang et al , 2010a. Our current study here proved one more time the most special features of bacterial structure in the D1 station.…”

“…The cleaned PCR products were cloned into Takara pMD-18T simple cloning vector (Takara, Japan), and the ligation products were transformed into competent Escherichia coli TOP10 cells. Recombinants were isolated on Luria-Bertani (LB) indicator plates supplemented with X-Gal-IPTG and 100 μg ml −1 ampicillin at 37°C for 12-14 h (Dang et al 2010a). Approximately 180 randomly selected white colonies per sample were cultured overnight in 1.5 ml Luria Broth media at 37°C placed on an orbital shaker at 250 rpm.…”

An overlooked nitrogen loss linked to anaerobic ammonium oxidation in estuarine sediments in China

“…Heterotrophic denitrification was considered to be the only known pathway for the loss of fixed nitrogen to the atmosphere for decades until the discovery of anammox bacteria in a wastewater treatment plant (Mulder et al 1995). Subsequently, anammox bacteria were detected with broad biogeographic distribution in various natural ecosystems, including marine sediments (Thamdrup and Dalsgaard 2002;Trimmer and Nicholls 2009;Brabandere et al 2014;Shao et al 2014;Dang et al 2016), estuarine sediments (Dale et al 2009;Dang et al 2010;Li et al 2011;Wang et al 2012a, b;Dang et al 2013), and paddy soils (Zhu et al 2011;Nie et al 2015;Yang et al 2015). The relative contribution of anammox to dinitrogen production can vary widely, with >80% of total N 2 production observed in the eastern tropical South Pacific oxygen minimum zone (OMZ) off the coast of northern Chile (Brabandere et al 2014).…”

“…On the basis of previous studies (Dang et al 2010;Li et al 2011;Hu et al 2012;Zhu et al 2013;Hou et al 2015), we hypothesize that coastal estuaries are hotspots of anammox processes. Therefore, we sampled estuarine sediments from 18 rivers (from north to south China) in order to (i) determine anammox abundance via qPCR of the hydrazine synthase (hzsB) gene and investigate the community composition of anammox bacteria; (ii) evaluate the contribution of denitrification and anammox to N 2 production using an 15 N-tracer technique; and (iii) elucidate the impact of environmental factors on anammox process in estuarine sediments along the coastal zone in China.…”

“…Thus, estuaries are thought to be a potential sink of nitrogen, especially nitrate, which is the substrate for many nitrogen cycling processes (e.g., denitrification and anammox). Several studies have reported anammox processes in estuarine sediments in China (Dang et al 2010;Li et al 2011;Hu et al 2012;Dang et al 2013;Zhu et al 2013), but understanding of N cycling and the release of fixed N as dinitrogen gas (N 2 ) is lacking due to the high heterogeneity of the anammox activity in different estuarine and coastal sediments. Therefore, it is crucial to estimate the contributions of N 2 from anammox in different estuarine environments and discover the key factors governing activity and microbial diversity at a large scale.…”