A research team has discovered a variety of bacteria that can break down certain toxic wastes into a component of ordinary table salt and other harmless chemicals. As an added bonus, the microbes can be made to produce oxygen as a by-product of the breakdown process, meaning this may be a new source of that essential, life-giving, breathable gas.
As you're reading this article, you may find yourself wondering about a few things such as, what are the names of these bacteria? Where were they discovered? How do they break apart these toxic wastes to make salt and oxygen? I sure wondered, so I went to the scientists themselves, Dr. Laurie Achenbach and Dr. John Coates, to get the answers.
The scientists have discovered about 40 different bacteria. Most, they say, represent new genera. (Scientists classify living things into various groups, from broad to increasingly narrow: kingdom, phylum, class, order, family, genus, species. For examples, see this page. 'Genera' is plural for 'genus.') Achenbach and Coates have named four of these new bacterial genera: (1) Dechloromonas <deh-klor-uh-moan-us> (2) Dechlorosoma <deh-klor-uh-soh-muh> (3) Dechlorospirillum <deh-klor-uh-spur-ill-um> and (4) Dechloromarinus <deh-klor-uh-mare-ih-nus>. They are all part of the larger family of bacteria called the Proteobacteria <pro-tee-oh-back-teer-ee-uh>.
Achenbach and Coates found these bacteria in almost every place they looked, including underground water, polluted and unpolluted soils, sediments from freshwater sources and ocean sources, manure dumps on farms and even in soil samples collected from Antarctica.
The news article says that the bacteria use iron to turn liquid toxic wastes into harmless solids. Achenbach and Coates explain further how the bacteria do this: The microbes turn iron dissolved in wastewater, or ferrous <fair-us> iron, into a solid form called ferric <fair-ick> iron through a chemical reaction called oxidation <ox-ih-day-shun>. This involves stripping an electron away from each atom of ferrous iron so that it no longer can dissolve in water and it becomes solid. The microbes use the electrons they grab as energy to power their cellular activities. Meanwhile, the newly formed ferric iron acts kind of like a magnet—it latches onto atoms of toxic compounds, other metals and radioactive substances. When the solid iron is collected out of the soil or water, the harmful substances are removed with it.
And how do the bacteria make salt and oxygen during this process? The researchers explain: First, the microbes turn the waste product perchlorate <per-klor-ate> (ClO4-) into chlorite <klor-ite> (ClO2-). The chlorite is then broken down into chloride (Cl-) and oxygen (O2). Chloride is one of the two components of table salt, a.k.a. sodium chloride. The news article makes it sound like the bacteria will always turn perchlorate directly into salt. However, that will happen only if sodium, the other component of salt, happens to be present or is put into mix with the microbes. As for the oxygen produced, so long as the microbes are actively growing, they will use up all the oxygen themselves. If the bacteria are given extra chlorite, however, they will release the oxygen produced without using it themselves. This is how these microbes could be used as a new source of oxygen production.
If these bacteria exist all over the place and they naturally break down toxic wastes such as perchlorate, why then is perchlorate pollution a problem anywhere? Well, in some cases, the microbes are breaking down these toxic wastes without any help from us. But the reason it's not happening at a faster pace all over is that the right carbon sources are often lacking, Achenbach and Coates explain. Carbon sources are like food for the bacteria. By adding acetate <ass-ih-tate> or other cheap carbon sources to soil or water targeted for cleanup, the researchers were able to kick the bacteria's natural toxic waste degrading abilities into high gear.
Why is it that the toxic wastes the bacteria degrade don't harm the bacteria? Well, Achenbach and Coates admit, we just don't know yet.
One final note: The ABC news article makes a common grammatical mistake. It uses the word "bacteria" as a singular noun sometimes. But you know better, right? "Bacteria" means many little one-celled creatures. "Bacterium" means a single one of those creatures.
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