ABSTRACT
The Firmicutes bacteria participate extensively in virulence and pathological processes. Enterococcus faecalis is a commensal microorganism; however, it is also a pathogenic bacterium mainly associated with nosocomial infections in immunocompromised patients. Iron-sulfur [Fe-S] clusters are inorganic prosthetic groups involved in diverse biological processes, whose in vivo formation requires several specific protein machineries. Escherichia coli is one of the most frequently studied microorganisms regarding [Fe-S] cluster biogenesis and encodes the iron-sulfur cluster and sulfur assimilation systems. In Firmicutes species, a unique operon composed of the sufCDSUB genes is responsible for [Fe-S] cluster biogenesis. The aim of this study was to investigate the potential of the E. faecalis sufCDSUB system in the [Fe-S] cluster assembly using oxidative stress and iron depletion as adverse growth conditions. Quantitative real-time polymerase chain reaction demonstrated, for the first time, that Gram-positive bacteria possess an OxyR component responsive to oxidative stress conditions, as fully described for E. coli models. Likewise, strong expression of the sufCDSUB genes was observed in low concentrations of hydrogen peroxide, indicating that the lowest concentration of oxygen free radicals inside cells, known to be highly damaging to [Fe-S] clusters, is sufficient to trigger the transcriptional machinery for prompt replacement of [Fe-S] clusters.
Subject(s)
Enterococcus faecalis/metabolism , Iron-Sulfur Proteins/genetics , Oxidative Stress , Biosynthetic Pathways , Iron-Sulfur Proteins/biosynthesis , Models, Molecular , Real-Time Polymerase Chain Reaction , Substrate SpecificityABSTRACT
Mitochondrial protein Nfu1 plays an important role in the assembly of mitochondrial Fe-S clusters and intracellular iron homeostasis in the model yeast Saccharomyces cerevisiae. In this study, we identified the Nfu1 ortholog in the human fungal pathogen Cryptococcus neoformans. Our data showed that C. neoformans Nfu1 localized in the mitochondria and influenced homeostasis of essential metals such as iron, copper and manganese. Marked growth defects were observed in the mutant lacking NFU1, which suggests a critical role of Nfu1 in Fe-S cluster biosynthesis and intracellular metal homeostasis in C. neoformans.
Subject(s)
Humans , Copper , Cryptococcus neoformans , Homeostasis , Iron , Manganese , Metals , Mitochondria , Mitochondrial Proteins , Saccharomyces cerevisiae , YeastsABSTRACT
Two synthetic oligonucleotide probe mixtures, whose sequences were inferred from two separate stretches of amino acids, one closer to the carboxy terminal and the other closer to the amino terminal, of ferredoxin I protein of Azotobacter vinelandii, were used to select ferredoxin I gene clones from a cosmid gene library of Azotobacter vinelandii. Restriction analysis revealed that 7 out of 10 selected clones were of the same type. All these clones were found to hybridize with fixABCX genes of Rhizobium meliloti.