Structural succession and its driving factors for nitrogen (N) cycling microbial communities during the early stages of soil development (0-44 years) were studied along a chronosequence in the glacial forelands of the Tianshan Mountain No.1 glacier in the arid and semi-arid region of central Asia. We assessed the abundance and population of functional genes affiliated with N-fixation (nifH), ni...

Nitrogen fixation, as measured by acetylene reduct~on, has been detected to be associated with various hermatypic corals. Experiments were carried out on the massive coral Favia f a v u s both in situ and in the laboratory. Nitrogen fixation activity was found to be light dependent and fully inhibited by 5 X 10-6 M DCMU [3-(3,4-dichloropheny1)-1,l-dimethylurea Addition of glucose restored nitro...

Abstract Fertilizer-N strongly limits non-leguminous crop yields; however, sweet potato ( Ipomoea batatas ) is an exception, likely due to its ability acquire atmospheric N 2 via endophytic diazotrophs. Using Raman spectroscopy, we found that in 15 -fed potato, some bacteria contained N, providing direct evidence of fixation planta . To assess -fixing capability, pot experiments were conducted ...

12 The potential coupling of nitrogen (N2) fixation and sulfate reduction (SR) was explored in 13 sediments of the Peruvian oxygen minimum zone (OMZ). Sediment samples were retrieved 14 by a multiple corer at six stations along a depth transect (70 1025 m water depth) at 12°S, 15 covering anoxic and hypoxic bottom water conditions. Benthic N2 fixation, determined by 16 the acetylene reduction a...

Many symbioses between bacteria and insects resulted from ancient infections followed by strict vertical transmission within host lineages. The strong bottlenecks under which this transmission occurs promote the neutral fixation of slightly deleterious mutations by genetic drift. As predicted by Muller's ratchet, this fixation will drive endosymbiotic bacteria through an irreversible dynamics o...

A double immunofluorescence staining technique is described for differentiation between cell-attached (extracellular) and ingested (intracellular) bacteria by HEp-2 cells in cell culture monolayers. This method is based upon the observation that membranes of viable mammalian cells are impermeable for antibodies but are rendered permeable by treatment with fixatives. Consequently, extracellular ...

Symbioses between marine invertebrates and their chemoautotrophic and methanotrophic symbionts are now known to exist in a variety of habitats where reduced chemical species are present. The utilization of chemical energy and reliance on C(1) compounds by these symbioses are well documented. Much less is known about their metabolism of nitrogen. Earlier work has shown that the tissues of organi...

Benthic microbial communities contribute to nitrogen (N) cycling in coastal ecosystems through taxon-specific processes such as anammox, nitrification and N-fixation community attributed pathways denitrification. By measuring the total (DNA-based) active (RNA-based) surface sediment composition abundance activity profiles of key N-cycling genes a semi-enclosed embayment—Port Phillip Bay (PPB), ...

five common tetracycline resistance genes tet(a), tet(b), tet(m), tet(o) and tet(s) were studied by polymerase chain reaction in 100 bacteria isolated from iranian fish farms. in the antibiogram test most of the bacteria were either intermediately or completely resistant to tetracycline. nine isolates out of 46 aeromonas spp. contained either tet(a/m/s) resistant genes as follows: tet(a) in a. ...

Nitrogen fixation by aerobic prokaryotes appears paradoxical: the nitrogen-fixing enzymes— nitrogenases—are notoriously oxygen-labile, yet many bacteria fix nitrogen aerobically. This review summarises the evidence that cytochrome bd, a terminal oxidase unrelated to the mitochondrial and many other bacterial oxidases, plays a crucial role in aerotolerant nitrogen fixation in Azotobacter vinelan...