In the methanogenic archaeon Methanococcus maripaludis, growth with ammonia results in conditions of nitrogen excess. Complete repression of nitrogen fixation (nif) gene transcription occurs, and glutamine synthetase (glnA) gene transcription falls to a basal constitutive level. In addition, ammonia completely switches off nitrogenase enzyme activity. In contrast, growth with dinitrogen as the ...

M icroorganisms such as Escherichia coli live in environments subject to rapid changes in the availability of the carbon and nitrogen compounds necessary to provide energy and building blocks for the synthesis of cell material. Their survival depends on their ability to regulate the expression of genes coding for the enzymes and transport proteins required for growth in the altered environment....

Carbamoyl phosphate synthetase (CPS) from Escherichia coli consists of a small subunit (approximately 42 kDa) and a large subunit (approximately 118 kDa) and catalyzes the biosynthesis of carbamoyl phosphate from MgATP, bicarbonate, and glutamine. The enzyme is able to utilize external ammonia as an alternative nitrogen source when glutamine is absent. CPS contains an internal molecular tunnel,...

The purpose of this study was to investigate the nitrification and nitrogen removal from centrate produced in the dewatering process of anaerobically digested sludge, using a single-unit, single-zone submerged attached-growth bioreactor. The nitrogen loading varied from 0.54 to 1.51 kg-N/m3 x d. Stable ammonia oxidation (nitritification) to nitrite was demonstrated. A nitritification efficiency...

The nitrogen-regulated genes and operons of the Ntr regulon of Escherichia coli are activated by the enhancer-binding transcriptional activator NRI approximately P (NtrC approximately P). Here, we examined the activation of the glnA, glnK, and nac promoters as cells undergo the transition from growth on ammonia to nitrogen starvation and examined the amplification of NRI during this transition....

Chopped wheat straw, containing increasing amounts of added water was treated with a constant level of ammonia (3.3 percent of straw dry matter) as ammonium hydroxide, and stored for I to 60 days before determing in vitro dry matter digestibility (IVD MD), nitrogen content and fiber-bound nitrogen (ADF-N) versus free ammonia nitrogen (NH3N) of the treated sample. The overall improvement (e.g., ...

1. In focal and diffuse necroses of the liver due to haemotoxic sera there occurs an increased elimination of total nitrogen with a corresponding augmented output of urea. The ammonia excretion becomes slightly diminished at first, but later rises somewhat above normal. The undetermined nitrogen is markedly increased. 2. In diffuse degeneration with no necrosis on the other hand only a slightly...

Lava caves are an understudied ecosystem in the subterranean world, particularly in regard to nitrogen cycling. The diversity of ammonia oxidation (amoA) and nitrogen fixation (nifH) genes in bacterial mats collected from lava cave walls on the island of Terceira (Azores, Portugal) was investigated using denaturing gradient gel electrophoresis (DGGE). A total of 55 samples were collected from 1...

This paper presents research on applications of fuzzy logic and higher-order fuzzy logic systems to control filters reducing air pollution [1]. The filters use Selective Catalytic Reduction (SCR) method and, as for now, this process is controlled manually by a human expert. The goal of the research is to control an SCR system responsible for emission of nitrogen oxide (NO) and nitrogen dioxide ...

Nitrogen deposition is changing biodiversity on Earth. We need to understand the underlying mechanisms to conserve biodiversity better. Both selection and chance are potential mechanisms, and they may operate concurrently. Then, what are the respective effects of selection and chance, what is their relative importance and how do they change with increasing nitrogen deposition rate? Here, we per...