Regulation of the Emissions of the Greenhouse Gas Nitrous Oxide by the Soybean Endosymbiont .

The greenhouse gas nitrous oxide (NO) has strong potential to drive climate change. Soils are a major source of NO, with microbial nitrification and denitrification being the primary processes involved in such emissions. The soybean endosymbiont is a model microorganism to study denitrification, a process that depends on a set of reductases, encoded by the , , , and genes, which sequentially reduce nitrate (NO) to nitrite (NO), nitric oxide (NO), NO, and dinitrogen (N).

Competition for electrons favours N O reduction in denitrifying Bradyrhizobium isolates.

Bradyrhizobia are common members of soil microbiomes and known as N -fixing symbionts of economically important legumes. Many are also denitrifiers, which can act as sinks or sources for N O. Inoculation with compatible rhizobia is often needed for optimal N -fixation, but the choice of inoculant may have consequences for N O emission.

NO and N O transformations of diverse fungi in hypoxia: evidence for anaerobic respiration only in Fusarium strains.

Fungal denitrification is claimed to produce non-negligible amounts of N O in soils, but few tested species have shown significant activity. We hypothesized that denitrifying fungi would be found among those with assimilatory nitrate reductase, and tested 20 such batch cultures for their respiratory metabolism, including two positive controls, Fusarium oxysporum and Fusarium lichenicola, throughout the transition from oxic to anoxic conditions in media supplemented with . Enzymatic reduction of (NIR) and NO (NOR) was assessed by correcting measured NO- and N O-kinetics for abiotic NO- and N O-production (sterile controls).

A common mechanism for efficient N O reduction in diverse isolates of nodule-forming bradyrhizobia.

Bradyrhizobia are abundant soil bacteria, which can form nitrogen-fixing symbioses with leguminous plants, including important crops such as soybean, cowpea and peanut. Many bradyrhizobia can denitrify, but studies have hitherto focused on a few model organisms. We screened 39 diverse Bradyrhizobium strains, isolated from legume nodules.

Regulation of nitrogen metabolism in the nitrate-ammonifying soil bacterium Bacillus vireti and evidence for its ability to grow using N2 O as electron acceptor.

Bacillus vireti is a nitrate-ammonifying bacterium and a partial denitrifier, reducing NO3 (-) , NO2 (-) , NO and N2 O with NarG, NrfA, CbaA and NosZ respectively. Growth is optimized through successive use of the electron acceptors O2 and NO3 (-) , followed by NO2 (-) , NO and N2 O. Fermentation takes place simultaneously with anaerobic respiration.

Anoxic growth of Ensifer meliloti 1021 by N2O-reduction, a potential mitigation strategy.

Denitrification in agricultural soils is a major source of N2O. Legume crops enhance N2O emission by providing N-rich residues, thereby stimulating denitrification, both by free-living denitrifying bacteria and by the symbiont (rhizobium) within the nodules. However, there are limited data concerning N2O production and consumption by endosymbiotic bacteria associated with legume crops.

Production and consumption of nitrous oxide in nitrate-ammonifying Wolinella succinogenes cells.

Global warming is moving more and more into the public consciousness. Besides the commonly mentioned carbon dioxide and methane, nitrous oxide (N2O) is a powerful greenhouse gas in addition to its contribution to depletion of stratospheric ozone. The increasing concern about N2O emission has focused interest on underlying microbial energy-converting processes and organisms harbouring N2O reductase (NosZ), such as denitrifiers and ammonifiers of nitrate and nitrite.

The nitrate-ammonifying and nosZ-carrying bacterium Bacillus vireti is a potent source and sink for nitric and nitrous oxide under high nitrate conditions.

Several Gram-positive bacteria carry genes for anaerobic reduction of NO3(-) via NO2(-) to NH4(+) or gaseous nitrogen compounds, but the processes are understudied for these organisms. Here, we present results from a whole-genome analysis of the soil bacterium Bacillus vireti and a phenotypic characterization of intermediate and end-products, formed under anoxic conditions in the presence of NO3(-). Bacillus vireti has a versatile metabolism.

The cell-end marker TeaA and the microtubule polymerase AlpA contribute to microtubule guidance at the hyphal tip cortex of Aspergillus nidulans to provide polarity maintenance.

In the absence of landmark proteins, hyphae of Aspergillus nidulans lose their direction of growth and show a zigzag growth pattern. Here, we show that the cell-end marker protein TeaA is important for localizing the growth machinery at hyphal tips. The central position of TeaA at the tip correlated with the convergence of the microtubule (MT) ends to a single point.

Screening for antifungal peptides and their modes of action in Aspergillus nidulans.

Many short cationic peptides have been identified as potent antimicrobial agents, but their modes of action are not well understood. Peptide synthesis on cellulose membranes has resulted in the generation of peptide libraries, while high-throughput assays have been developed to test their antibacterial activities. In this paper a microtiter plate-based screening method for fungi has been developed and used to test nine antibacterial peptides against the model fungus Aspergillus nidulans.