Review of "Adaptation to life at high salt concentrations in Archaea, Bacteria, and Eukarya" Edited by Nina Gunde-Cimerman, Aharon Oren, and Ana Plemenitaš

The diversity of hypersaline environments and the physiology of representative organisms are only beginning to be understood. Recent progress in this area is documented in "Adaptation to life at high salt concentrations in Archaea, Bacteria, and Eukarya" – eds. Nina Gunde-Cimerman, Aharon Oren and Ana Plemenitas. The 34 chapters successfully paint a fascinating emerging picture of these environments and the microorganisms inhabiting them

Genes involved in arsenic transformation and resistance associated with different levels of arsenic-contaminated soils

<p>Abstract</p> <p>Background</p> <p>Arsenic is known as a toxic metalloid, which primarily exists in inorganic form [As(III) and As(V)] and can be transformed by microbial redox processes in the natural environment. As(III) is much more toxic and mobile than As(V), hence microbial arsenic redox transformation has a major impact on arsenic toxicity and mobility which can greatly influence the human health. Our main purpose was to investigate the distribution and diversity of microbial arsenite-resistant species in three different arsenic-contaminated soils, and further study the As(III) resistance levels and related functional genes of these species.</p> <p>Results</p> <p>A total of 58 arsenite-resistant bacteria were identified from soils with three different arsenic-contaminated levels. Highly arsenite-resistant bacteria (MIC > 20 mM) were only isolated from the highly arsenic-contaminated site and belonged to <it>Acinetobacter</it>, <it>Agrobacterium</it>, <it>Arthrobacter</it>, <it>Comamonas</it>, <it>Rhodococcus</it>, <it>Stenotrophomonas </it>and <it>Pseudomonas</it>. Five arsenite-oxidizing bacteria that belonged to <it>Achromobacter</it>, <it>Agrobacterium </it>and <it>Pseudomonas </it>were identified and displayed a higher average arsenite resistance level than the non-arsenite oxidizers. 5 <it>aoxB </it>genes encoding arsenite oxidase and 51 arsenite transporter genes [18 <it>arsB</it>, 12 <it>ACR3</it>(<it>1</it>) and 21 <it>ACR3</it>(<it>2</it>)] were successfully amplified from these strains using PCR with degenerate primers. The <it>aoxB </it>genes were specific for the arsenite-oxidizing bacteria. Strains containing both an arsenite oxidase gene (<it>aoxB</it>) and an arsenite transporter gene (<it>ACR3 or arsB</it>) displayed a higher average arsenite resistance level than those possessing an arsenite transporter gene only. Horizontal transfer of <it>ACR3</it>(<it>2</it>) and <it>arsB </it>appeared to have occurred in strains that were primarily isolated from the highly arsenic-contaminated soil.</p> <p>Conclusion</p> <p>Soils with long-term arsenic contamination may result in the evolution of highly diverse arsenite-resistant bacteria and such diversity was probably caused in part by horizontal gene transfer events. Bacteria capable of both arsenite oxidation and arsenite efflux mechanisms had an elevated arsenite resistance level.</p

Evolution of the Symbiosis-Specific GRAS Regulatory Network in Bryophytes

Arbuscular mycorrhiza is one of the most common plant symbiotic interactions observed today. Due to their nearly ubiquitous occurrence and their beneficial impact on both partners it was suggested that this mutualistic interaction was crucial for plants to colonize the terrestrial habitat approximately 500 Ma ago. On the plant side the association is established via the common symbiotic pathway (CSP). This pathway allows the recognition of the fungal symbiotic partner, subsequent signaling to the nucleus, and initiation of the symbiotic program with respect to specific gene expression and cellular re-organization. The downstream part of the CSP is a regulatory network that coordinates the transcription of genes necessary to establish the symbiosis, comprising multiple GRAS transcription factors (TFs). These regulate their own expression as an intricate transcriptional network. Deduced from non-host genome data the loss of genes encoding CSP components coincides with the loss of the interaction itself. Here, we analyzed bryophyte species with special emphasis on the moss Physcomitrella patens, supposed to be a non-host, for the composition of the GRAS regulatory network components. We show lineage specific losses and expansions of several of these factors in bryophytes, potentially coinciding with the proposed host/non-host status of the lineages. We evaluate losses and expansions and infer clade-specific evolution of GRAS TFs

Plasma Disappearance Rate of Indocyanine Green for Determination of Liver Function in Three Different Models of Shock

The measurement of the liver function via the plasma disappearance rate of indocyanine green (PDRICG) is a sensitive bed-side tool in critical care. Yet, recent evidence has questioned the value of this method for hyperdynamic conditions. To evaluate this technique in different hemodynamic settings, we analyzed the PDRICG and corresponding pharmacokinetic models after endotoxemia or hemorrhagic shock in rats. Male anesthetized Sprague-Dawley rats underwent hemorrhage (mean arterial pressure 35 ± 5 mmHg, 90 min) and 2 h of reperfusion, or lipopolysaccharide (LPS) induced moderate or severe (1.0 vs. 10 mg/kg) endotoxemia for 6 h (each n = 6). Afterwards, PDRICG was measured, and pharmacokinetic models were analyzed using nonlinear mixed effects modeling (NONMEM®). Hemorrhagic shock resulted in a significant decrease of PDRICG, compared with sham controls, and a corresponding attenuation of the calculated ICG clearance in 1- and 2-compartment models, with the same log-likelihood. The induction of severe, but not moderate endotoxemia, led to a significant reduction of PDRICG. The calculated ICG blood clearance was reduced in 1-compartment models for both septic conditions. 2-compartment models performed with a significantly better log likelihood, and the calculated clearance of ICG did not correspond well with PDRICG in both LPS groups. 3-compartment models did not improve the log likelihood in any experiment. These results demonstrate that PDRICG correlates well with ICG clearance in 1- and 2-compartment models after hemorrhage. In endotoxemia, best described by a 2-compartment model, PDRICG may not truly reflect the ICG clearance

Genome Sequences of Two Copper-Resistant Escherichia coli Strains Isolated from Copper-Fed Pigs.

The draft genome sequences of two copper-resistant Escherichia coli strains were determined. These had been isolated from copper-fed pigs and contained additional putative operons conferring copper and other metal and metalloid resistances

<em>In silico</em> analysis of bacterial arsenic islands reveals remarkable synteny and functional relatedness between arsenate and phosphate

In order to construct a more universal model for understanding the genetic requirements for bacterial AsIII oxidation, an in silico examination of the available sequences in the GenBank was assessed and revealed 21 conserved 5–71 kb arsenic islands within phylogenetically diverse bacterial genomes. The arsenic islands included the AsIII oxidase structural genes aioBA, ars operons (e.g., arsRCB) which code for arsenic resistance, and pho, pst, and phn genes known to be part of the classical phosphate stress response and that encode functions associated with regulating and acquiring organic and inorganic phosphorus. The regulatory genes aioXSR were also an island component, but only in Proteobacteria and orientated differently depending on whether they were in α-Proteobacteria or β-/γ-Proteobacteria. Curiously though, while these regulatory genes have been shown to be essential to AsIII oxidation in the Proteobacteria, they are absent in most other organisms examined, inferring different regulatory mechanism(s) yet to be discovered. Phylogenetic analysis of the aio, ars, pst, and phn genes revealed evidence of both vertical inheritance and horizontal gene transfer (HGT). It is therefore likely the arsenic islands did not evolve as a whole unit but formed independently by acquisition of functionally related genes and operons in respective strains. Considering gene synteny and structural analogies between arsenate and phosphate, we presumed that these genes function together in helping these microbes to be able to use even low concentrations of phosphorus needed for vital functions under high concentrations of arsenic, and defined these sequences as the arsenic islands

Disrupting ROS-protection mechanism allows hydrogen peroxide to accumulate and oxidize Sb(III) to Sb(V) in Pseudomonas stutzeri TS44

Primers used in this study. (DOC 35 kb

Draft Genome Sequence of Se(IV)-Reducing Bacterium Pseudomonas migulae ES3-33

Pseudomonas migulae ES3-33 is a Gram-negative strain that strongly reduces Se(IV) and was isolated from a selenium mining area in Enshi, southwest China. Here we present the draft genome of this strain containing potential genes involved in selenite reduction and a large number of genes encoding resistances to copper and antibiotics

Chaperone-mediated copper handling in the periplasm

Metal transport systems are broadly utilized to maintain low levels of metals to prevent cellular malfunction caused by an overabundance of metals. The CusCFBA Cu(I)/Ag(I) resistance system, commonly found in Gram-negative organisms, typically consists of a tripartite CBA transport complex that spans both the inner and outer membranes as well as a small periplasmic protein, CusF. In the CusCFBA system, CusF functions as a metallochaperone which transfers metal to the tripartite complex to aid in metal resistance. However, CusF-like proteins have also been observed in genomic contexts apart from the CBA-type transport systems, suggesting it could either play a role as a metallochaperone to other systems or have other roles than that of a metallochaperone. In this review, we focus on the molecular function of CusF in the CusCFBA transport system and discuss the metal transport pathway through this system. In addition we briefly discuss the potential functions of CusF-like proteins in other contexts

Distribution of Arsenic Resistance Genes in Prokaryotes

Arsenic is a metalloid that occurs naturally in aquatic and terrestrial environments. The high toxicity of arsenic derivatives converts this element in a serious problem of public health worldwide. There is a global arsenic geocycle in which microbes play a relevant role. Ancient exposure to arsenic derivatives, both inorganic and organic, has represented a selective pressure for microbes to evolve or acquire diverse arsenic resistance genetic systems. In addition, arsenic compounds appear to have been used as a toxin in chemical warfare for a long time selecting for an extended range of arsenic resistance determinants. Arsenic resistance strategies rely mainly on membrane transport pathways that extrude the toxic compounds from the cell cytoplasm. The ars operons, first discovered in bacterial R-factors almost 50 years ago, are the most common microbial arsenic resistance systems. Numerous ars operons, with a variety of genes and different combinations of them, populate the prokaryotic genomes, including their accessory plasmids, transposons, and genomic islands. Besides these canonical, widespread ars gene clusters, which confer resistance to the inorganic forms of arsenic, additional genes have been discovered recently, which broadens the spectrum of arsenic tolerance by detoxifying organic arsenic derivatives often used as toxins. This review summarizes the presence, distribution, organization, and redundance of arsenic resistance genes in prokaryotes