PrsQ2, a small periplasmic protein involved in increased uranium resistance in the bacterium Cupriavidus metallidurans

Uranium contamination is a widespread problem caused by natural and anthropogenic activities. Although microorganisms thrive in uranium-contaminated environments, little is known about the actual molecular mechanisms mediating uranium resistance. Here, we investigated the resistance mechanisms driving the adaptation of Cupriavidus metallidurans NA4 to toxic uranium concentrations. We selected a spontaneous mutant able to grow in the presence of 1 mM uranyl nitrate compared to 250 μM for the parental strain. The increased uranium resistance was acquired via the formation of periplasmic uranium-phosphate precipitates facilitated by the increased expression of a genus-specific small periplasmic protein, PrsQ2, regulated as non-cognate target of the CzcS2-CzcR2 two-component system. This study shows that bacteria can adapt to toxic uranium concentrations and explicates the complete genetic circuit behind the adaptation

Variation in genomic islands contribute to genome plasticity in cupriavidus metallidurans

<p>Abstract</p> <p>Background</p> <p>Different <it>Cupriavidus metallidurans </it>strains isolated from metal-contaminated and other anthropogenic environments were genotypically and phenotypically compared with <it>C. metallidurans </it>type strain CH34. The latter is well-studied for its resistance to a wide range of metals, which is carried for a substantial part by its two megaplasmids pMOL28 and pMOL30.</p> <p>Results</p> <p>Comparative genomic hybridization (CGH) indicated that the extensive arsenal of determinants involved in metal resistance was well conserved among the different <it>C. metallidurans </it>strains. Contrary, the mobile genetic elements identified in type strain CH34 were not present in all strains but clearly showed a pattern, although, not directly related to a particular biotope nor location (geographical). One group of strains carried almost all mobile genetic elements, while these were much less abundant in the second group. This occurrence was also reflected in their ability to degrade toluene and grow autotrophically on hydrogen gas and carbon dioxide, which are two traits linked to separate genomic islands of the Tn<it>4371</it>-family. In addition, the clear pattern of genomic islands distribution allowed to identify new putative genomic islands on chromosome 1 and 2 of <it>C. metallidurans </it>CH34.</p> <p>Conclusions</p> <p>Metal resistance determinants are shared by all <it>C. metallidurans </it>strains and their occurrence is apparently irrespective of the strain's isolation type and place. <it>Cupriavidus metallidurans </it>strains do display substantial differences in the diversity and size of their mobile gene pool, which may be extensive in some (including the type strain) while marginal in others.</p

Soil microbial community structure and functionality changes in response to long-term metal and radionuclide pollution

Microbial communities are essential for a healthy soil ecosystem. Metals and radionuclides can exert a persistent pressure on the soil microbial community. However, little is known on the effect of long-term co-contamination of metals and radionuclides on the microbial community structure and functionality. We investigated the impact of historical discharges of the phosphate and nuclear industry on the microbial community in the Grote Nete river basin in Belgium. Eight locations were sampled along a transect to the river edge and one location further in the field. Chemical analysis demonstrated a metal and radionuclide contamination gradient and revealed a distinct clustering of the locations based on all metadata. Moreover, a relation between the chemical parameters and the bacterial community structure was demonstrated. Although no difference in biomass was observed between locations, cultivation-dependent experiments showed that communities from contaminated locations survived better on singular metals than communities from control locations. Furthermore, nitrification, a key soil ecosystem process seemed affected in contaminated locations when combining metadata with microbial profiling. These results indicate that long-term metal and radionuclide pollution impacts the microbial community structure and functionality and provides important fundamental insights into microbial community dynamics in co-metal-radionuclide contaminated sites

Adaptive silver resistance in Cupriavidus metallidurans

Assessing and controlling microbial contamination during long-term manned spaceflight is of paramount importance as contamination can cause problems for the astronaut’s health and the infrastructure of the space station. Strains from the β-proteobacterial genera Cupriavidus and Ralstonia were identified and isolated during numerous monitoring campaigns from different space-related environments. This study aimed to gather more insights in the ability of these strains to thrive in these environments. All isolates acquired moderate to high tolerance against several stressors and can grow in oligotrophic conditions, enabling them to persist in the International Space Station and related environments in spite of the implemented disinfection and sterilization procedures. An important part of this study investigated the silver resistance mechanisms of the isolates, as silver is used to sanitize water sources in space. All isolates tolerated silver concentrations higher than those regularly measured in the drinking water aboard the ISS, and survived a 23-month exposure to silver in drinking water. Furthermore, rapid evolution towards significantly increased silver resistance (> 10-fold compared to the parental strain) was observed in C. metallidurans strains. Interestingly, the identified silver efflux pumps did not participate in this adaptive response. By contrast, the agrS gene coding for the histidine kinase of the two-component regulatory system AgrR-AgrS was shown to be affected either by an insertion sequence element or by point mutation, resulting in the increased transcriptional expression of the response regulator AgrR. AgrR on its turn cross-activated the expression of mmmQ coding for a small periplasmic protein, resulting in the increased silver resistance.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 201

Antimicrobial silver: Uses, toxicity and potential for resistance

This review gives a comprehensive overview of the widespread use and toxicity of silver compounds in many biological applications. Moreover, the bacterial silver resistance mechanisms and their spread in the environment are discussed. This study shows that it is important to understand in detail how silver and silver nanoparticles exert their toxicity and to understand how bacteria acquire silver resistance. Silver ions have shown to possess strong antimicrobial properties but cause no immediate and serious risk for human health, which led to an extensive use of silver-based products in many applications. However, the risk of silver nanoparticles is not yet clarified and their widespread use could increase silver release in the environment, which can have negative impacts on ecosystems. Moreover, it is shown that silver resistance determinants are widely spread among environmental and clinically relevant bacteria. These resistance determinants are often located on mobile genetic elements, facilitating their spread. Therefore, detailed knowledge of the silver toxicity and resistance mechanisms can improve its applications and lead to a better understanding of the impact on human health and ecosystems. © 2013 Springer Science+Business Media New York

Molecular Mechanisms Underlying Bacterial Uranium Resistance

Environmental uranium pollution due to industries producing naturally occurring radioactive material or nuclear accidents and releases is a global concern. Uranium is hazardous for ecosystems as well as for humans when accumulated through the food chain, through contaminated groundwater and potable water sources, or through inhalation. In particular, uranium pollution pressures microbial communities, which are essential for healthy ecosystems. In turn, microorganisms can influence the mobility and toxicity of uranium through processes like biosorption, bioreduction, biomineralization, and bioaccumulation. These processes were characterized by studying the interaction of different bacteria with uranium. However, most studies unraveling the underlying molecular mechanisms originate from the last decade. Molecular mechanisms help to understand how bacteria interact with radionuclides in the environment. Furthermore, knowledge on these underlying mechanisms could be exploited to improve bioremediation technologies. Here, we review the current knowledge on bacterial uranium resistance and how this could be used for bioremediation applications.</jats:p

Cupriavidus metallidurans Strains with Different Mobilomes and from Distinct Environments Have Comparable Phenomes

Cupriavidus metallidurans has been mostly studied because of its resistance to numerous heavy metals and is increasingly being recovered from other environments not typified by metal contamination. They host a large and diverse mobile gene pool, next to their native megaplasmids. Here, we used comparative genomics and global metabolic comparison to assess the impact of the mobilome on growth capabilities, nutrient utilization, and sensitivity to chemicals of type strain CH34 and three isolates (NA1, NA4 and H1130). The latter were isolated from water sources aboard the International Space Station (NA1 and NA4) and from an invasive human infection (H1130). The mobilome was expanded as prophages were predicted in NA4 and H1130, and a genomic island putatively involved in abietane diterpenoids metabolism was identified in H1130. An active CRISPR-Cas system was identified in strain NA4, providing immunity to a plasmid that integrated in CH34 and NA1. No correlation between the mobilome and isolation environment was found. In addition, our comparison indicated that the metal resistance determinants and properties are conserved among these strains and thus maintained in these environments. Furthermore, all strains were highly resistant to a wide variety of chemicals, much broader than metals. Only minor differences were observed in the phenomes (measured by phenotype microarrays), despite the large difference in mobilomes and the variable (shared by two or three strains) and strain-specific genomes.status: publishe

Cupriavidus metallidurans NA4 actively forms polyhydroxybutyrate-associated uranium-phosphate precipitates

Cupriavidus metallidurans is a model bacterium to study molecular metal resistance mechanisms and its use for the bioremediation of several metals has been shown. However, its mechanisms for radionuclide resistance are unexplored. We investigated the interaction with uranium and associated cellular response to uranium for Cupriavidus metallidurans NA4. Strain NA4 actively captured 98 +/- 1% of the uranium in its biomass after growing 24 h in the presence of 100 mu M uranyl nitrate. TEM HAADF-EDX microscopy confirmed intracellular uranium-phosphate precipitates that were mainly associated with polyhydroxybutyrate. Furthermore, whole transcriptome sequencing indicated a complex transcriptional response with upregulation of genes encoding general stress-related proteins and several genes involved in metal resistance. More in particular, gene clusters known to be involved in copper and silver resistance were differentially expressed. This study provides further insights into bacterial interactions with and their response to uranium. Our results could be promising for uranium bioremediation purposes with the multi-metal resistant bacterium C. metallidurans NA4

Cupriavidus metallidurans Strains with Different Mobilomes and from Distinct Environments Have Comparable Phenomes

Cupriavidus metallidurans has been mostly studied because of its resistance to numerous heavy metals and is increasingly being recovered from other environments not typified by metal contamination. They host a large and diverse mobile gene pool, next to their native megaplasmids. Here, we used comparative genomics and global metabolic comparison to assess the impact of the mobilome on growth capabilities, nutrient utilization, and sensitivity to chemicals of type strain CH34 and three isolates (NA1, NA4 and H1130). The latter were isolated from water sources aboard the International Space Station (NA1 and NA4) and from an invasive human infection (H1130). The mobilome was expanded as prophages were predicted in NA4 and H1130, and a genomic island putatively involved in abietane diterpenoids metabolism was identified in H1130. An active CRISPR-Cas system was identified in strain NA4, providing immunity to a plasmid that integrated in CH34 and NA1. No correlation between the mobilome and isolation environment was found. In addition, our comparison indicated that the metal resistance determinants and properties are conserved among these strains and thus maintained in these environments. Furthermore, all strains were highly resistant to a wide variety of chemicals, much broader than metals. Only minor differences were observed in the phenomes (measured by phenotype microarrays), despite the large difference in mobilomes and the variable (shared by two or three strains) and strain-specific genomes