A short review of literature in the last 6 years

With the discovery of Penicillin by Alexander Fleming in 1928 a new door was opened to humanity, of how simple microorganisms and their products can have a huge effect on different problems for the human race. While antibiotics have changed the face of medicine, bacteria are also being increasingly studied for their potential as bio remediators for environmental problems today and our future . While already bacteria have been used as bio remediators for oil spills on roads and in the ocean, our project with iGEM 2021 takes a more futuristic look at bacteria as bio remediators as we look to use our bioengineered bacteria as bio remediators to remove sodium perchlorate from the Martian soil to facilitate growth of food and vegetables for human consumption.

This short review will look at the recent literature regarding trying to remediate Martian soil whether it is using bacteria or different methods, and to realise the recent trends in this subject.

One study in 2018 studied bacterial strains from Columbian Caribbean soil and their effects on reducing perchorates in soil. these strains were isolated from halotolerant organisms belonging to the Vibrio, Bacillus, Salinovibrio, Staphylococcus, and Nesiotobacter genera.

The study found that These strains could reduce KClO4 levels in aqueous solutions from 10 up to 25%. Bacteria-mediated remediation of perchlorate is a suitable process to control pollution by this toxic chemical(perchlorate). (Acevedo-Barrios et al 2018)

Another study in the last few years has been using extremophiles from wide range of extreme environments: salars, geothermal springs, and geysers for their potential as bio remediators. One study by Orellana et al 2018, where some of these bacteria were isolated from desert conditions not too distant from Mars, were used to bioremediate waste and polluted water. (Orellana et al 2018). From the literature in the last 5 years a study in 2015, found that bioremediation was possible in perchlorate contaminated water via heterotrophic perchlorate reducing bacterium creates a multiple electron acceptor-donor system. (Xu et al 2015). The study used Azospira sp KJ, which is a Gram-negative, facultatively anaerobic rod capable of coupling the oxidation of lactate or acetate to the complete reduction of perchlorate. The results determined that while Azospira sp KJ, was an effective degrader of Sodium perchlorate. The Bacterium was affected by environmental factors (PH and oxygen exposure) 7.5 to 8.0 was seen to be the best range for accelerating the perchlorate reducing process and anything outside it had a lessening effect on reduction of perchlorate. Oxygen exposure to the facultative anaerobe inhibited perchlorate reduction in tests. (Xu et al 2015).

One study in 2020 by Gallardo-Carreño et al 2020 also like iGEM MTU looked at perchlorate in a more interplanetary sense as they reiterated that the accumulation of perchlorate in grown food in contaminated soil can interrupt thyroid function in humans when ingested. (Gallardo- Carreño et al 2020). The study revealed that through perchlorate-reducing bacteria (PRB), respire perchlorate as the sole electron acceptor. (Gallardo-Carreño et al 2020). But in their study the researchers were looking for an immunoassay for detecting PRB’s. They were successful in using a PRB detecting chip (PRBCHIP), which allowed the researchers to detect and classify environmental isolates in the soil while also being able to detect similar isolates from poor soils with low organic matter levels (<103 cells/g of soil obtained). (Gallardo-Carreño et al 2020).