Members of the genus Leptospirillum are aerobic iron-oxidizing bacteria belonging to the phylum Nitrospira. They are important members of microbial communities that catalyze the biomining of sulfidic ores, thereby solubilizing metal ions. These microorganisms live under extremely acidic and metal-loaded environments and thus must tolerate high concentrations of reactive oxygen species (ROS). Cobalamin (vitamin B12) is a cobalt-containing tetrapyrrole cofactor involved in intramolecular rearrangement reactions and has recently been suggested to be an intracellular antioxidant. In this work, we investigated the effect of the exogenous addition of cobalamin on oxidative stress parameters in Leptospirillum group II strain CF-1. Our results revealed that the external supplementation of cobalamin reduces the levels of intracellular ROSs and the damage to biomolecules, and also stimulates the growth and survival of cells exposed to oxidative stress exerted by ferric ion, hydrogen peroxide, chromate and diamide. Furthermore, exposure of strain CF-1 to oxidative stress elicitors resulted in the transcriptional activation of the cbiA gene encoding CbiA of the cobalamin biosynthetic pathway. Altogether, these data suggest that cobalamin plays an important role in redox protection of Leptospirillum strain CF-1, supporting survival of this microorganism under extremely oxidative environmental conditions. Understanding the mechanisms underlying the protective effect of cobalamin against oxidative stress may help to develop strategies to make biomining processes more effective.

Microcins are low-molecular-weight proteins secreted by certain bacteria that act by limiting the growth of other bacteria that share the same ecological niche. In the present work, the previous microcin 24 system was resequenced.We detected three nucleotide differences in the microcin-coding gene that partially change the amino acid sequence. According to the present microcin nomenclature, we renamed the five genes constituting this microcin system (mcnRINAB), which are arranged in an operon-like structure: mcnR codes for a putative histone-like nucleoid protein regulator; mcnI codes for the immunity protein; mcnN encodes microcin N; and mcnA and mcnB correspond to an ATP-binding cassette transporter system. Purified microcin N has a molecular weight of 7274.23 Da, as determined by MS. This peptide was stable up to 100°C, resistant to treatment with lipase, lysozyme, trypsin, and chymotrypsin, and susceptible to degradation by proteinase K.

Acidophiles are life-forms that grow preferentially in natural or man-made environments where the pH is well below seven. Together with other categories of extremophiles, they have greatly expanded our knowledge of the diversity of life, our understanding on how microorganisms can adapt to seemingly hostile situations, and provided scenarios for the possibility that life-forms may be found outside of our solar system.Written by experts in their field, this important volume provides a comprehensive account of acidophilic microbiology from fundamental to applied aspects. The seventeen chapters are arranged in five sections, each dealing with a specific area. The first section looks at the challenges faced by life-forms that grow in extremely acidic environments and how they adapt to meet these challenges. The next section describes the physiological and phylogenetic diversities of acidophilic microorganisms including archaea, bacteria and eukaryotes. Section three covers acidophile community dynamics, quorum sensing and the formation of biofilms. The next section deals with the various omic technologies that are used to study acidophiles including genomic and metagenomic studies, proteomic-, mobilomic-and metabolomic-focused research. The final section considers the ways in which acidophiles are used in established and emerging biotechnologies and describes why these fascinating microorganisms are considered potential candidates for life on other solar bodies, such as Mars, and beyond.This up-to-date and comprehensive book will be indispensable for environmental scientists and microbiologists and is a recommended acquisition for all microbiology libraries. Chapter 1. Acidophile Microbiology in Space and Time (D. Barrie Johnson and Raquel Quatrini) Chapter 2. Energy Acquisition in Low pH Environments (Wolfgang Nitschke and Violaine Bonnefoy) Chapter 3. Adaptation to Extreme Acidity and Osmotic Stress

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We report Nitrincola sp. strain A-D6, which was characterized as an arsenic-resistant bacterium isolated from the Ascotán Salt Flat in northern Chile. The size of the genome is 3,795,776 bp, with a G+C content of 49.96%. Genes for the arsenic-resistant Ars system and arsenic oxidation have been encoded.