Nitrite reductase (NirK) of Nitrosomonas europaea confers tolerance to nitrite (NO2-). The nirK gene is clustered with three genes of unknown physiological function: ncgABC. At present, this organization is unique to nitrifying bacteria. Here we report that the ncgABC gene products facilitate NirK-dependent NO2- tolerance by reversing the negative physiological effect that is associated with th...

This thesis is based on the following articles and manuscripts, which are referred to in the text by their Roman numerals: Mesocosms mimic natural meadows as regards greenhouse gas fluxes and potential activities of nitrifying and denitrifying bacteria. Plant and Soil 276: 287-299. soil microbial community structure under elevated tropospheric O 3 and CO 2. Submitted for publication. Difference...

The ability of marine microbes to develop tolerance to polycyclic aromatic hydrocarbons (PAHs) was examined in a 90-day experiment. PAH levels in sediment were increased 0.3 and 1.6 times compared to the control sediment. Day 30, 60, and 90 the microbes were re-exposed to PAHs in a short-term toxicity test to detect tolerance, where nitrification and denitrification were used as endpoints. In a...

Nitric oxide (NO) and nitrous oxide (N2O) emissions from nitrifying ecosystems are a serious threat to the environment. The factors influencing the emission and the responsible microorganisms and pathways were studied using a laboratory-scale nitrifying reactor system. The nitrifying culture was established at growth rates relevant to wastewater treatment plants (WWTPs). During stable ammonia o...

Primary urban wastewater was processed using the microalga Scenedesmus sp. in an outdoor pilot-scale raceway reactor connected to ultrafiltration membrane. The goal separate cellular retention time from hydraulic time. This strategy led a 129.3% increase daily volume of treated per square meter, and 48.7% biomass productivity final value 22.2 ± 1.9 g·m−2·day−1. Nutrient removal highly influence...

Objective To characterize the heterotrophic nitrifying bacteria. Methods The bacteria were isolated from membrane bioreactor for treating synthetic wastewater using the method newly introduced in this study. Fluorescence in situ hybridization (FISH) was used to validate the nonexistence of autotrophic ammonia oxidizers and nitrite oxidizers. Batch tests were carried out to investigate the capab...