is a method that includes the reduction of As (V) to As (III) which is followed by a
conversion to dimethyl As (V) DMA (V), TMA (III) (trimethylarsine), and TMA
(III) oxide (TMAO) in the presence of glutathione (GSH) and SAM (S-adenosyl
methionine). It was primarily established in fungi in the 1980s and afterward seen in
bacteria, archaea, algae, plants, marine animals, and humans. Aspergillus fumigatus
and Pseudomonas spp. (Shariatpanahi et al. 1981), Tetrahymena pyriformis
(Chatterjee et al. 2017), methanogens (Michalke et al. 2000), and
Rhodopseudomonas palustris (Ke et al. 2018) were also involved in biomethylation
and volatilization. Bioremediation is the important process known for its advantages:
1. no secondary pollution, 2. no complexity in the technical process, 3.very low
energy consumption, 4. very efficient method, 5. no additional construction required,
and 6. Long-term viability (Shishir and Mahbub 2019). Therefore, it has been
extensively and successfully implemented worldwide for several purposes. Shishir
and Mahbub (2019) state that there are restrictions to bioremediation, in which it is
restricted to biodegradable compounds only; therefore, all heavy metal contaminants
may not be treated using this technology. Henceforth, biodegradation is still considered to be safe, as biodegradation residues can sometimes be more difficult and
unsafe than the parent compound. In addition, these techniques are often very
specific and depend on many parameters such as the concentration of pollutants,
microbial population, site factors, environmental conditions, and nutrient levels that
make the process difficult. Bioremediation is less efficient and unsuccessful in
natural condition but serves as an environment conducive to microbial growth and
activity (Shishir and Mahbub 2019).
8 Conclusion
Arsenic transformation and sequestration are important processes in toxicity reduction. A huge number of populations depend on water containing unacceptable levels
of arsenic for drinking as well as economic activities. The investigation of microbial
behavior and identifying microorganisms for bioremediation is vital in understanding arsenic-tolerant microbes in contaminated areas. Of the several possible
methods, one highly efficient and eco-friendly as well as economically sound
strategy is to consider biologically remediation processes. Several previous studies
have shown that some microbes have the capacity of detoxifying and reducing
toxicity by transforming one form of arsenic to another. Moreover, some microbes
have immobilized toxic forms of arsenic in contaminated areas. In addition, different
hyperaccumulator plants also have the capacity to remediate the toxicity of arsenic in
different contaminated agroecosystems. Some microbes have also been found to
contain certain genes that facilitate the oxidization and reduction in arsenic toxicity.
This has led to the demand for greater exploration in order to identify microbes with
the bioremediation capacity to immobilize and reduce the toxicity of arsenic contamination in the environment (Al-Makishah et al. 2020) (Tables 12.1 and 12.2).
12 Arsenic-Transforming Bacteria: A Potential Weapon for Arsenic-Contaminated Soil
253
conversion to dimethyl As (V) DMA (V), TMA (III) (trimethylarsine), and TMA
(III) oxide (TMAO) in the presence of glutathione (GSH) and SAM (S-adenosyl
methionine). It was primarily established in fungi in the 1980s and afterward seen in
bacteria, archaea, algae, plants, marine animals, and humans. Aspergillus fumigatus
and Pseudomonas spp. (Shariatpanahi et al. 1981), Tetrahymena pyriformis
(Chatterjee et al. 2017), methanogens (Michalke et al. 2000), and
Rhodopseudomonas palustris (Ke et al. 2018) were also involved in biomethylation
and volatilization. Bioremediation is the important process known for its advantages:
1. no secondary pollution, 2. no complexity in the technical process, 3.very low
energy consumption, 4. very efficient method, 5. no additional construction required,
and 6. Long-term viability (Shishir and Mahbub 2019). Therefore, it has been
extensively and successfully implemented worldwide for several purposes. Shishir
and Mahbub (2019) state that there are restrictions to bioremediation, in which it is
restricted to biodegradable compounds only; therefore, all heavy metal contaminants
may not be treated using this technology. Henceforth, biodegradation is still considered to be safe, as biodegradation residues can sometimes be more difficult and
unsafe than the parent compound. In addition, these techniques are often very
specific and depend on many parameters such as the concentration of pollutants,
microbial population, site factors, environmental conditions, and nutrient levels that
make the process difficult. Bioremediation is less efficient and unsuccessful in
natural condition but serves as an environment conducive to microbial growth and
activity (Shishir and Mahbub 2019).
8 Conclusion
Arsenic transformation and sequestration are important processes in toxicity reduction. A huge number of populations depend on water containing unacceptable levels
of arsenic for drinking as well as economic activities. The investigation of microbial
behavior and identifying microorganisms for bioremediation is vital in understanding arsenic-tolerant microbes in contaminated areas. Of the several possible
methods, one highly efficient and eco-friendly as well as economically sound
strategy is to consider biologically remediation processes. Several previous studies
have shown that some microbes have the capacity of detoxifying and reducing
toxicity by transforming one form of arsenic to another. Moreover, some microbes
have immobilized toxic forms of arsenic in contaminated areas. In addition, different
hyperaccumulator plants also have the capacity to remediate the toxicity of arsenic in
different contaminated agroecosystems. Some microbes have also been found to
contain certain genes that facilitate the oxidization and reduction in arsenic toxicity.
This has led to the demand for greater exploration in order to identify microbes with
the bioremediation capacity to immobilize and reduce the toxicity of arsenic contamination in the environment (Al-Makishah et al. 2020) (Tables 12.1 and 12.2).
12 Arsenic-Transforming Bacteria: A Potential Weapon for Arsenic-Contaminated Soil
253