The Escherichia coli BtuE Protein Functions as a Resistance Determinant against Reactive Oxygen Species

This work shows that the recently described Escherichia coli BtuE peroxidase protects the bacterium against oxidative stress that is generated by tellurite and by other reactive oxygen species elicitors (ROS). Cells lacking btuE (ΔbtuE) displayed higher sensitivity to K2TeO3 and other oxidative stress-generating agents than did the isogenic, parental, wild-type strain. They also exhibited increased levels of cytoplasmic reactive oxygen species, oxidized proteins, thiobarbituric acid reactive substances, and lipoperoxides. E. coli ΔbtuE that was exposed to tellurite or H2O2 did not show growth changes relative to wild type cells either in aerobic or anaerobic conditions. Nevertheless, the elimination of btuE from cells deficient in catalases/peroxidases (Hpx−) resulted in impaired growth and resistance to these toxicants only in aerobic conditions, suggesting that BtuE is involved in the defense against oxidative damage. Genetic complementation of E. coli ΔbtuE restored toxicant resistance to levels exhibited by the wild type strain. As expected, btuE overexpression resulted in decreased amounts of oxidative damage products as well as in lower transcriptional levels of the oxidative stress-induced genes ibpA, soxS and katG

Molecular systematics of the genus Acidithiobacillus:insights into the phylogenetic structure and diversification of the taxon

The acidithiobacilli are sulfur-oxidizing acidophilic bacteria that thrive in both natural and anthropogenic low pH environments. They contribute to processes that lead to the generation of acid rock drainage in several different geoclimatic contexts, and their properties have long been harnessed for the biotechnological processing of minerals. Presently, the genus is composed of seven validated species, described between 1922 and 2015: Acidithiobacillus thiooxidans, A. ferrooxidans, A. albertensis, A. caldus, A. ferrivorans, A. ferridurans, and A. ferriphilus. However, a large number of Acidithiobacillus strains and sequence clones have been obtained from a variety of ecological niches over the years, and many isolates are thought to vary in phenotypic properties and cognate genetic traits. Moreover, many isolates remain unclassified and several conflicting specific assignments muddle the picture from an evolutionary standpoint. Here we revise the phylogenetic relationships within this species complex and determine the phylogenetic species boundaries using three different typing approaches with varying degrees of resolution: 16S rRNA gene-based ribotyping, oligotyping, and multi-locus sequencing analysis (MLSA). To this end, the 580 16S rRNA gene sequences affiliated to the Acidithiobacillus spp. were collected from public and private databases and subjected to a comprehensive phylogenetic analysis. Oligotyping was used to profile high-entropy nucleotide positions and resolve meaningful differences between closely related strains at the 16S rRNA gene level. Due to its greater discriminatory power, MLSA was used as a proxy for genome-wide divergence in a smaller but representative set of strains. Results obtained indicate that there is still considerable unexplored diversity within this genus. At least six new lineages or phylotypes, supported by the different methods used herein, are evident within the Acidithiobacillus species complex. Although the diagnostic characteristics of these subgroups of strains are as yet unresolved, correlations to specific metadata hint to the mechanisms behind econiche-driven divergence of some of the species/phylotypes identified. The emerging phylogenetic structure for the genus outlined in this study can be used to guide isolate selection for future population genomics and evolutionary studies in this important acidophile model

Draft genome sequence of the type strain of the sulfur-oxidizing acidophile, Acidithiobacillus albertensis (DSM 14366)

Abstract Acidithiobacillus albertensis is an extremely acidophilic, mesophilic, obligatory autotrophic sulfur-oxidizer, with potential importance in the bioleaching of sulfidic metal ores, first described in the 1980s. Here we present the draft genome sequence of Acidithiobacillus albertensis DSM 14366T, thereby both filling a long-standing gap in the genomics of the acidithiobacilli, and providing further insight into the understanding of the biology of the non iron-oxidizing members of the Acidithiobacillus genus. The assembled genome is 3,1 Mb, and contains 47 tRNAs, tmRNA gene and 2 rRNA operons, along with 3149 protein-coding predicted genes. The Whole Genome Shotgun project was deposited in DDBJ/EMBL/GenBank under the accession MOAD00000000

Draft genome sequence of chloride-tolerant Leptospirillum ferriphilum Sp-Cl from industrial bioleaching operations in northern Chile

Indexación: Web of Science; PubMedLeptospirillum ferriphilum Sp-Cl is a Gram negative, thermotolerant, curved, rod- shaped bacterium, isolated from an industrial bioleaching operation in northern Chile, where chalcocite is the major copper mineral and copper hydroxychloride atacamite is present in variable proportions in the ore. This strain has unique features as compared to the other members of the species, namely resistance to elevated concentrations of chloride, sulfate and metals. Basic microbiological features and genomic properties of this biotechnologically relevant strain are described in this work. The 2,475,669 bp draft genome is arranged into 74 scaffolds of 74 contigs. A total of 48 RNA genes and 2,834 protein coding genes were predicted from its annotation; 55 % of these were assigned a putative function. Release of the genome sequence of this strain will provide further understanding of the mechanisms used by acidophilic bacteria to endure high osmotic stress and high chloride levels and of the role of chloride-tolerant iron-oxidizers in industrial bioleaching operations.https://standardsingenomics.biomedcentral.com/articles/10.1186/s40793-016-0142-

Selection and evaluation of reference genes for improved interrogation of microbial transcriptomes: case study with the extremophile <it>Acidithiobacillus ferrooxidans</it>

<p>Abstract</p> <p>Background</p> <p>Normalization is a prerequisite for accurate real time PCR (qPCR) expression analysis and for the validation of microarray profiling data in microbial systems. The choice and use of reference genes that are stably expressed across samples, experimental conditions and designs is a key consideration for the accurate interpretation of gene expression data.</p> <p>Results</p> <p>Here, we evaluate a carefully selected set of reference genes derived from previous microarray-based transcriptional profiling experiments performed on <it>Acidithiobacillus ferrooxidans </it>and identify a set of genes with minimal variability under five different experimental conditions that are frequently used in Acidithiobacilli research. Suitability of these and other previously reported reference genes to monitor the expression of four selected target genes from <it>A. ferrooxidans </it>grown with different energy sources was investigated. Utilization of reference genes <it>map</it>, <it>rpoC</it>, <it>alaS </it>and <it>era </it>results in improved interpretation of gene expression profiles in <it>A. ferrooxidans</it>.</p> <p>Conclusion</p> <p>This investigation provides a validated set of reference genes for studying <it>A. ferrooxidans </it>gene expression under typical biological conditions and an initial point of departure for exploring new experimental setups in this microorganism and eventually in other closely related Acidithiobacilli. The information could also be of value for future transcriptomic experiments in other bacterial systems.</p

Type IV secretion systems diversity in the Acidithiobacillus genus

Dispersal between genomes of certain mobile genetic elements and their gene cargo depends on conjugative type IV secretion systems. In this work, variants of these nanomachines, tra and trb, have been profiled in publicly available genomes of the genus Acidithiobacillus and in a set of relevant strains. Our analyses show that the trb system is of broad distribution, being present in most of the strains analyzed. In turn, the tra type is present in fewer strains of A. ferrooxidans, A. ferrivorans, A. ferriphilus and A. thiooxidans, and generally correlates with the presence of larger ICE in the respective genomes. Herein, sequence conservation, genomic context, integration site and synteny analyses are performed to infer functionality of the T4SS systems of the acidithiobacilli

Metagenome-derived draft genome sequence of acidithiobacillus ferrooxidans RV1 from an abandoned gold tailing in neuquén, Argentina

In this work we report the metagenome-derived draft genomic sequence of an enrichment culture dominated by A. ferrooxidans obtained from an airlift bioreactor inoculated with the microbial consortium recovered from the “Relave Viejo” tailing. The genome of this culture was assembled de-novo and by reference, generating a consensus assembly of 3.0 Mb. On the basis of 16S rRNA (100 % identity), average nucleotide identity analysis (99.33% identity) and in silico DNA-DNA hybridization against A. ferrooxidans ATCC 23270T (97.9%), the recovered genome is confirmed to pertain to A. ferrooxidans species. Comparative genomics results are presented to uncover the genetic traits of the variant surviving lime treatment and to further explore the genomic diversity of these model iron oxidizing species.Fil: Ulloa, José Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Moya Beltrán, Ana. Fundación Ciencia & Vida; ChileFil: Issotta, Francisco. Fundación Ciencia & Vida; ChileFil: Nuñez, Harold. Fundación Ciencia & Vida; ChileFil: Covarrubias, Paulo C.. Fundación Ciencia & Vida; ChileFil: Donati, Edgardo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; ArgentinaFil: Quatrini, Raquel. Fundación Ciencia & Vida; ChileFil: Giaveno Filippa, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; Argentin

Architecture and gene repertoire of the flexible genome of the extreme acidophile Acidithiobacillus caldus

CITATION: Acuna, L. G. et al. 2013. Architecture and gene repertoire of the flexible genome of the extreme acidophile Acidithiobacillus caldus. PLoS ONE, 8(11):e78237, doi:10.1371/journal.pone.0078237.The original publication is available at http://journals.plos.orgBackground: Acidithiobacillus caldus is a sulfur oxidizing extreme acidophile and the only known mesothermophile within the Acidithiobacillales. As such, it is one of the preferred microbes for mineral bioprocessing at moderately high temperatures. In this study, we explore the genomic diversity of A. caldus strains using a combination of bioinformatic and experimental techniques, thus contributing first insights into the elucidation of the species pangenome. Principal Findings: Comparative sequence analysis of A. caldus ATCC 51756 and SM-1 indicate that, despite sharing a conserved and highly syntenic genomic core, both strains have unique gene complements encompassing nearly 20% of their respective genomes. The differential gene complement of each strain is distributed between the chromosomal compartment, one megaplasmid and a variable number of smaller plasmids, and is directly associated to a diverse pool of mobile genetic elements (MGE). These include integrative conjugative and mobilizable elements, genomic islands and insertion sequences. Some of the accessory functions associated to these MGEs have been linked previously to the flexible gene pool in microorganisms inhabiting completely different econiches. Yet, others had not been unambiguously mapped to the flexible gene pool prior to this report and clearly reflect strain-specific adaption to local environmental conditions. Significance: For many years, and because of DNA instability at low pH and recurrent failure to genetically transform acidophilic bacteria, gene transfer in acidic environments was considered negligible. Findings presented herein imply that a more or less conserved pool of actively excising MGEs occurs in the A. caldus population and point to a greater frequency of gene exchange in this econiche than previously recognized. Also, the data suggest that these elements endow the species with capacities to withstand the diverse abiotic and biotic stresses of natural environments, in particular those associated with its extreme econiche.http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0078237Publisher's versio