scholarly journals Mechanisms of Metal Resistance and Homeostasis in Haloarchaea

Archaea ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Pallavee Srivastava ◽  
Meenal Kowshik
Keyword(s):  
Molecular Mechanisms ◽  
High Salinity ◽  
Metal Tolerance ◽  
Metal Speciation ◽  
Soda Lakes ◽  
Resistance Mechanisms ◽  
Metal Resistance ◽  
Metal Species ◽  
Physiological Processes ◽  
High Concentrations

Haloarchaea are the predominant microflora of hypersaline econiches such as solar salterns, soda lakes, and estuaries where the salinity ranges from 35 to 400 ppt. Econiches like estuaries and solar crystallizer ponds may contain high concentrations of metals since they serve as ecological sinks for metal pollution and also as effective traps for river borne metals. The availability of metals in these econiches is determined by the type of metal complexes formed and the solubility of the metal species at such high salinity. Haloarchaea have developed specialized mechanisms for the uptake of metals required for various key physiological processes and are not readily available at high salinity, beside evolving resistance mechanisms for metals with high solubility. The present paper seeks to give an overview of the main molecular mechanisms involved in metal tolerance in haloarchaea and focuses on factors such as salinity and metal speciation that affect the bioavailability of metals to haloarchaea. Global transcriptomic analysis during metal stress in these organisms will help in determining the various factors differentially regulated and essential for metal physiology.

scholarly journals EpABC Genes in the Adaptive Responses of Exophiala pisciphila to Metal Stress: Functional Importance and Relation to Metal Tolerance

2019 ◽  
Vol 85 (23) ◽  
Author(s):  
Guan-Hua Cao ◽  
Sen He ◽  
Di Chen ◽  
Tao Li ◽  
Zhi-Wei Zhao
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Abc Transporters ◽  
Molecular Mechanisms ◽  
Metal Tolerance ◽  
Metal Resistance ◽  
Metal Species ◽  
Cd Uptake ◽  
Content Type ◽  
Exophiala Pisciphila

ABSTRACT Exophiala pisciphila is one of the dominant dark septate endophytes (DSEs) colonizing metal-polluted slag heaps in southwest China. It shows numerous super-metal-tolerant characteristics, but the molecular mechanisms involved remain largely unknown. In the present study, the functional roles of a specific set of ATP-binding cassette (ABC) transporters in E. pisciphila were characterized. In total, 26 EpABC genes belonging to 6 subfamilies (ABCA to ABCG) were annotated in previous transcriptome sequencing libraries, and all were regulated by metal ions (Pb, Zn, and Cd), which was dependent on the metal species and/or concentrations tested. The results from the heterologous expression of 3 representative EpABC genes confirmed that the expression of EpABC2.1, EpABC3.1, or EpABC4.1 restored the growth of metal-sensitive mutant Saccharomyces cerevisiae strains and significantly improved the tolerance of Arabidopsis thaliana to Pb, Zn, and Cd. Interestingly, the expression of the 3 EpABC genes further altered metal (Pb, Zn, and Cd) uptake and accumulation and promoted growth by alleviating the inhibitory activity in yeast and thale cress caused by toxic ions. These functions along with their vacuolar location suggest that the 3 EpABC transporters may enhance the detoxification of vacuolar compartmentation via transport activities across their membranes. In conclusion, the 26 annotated EpABC transporters may play a major role in maintaining the homeostasis of various metal ions in different cellular compartments, conferring an extreme adaptative advantage to E. pisciphila in metal-polluted slag heaps. IMPORTANCE Many ABC transporters and their functions have been identified in animals and plants. However, little is known about ABC genes in filamentous fungi, especially DSEs, which tend to dominantly colonize the roots of plants growing in stressed environments. Our results deepen the understanding of the function of the ABC genes of a super-metal-tolerant DSE (E. pisciphila) in enhancing its heavy metal resistance and detoxification. Furthermore, the genetic resources of DSEs, e.g., numerous EpABC genes, especially from super-metal-tolerant strains in heavy metal-polluted environments, can be directly used for transgenic applications to improve tolerance and phytoextraction potential.

Copper Resistance Mechanisms of Biomining Bacteria and Archaea Living under Extremely High Concentrations of Metals

2009 ◽  
Vol 71-73 ◽  
pp. 279-282 ◽  
Author(s):  
A. Orell ◽  
C.A. Navarro ◽  
Carlos A. Jerez
Keyword(s):  
Resistance Mechanisms ◽  
Metal Resistance ◽  
Copper Resistance ◽  
Inorganic Polyphosphate ◽  
Resistance Determinants ◽  
High Metal ◽  
Pi Complex ◽  
Cu Resistance ◽  
High Concentrations ◽  
Cu Tolerance

Extremophiles such as the acidophilic Sulfolobus metallicus (Archaea) and Acidithiobacillus ferrooxidans (Bacteria) can resist Cu (CuSO4) concentrations of 200 mM and 800 mM respectively. These microorganisms are important in biomining processes to extract copper and other metals. A. ferrooxidans grown at low Cu concentrations (5 mM) expressed genes coding for ATPases most likely involved in pumping the metal from the cytoplasm to the periplasm of the bacterium. At 100 mM Cu the previous systems were repressed and there was a great induction in the expression of efflux systems known to use the proton motive force energy to export the metal outside the cell. These Cu-resistance determinants from A. ferrooxidans were found to be functional since when expressed in Escherichia coli they conferred higher Cu tolerance to it. Novel Cu-resistance determinants for A. ferrooxidans were found and characterized. S. metallicus possessed at least 2 CopM metallochaperones and 2 CopA ATPases whose expressions were induced by Cu (5 to 50 mM). Furthermore, we previously reported that both microorganisms accumulate high levels of inorganic polyphosphate (PolyP) and that intracellular Cu concentration stimulates polyP hydrolysis. The resulting Pi would then be transported out of the cell as a metal-Pi complex to detoxify the cells. In addition, our results suggest that at high Cu concentrations polyP could also provide energy for the metal efflux. All the data suggest that both biomining microorganisms use different systems to respond to Cu depending on the extracellular concentrations of the metal and suggest that the presence of different additional systems to respond to Cu may explain the extremely high metal resistance of these extremophiles.

scholarly journals Multiple Megaplasmids Confer Extremely High Levels of Metal Tolerance in Alteromonas Strains

2019 ◽  
Vol 86 (3) ◽  
Author(s):  
Kathleen D. Cusick ◽  
Shawn W. Polson ◽  
Gabriel Duran ◽  
Russell T. Hill
Keyword(s):  
Gene Transfer ◽  
Pseudomonas Syringae ◽  
Molecular Mechanisms ◽  
Metal Tolerance ◽  
Bioinformatic Analysis ◽  
Metal Resistance ◽  
Copper Resistance ◽  
The Other ◽  
Copper Tolerance ◽  
Content Type

ABSTRACT Alteromonas is a widely distributed genus of marine Gammaproteobacteria, with representatives shown to be key players in diverse processes, including biogeochemical cycling and biofouling of marine substrata. While Alteromonas spp. are early colonizers of copper-based antifouling paints on marine vessels, their mechanism of tolerance is poorly understood. PacBio whole-genome sequencing of Alteromonas macleodii strains CUKW and KCC02, isolated from Cu/Ni alloy test coupons submerged in oligotrophic coastal waters, indicated the presence of multiple megaplasmids (ca. 200 kb) in both. A pulsed-field gel electrophoresis method was developed and used to confirm the presence of multiple megaplasmids in these two strains; it was then used to screen additional Alteromonas strains for which little to no sequencing data exist. Plasmids were not detected in any of the other strains. Bioinformatic analysis of the CUKW and KCC02 plasmids identified numerous genes associated with metal resistance. Copper resistance orthologs from both the Escherichia coli Cue and Cus and Pseudomonas syringae Cop systems were present, at times as multiple copies. Metal growth assays in the presence of copper, cobalt, manganese, and zinc performed with 10 Alteromonas strains demonstrated the ability of CUKW and KCC02 to grow at metal concentrations inhibitory to all the other strains tested. This study reports multiple megaplasmids in Alteromonas strains. Bioinformatic analysis of the CUKW and KCC02 plasmids indicate that they harbor elements of the Tra system conjugation apparatus, although their type of mobility remains to be experimentally verified. IMPORTANCE Copper is commonly used as an antifouling agent on ship hulls. Alteromonas spp. are early colonizers of copper-based antifouling paint, but their mechanism of tolerance is poorly understood. Sequencing of A. macleodii strains isolated from copper test materials for marine ships indicated the presence of multiple megaplasmids. Plasmids serve as key vectors in horizontal gene transfer and confer traits such as metal resistance, detoxification, ecological interaction, and antibiotic resistance. Bioinformatic analysis identified many metal resistance genes and genes associated with mobility. Understanding the molecular mechanisms and capacity for gene transfer within marine biofilms provides a platform for the development of novel antifouling solutions targeting genes involved in copper tolerance and biofilm formation.

scholarly journals Increasing Temperature Alters the Effects of Extracellular Copper on Thalassiosira pseudonana Physiology and Transcription

2021 ◽  
Vol 9 (8) ◽  
pp. 816
Author(s):  
Xinjie Wang ◽  
Wang Cao ◽  
Hong Du ◽  
Wenhua Liu ◽  
Ping Li
Keyword(s):  
Molecular Mechanisms ◽  
Thalassiosira Pseudonana ◽  
Transport Systems ◽  
Centric Diatom ◽  
Copper Transporter ◽  
Ambient Temperatures ◽  
Cu Content ◽  
Physiological Processes ◽  
High Concentrations ◽  
Increasing Temperature

Copper (Cu) is essential for many physiological processes in phytoplankton, including electron-transfer reactions and high-affinity Fe transport systems. However, at high concentrations, Cu can have a toxic effect on phytoplankton. Phytoplankton’s tolerance to certain toxicants in marine ecosystems cannot always be solely attributed to the presence of compounds, as various environmental factors including temperature can also indirectly influence their effects on organisms. In this study, we investigated the effects of different Cu concentrations (0, 19.6, 160, 800, and 8000 nM) on the growth and physiological changes in the centric diatom Thalassiosira pseudonana (CCMP 1335) when simultaneously applied with temperature cultivation of 20 °C and 25 °C. At low (0 nM) and high (8000 nM) Cu concentrations, the growth rate of T. pseudonana was inhibited, though an increase in temperature lessened this inhibition. There were no significant changes in the POC:PON ratio during all of the treatments. However, increasing the temperature significantly decreased the POC: POP, PON: POP and BSi: POP ratios of T. pseudonana. The intracellular Cu content of T. pseudonana varied from 0.13 to 13.28 fg cell−1 in response to increases in ambient Cu concentrations. Lastly, an increase in the Cu concentration decreased the transcriptional expression of CTR (copper transporter), 3Hfcp (photosynthetic protein), and Sit1 (silica shell formation) encoding genes. In conclusion, our results indicated that T. pseudonana can adapt to physiological processes and molecular mechanisms in response to varying Cu concentrations and ambient temperatures.

scholarly journals Genomic and Transcriptomic Insights into How Bacteria Withstand High Concentrations of Benzalkonium Chloride Biocides

2018 ◽  
Vol 84 (12) ◽  
pp. e00197-18 ◽  
Author(s):  
Minjae Kim ◽  
Janet K. Hatt ◽  
Michael R. Weigand ◽  
Raj Krishnan ◽  
Spyros G. Pavlostathis ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Genetic Markers ◽  
Molecular Mechanisms ◽  
Efflux Pump ◽  
Integrated Approach ◽  
Resistance Mechanisms ◽  
Health Care Facilities ◽  
Typical Application ◽  
Content Type ◽  
High Concentrations

ABSTRACTBenzalkonium chlorides (BAC) are commonly used biocides in broad-spectrum disinfectant solutions. How microorganisms cope with BAC exposure remains poorly understood, despite its importance for disinfection and disinfectant-induced antibiotic resistance. To provide insights into these issues, we exposed two isolates of an opportunistic pathogen,Pseudomonas aeruginosa, to increasing concentrations of BAC. One isolate was preadapted to BAC, as it originated from a bioreactor fed with subinhibitory concentrations of BAC for 3 years, while the other originated from a bioreactor that received no BAC. Replicated populations of both isolates were able to survive high concentrations of BAC, up to 1,200 and 1,600 mg/liter for the non- and preadapted strains, respectively, exceeding typical application doses. Transcriptome sequencing (RNA-seq) analysis revealed upregulation of efflux pump genes and decreased expression of porins related to BAC transport as well as reduced growth rate. Increased expression of spermidine (a polycation) synthase genes and mutations in thepmrB(polymyxin resistance) gene, which cause a reduction in membrane negative charge, suggested that a major adaptation to exposure to the cationic surfactant BAC was to actively stabilize cell surface charge. Collectively, these results revealed thatP. aeruginosaadapts to BAC exposure by a combination of mechanisms and provided genetic markers to monitor BAC-resistant organisms that may have applications in the practice of disinfection.IMPORTANCEBAC are widely used as biocides in disinfectant solutions, food-processing lines, domestic households, and health care facilities. Due to their wide use and mode of action, there has been rising concern that BAC may promote antibiotic resistance. Consistent with this idea, at least 40 outbreaks have been attributed to infection by disinfectant- and antibiotic-resistant pathogens such asP. aeruginosa. However, the underlying molecular mechanisms that bacteria use to deal with BAC exposure remain poorly elucidated. Elucidating these mechanisms may be important for monitoring and limiting the spread of disinfectant-resistant pathogens. Using an integrated approach that combined genomics and transcriptomics with physiological characterization of BAC-adapted isolates, this study provided a comprehensive understanding of the BAC resistance mechanisms inP. aeruginosa. Our findings also revealed potential genetic markers to detect and monitor the abundance of BAC-resistant pathogens across clinical or environmental settings. This work contributes new knowledge about high concentrations of benzalkonium chlorides disinfectants-resistance mechanisms at the whole-cell genomic and transcriptomic level.

scholarly journals Metagenomic and Metatranscriptomic Study of Microbial Metal Resistance in an Acidic Pit Lake

2020 ◽  
Vol 8 (9) ◽  
pp. 1350
Author(s):  
Diana Ayala-Muñoz ◽  
William D. Burgos ◽  
Javier Sánchez-España ◽  
Estelle Couradeau ◽  
Carmen Falagán ◽  
...  
Keyword(s):  
Deep Layer ◽  
Expression Patterns ◽  
Iberian Pyrite Belt ◽  
Resistance Mechanisms ◽  
Metal Resistance ◽  
Metal Species ◽  
Nutrient Concentrations ◽  
Pit Lake ◽  
Metal Concentrations ◽  
Resistance Strategies

Cueva de la Mora (CM) is an acidic, meromictic pit lake in the Iberian Pyrite Belt characterized by extremely high metal(loid) concentrations and strong gradients in oxygen, metal, and nutrient concentrations. We hypothesized that geochemical variations with depth would result in differences in community composition and in metal resistance strategies among active microbial populations. We also hypothesized that metal resistance gene (MRG) expression would correlate with toxicity levels for dissolved metal species in the lake. Water samples were collected in the upper oxic layer, chemocline, and deep anoxic layer of the lake for shotgun metagenomic and metatranscriptomic sequencing. Metagenomic analyses revealed dramatic differences in the composition of the microbial communities with depth, consistent with changing geochemistry. Based on relative abundance of taxa identified in each metagenome, Eukaryotes (predominantly Coccomyxa) dominated the upper layer, while Archaea (predominantly Thermoplasmatales) dominated the deep layer, and a combination of Bacteria and Eukaryotes were abundant at the chemocline. We compared metal resistance across communities using a curated list of protein-coding MRGs with KEGG Orthology identifiers (KOs) and found that there were broad differences in the metal resistance strategies (e.g., intracellular metal accumulation) expressed by Eukaryotes, Bacteria, and Archaea. Although normalized abundances of MRG and MRG expression were generally higher in the deep layer, expression of metal-specific genes was not strongly related to variations in specific metal concentrations, especially for Cu and As. We also compared MRG potential and expression in metagenome assembled genomes (MAGs) from the deep layer, where metal concentrations are highest. Consistent with previous work showing differences in metal resistance mechanisms even at the strain level, MRG expression patterns varied strongly among MAG populations from the same depth. Some MAG populations expressed very few MRG known to date, suggesting that novel metal resistance strategies remain to be discovered in uncultivated acidophiles.

Metal and phosphate speciation during anaerobic digestion of phosphorus rich sludge

1997 ◽  
Vol 36 (6-7) ◽  
pp. 191-200 ◽  
Author(s):  
C. M. Carliell ◽  
A. D. Wheatley
Keyword(s):  
Anaerobic Digestion ◽  
Metal Speciation ◽  
Extraction Methods ◽  
Phosphate Removal ◽  
Metal Species ◽  
Chemical Extraction ◽  
Inorganic P ◽  
Similar Work ◽  
Extractable P ◽  
Phosphate Speciation

Chemical extraction methods are used to investigate metal and phosphate speciation during anaerobic digestion of phosphorus-rich sludge. Tests were performed using model compounds to evaluate the efficacy of the reagents in the extraction sequences and these results compared with similar work by other researchers. The metal speciation method was found to be suitable for identifying shifts in metal distribution but was unrepresentative of actual metal species. The phosphate speciation method did give adequate separation of the phosphate compounds tested. Full-scale digesters treating chemical and biological phosphate removal (CPR and BPR) sludge were analysed according to the methods developed. Results show that digestion of CPR sludge did not increase the soluble P concentration in the digester and that most of the precipitated phosphorus appeared to be retained in the sludge as inorganic P. The digester treating BPR sludge showed increased soluble and water-extractable P, in comparison to the control digester. Trace metal speciation profiles were found to be affected by addition of CPR sludge.

Anticancer Agents Based on Vulnerable Components in a Signalling Pathway

2020 ◽  
Vol 20 (10) ◽  
pp. 886-907 ◽  
Author(s):  
Ankur Vaidya ◽  
Shweta Jain ◽  
Sanjeev Sahu ◽  
Pankaj Kumar Jain ◽  
Kamla Pathak ◽  
...  
Keyword(s):  
Anticancer Agents ◽  
Dna Methyltransferase ◽  
Leucine Zipper ◽  
Molecular Mechanisms ◽  
Resistance Mechanisms ◽  
Sphingosine Kinase 2 ◽  
Family Protein ◽  
Rational Combination ◽  
Protein Kinase Akt ◽  
Parp 1

Traditional cancer treatment includes surgery, chemotherapy, radiotherapy and immunotherapy that are clinically beneficial, but are associated with drawbacks such as drug resistance and side effects. In quest for better treatment, many new molecular targets have been introduced in the last few decades. Finding new molecular mechanisms encourages researchers to discover new anticancer agents. Exploring the mechanism of action also facilitates anticipation of potential resistance mechanisms and optimization of rational combination therapies. The write up describes the leading molecular mechanisms for cancer therapy, including mTOR, tyrosine Wee1 kinase (WEE1), Janus kinases, PI3K/mTOR signaling pathway, serine/threonine protein kinase AKT, checkpoint kinase 1 (Chk1), maternal embryonic leucine-zipper kinase (MELK), DNA methyltransferase I (DNMT1), poly (ADP-ribose) polymerase (PARP)-1/-2, sphingosine kinase-2 (SK2), pan-FGFR, inhibitor of apoptosis (IAP), murine double minute 2 (MDM2), Bcl-2 family protein and reactive oxygen species 1 (ROS1). Additionally, the manuscript reviews the anticancer drugs currently under clinical trials.

scholarly journals Heavy Metal Tolerance Trend in Extended-Spectrum β-Lactamase Encoding Strains Recovered from Food Samples

2021 ◽  
Vol 18 (9) ◽  
pp. 4718
Author(s):  
Kashaf Junaid ◽  
Hasan Ejaz ◽  
Iram Asim ◽  
Sonia Younas ◽  
Humaira Yasmeen ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Metal Tolerance ◽  
Heavy Metal Tolerance ◽  
Heavy Metal Resistance ◽  
Metal Resistance ◽  
Food Samples ◽  
Esbl Production ◽  
Extended Spectrum ◽  
Retail Food ◽  
Esbl Producers

This study evaluates bacteriological profiles in ready-to-eat (RTE) foods and assesses antibiotic resistance, extended-spectrum β-lactamase (ESBL) production by gram-negative bacteria, and heavy metal tolerance. In total, 436 retail food samples were collected and cultured. The isolates were screened for ESBL production and molecular detection of ESBL-encoding genes. Furthermore, all isolates were evaluated for heavy metal tolerance. From 352 culture-positive samples, 406 g-negative bacteria were identified. Raw food samples were more often contaminated than refined food (84.71% vs. 76.32%). The predominant isolates were Klebsiella pneumoniae (n = 76), Enterobacter cloacae (n = 58), and Escherichia coli (n = 56). Overall, the percentage of ESBL producers was higher in raw food samples, although higher occurrences of ESBL-producing E. coli (p = 0.01) and Pseudomonas aeruginosa (p = 0.02) were observed in processed food samples. However, the prevalence of ESBL-producing Citrobacter freundii in raw food samples was high (p = 0.03). Among the isolates, 55% were blaCTX-M, 26% were blaSHV, and 19% were blaTEM. Notably, heavy metal resistance was highly prevalent in ESBL producers. These findings demonstrate that retail food samples are exposed to contaminants including antibiotics and heavy metals, endangering consumers.

scholarly journals Transport, functions, and interaction of calcium and manganese in plant organellar compartments

2021 ◽  
Author(s):  
Jie He ◽  
Nico Rössner ◽  
Minh T T Hoang ◽  
Santiago Alejandro ◽  
Edgar Peiter
Keyword(s):  
Molecular Mechanisms ◽  
Metal Tolerance ◽  
Essential Elements ◽  
Natural Resistance ◽  
Ionic Radii ◽  
Bivalent Cation ◽  
Cyclic Nucleotide Gated Channels ◽  
Complex Processes ◽  
Open Questions ◽  
Golgi Network

Abstract Calcium (Ca2+) and manganese (Mn2+) are essential elements for plants and have similar ionic radii and binding coordination. They are assigned specific functions within organelles, but share many transport mechanisms to cross organellar membranes. Despite their points of interaction, those elements are usually investigated and reviewed separately. This review takes them out of this isolation. It highlights our current mechanistic understanding and points to open questions of their functions, their transport, and their interplay in the endoplasmic reticulum (ER), vesicular compartments [Golgi apparatus, trans-Golgi Network (TGN), prevacuolar compartment (PVC)], vacuoles, chloroplasts, mitochondria, and peroxisomes. Complex processes demanding these cations, such as Mn2+-dependent glycosylation or systemic Ca2+ signaling, are covered in some detail if they have not been reviewed recently or if recent findings add to current models. The function of Ca2+ as signaling agent released from organelles into the cytosol and within the organelles themselves is a recurrent theme of this review, again keeping the interference by Mn2+ in mind. The involvement of organellar channels [e.g., Glutamate-Receptor-Likes (GLRs), Cyclic-Nucleotide-Gated Channels (CNGCs), Mitochondrial Conductivity Units (MCUs), Two-Pore Channel1 (TPC1)], transporters [e.g., Natural-Resistance-Associated Macrophage Proteins (NRAMPs), Calcium Exchangers (CAXs), Metal-Tolerance Proteins (MTPs), Bivalent-Cation Transporters (BICATs)] and pumps [Autoinhibited Ca2+-ATPases (ACAs), ER Ca2+-ATPases (ECAs)] in the import and export of organellar Ca2+ and Mn2+ is scrutinized, whereby current controversial issues are pointed out. Mechanisms in animals and yeast are taken into account where they may provide a blueprint for processes in plants, in particular with respect to tunable molecular mechanisms of Ca2+-versus-Mn2+ selectivity.

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