Influence of oxygen partial pressure and salinity on the community composition of ammonia-oxidizing bacteria in the Schelde estuary

Abstract

The influence of environmental factors on the community structure of ammoniaoxidizing bacteria (AOB) was investigated in the Schelde estuary. Simultaneously with the increase of oxygen and salinity, a shift of the dominant AOB was observed. Molecular analysis based on 16S rRNA genes showed that the freshwater area was dominated by Nitrosomonas-like sequences which were closely related to N. ureae and N. oligotropha. In the brackish area, sequences of a novel group of Nitrosomonas-like bacteria and relatives of N. marina and N. aestuarii were found. Batch and continuous culture experiments were used to investigate the reason behind the community shift. Batch incubations showed a positive influence of the natural water from the Schelde estuary on ammonia oxidation, compared to mineral medium. The ammonia oxidation rates of the AOB originating from the brackish water were higher in the absence of salt. Water from the freshwater part was incubated in continuous cultures under 3 different conditions of salinity and oxygen partial pressure. Under all conditions, ammonia consumption in the continuous cultures started at once. Molecular analysis resulted in a clear phylogenetic difference between the absence and presence of salt, indicating that salt is the factor which causes the community shift of the AOB in the Schelde estuary.

Denaturing Gradient Gel Electrophoretic Analysis of Ammonia-Oxidizing Bacterial Community Structure in the Lower Seine River: Impact of Paris Wastewater Effluents

“…N. mobilis, probably introduced by tidal cycles, was found in samples taken within the salinity gradient (1 to 8 0 / 00 ) and was characteristic of the downstream estuary at low tide. The closest relatives reported were some uncultured AOB such as clone K_8 (99% homology), collected in surface sediments from Denmark Fjord, where the salinity value was 14 0 / 00 (40); clone LD1-B6 (98% homology), found in anoxic marine sediments (21); and DGGE band 423 (98% homology), obtained from the Schelde estuary water with a low ammonia level and high salinity (7).…”

“…Furthermore, in the freshwater estuary, a new AOB (band C) was selected in the sector of maximum nitrifying activity where oxygen and ammonia concentrations decrease and suspended-matter concentrations increase. Whereas many studies have shown that oxygen has no effect on the composition of the AOB community (4,7,32), the "band C" population may thrive on freshly produced ammonia, organic compounds, or new mineral ions (14) specific to the estuary, where the organic-matter turnover is generally high (23,50). This niche differentiation may be due to physiological differences such as the ability to produce extracellular polymeric substances (57), allowing an attached versus free-living AOB selection (42).…”

“…Most research has focused on AOB community composition in WWTP activated sludge (15,17,28,29,48,52). Only a few studies on AOB diversity in freshwater environments or estuaries are available (7,16,26,27,56,57). The diversity of AOB has been analyzed previously at two sites in the Seine River: one station just downstream of the WWTP input and another in the upper freshwater estuary (12).…”

Effects of Bacterial Community Members on the Proteome of the Ammonia-Oxidizing Bacterium Nitrosomonas sp. Strain Is79

“…Within the genus Nitrosomonas, AOB form several clusters that can be distinguished by ecophysiological characteristics, such as affinity for NH 4 ϩ and tolerance to increasing salt or NO 2 Ϫ concentrations (1,6,12). Nitrosomonas cluster 6a is comprised of AOB adapted to low ammonium (NH 4 ϩ ) concen-trations that can be found in a range of environments (13)(14)(15)(16)(17). Nitrosomonas sp.…”

Spatial variability of nitrous oxide in the Minho and Lima estuaries (Portugal)

“…Dong and Nedwell 2006). In addition to the supply of oxygen and ammonia, which are the main controls on nitrification, other environmental variables may affect this biological process: temperature (Dai et al 2008), salinity (Bollmann and Laanbroek 2002) and pH (Strauss et al 2002).…”