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Ammonia-oxidizing bacterial community composition in estuarine and oceanic environments assessed using a functional
Bess B Ward1, Damien Eveillard, Julie D Kirshtein
1Department of Geosciences, Guyot Hall, Princeton University, Princeton, NJ, USA. bbw@princeton.edu
Environmental Microbiology
|September 7, 2007
Summary
Environmental factors shape ammonia-oxidizing bacteria (AOB) functional gene diversity in estuaries. Marine AOB dominate as salinity increases, suggesting niche specialization and a shift towards Archaea in the ocean.
Area of Science:
- Environmental microbiology
- Marine microbial ecology
- Estuarine biogeochemistry
Background:
- Ammonia-oxidizing bacteria (AOB) are crucial for nitrification in aquatic ecosystems.
- Understanding AOB functional gene diversity is key to comprehending nitrogen cycling.
- Estuarine and marine environments present unique challenges and niches for microbial communities.
Purpose of the Study:
- To investigate the relationship between environmental factors and the diversity of ammonia monooxygenase (amoA) genes from AOB.
- To characterize AOB community composition across a salinity gradient from freshwater to marine environments.
- To identify ecological niches occupied by different AOB groups.
Main Methods:
- Development of a microarray using oligonucleotide probes targeting diverse amoA genes.
- Hybridization analysis of 14 samples collected along a transect from Chesapeake Bay to the Sargasso Sea.
- Statistical analyses including discrimination analysis and principal components analysis.
Main Results:
- Significant variations in amoA gene community composition were observed along the transect.
- Uncultivated Nitrosospira-like AOB dominated, particularly in marine samples.
- Two distinct AOB guilds were identified: Guild 1 correlated with marine conditions (salinity, temperature, chlorophyll a), and Guild 2 with freshwater conditions (oxygen, DOC, particulate N/C).
Conclusions:
- Different amoA sequences represent AOB occupying distinct ecological niches within estuarine and marine systems.
- AOB diversity decreases with increasing salinity, with a shift towards dominance by specific types in higher salinity regions.
- The findings support the hypothesis that Archaea play a more significant role in ammonia oxidation in the open ocean.
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