crucial precursor to the bioremediation process. fungi that have been genetically modified with cold-adapted enzymes to tolerate differing ph levels and temperatures have been shown to be effective at remediating hydrocarbon contamination in freezing conditions in the antarctic. metals acidithiubacillus ferroxidans has been shown to be effective in remediating mercury in acidic soil due to its mera gene making it mercury resistant. industrial effluent contain high levels of metals that can be detrimental to both human and ecosystem health. in extreme heat environments the extremophile geobacillus thermodenitrificans has been shown to effectively manage the concentration of these metals within twelve hours of introduction. some acidophilic microorganisms are effective at metal remediation in acidic environments due to proteins found in their periplasm, not present in any mesophilic organisms, allowing them to protect themselves from high proton concentrations. rice paddies are highly oxidative environments that can produce high levels of lead or cadmium. deinococcus radiodurans are resistant to the harsh conditions of the environment and are therefore candidate species for limiting the extent of contamination of these metals. some bacteria are known to also use rare earth elements on their biological processes for example methylacidiphilum fumariolicum, methylorubrum extorquens and methylobacterium radiotolerans are known to be able to use lanthanides as cofactors to increase their methanol dehydrogenase activity. acid mine drainage acid mine drainage is a major environmental concern associated with many metal mines. one of the most productive methods of its remediation is through the introduction of the extremophile organism thiobacillus ferrooxidans. radioactive materials any bacteria capable of inhabiting radioactive mediums can be classified as an extremophile. radioresistant organisms are therefore critical in the bioremediation of radionuclides. uranium is particularly challenging to contain when released into an environment and very harmful to both human and ecosystem health. the nanobinders project is equipping bacteria that can survive in uranium rich environments with gene sequences that enable proteins to bind to uranium in mining effluent, making it more convenient to collect and dispose of. some examples are shewanella putrefaciens, geobacter metallireducens and some strains of burkholderia fungorum. radiotrophic fungus, which use radiation as an energy source have been found inside and around the chernobyl nuclear power plant. radioresistance has also been observed in certain species of macroscopic lifeforms. the lethal dose required to kill up to 50% of a tortoise population is 40,000 roentgens, compared to only 800 roentgens needed to kill 50% of a human population. in experiments exposing lepidopteran insects to gamma radiation, significant dna damage was detected only at 20 gy and higher doses, in contrast with human cells that showed similar damage at only 2 gy. examples and recent findings new sub-types of extremophiles are identified frequently and the sub-category list for extremophiles is always growing. for example, microbial life lives in the liquid asphalt lake, pitch lake. research indicates that extremophiles inhabit the asphalt lake in populations ranging between 106 to 107 cells/gram. likewise, until recently boron tolerance was unknown but a strong borophile was discovered in bacteria. with the recent isolation of bacillus boroniphilus, borophiles came into discussion. studying these borophiles may help illuminate the mechanisms of both boron toxicity and boron deficiency. in july 2019, a scientific study of kidd mine in canada discovered sulfur-breathing organisms which live 7900 feet below the surface, and which breathe sulfur in order to survive. these organisms are also remarkable due to eating rocks such as pyrite as their regular food source. biotechnology the thermoalkaliphilic catalase, which initiates the breakdown of hydrogen peroxide into oxygen and water, was isolated from an organism, thermus brockianus, found in yellowstone national park by idaho national laboratory researchers. the catalase operates over a temperature range from 30 °c to over 94 °c and a ph range from 6–10. this catalase is extremely stable compared to other catalases at high temperatures and ph. in a comparative study, the t. brockianus catalase exhibited a half life of 15 days at 80 °c and ph 10 while a catalase derived from aspergillus niger had a half life of 15 seconds under the same conditions. the catalase will have applications for removal of hydrogen peroxide in industrial processes such as pulp and paper bleaching, textile bleaching, food pasteurization, and surface decontamination of food packaging. dna modifying enzymes such as taq dna polymerase and some bacillus enzymes used in clinical diagnostics and starch liquefaction are produced commercially by several biotechnology companies. dna transfer over 65 prokaryotic species are known to be naturally competent for genetic transformation, the ability to transfer dna from one cell to another cell followed by integration of the donor dna into the recipient cell's chromosome. several extremophiles are able to carry out species-specific dna transfer, as described below. however, it is not yet clear how common such a capability is among extremophiles. the bacterium deinococcus radiodurans is one of the most radioresistant organisms known. this bacterium can also survive cold, dehydration, vacuum and acid and is thus known as a polyextremophile. d. radiodurans is competent to perform genetic transformation. recipient cells are able to repair dna damage in donor transforming dna that had been uv irradiated as efficiently as they repair cellular dna when the cells themselves are irradiated. the extreme thermophilic bacterium thermus thermophilus and other related thermus species are also capable of genetic transformation. halobacterium volcanii, an extreme halophilic (saline tolerant) archaeon, is capable of natural genetic transformation. cytoplasmic bridges are formed between cells that appear to be used for dna transfer from one cell to another in either direction. sulfolobus solfataricus and sulfolobus acidocaldarius are hyperthermophilic archaea. exposure of these organisms to the dna damaging agents uv irradiation, bleomycin or mitomycin c induces species-specific cellular aggregation. uv-induced cellular aggregation of s. acidocaldarius mediates chromosomal marker exchange with high frequency. recombination rates exceed those of uninduced cultures by up to three orders of magnitude. frols et al. and ajon et al. hypothesized that cellular aggregation enhances species-specific dna transfer between sulfolobus cells in order to repair damaged dna by means of homologous recombination. van wolferen et al. noted that this dna exchange process may be crucial under dna damaging conditions such as high temperatures. it has also been suggested that dna transfer in sulfolobus may be an early form of sexual interaction similar to the more well-studied bacterial transformation systems that involve species-specific dna transfer leading to homologous recombinational repair of dna damage (and see transformation (genetics)). extracellular membrane vesicles (mvs) might be involved in dna transfer between different hyperthermophilic archaeal species. it has been shown that both plasmids and viral genomes can be transferred via mvs. notably, a horizontal plasmid transfer has been documented between hyperthermophilic thermococcus and methanocaldococcus species, respectively belonging to the orders thermococcales and methanococcales.