Cellular Response of Adapted and Non-Adapted Strains to Europium Eu(III) Compounds.

Europium is one of the most reactive lanthanides and humans use it in many different applications, but we still know little about its potential toxicity and cellular response to its exposure. Two strains of the eukaryotic microorganism model were adapted to high concentrations of two Eu(III) compounds (EuCl or EuO) and compared to a control strain and cultures treated with both compounds. In this ciliate, EuCl is more toxic than EuO.

Protozoan predation enhances stress resistance and antibiotic tolerance in Burkholderia cenocepacia by triggering the SOS response.

Bacterivorous protists are thought to serve as training grounds for bacterial pathogens by subjecting them to the same hostile conditions that they will encounter in the human host. Bacteria that survive intracellular digestion exhibit enhanced virulence and stress resistance after successful passage through protozoa but the underlying mechanisms are unknown. Here we show that the opportunistic pathogen Burkholderia cenocepacia survives phagocytosis by ciliates found in domestic and hospital sink drains, and viable bacteria are expelled packaged in respirable membrane vesicles with enhanced resistance to oxidative stress, desiccation, and antibiotics, thereby contributing to pathogen dissemination in the environment.

Quantitative proteomic analyses of a Pb-adapted Tetrahymena thermophila strain reveal the cellular strategy to Pb(II) stress including lead biomineralization to chloropyromorphite.

A strain of the protozoan ciliate Tetrahymena thermophila adapted to increasing Pb(II) concentrations over two years has shown that one of the resistance mechanisms to this extreme metal stress is the lead biomineralization to chloropyromorphite, one of the most stable minerals in the earth's crust. Several techniques such as microanalysis coupled to transmission and scanning electron microscopy (X-Ray Energy Disperse Spectroscopy), fluorescence microscopy and X-ray power diffraction analysis have revealed the presence of chloropyromorphite as crystalline aggregates of nano-globular structure, together with the presence of other secondary lead minerals. This is the first time that the existence of this type of biomineralization in a ciliate protozoan is described.

Heterologous Expression of the Phytochelatin Synthase from and Its Effect on Different Stress Factors in .

Phytochelatins (PCs) are cysteine-rich small peptides, enzymatically synthesized from reduced glutathione (GSH) by cytosolic enzyme phytochelatin synthase (PCS). The open reading frame (ORF) of the gene from the microalgae was heterologously expressed in strain DH5α, to analyze its role in protection against various abiotic agents that cause cellular stress. The transformed strain showed increased tolerance to exposure to different heavy metals (HMs) and arsenic (As), as well as to acidic pH and exposure to UVB, salt, or perchlorate.

Arsenate and arsenite differential toxicity in Tetrahymena thermophila.

A comparative analysis of toxicities of both arsenic forms (arsenite and arsenate) in the model eukaryotic microorganism Tetrahymena thermophila (ciliate protozoa) has shown the presence of various detoxification mechanisms and cellular effects comparable to those of animal cells under arsenic stress. In the wild type strain SB1969 arsenate is almost 2.5 times more toxic than arsenite.

Interactions with Arsenic: Mechanisms of Toxicity and Cellular Resistance in Eukaryotic Microorganisms.

Arsenic (As) is quite an abundant metalloid, with ancient origin and ubiquitous distribution, which represents a severe environmental risk and a global problem for public health. Microbial exposure to As compounds in the environment has happened since the beginning of time. Selective pressure has induced the evolution of various genetic systems conferring useful capacities in many microorganisms to detoxify and even use arsenic, as an energy source.

Glutathione Peroxidase Family: A Comparative Analysis of These Antioxidant Enzymes and Differential Gene Expression to Metals and Oxidizing Agents.

In the present work, an extensive analysis of the putative glutathione peroxidases (GPx) of the eukaryotic microorganism model is carried out. A comparative analysis with GPx present in other species and other very taxonomically diverse ciliates is also performed. A majority of ciliate GPx have replaced the selenocysteine (Sec) by Cys in its catalytic center, so they can be considered as phospholipid hydroperoxide glutathione peroxidases (PHGPx).

Toxicity, Physiological, and Ultrastructural Effects of Arsenic and Cadmium on the Extremophilic Microalga .

The cytotoxicity of cadmium (Cd), arsenate (As(V)), and arsenite (As(III)) on a strain of , isolated from the Rio Tinto, an acidic environment containing high metal(l)oid concentrations, was analyzed. We used a broad array of methods to produce complementary information: cell viability and reactive oxygen species (ROS) generation measures, ultrastructural observations, transmission electron microscopy energy dispersive x-ray microanalysis (TEM-XEDS), and gene expression. This acidophilic microorganism was affected differently by the tested metal/metalloid: It showed high resistance to arsenic while Cd was the most toxic heavy metal, showing an LC = 1.

Selenium cytotoxicity in Tetrahymena thermophila: New clues about its biological effects and cellular resistance mechanisms.

Selenium is an essential micronutrient but at high concentrations can produce severe cytotoxicity and genomic damage. We have evaluated the cytotoxicity, ultrastructural and mitochondrial alterations of the two main selenium inorganic species; selenite and selenate, in the eukaryotic microorganism Tetrahymena thermophila. In this ciliate, selenite is more toxic than selenate.

AP-1 (bZIP) Transcription Factors as Potential Regulators of Metallothionein Gene Expression in .

Metallothioneins (MT) are multi-stress proteins mainly involved in metal detoxification. MT gene expression is normally induced by a broad variety of stimulus and its gene expression regulation mainly occurs at a transcriptional level. Conserved motifs in the MT promoters have been described.

Genome plasticity in response to stress in Tetrahymena thermophila: selective and reversible chromosome amplification and paralogous expansion of metallothionein genes.

Extreme stress situations can induce genetic variations including genome reorganization. In ciliates like Tetrahymena thermophila, the approximately 45-fold ploidy of the somatic macronucleus may enable adaptive responses that depend on genome plasticity. To identify potential genome-level adaptations related to metal toxicity, we isolated three Tetrahymena thermophila strains after an extended adaptation period to extreme metal concentrations (Cd , Cu or Pb ).

Extreme metal adapted, knockout and knockdown strains reveal a coordinated gene expression among different Tetrahymena thermophila metallothionein isoforms.

Metallothioneins (MT) constitute a superfamily of small cytosolic proteins that are able to bind metal cations through numerous cysteine (Cys) residues. Like other organisms the ciliate Tetrahymena thermophila presents several MT isoforms, which have been classified into two subfamilies (Cd- and Cu-metallothioneins). The main aim of this study was to examine the specific functions and transcriptional regulation of the five MT isoforms present in T.

The Tetrahymena metallothionein gene family: twenty-one new cDNAs, molecular characterization, phylogenetic study and comparative analysis of the gene expression under different abiotic stressors.

Background: Ciliate metallothioneins (MTs) are included in family 7 of the MT superfamily. This family has been divided into two main subfamilies: 7a or CdMTs and 7b or CuMTs. All ciliate MTs reported have been isolated from different Tetrahymena species and present unique features with regard to standard MTs.