Controlling the spread of antibiotic resistant bacteria. Credit: Shutterstock
An Invisible Solution to the Highly Visible Problem
Bacteria, the first forms of life to appear on Earth and still the largest population on our planet. They are mostl invisible to naked eyes, but they inhabit everywhere. From soil to water to air, to extremely harsh environments such as radioactive wastes and deep portions of Earth's crust, you can always find them (under your microscopes of course).
Pseudomonas,Bacillus, and Enterobacteriaceae are three most researched bacteria species that can successfully degrade azo dyes. For all three species, they are both ubiquitous in nature. They can be easily found in urban wastewater systems, and the breaking of azo bonds or decolorization process is preferably happening under the anaerobic conditions (or anaerobic/aerobic alternately conditions) where the presence of free oxygen in the environment will be strictly controlled.
Pseudomonas aeruginosa (P. aeruginosa -Pseudomonas means "false unit" in Greek and aeruginosa means "copper rust" in Latin.) P. aeruginosa is a rod-shaped, Gram-negative bacterium that well-known for its intrinsically advanced antibiotic resistance mechanisms. P. aeruginosa live in soil, water, skin flora, and most man-made environments. Isolated Pseudomonas aeruginosa strainshave already been widely used for degrading azo dyes.
Bacillus subtilis (B.subtilis) as known as hay bacillus or grass bacillus, it is a rod-shaped catalase-positive and Gram-positive bacterium. As a member of the bacillus, B.subtilis was firstly used by human to treat gastrointestinal and urinary tract diseases. It has very high enzyme production, and some enzymes produced by B.subtilis are also used as additives in laundry detergents. It produces some specific enzymes that can break down azo bonds.
Agar plates pre-mixed with 0.03% (left) and 0.15% (right) dye concentration
To see whether it was possible to replicate the effect bacteria can have on dyes with our own sample, a simple experiment was carried out: a nutrient-rich mixture was made containing concentrations of dye at 0.03% and 0.15%, and samples were taken at different places to gather microbes. Some samples were a mixture of both bacteria and fungi, with the fungi showing better decolourisation.
Bacteria sampled from the pond after 72hrs cultivation
Bacteria sampled from the domestic effluent after 72hrs cultivation
Bacteria sampled from the shower drain after 72hrs cultivation
Bacteria sampled from the washing machine after 72hrs cultivation.
Bacteria sampled from the garden after 72hrs cultivation