Microbial (per)chlorate reduction in hot subsurface environments

The microbial reduction of chlorate and perchlorate has been known for long as a respiratory process of mesophilic bacteria that thrive in diverse environments such as soils, marine and freshwater sediments. Chlorate and perchlorate are found in nature deriving from anthropogenic and natural sources and can, in the absence of oxygen, be reduced by respective microorganisms to chloride coupled to energy conservation and growth. These classical chlorate- and perchlorate-reducing microorganisms employ enzymes that reduce perchlorate (or chlorate) to the intermediate chlorite, followed by the disproportionation of chlorite to chloride and dioxygen. The latter has been regarded as key reaction for complete (per)chlorate reduction, catalyzed by the enzyme chlorite dismutase, which forms oxygen under anaerobic conditions. This de novo produced oxygen is reduced by terminal oxidases in the metabolism of facultative anaerobic (per)chlorate-reducing microorganisms and can be used by oxygenases for the activation of recalcitrant substrates, as was shown earlier for hydrocarbons. The potentially stimulating effect of chlorate and perchlorate on microorganisms indigenous to petroleum reservoirs was discussed, seeking new strategies for microbial enhanced oil recovery (based on subsurface growth stimulation and partial hydrocarbon degradation) and reservoir souring control (by inhibiting sulfate-reducing prokaryotes and diminishing sulfide formation). This thesis reports the capability of hyperthermophilic and thermophilic prokaryotes that originate from subsurface environments to grow by the reduction of chlorate and/or perchlorate. In contrast to the classical metabolism of mesophilic (per)chlorate-reducing microorganisms this study demonstrated that a chlorite-disproportionating enzyme is commonly absent in (hyper)thermophilic (per)chlorate reducers. The absence of this enzyme that was previously defined as prerequisite for (per)chlorate reduction is overcome by the chemical reactivity of reduced sulfur compounds with chlorite generated. In the here more closely investigated hyperthermophilic archaea (Archaeoglobus fulgidus and Aeropyrum pernix) and thermophilic Firmicutes (Carboxydothermus hydrogenoformans and Moorella glycerini strain NMP) chlorite is formed by the activity of molybdopterin oxidoreductases. The respective enzymes are remotely related to perchlorate reductases of mesophilic bacteria and nitrate reductases of the bacterial Nar-type. In contrast to classical bacterial Nar-type enzymes, above-mentioned enzymes seem to have their catalytic subunits outside of the cell. As a consequence the reduction of (per)chlorate forms chlorite extracellularly where it reacts with reduced sulfur species present in the medium/environment (e.g. sulfide), forming chloride anions and oxidized sulfur species (SxOyz-). The hyperthermophilic archaeon Archaeoglobus fulgidus reduces these chemically formed sulfur species concomitantly to (per)chlorate reduction, which regenerates sulfide for the continuous reduction of (per)chlorate. This interaction of biotic and abiotic reactions during (per)chlorate reduction establishes an intraspecies “sulfur loop” that enables complete reduction of perchlorate to chloride. Whereas A. pernix also relies on the chemical reactivity of chlorite with thiosulfate, this archaeon does not employ systems for regenerating the reducing agents biologically; which is reflected by the accumulation of sulfate during perchlorate reduction. The Crenarchaeon A. pernix, formerly known as a strictly aerobic microorganism, expands the trait of microbial (per)chlorate reduction up to 100°C. In addition to the intraspecies “sulfur loop” of A. fulgidus, there were indications that the reduction of perchlorate may also proceed syntrophically, as indicated by a thermophilic bacterial consortium. In the respective culture, it seems that one microorganism reduces perchlorate, forming chlorite, which is chemically reduced by sulfide to chloride anions and oxidized sulfur compounds. Another group of microorganisms uses the respective sulfur compounds as electron acceptors and regenerates sulfide. Sulfur (of different redox states) depicts the mediating agent in this interspecies “sulfur loop”, but may possibly be substituted in nature by other compounds such as ferrous/ferric iron. Here presented (per)chlorate reduction sensu lato, which lacks the action of a chlorite-disproportionating enzyme may be widely spread among prokaryotes. For example enzymes closely resembling the designated (per)chlorate-reducing enzyme in Archaeoglobus fulgidus are also found in other strictly anaerobic thermophiles, of which C. hydrogenoformans and M. glycerini NMP were already confirmed to grow by the reduction of (per)chlorate as well. The substrate ambiguity of particular periplasmic DMSO enzymes may enable a broader group of microorganisms of (per)chlorate reduction sensu lato, in case sulfide is present in the environment. A broadened substrate spectrum of respective enzymes (beyond their canonical function) may possibly have had evolutionary advantages. Chlorine oxyanions are naturally formed and have been introduced on Earth for ages already. The reduction of (per)chlorate and formation of chlorite in ancient anaerobic microorganisms may even have contributed to the evolution of proteins adapted to oxidizing conditions on early Earth and preceded the evolution of oxygenic photosynthesis. It is shown that subsurface-inhabiting (hyper)thermophiles are able to grow by the reduction of (per)chlorate, which is also of interest for applications in the field of oil recovery. The finding that (per)chlorate reduction is interfering with the sulfur metabolism of a major contributor to reservoir souring in hot oil fields, A. fulgidus, draws promising scenarios for future attempts in developing novel souring control strategies. (Per)chlorate reduction by A. fulgidus was also coupled to the oxidation of butyrate, a volatile fatty acid commonly present in petroleum reservoirs. For sustainable applications in the oil recovery business, it is desirable to rely, as little as possible, on external substrates. In this respect the fact that A. fulgidus couples (per)chlorate reduction to the oxidation of butyrate is advantageous. Possibly the microorganism can also degrade long-chain alkanes and alkenes coupled to (per)chlorate reduction, a feature that was shown earlier coupled to sulfate reduction. All together a shift of A. fulgidus from sulfate reduction to (per)chlorate reduction in oil fields would not only diminish souring, but maintain/stimulate in-situ growth of the microorganism (based on intrinsic carbon sources) which has additionally advantageous effects for improved sweeping efficiencies during water flooding. </p

Microbial synthesis and transformation of inorganic and organic chlorine compounds

Organic and inorganic chlorine compounds are formed by a broad range of natural geochemical, photochemical and biological processes. In addition, chlorine compounds are produced in large quantities for industrial, agricultural and pharmaceutical purposes, which has led to widespread environmental pollution. Abiotic transformations and microbial metabolism of inorganic and organic chlorine compounds combined with human activities constitute the chlorine cycle on Earth. Naturally occurring organochlorines compounds are synthesized and transformed by diverse groups of (micro)organisms in the presence or absence of oxygen. In turn, anthropogenic chlorine contaminants may be degraded under natural or stimulated conditions. Here, we review phylogeny, biochemistry and ecology of microorganisms mediating chlorination and dechlorination processes. In addition, the co-occurrence and potential interdependency of catabolic and anabolic transformations of natural and synthetic chlorine compounds are discussed for selected microorganisms and particular ecosystems.The authors thank METAEXPLORE, funded by the European Union Seventh Framework Program (Grant No. 222625), BEBASIC-FES funds from the Dutch Ministry of Economic Affairs (Projects F07.001.05 and F08.004.01), Shell Global Solutions International BV, the ERC Advanced grant “Novel Anaerobes” (Project 323009), the SIAM Gravitation grant “Microbes for Health and the Environment” (Project 024.002.002) of the Netherlands Ministry of Education, Culture and Science, and the Netherlands Science Foundation (NWO) for funding.info:eu-repo/semantics/publishedVersio

Perchlorate and chlorate reduction by the Crenarchaeon Aeropyrum pernix and two thermophilic Firmicutes

This study reports the ability of one hyperthermophile and two thermophilic microorganisms to grow anaerobically by the reduction of chlorate and perchlorate. Physiological, genomic and proteome analyses suggest that the Crenarchaeon Aeropyrum pernix reduces perchlorate with a periplasmic enzyme related to nitrate reductases, but that it lacks a functional chlorite-disproportionating enzyme (Cld) to complete the pathway. A. pernix, previously described as a strictly aerobic microorganism, seems to rely on the chemical reactivity of reduced sulfur compounds with chlorite, a mechanism previously reported for perchlorate-reducing Archaeoglobus fulgidus. The chemical oxidation of thiosulfate (in excessive amounts present in the medium) and the reduction of chlorite result in the release of sulfate and chloride, which are the products of a biotic-abiotic perchlorate reduction pathway in A. pernix. The apparent absence of Cld in two other perchlorate-reducing microorganisms, Carboxydothermus hydrogenoformans and Moorella glycerini strain NMP, and their dependence on sulfide for perchlorate reduction is consistent with observations made on A. fulgidus. Our findings suggest that microbial perchlorate reduction at high temperature differs notably from the physiology of perchlorate- and chlorate-reducing mesophiles and that it is characterized by the lack of a chlorite dismutase and is enabled by a combination of biotic and abiotic reactions.This research was financially supported by Shell Global Solutions International BV. Research of AJMS is supported by ERC grant (project 323009) and the Gravitation grant (project 024.002.002) of the Netherlands Ministry of Education, Culture and Science and the Netherlands Science Foundation (NWO). Sequencing data for strain NMP have been submitted to the European Nucleotide Archive (ENA) under accession number PRJEB8377. Mass spectrometry proteomics data and database search results have been deposited to the ProteomeXchange Consortium (Vizcaino et al., 2014) via the PRIDE partner repository with the dataset identifier PXD001683 and DOI 0.6019/PXD001683

Brake response time before and after total knee arthroplasty: a prospective cohort study

<p>Abstract</p> <p>Background</p> <p>Although the numbers of total knee arthroplasty (TKA) are increasing, there is only a small number of studies investigating driving safety after TKA. The parameter 'Brake Response Time (BRT)' is one of the most important criteria for driving safety and was therefore chosen for investigation.</p> <p>The present study was conducted to test the hypotheses that patients with right- or left-sided TKA show a significant increase in BRT from pre-operative (pre-op, 1 day before surgery) to post-operative (post-op, 2 weeks post surgery), and a significant decrease in BRT from post-op to the follow-up investigation (FU, 8 weeks post surgery). Additionally, it was hypothesized that the BRT of patients after TKA is significantly higher than that of healthy controls.</p> <p>Methods</p> <p>31 of 70 consecutive patients (mean age 65.7 +/- 10.2 years) receiving TKA were tested for their BRT pre-op, post-op and at FU. BRT was assessed using a custom-made driving simulator. We used normative BRT data from 31 healthy controls for comparison.</p> <p>Results</p> <p>There were no significant increases between pre-op and post-op BRT values for patients who had undergone left- or right-sided TKA. Even the proportion of patients above a BRT threshold of 700 ms was not significantly increased postop. Controls had a BRT which was significantly better than the BRT of patients with right- or left-sided TKA at all three time points.</p> <p>Conclusion</p> <p>The present study showed a small and insignificant postoperative increase in the BRT of patients who had undergone right- or left-sided TKA. Therefore, we believe it is not justified to impair the patient's quality of social and occupational life post-surgery by imposing restrictions on driving motor vehicles beyond an interval of two weeks after surgery.</p

Resuming elective hip and knee arthroplasty after the first phase of the SARS-CoV-2 pandemic: the European Hip Society and European Knee Associates recommendations

The Covid-19 pandemic has disrupted health care systems all over the world. Elective surgical procedures have been postponed and/or cancelled. Consensus is, therefore, required related to the factors that need to be in place before elective surgery, including hip and knee replacement surgery, which is restarted. Entirely new pathways and protocols need to be worked out. Methods A panel of experts from the European Hip Society and European Knee Association have agreed to a consensus statement on how to reintroduce elective arthroplasty surgery safely. The recommendations are based on the best available evidence and have been validated in a separate survey. Results The guidelines are based on five themes: modification and/or reorganisation of hospital wards. Restrictions on orthopaedic wards and in operation suite(s). Additional disinfection of the environment. The role of ultra-clean operation theatres. Personal protective equipment enhancement. Conclusion Apart from the following national and local guidance, protocols need to be put in place in the patient pathway for primary arthroplasty to allow for a safe retur

Recommendations for resuming elective hip and knee arthroplasty in the setting of the SARS‑CoV‑2 pandemic: the European Hip Society and European Knee Associates Survey of Members

The COVID-19 pandemic has disrupted the health care system around the entire globe. A consensus is needed about resuming total hip and knee procedures. The European Hip Society (EHS) and the European Knee Association (EKA) formed a panel of experts that have produced a consensus statement on how the safe re-introduction of elective hip and knee arthroplasty should be undertaken. Methods A prospective online survey was done among members of EHS and EKA. The survey consisted of 27 questions. It includes basic information on demographics and details the participant’s agreement with each recommendation. The participant could choose among three options (agree, disagree, abstain). Recommendations focussed on pre-operative, perioperative, and post-operative handling of patients and precautions. Results A total of 681 arthroplasty surgeons participated in the survey, with 479 fully completing the survey. The participants were from 44 countries and 6 continents. Apart from adhering to National and Local Guidelines, the recommendations concerned how to make elective arthroplasty safe for patients and staf. Conclusion The survey has shown good-to-excellent agreement of the participants with regards to the statements made in the recommendations for the safe return to elective arthroplasty following the frst wave of the COVID-19 pandemi

Microbial redox processes in deep subsurface environments and the potential application of (per)chlorate in oil reservoirs

The ability of microorganisms to thrive under oxygen-free conditions in subsurface environments relies on the enzymatic reduction of oxidized elements, such as sulfate, ferric iron, or CO2, coupled to the oxidation of inorganic or organic compounds. A broad phylogenetic and functional diversity of microorganisms from subsurface environments has been described using isolation-based and advanced molecular ecological techniques. The physiological groups reviewed here comprise iron-, manganese-, and nitrate-reducing microorganisms. In the context of recent findings also the potential of chlorate and perchlorate [jointly termed (per)chlorate] reduction in oil reservoirs will be discussed. Special attention is given to elevated temperatures that are predominant in the deep subsurface. Microbial reduction of (per)chlorate is a thermodynamically favorable redox process, also at high temperature. However, knowledge about (per)chlorate reduction at elevated temperatures is still scarce and restricted to members of the Firmicutes and the archaeon Archaeoglobus fulgidus. By analyzing the diversity and phylogenetic distribution of functional genes in (meta)genome databases and combining this knowledge with extrapolations to earlier-made physiological observations we speculate on the potential of (per)chlorate reduction in the subsurface and more precisely oil fields. In addition, the application of (per)chlorate for bioremediation, souring control, and microbial enhanced oil recovery are addressed.This research was funded by Shell Global Solutions International BV. Research of Alfons J. M. Stams is funded by ERC (project 323009) and Gravitation grant (project 024.002.002) of the Dutch Ministry of Education, Culture and Science and the Netherlands Science Foundation