Nitrogenase resurrection and the evolution of a singular enzymatic mechanism.

The planetary biosphere is powered by a suite of key metabolic innovations that emerged early in the history of life. However, it is unknown whether life has always followed the same set of strategies for performing these critical tasks. Today, microbes access atmospheric sources of bioessential nitrogen through the activities of just one family of enzymes, nitrogenases.

Iron homeostasis in relies on three differentially expressed efflux systems.

In iron homeostasis is maintained by the ferric uptake regulator (Fur) and manganese homeostasis relies on the manganese transport regulator (MntR). Both Fur and MntR function as bi-functional metalloregulators that repress import and activate metal ion efflux systems. The ferrous iron efflux ATPase, PfeT, is derepressed by hydrogen peroxide (HO) as sensed by PerR and induced by iron as sensed by Fur.

Bacillus subtilis Fur Is a Transcriptional Activator for the PerR-Repressed Gene, Encoding an Iron Efflux Pump.

The physiological relevance of bacterial iron efflux has only recently been appreciated. The P-type ATPase PfeT (eroxide-induced errous fflux ransporter) was one of the first iron efflux pumps to be characterized, and cells lacking accumulate high levels of intracellular iron. The promoter region has binding sites for both PerR, a peroxide-sensing Fur-family metalloregulator, and the ferric uptake repressor Fur.

TerC Family Proteins Help Prevent Manganese Intoxication.

Manganese (Mn) is an essential element and is required for the virulence of many pathogens. In , Mn(II) homeostasis is regulated by MntR, a Mn(II)-responsive, DNA-binding protein. MntR serves as both a repressor of Mn(II) uptake transporters and as a transcriptional activator for expression of two cation diffusion facilitator Mn(II) efflux pumps, MneP and MneS.

Redox Sensing by Fe in Bacterial Fur Family Metalloregulators.

Significance: Iron is required for growth and is often redox active under cytosolic conditions. As a result of its facile redox chemistry, iron homeostasis is intricately involved with oxidative stress. Bacterial adaptation to iron limitation and oxidative stress often involves ferric uptake regulator (Fur) proteins: a diverse set of divalent cation-dependent, DNA-binding proteins that vary widely in both metal selectivity and sensitivity to metal-catalyzed oxidation.

Iron Efflux by PmtA Is Critical for Oxidative Stress Resistance and Contributes Significantly to Group A Streptococcus Virulence.

Group A (GAS) is a human-only pathogen that causes a spectrum of disease conditions. Given its survival in inflamed lesions, the ability to sense and overcome oxidative stress is critical for GAS pathogenesis. PerR senses oxidative stress and coordinates the regulation of genes involved in GAS antioxidant defenses.

Bacillus subtilis MntR coordinates the transcriptional regulation of manganese uptake and efflux systems.

The Bacillus subtilis MntR metalloregulatory protein senses manganese, an essential element required for central metabolism, oxidative stress resistance and replication. An mntR null mutant is highly sensitive to Mn(II) intoxication, which is attributed in part to the constitutive expression of two importers: the proton-dependent NRAMP family transporter MntH and the ABC transporter MntABCD. Here, we show that an mntR null mutant is still sensitive to Mn(II) intoxication even if both of the import systems are absent.

PfeT, a P1B4 -type ATPase, effluxes ferrous iron and protects Bacillus subtilis against iron intoxication.

Iron is an essential element for nearly all cells and limited iron availability often restricts growth. However, excess iron can also be deleterious, particularly when cells expressing high affinity iron uptake systems transition to iron rich environments. Bacillus subtilis expresses numerous iron importers, but iron efflux has not been reported.