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The capture and reduction of atmospheric dinitrogen gas to ammonium can be accomplished through the enzyme nitrogenase in a process known as biological nitrogen fixation (BNF), by a class of microbes known as diazotrophs. The diazotroph Azotobacter vinelandii is a model organism for the study of aerobic nitrogen fixation, and in recent years has been promoted as a potential producer of biofertilizers. Prior reports have demonstrated the potential to partially deregulate BNF in A. vinelandii, resulting in accumulation and extracellular release of ammonium. In many cases, deregulation requires the introduction of transgenic genes or elements to yield the desired phenotype, and the long‐term stability of these strains has been reported to be somewhat problematic. In this work, we constructed two strains of A. vinelandii where regulation can be precisely controlled without the addition of any foreign genes or genetic markers. Regulation is maintained through native promoters found in A. vinelandii that can be induced through the addition of extraneous galactose. These strains result in varied degrees of regulation of BNF, and as a result, the release of extracellular ammonium is controlled in a precise, and galactose concentration‐dependent manner. In addition, these strains yield high biomass levels, similar to the wild‐type A. vinelandii strain and are further able to produce high percentages of the bioplastic polyhydroxybutyrate. [ABSTRACT FROM AUTHOR]

A study is conducted to demonstrate that wild-type nitrogenase reduces diazene to ammonia. The findings suggest that the reduction of [N.sub.2] and diazene is inhibited by [H.sub.2].

A strategy is described that results in the trapping of the substrate hydrazine (H2N-NH2) as an adduct bound to the active site metal cluster of nitrogenase, and this bound adduct is characterized by EPR (electron paramagnetic resonance) and ENDOR (electron-nuclear double resonance) spectroscopies. The EPR signal showed Curie law temperature dependence similar to the resting state EPR signal.

The biosynthesis of lipid-based biofuels is an important aspect of developing sustainable alternatives to conventional oils derived from fossil fuel reserves. Many biosynthetic approaches to biodiesel fuels and oils involve fatty acid derivatives as a precursor, and thioesterases have been employed in various strategies to increase fatty acid pools. Thioesterases liberate fatty acids from fatty acyl-coenzyme A or fatty acyl-acyl carrier protein substrates. The role played by thioesterases has not been extensively studied in model bacteria that accumulate elevated levels of biological oils based on fatty acid precursors. In this report, two primary thioesterases from the wax ester accumulating bacterium Marinobacter aquaeolei VT8 were heterologously expressed, isolated and characterized. These genes were further analyzed at the transcriptional level in the native bacterium during wax ester accumulation, and their genes were disrupted to determine the effect these changes had on wax ester levels. Combined, these results indicate that these two thioesterases do not play an integral role in wax ester accumulation in this natural lipid-accumulating model bacterium. [ABSTRACT FROM AUTHOR]

The catalytic reduction of hydrazine ([N.sub.2][H.sub.4]) to ammonia by a [[beta]-98.sup.Tyr?His] MoFe protein in the absence of the Fe protein or ATP is reported. The [[beta]-98.sup.His] MoFe protein reduction of hydrazine in the absence of the Fe protein which revealed saturation kinetics for the concentration of reductant and substrate have significant implications for understanding the nitrogenase mechanism.

The intermediate generated at a high concentration during reduction of the natural nitrogenase substrate ([N.sub.2]) by wild-type MoFe protein has shown that it contains [N.sub.2] bound to the active-site FeMo cofactor. The single type of [super 15]N-coupled nucleus from the field dependence, along with the absence of an associated exchangeable [super 1]H ENDOR signal, is shown to be consistent with the [N.sub.2] molecule bound end-on to the FeMo cofactor.

The purification, X-ray structure determination, and nucleotide interaction of the L protein (BchL) of the dark-operative protochlorophyllide reductase (DPOR) from Rhodobacter sphaeroides is described. The results from the comparison of structure of BchL with its close homologue, the nitrogenase Fe protein, provide insight into the discrimination between respective functions of proteins in microbial systems.

Quercetin 2,3-dioxygenase from Bacillus subtilis (QueD) converts the flavonol quercetin and molecular oxygen to 2-protocatechuoyplphlorogluinolcarboxylic acid and carbon monoxide. QueD the only known quercetin 2,3-diocygenase from a prokaryotic organism, is described as Fe(super 2+) dependent bicupin dioxygenase, where the turnover number of enzyme is higher than that of Fe(super 2+) containing quercetin 2,3-dioxygenase.

The first report of a high-population intermediate trapped during an early (e) stage of N2 reduction by nitrogenase is presented. Intermediates are trapped during the reduction of a diazene and of hydrazine in an attempt to visualize intermediates corresponding to middle (m) and late stages of N2 reduction.

The characterization of a novel small metal binding (SmbP) isolated from the periplasm of Nitrosomonas europaea is described. The analysis suggests that SmbP is a metal scavenging protein in N. europaea, which is induced to deal with high concentrations of copper.

Summary: Green algae represent a key segment of the global species capable of photoautotrophic‐driven biological carbon fixation. Algae partition fixed‐carbon into chemical compounds required for biomass, while diverting excess carbon into internal storage compounds such as starch and lipids or, in certain cases, into targeted extracellular compounds. Two green algae were selected to probe for critical components associated with sugar production and release in a model alga. Chlorella sorokiniana UTEX 1602 – which does not release significant quantities of sugars to the extracellular space – was selected as a control to compare with the maltose‐releasing Micractinium conductrix SAG 241.80 – which was originally isolated from an endosymbiotic association with the ciliate Paramecium bursaria. Both strains were subjected to three sequencing approaches to assemble their genomes and annotate their genes. This analysis was further complemented with transcriptional studies during maltose release by M. conductrix SAG 241.80 versus conditions where sugar release is minimal. The annotation revealed that both strains contain homologs for the key components of a putative pathway leading to cytosolic maltose accumulation, while transcriptional studies found few changes in mRNA levels for the genes associated with these established intracellular sugar pathways. A further analysis of potential sugar transporters found multiple homologs for SWEETs and tonoplast sugar transporters. The analysis of transcriptional differences revealed a lesser and more measured global response for M. conductrix SAG 241.80 versus C. sorokiniana UTEX 1602 during conditions resulting in sugar release, providing a catalog of genes that might play a role in extracellular sugar transport. [ABSTRACT FROM AUTHOR]