In alignment with Circular Economy principles, the recovery and upcycling of Tellurium (Te) for the production of advanced sensors and particles for therapy and bioimaging bioimaging-particularly through bio-based strategies-has garnered significant interest. The bioproduction of tellurium-particles (TePs) offers an efficient and eco-friendly alternative to conventional hydrothermal and chemical processes. However, downstream processing (DSP), specifically the recovery and separation of TePs, remains a major challenge for the practical implementation of these biogenic approaches. Therefore, innovative, eco-friendly, and low-energy extraction are urgently needed to replace existing techniques that rely on energy-intensive processes or hazardous chemicals. This study presents a novel approach for the room-temperature biogenic production of TePs using strain Paenibacillus pabulis ALJ109b. The key lies in the process's reliance solely on a nitrogen-enriched growth medium and the mid-to-late growth phase addition of Te(IV) to enhance TePs yields. Notably, our integrated and simple recovery strategy employs eco-friendly solvents for the efficient separation of TePs, ensuring a sustainable and scalable approach. Optimal bacterial growth and tellurite reduction were achieved with Trypticase Soy Broth when the metalloid was added during the late exponential phase (4 h), resulting in a 24 % reduction in Te(IV) concentration after 20 h. Various cell disruption methods were evaluated for the TePs recovery, with 3 min of sonication in water providing the most effective for particle release. Additionally, a 1:1 mixture of water and ethanol emerged as the most efficient solvent for separating TePs from cell debris. TePs recovered after 8 h of bacterial growth exhibited smaller and more stable aggregates compared to those recovered after 24 h. Lowintensity sonication had minimal effects on particle size and surface charge. These findings confirm the potential of P. pabulis ALJ109b for the biogenic production of TePs. Furthermore, the integration of low-cost and ecofriendly solvents in straightforward solid-liquid extraction processes provides a sustainable and efficient solution for cell lysis and recovering of these microparticles from bacterial biomass.

Yttrium (Y), classified among the rare earth elements (REEs), plays an important role in modern technologies, contributing to the increase in mineral extraction and processing activities. Consequently, this trend leads to an elevated release of economically significant but potentially dangerous elements into the environment. Acid mine drainage (AMD) is recognized as a concern due to the presence of hazardous elements, however, it simultaneously serves as a valuable secondary source of critical elements.This study explores the recovery of Y(III) from multi-element solutions that simulate real AMD in terms of pH, the presence of various divalent cations, and sulfate. It investigates the recovery of Y(III) from multi-element solutions using a two-stage approach: cation exchange membrane (CEM) for Donnan dialytic Y(III) transport followed by biological treatment for Y recovery. The efficiency of Y(III) transport across the acid-resistant CEM, Fumasep FKS-PEP-130, reached 68.6 %, even in the presence of accompanying cations. The addition of strain J19, highly resistant to Y, led to approximately 89 % removal of Y(III) from the feed compartment.The proposed CEM transport/biological treatment concept offers the first efficient Y(III) recovery approach. This method will benefit future assays with real-field AMD, as it minimizes waste generation while effectively separating metals from sulfate, thereby reducing environmental impact.

Aims Yttrium (Y) holds significant industrial and economic importance, being listed as a critical element on the European list of critical elements, thus emphasizing the high priority for its recovery. Bacterial strategies play a crucial role in the biorecovery of metals, offering a promising and environmentally friendly approach. Therefore, gaining a comprehensive understanding of the underlying mechanisms behind bacterial resistance, as well as the processes of bioaccumulation and biotransformation, is of paramount importance.Methods and results A total of 207 Alphaproteobacteria strains from the University of Coimbra Bacteria Culture Collection were tested for Y-resistance. Among these, strain Mesorhizobium qingshengii J19 exhibited high resistance (up to 4 mM Y) and remarkable Y accumulation capacity, particularly in the cell membrane. Electron microscopy revealed Y-phosphate interactions, while X-ray diffraction identified Y(PO3)39H2O biocrystals produced by J19 cells.Conclusion This study elucidates Y immobilization through biomineralization within phosphate biocrystals using M. qingshengii J19 cells.

The genus Belliella belongs to the family Cyclobacteriaceae (order Cytophagales, phylum Bacteroidota) and harbours aerobic chemoheterotrophic bacteria. Members of this genus were isolated from various aquatic habitats, and our analysis based on global amplicon sequencing data revealed that their relative abundance can reach up to 5-10 % of the bacterioplankton in soda lakes and pans. Although a remarkable fraction of the most frequent genotypes that we identified from continental aquatic habitats is still uncultured, five new alkaliphilic Belliella strains were characterized in detail in this study, which were isolated from three different soda lakes and pans of the Carpathian Basin (Hungary). Cells of all strains were Gram-stain-negative, obligate aerobic, rod-shaped, non-motile and non-spore-forming. The isolates were oxidase- and catalase-positive, red-coloured, but did not contain flexirubin-type pigments; they formed bright red colonies that were circular, smooth and convex. Their major isoprenoid quinone was MK-7 and the predominant fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH and summed feature 3 containing C16 : 1  ω6c and/or C16 : 1  ω7c. The polar lipid profiles contained phosphatidylethanolamine, an unidentified aminophospholipid, an unidentified glycolipid, and several unidentified lipids and aminolipids. Based on whole-genome sequences, the DNA G+C content was 37.0, 37.1 and 37.8 mol % for strains R4-6T, DMA-N-10aT and U6F3T, respectively. The distinction of three new species was confirmed by in silico genomic comparison. Orthologous average nucleotide identity (<85.4 %) and digital DNA-DNA hybridization values (<38.9 %) supported phenotypic, chemotaxonomic and 16S rRNA gene sequence data and, therefore, the following three novel species are proposed: Belliella alkalica sp. nov. (represented by strains R4-6T=DSM 111903T=JCM 34281T=UCCCB122T and S4-10), Belliella calami sp. nov. (DMA-N-10aT=DSM 107340T=JCM 34280T=UCCCB121T) and Belliella filtrata sp. nov. (U6F3T=DSM 111904T=JCM 34282T=UCCCB123T and U6F1). Emended descriptions of species Belliella aquatica, Belliella baltica, Belliella buryatensis, Belliella kenyensis and Belliella pelovolcani are also presented.

New amphiphilic cationic copolymers based on poly((methacryloyloxy) ethyl trimethylammonium chloride) (PMETAC) and bio-based poly(thymol methacrylate) (PTMA) were prepared by atom transfer radical polymerization (ATRP) methods, using low concentration of metal catalyst and a bio-based eutectic mixture (EM), composed of L-menthol and thymol. The antimicrobial activity of the polymers was evaluated against Grampositive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria.The results in solution showed that increasing the terpenic segment (PTMA) in the copolymers resulted in lower antimicrobial activity against S. aureus (as the MIC increases from 3.1 to 100 & mu;M) and higher activity against E. coli (as the MIC decreases from 400 to 200 & mu;M).Scanning electron microscopy (SEM) analysis suggests that polymers affected the bacterial viability by damaging the cell structure. The synthesized biocidal polymers were used as additives in polyurethane-based varnish formulations to produce bioactive coated surfaces that were found to be more active against E. coli. Coatings containing either PTMA or PMETAC homopolymers were more efficient than those containing PMETAC-co-PTMA copolymers. A dramatic improvement in the antimicrobial activity of PMETAC-containing varnish against both S. aureus (3 orders of magnitude) and E. coli (4 orders of magnitude) was observed when an aqueous solution of the homopolymer was applied to the dried varnish instead of being incorporated into the varnish formulation. The strategy presented here is simple and opens the door for the preparation of customized bioactive surfaces to prevent bacterial infections.

Untreated mining wastes and improper disposal of high-tech devices generate an environmental increase of bioavailable metalloids, exerting stress on autochthonous microbial populations. Tellurium is a metalloid, an element with raising economic importance; nevertheless, its interaction with living organisms is not yet fully understood. Here we characterized aerobic heterotrophic bacteria, isolated from high metal-content mining residues, able to resist/reduce tellurite into tellurium structures and to determine the presence of confirmed tellurite resistance genetic determinants in resistant strains. We identified over 50 tellurite-resistant strains, among 144 isolates, eight strains reduced tellurite to tellurium at different rates, with the concomitant production of tellurium deposits. Most tellurite resistance genes were found in strains from Bacillales, with the prevalence of genes of the ter operon. This work demonstrated that bacterial isolates, from environments with a persistent selective pressure, are potential candidates for uncovering strategies for tellurite resistance and/or production of valuable Te-containing materials.

The need to secure public health and mitigate the environmental impact associated with the massified use of respiratory protective devices (RPD) has been raising awareness for the safe reuse of decontaminated masks by individuals and organizations. Among the decontamination treatments proposed, in this work, three methods with the potential to be adopted by households and organizations of different sizes were analysed: contact with nebulized hydrogen peroxide (H2O2); immersion in commercial bleach (NaClO) (sodium hypochlorite, 0.1% p/v); and contact with steam in microwave steam-sanitizing bags (steam bag). Their decontamination effectiveness was assessed using reference microorganisms following international standards (issued by ISO and FDA). Furthermore, the impact on filtration efficiency, air permeability and several physicochemical and structural characteristics of the masks, were evaluated for untreated masks and after 1, 5 and 10 cycles of treatment. Three types of RPD were analysed: surgical, KN95, and cloth masks. Results demonstrated that the H2O2 protocol sterilized KN95 and surgical masks (reduction of >6 log10 CFUs) and disinfected cloth masks (reduction of >3 log10 CFUs). The NaClO protocol sterilized surgical masks, and disinfected KN95 and cloth masks. Steam bags sterilized KN95 and disinfected surgical and cloth masks. No relevant impact was observed on filtration efficiency.

The worldwide demand on bionematicides is in a growing trend, fueled by environmental concerns with potential negative impacts of synthetic products on ecosystems and non-target organisms, as well as by the need to provide solutions to organic farming management. As such, the main goal of the present study was to evaluate the impact of 1,4-naphthoquinone (NTQ), a nematicidal compound found in natural products such as walnut husk, on soil microbial community (non-target organisms), and determine ecotoxicological indicators in order to follow and quantify the effect of this compound. The effects on diversity and metabolic state of the microbial community were evaluated using a Phospholipid-derived Fatty Acid analysis (PLFA) method. Tests were conducted on a natural uncontaminated soil spiked with a range of NTQ concentrations (up to 768 mg/kg), as well as comparable control solutions containing solubilization enhancer Triton X-100 (TX100). NTQ impacted the soil microbial community, causing significant changes on global PLFA profile at 12 mg/kg, and significant changes on taxonomic biomarker balance at 96 mg/kg. TX100 also caused a significant effect on the global profile, but only at 192 mg/kg NTQ-equivalent. The modifications brought by either compounds were distinct, as different indicators were affected. The effects of NTQ on microbial community were quantifiable for several indicators by calculating half maximal effective concentrations (EC50). The method used proved to be suitable for the assessment of NTQ ecotoxicity in soils.

The emergence of the coronavirus disease 2019 (COVID-19) pandemic highlighted the importance of disinfection processes in health safety. Textiles and footwear have been identified as vectors for spreading infections. Therefore, their disinfection can be crucial to controlling pathogens' dissemination. The present work aimed to evaluate the effectiveness of a commercial disinfectant aerosolized by an ultrasonic nebulizer closet as an effective method for disinfecting textiles and footwear. The disinfection was evaluated in three steps: suspension tests; nebulization in a 0.08 m(3) closet; nebulization in the upscaled 0.58 m(3) closet. The disinfection process of textiles and footwear was followed by the use of bacteriophages, bacterial spores, and bacterial cells. The disinfection in the 0.58 m(3) closet was efficient for textiles (4 log reduction) when bacteriophage Lambda, Pseudomonas aeruginosa, and Bacillus subtilis were used. The footwear disinfection was achieved (4 log reduction) in the 0.08 m(3) closet for Escherichia coli and Staphylococcus aureus. Disinfection in an ultrasonic nebulization closet has advantages such as being quick, not wetting, being efficient on porous surfaces, and is performed at room temperature. Ultrasonic nebulization disinfection in a closet proves to be useful in clothing and footwear stores to prevent pathogen transmission by the items' widespread handling.

Bacterial strain A52C2T was isolated from the endophytic microbial community of a Pinus pinaster tree trunk and characterized. Strain A52C2T stained Gram-negative and formed rod-shaped cells that grew optimally at 30 °C and at pH 6.0-7.0. The G+C content of the DNA was 65.1 mol %. The respiratory quinone was ubiquinone 10, and the major fatty acids were cyclo-C19:0 ω8c and C18:0, representing 70.1 % of the total fatty acids. Phylogenetic analyses based on the 16S rRNA gene sequences placed strain A52C2T in a distinct lineage within the order Hyphomicrobiales, family Pleomorphomonadaceae. The 16S rRNA gene sequence similarities of A52C2T to that of Mongoliimonas terrestris and Oharaeibacter diazotrophicus were 93.15 and 93.2 %, respectively. The draft genome sequence of strain A52C2T comprises 4 196 045 bases with a 195-fold mapped coverage of the genome. The assembled genome consists of 43 contigs of more than 1 000 bp (N50 contig size was 209 720 bp). The genome encodes 4033 putative coding sequences. The phylogenetic, phenotypic and chemotaxonomic data showed that strain A52C2T (=UCCCB 130T=CECT 8949T=LMG 29042T) represents the type of a novel species and genus, for which we propose the name Faunimonas pinastri gen. nov., sp. nov.

Bursaphelenchus xylophilus, also known as pinewood nematode (PWN), is the pathogenic agent of pine wilt disease (PWD), which affects pine trees around the world. Infection spread globally through international wood commerce and locally by vector beetles, threatening the wood world economy. As climate changes, more countries are becoming susceptible to PWD and, to prevent disease spread and limit economic and ecological losses, better knowledge about this pathogenic agent is needed. Serratia strains, present in the endophytic community of pine trees and carried by PWN, may play an important role in PWD. This work aimed to better understand the interaction between Serratia strains and B. xylophilus and to assess the nematicidal potential of serratomolide-like molecules produced by Serratia strains. Serrawettin gene presence was evaluated in selected Serratia strains. Mortality tests were performed with bacteria supernatants, and extracted amino lipids, against Caenorhabditis elegans (model organism) and B. xylophilus to determine their nematicidal potential. Attraction tests were performed with C. elegans. Concentrated supernatants of Serratia strains with serratamolide-like lipopeptides were able to kill more than 77% of B. xylophilus after 72 h. Eight specific amino lipids showed a high nematicidal activity against B. xylophilus. We conclude that, for some Serratia strains, their supernatants and specific amino lipids showed nematicidal activity against B. xylophilus.

Evidence has shown that hospital surfaces are one of the major vehicles of nosocomial infections caused by drug-resistant pathogens. Smart surface coatings presenting multiple antimicrobial activity mechanisms have emerged as an advanced approach to safely prevent this type of infection. In this work, industrial waterborne polyurethane varnish formulations containing for the first time cationic polymeric biocides (SPBs) combined with photosensitizer curcumin were developed to afford contact-active and light-responsive antimicrobial surfaces. SPBs were prepared by atom transfer radical polymerization, which allows control over the polymer features that influence antimicrobial efficiency (e.g., molecular weight), while natural curcumin was employed to impart photodynamic activity to the surface. Antibacterial testing against Gram-negative Escherichia coli revealed that glass surfaces coated with the new formulations displayed photokilling effect under white-light (42 mW/cm(2)) irradiation within only 15 min of exposure. In addition, it was observed a combined antimicrobial effect between the two biocides (cationic SPB and curcumin), with a higher reduction in the number of viable bacteria observed for the surfaces containing cationic SPB/curcumin mixtures in comparison with the one obtained for surfaces only with polymer or without biocides. The waterborne industrial varnish formulations allowed the formation of homogeneous films without the need for addition of a coalescing agent, which can be potentially applied in diverse surface substrates to reduce bacterial transmission infections in healthcare environments.

The building of civil engineering structures on some soils requires their stabilisation. Although Portland cement is the most used substance to stabilise soils, it is associated with a lot of environmental concerns. Therefore, it is very pertinent to study more sustainable alternative methodologies to replace the use of cement. Thus, this work analyses the ability of the more sustainable xanthan-like biopolymer, produced by Stenotrophomonas maltophilia Faro439 strain (LabXLG), to reduce the permeability of a sandy soil. Additionally, the effectiveness of this LabXLG is compared with the use of a commercial xanthan gum (XG) and cement for various hydraulic gradients and curing times. The results show that a treatment with either type of XG can be used to replace the cement over the short term (curing time less than 14 days), although a greater level of effectiveness is obtained with the use of the commercial XG, due to its higher level of purity. The soil treatment with LabXLG creates a network of fibres that link the soil particles, while the commercial XG fills the voids with a homogeneous paste.

Artificial laboratory evolution was used to produce mutant strains of Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) able to survive on antimicrobial metallic copper surfaces. These mutants were 12- and 60-fold less susceptible to the copper-mediated contact killing process than their respective parent strains. Growth levels of the mutant and its parent in complex growth medium were similar. Tolerance to copper ions of the mutants was unchanged. The mutant phenotype remained stable over about 250 generations under nonstress conditions. The mutants and their respective parental strains accumulated copper released from the metallic surfaces to similar extents. Nevertheless, only the parental strains succumbed to copper stress when challenged on metallic copper surfaces, suffering complete destruction of the cell structure. Whole-genome sequencing and global transcriptome analysis were used to decipher the genetic alterations in the mutant strains; however, these results did not explain the copper-tolerance phenotypes on the systemic level. Instead, the mutants shared features with those of stressed bacterial subpopulations entering the early or "shallow" persister state. In contrast to the canonical persister state, however, the ability to survive on solid copper surfaces was adopted by the majority of the mutant strain population. This indicated that application of solid copper surfaces in hospitals and elsewhere has to be accompanied by strict cleaning regimens to keep the copper surfaces active and prevent evolution of tolerant mutant strains.IMPORTANCE Microbes are rapidly killed on solid copper surfaces by contact killing. Copper surfaces thus have an important role to play in preventing the spread of nosocomial infections. Bacteria adapt to challenging natural and clinical environments through evolutionary processes, for instance, by acquisition of beneficial spontaneous mutations. We wish to address the question of whether mutants can be selected that have evolved to survive contact killing on solid copper surfaces. We isolated such mutants from Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) by artificial laboratory evolution. The ability to survive on solid copper surfaces was a stable phenotype of the mutant population and not restricted to a small subpopulation. As a consequence, standard operation procedures with strict hygienic measures are extremely important to prevent the emergence and spread of copper-surface-tolerant persister-like bacterial strains if copper surfaces are to be sustainably used to limit the spread of pathogenic bacteria, e.g., to curb nosocomial infections.

Serratia strains are ubiquitous microorganisms with the ability to produce serratomolides, such as serrawettins. These extracellular lipopeptides are described as biocides against many bacteria and fungi and may have a nematicidal activity against phytopathogenic nematodes. Serrawettins W1 and W2 from different strains have different structures that might be correlated with distinct genomic organizations. This work used comparative genomics to determine the distribution and the organization of the serrawettins biosynthetic gene clusters in all the 84 publicly available genomes of the Serratia genus. The serrawettin W1 and W2 gene clusters’ organization was established using antiSMASH software and compared with single and short data previously described for YD25TSerratia. Here, the serrawettin W1 gene clusters’ organization is reported for the first time. The serrawettin W1 biosynthetic gene swrW was present in 17 Serratia genomes. Eighty different coding sequence (CDS) were assigned to the W1 gene cluster, 13 being common to all clusters. The serrawettin W2 swrA gene was present in 11 Serratia genomes. The W2 gene clusters included 68 CDS with 24 present in all the clusters. The genomic analysis showed the swrA gene constitutes five modules, four with three domains and one with four domains, while the swrW gene constitutes one module with four domains. This work identified four genes common to all serrawettin gene clusters, highlighting their essential potential in the serrawettins biosynthetic process.

Pine Wilt Disease (PWD) is caused by Bursaphelenchus xylophilus, the pinewood nematode, and affects several species of pine trees worldwide. The ecosystem of the Pinus pinaster trees was investigated as a source of bacteria producing metabolites affecting this ecosystem: P. pinaster trees as target-plant, nematode as disease effector and its insect-vector as shuttle. For example, metals and metal-carrying compounds contribute to the complex tree-ecosystems. This work aimed to detect novel secondary metabolites like metallophores and related molecules produced under iron limitation by PWD-associated bacteria and to test their activity on nematodes. After screening 357 bacterial strains from Portugal and United States, two promising metallophore-producing strains Erwinia sp. A41C3 and Rouxiella sp. Arv20#4.1 were chosen and investigated in more detail. The genomes of these strains were sequenced, analyzed, and used to detect genetic potential for secondary metabolite production. A combinatorial approach of liquid chromatography-coupled tandem mass spectrometry (LC-MS) linked to molecular networking was used to describe these compounds. Two major metabolites were detected by HPLC analyses and described. One HPLC fraction of strain Arv20#4.1 showed to be a hydroxamate-type siderophore with higher affinity for chelation of Cu. The HPLC fraction of strain A41C3 with highest metal affinity showed to be a catecholate-type siderophore with higher affinity for chelation of Fe. LC-MS allowed the identification of several desferrioxamines from strain Arv20#4.1, in special desferrioxamine E, but no hit was obtained in case of strain A41C3 which might indicate that it is something new. Bacteria and their culture supernatants showed ability to attract C. elegans. HPLC fractions of those supernatant-extracts of Erwinia strain A41C3, enriched with secondary metabolites such as siderophores, were able to kill pinewood nematode. These results suggest that metabolites secreted under iron limitation have potential to biocontrol B. xylophilus and for management of Pine Wilt Disease.

Seven endophytic strains were isolated from the halophyte Halimione portulacoides, collected from Ria de Aveiro, Portugal. To determine their exact taxonomic position, comparative analyses were performed with these strains and closely related type strains of Salinicola species. Genome sequencing and comparison indicated that five of the seven isolated strains comprised distinct and novel species (average nucleotide identity <0.95; in silico DNA-DNA hybridization <70%; G+C difference >1 %). Multilocus sequence analysis was performed using gyrB, rpoD and 16S rRNA gene sequences from the novel and type strains to determine their phylogenetic positions. The novel strains are facultative anaerobes, mesophilic, facultative alkaliphic and halophilic, test positive for catalase and oxidase activities, for hydrolysis of Tween 20 and phosphate, for production of indole-3-acetic acid, but do not produce H2S. Ubiquinone UQ-9 is present in major amounts in all strains. The major fatty acids include C-16:0 and the summed feature containing C-18:1 omega 7c and/or C-18:1 omega 6c. The DNA G+C content ranges from 60.6 to 65.8 mol%. Five strains were confirmed as new species belonging to the genus Salinicola, for which the names Salinicola halimionae sp. nov. (type strain CPA60(T)=CECT 9338(T)=LMG 30107(T)), Salinicola aestuarinus sp. nov. (type strain CPA62(T)=CECT 9339 =LMG 30108(T)), Salinicola endophyticus sp. nov. (type strain CPA92(T)=CECT 9340(T)=LMG 30109(T)), Salinicola halophyticus sp. nov. (type strain CR45(T)=CECT 9341(T)=LMG 30105(T)) and Salinicola lusitanus sp. nov. (type strain CR5O(T)=CECT 9342(T)=LMG 30106(T)) are proposed.

ABSTRACT Large-scale industrial use of chromium(VI) has resulted in widespread contamination with carcinogenic chromium(VI). The abilities of microorganisms to survive in these environments and to detoxify chromate require the presence of specific resistance systems. Here we report identification of the transposon-located (Tn OtChr ) chromate resistance genes from the highly tolerant strain Ochrobactrum tritici 5bvl1 surviving chromate concentrations of >50 mM. The 7,189-bp-long Tn OtChr of the mixed Tn 21 /Tn 3 transposon subfamily contains a group of chrB , chrA , chrC , and chrF genes situated between divergently transcribed resolvase and transposase genes. The chrB and chrA genes, but not chrF or chrC , were essential for establishment of high resistance in chromium-sensitive O. tritici . The chr promoter was strongly induced by chromate or dichromate, but it was completely unresponsive to Cr(III), oxidants, sulfate, or other oxyanions. Plasmid reporter experiments identified ChrB as a chromate-sensing regulator of chr expression. Induction of the chr operon suppressed accumulation of cellular Cr through the activity of a chromate efflux pump encoded by chrA . Expression of chrB , chrC , or chrF in an Escherichia coli sodA sodB double mutant restored its aerobic growth in minimal medium and conferred resistance to superoxide-generating agents menadione and paraquat. Nitroblue tetrazolium staining on native gels showed that ChrC protein had superoxide dismutase activity. Tn OtChr appears to represent a mobile genetic system for the distribution of the chromate-regulated resistance operon. The presence of three genes protecting against superoxide toxicity should provide an additional survival advantage to Tn OtChr -containing cells in the environments with multiple redox-active contaminants.