Bioremediation refers to the process whereby microorganisms (bacteria, fungi, algae, archaea, etc.) degrade/break down toxic chemical pollutants into less toxic forms. The process of Bioremediation has found extensive utilization in all types of ecosystems. There are exhaustive examples of bioremediation in real life as well. The natural ecosystem has been devastated by toxic waste materials, organic pollutants, and heavy metals. This has had detrimental effects on all living organisms. The toxic and hazardous substances, when consumed through the contaminated food chain, accumulate in the body of an organism. This accumulation poses serious health risks, can disrupt the normal functioning of an organism, and can, ultimately, lead to cell death. In this article, we will discuss the various types of bacteria which are involved in the process of bioremediation.

What is Bioremediation?

The technique used to eliminate contaminants from the ecosystem is known as bioremediation. Microorganisms, as well as plants, use their inherent properties to serve as cleaning agents employed by the environment to get the ecosystem back in shape. The underlying principle in the process of bioremediation involves curtailing the solubility of environmental pollutants by altering the adsorption of pollutants, pH, and the redox reactions in the contaminated environment. 

For facilitating the breakdown of chemical substances, certain reagents are added to the contaminated water. These reagents, in turn, alter the chemistry and microbiology of water through in situ chemical redox reactions. Heavy metals, especially As, Cr, Hg, and Se, which are present in polluted Soil are particularly converted into less toxic forms by redox reactions only. Several other factors like the nature of the microorganisms involved in the process of bioremediation, the environmental factors of the contaminated site, and the concentration of contaminants in the polluted site also influence the efficacy of the process of bioremediation. The degradation of contaminants is dependent on the metabolic potential of the microorganisms involved.

Examples of Bacteria in Bioremediation

• Pseudomonas: This genus of bacteria is known for its versatility and ability to degrade a wide range of pollutants, including hydrocarbons, pesticides, and heavy metals. Pseudomonas aeruginosa, in particular, is commonly used in bioremediation processes.

• Bacillus: Bacillus species are known for their ability to break down organic contaminants, such as petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and chlorinated solvents. Bacillus subtilis and Bacillus cereus are amongst the most commonly used species.

• Rhodococcus: Rhodococcus bacteria are highly efficient in degrading hydrocarbons and other pollutants. They have been successfully employed in cleaning up oil spills and contaminated soils. Rhodococcus erythropolis and Rhodococcus opacus are commonly utilized in bioremediation applications.

• Alcanivorax: These bacteria specialize in breaking down and consuming hydrocarbons, especially those found in oil spills. Alcanivorax borkumensis is one of the well-known species used in the bioremediation of oil-contaminated environments.

• Shewanella: Shewanella species are versatile bacteria that can reduce and detoxify various pollutants, including heavy metals, radionuclides, and organic compounds. They are commonly utilized in the bioremediation of contaminated sediments and groundwater.

• Deinococcus radiodurans: This bacterium is famous for its extraordinary resistance to radiation and its ability to repair DNA damage. It has shown potential in the bioremediation of radioactive waste and the cleanup of environments contaminated with ionizing radiation.

• Geobacter: Geobacter species are renowned for their ability to reduce and immobilize metals, such as uranium and chromium, through a process called metal reduction. They are often employed in the bioremediation of contaminated groundwater and soils.

• Nitrosomonas and Nitrobacter: These bacteria play a crucial role in the nitrogen cycle and are used in bioremediation processes to remove excess nitrogen from wastewater and contaminated soils. Nitrosomonas converts ammonia into nitrite, and Nitrobacter further oxidizes nitrite into nitrate.

• Methylobacterium: Methylobacterium species are known for their ability to degrade volatile organic compounds (VOCs) such as trichloroethylene (TCE), a common industrial solvent. They can be used in the bioremediation of contaminated groundwater and soil.

• Methanosarcina: Methanosarcina bacteria are methanogens that can convert organic pollutants, including certain toxic compounds, into methane gas through a process called anaerobic bioremediation. This method is particularly useful in treating organic-rich wastewater and sludge.

• Desulfovibrio: Desulfovibrio species are sulfate-reducing bacteria that can facilitate the bioremediation of heavy metals and organic compounds. They can convert sulfate into sulfide, which binds with metals and forms less toxic precipitates.

• Enterobacter: Enterobacter species are capable of degrading a wide range of contaminants, including hydrocarbons and chlorinated solvents. They have been utilized in bioremediation efforts targeting polluted soil and water.

• Arthrobacter: Arthrobacter species are commonly found in soil and have a broad metabolic capability, allowing them to degrade various organic compounds, including pesticides, herbicides, and polychlorinated biphenyls (PCBs).

• Comamonas: Comamonas species are known for their ability to degrade aromatic compounds and chlorinated solvents. They have been used in the bioremediation of contaminated soil and groundwater.

• Cupriavidus metallidurans: This bacterium is known for its resistance to heavy metals and its ability to detoxify metal-contaminated environments. It has been used in the bioremediation of sites contaminated with metals such as copper, zinc, and cadmium.

• Rhizobium: Rhizobium species form symbiotic relationships with leguminous plants and play a vital role in nitrogen fixation. They help improve soil fertility and nutrient availability, making them beneficial in the restoration of degraded lands.

• Stenotrophomonas maltophilia: This bacterium is known for its ability to degrade various aromatic compounds and hydrocarbons. It has been employed in the bioremediation of soil and water contaminated with petroleum products.

• Streptomyces: Streptomyces species are filamentous bacteria commonly found in soil. They produce enzymes and metabolites that can degrade a wide range of organic pollutants, including herbicides, pesticides, and petroleum hydrocarbons.

• Mycobacterium: Mycobacterium species are known for their ability to degrade complex organic compounds, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and chlorinated solvents. They have been used in the bioremediation of contaminated soil and groundwater.

• Methylococcus: Methylococcus bacteria are methanotrophs, which means they can consume methane gas as a carbon and energy source. They have been employed in bioremediation to mitigate methane emissions from landfills and contaminated sites.

• Achromobacter xylosoxidans: This bacterium has been used for the bioremediation of soils contaminated with hydrocarbons, specifically crude oil. It has demonstrated the ability to degrade a wide range of hydrocarbon compounds.

• Alcaligenes: Alcaligenes species are known for their versatility in degrading various organic compounds, including polycyclic aromatic hydrocarbons (PAHs), chlorinated solvents, and phenols. They have been utilized in the bioremediation of contaminated soils and wastewater.

• Acinetobacter: Acinetobacter species have been extensively studied for their ability to degrade hydrocarbons, including long-chain alkanes and aromatic compounds. They have been used in the bioremediation of oil spills and petroleum-contaminated environments.

• Ralstonia: Ralstonia species are known for their metabolic diversity and the ability to degrade a wide range of organic pollutants, including aromatic hydrocarbons, chlorinated solvents, and pesticides. They have been employed in the bioremediation of contaminated soils and groundwater.

• Nocardia: Nocardia species are soil bacteria that have been used in the bioremediation of hydrocarbon-contaminated soils. They possess enzymes that enable them to break down complex hydrocarbon compounds.

• Rhodococcus erythropolis: This bacterium has a remarkable ability to degrade a wide range of hydrocarbon compounds, including polycyclic aromatic hydrocarbons (PAHs) and petroleum derivatives. It has been used in the bioremediation of oil spills and contaminated soils.

• Thiobacillus: Thiobacillus species are sulfur-oxidizing bacteria that play a role in the bioremediation of sites contaminated with heavy metals. They can convert toxic metals into less harmful forms by facilitating their precipitation.

• Desulfotomaculum: Desulfotomaculum species are sulfate-reducing bacteria commonly used in the bioremediation of environments contaminated with heavy metals, organic pollutants, and radioactive materials. They facilitate the conversion of sulfate into sulfide, which helps in the precipitation and immobilization of metals.

• Methylosinus: Methylosinus species are methanotrophic bacteria that specialize in the oxidation of methane. They are used in bioremediation to mitigate methane emissions from landfills, wastewater treatment plants, and other methane-producing environments.

• Geobacter sulfurreducens: This bacterium is known for its ability to transfer electrons to insoluble metal ions, thereby facilitating the reduction and immobilization of heavy metals, such as uranium and chromium. It has been used in the bioremediation of metal-contaminated environments.

• Gordonia: Gordonia species are versatile bacteria known for their ability to degrade a wide range of pollutants, including hydrocarbons, chlorinated solvents, and aromatic compounds. They have been utilized in the bioremediation of contaminated soils and groundwater.

• Azospirillum: Azospirillum species are beneficial bacteria commonly found in the rhizosphere of plants. They promote plant growth by fixing atmospheric nitrogen and enhancing nutrient availability. While not directly involved in pollutant degradation, they play a role in phytoremediation, where they enhance plant growth and root development, thereby aiding in the uptake and degradation of contaminants by plants.

• Methylocystis: Methylocystis species are methane-oxidizing bacteria that contribute to the natural methane cycle. They have been studied for their potential in methane mitigation and bioremediation of methane-contaminated environments.

• Lysinibacillus sphaericus: This bacterium is used in the bioremediation of water bodies contaminated with mosquito larvae. It produces toxins that specifically target mosquito larvae, making it an effective biological control agent.

• Acidithiobacillus: Acidithiobacillus species are acidophilic bacteria commonly used in the bioremediation of acid mine drainage. They can oxidize sulfur compounds and reduce the acidity of contaminated water bodies.

• Shigella sonnei: Shigella sonnei is a bacterium commonly used in the bioremediation of wastewater and soil contaminated with fecal matter. It helps break down organic pollutants and improves the overall quality of the environment.

• Achromobacter piechaudii: This bacterium has been studied for its potential in the bioremediation of polyurethane plastics. It produces enzymes capable of degrading polyurethane, offering a promising solution for the management of plastic waste.