AsianScientist (Aug. 24, 2021) – While bacteria get a bad rap as disease-causing agents, some of these tiny organisms may just be the rescuers of the environment. An international team found that bacteria from Indian landfills could detoxify chemical wastes called hexabromocyclodecane (HBCD), publishing their study in Chemosphere.
For a long time, industrial production has been a major culprit of environmental pollution, releasing hazardous waste like HBCD. At peak production, HBCD hit scales of 10,000 tons a year as a flame retardant used in textile manufacturing and integrated in plastics for electronic devices.
By the time the chemical was banned worldwide in 2014, the damage had been done. As a long-lived environmental toxin, HBCD had already seeped into sewages, soil and the air—found even in the food chain and consequently, in human blood samples and breast milk.
Given HBCD’s persistence in the surroundings, researchers have been searching for ways to detoxify the chemical pollution from the past to create a cleaner future. Scientists from the University of Delhi and the India Habitat Center, together with collaborators from Sweden, found a solution from nature itself—showing that Sphingobium indicum bacteria inhabiting India’s landfills could digest these chemicals.
The detoxifying abilities of these bacteria come from an enzyme called LinA, which is involved in metabolizing another now-banned insecticide and chemical sibling of HBCD. Known as biological catalysts, enzymes speed up reactions like the breakdown of chemicals.
On the designated binding site, the toxin attaches itself to LinA, similar to a key being inserted into a lock. HBCD rapidly splits up into non-toxic fragments, which are then released to make room for the next chemical to latch onto the enzyme’s binding site.
By genetically modifying the bacteria, the team also altered the structure of the enzymes they produced. While LinA enzymes are highly selective about the molecules they can accept on the binding site, the genetic changes led to a more spacious site for accommodating larger chemicals.
According to the researchers, these experiments highlight the possibility of designing enzymes that can degrade other toxins besides HBCD. Through modifying biological structures, biotransformation may be key to engineering useful bacterial enzymes for remediating heavily polluted environments.
“This means that we now actually have a chance to use biological methods to render harmless these long-lived toxins produced by mankind and distributed over large areas,” said study first author Dr. Norbert Heeb from Empa, the Swiss Federal Laboratories for Materials Science and Technology.
The article can be found at: Heeb et al. (2021) Transformation of ε-HBCD with the Sphingobium indicum Enzymes LinA1, LinA2 and LinATM, a Triple Mutant of LinA2.
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Source: Swiss Federal Laboratories for Materials Science and Technology; Photo: Dipak Shelare/Shutterstock.
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