The discovery of the bacteria, Ideonella sakaiensis 201-F6T, was published in the journal Science in March 2016. The brand new species was identified by microbiologists from Kyoto Institute of Technology and Keio University while they were attempting to gather samples of sediment, soil, and wastewater that had been contaminated by poly(ethylene terephthalate) (PET) near plastic bottle recycling locations in Sakai, Japan. The intriguing characteristic of this novel bacterium is its ability to eat this type of plastic that was previously considered to be one of the most infamously resistant materials (1).
Ideonella sakaiensis is a Gram-negative, aerobic, non-spore forming, rod-shaped bacterium. It has a polar flagellum that allows for motility. In addition, the strain was positive for both the catalase and cytochrome oxidase tests. The bacterium grew best at 30-37 °C and 7.0-7.5 pH, but was able to survive between 15 °C and 42 °C and 5.5-9.0 pH. (2).
While the scientists originally discovered numerous different species of microbes that appeared to be breaking down PET, they ended up determining that Ideonella sakaiensis was the only one of them that could consume the plastic waste and metabolize it for growth. This strain can use the plastic both as its carbon and energy source by hydrolyzing the PET. The reaction intermediate formed in this process, mono(2-hydroxyethyl) terephthalic acid, is converted, using two powerful enzymes, into two nonthreatening monomers called terphthalic acid and ethylene glycol (1). After studying the bacterial metabolism more closely, scientists now believe that the bacteria first attaches to the plastic using some sort of short arm-like appendages. Next, it secretes one exoenzyme that generates the aforementioned chemical intermediate. Once the PET is substantially degraded, the material can be taken up into the cell where the second enzyme catabolically breaks it down for metabolic use. The researchers found that the microbe had consumed the PET comprehensively and after six months, the plastic was almost entirely depleted at 30 °C.
Since PET is the plastic component found in most water bottles, polyester garments, and dinner trays, scientists hope that the bacterial species will be able to be harnessed for widespread biodegradation. If used commercially, experts predict that the microbe could be able to deteriorate more than 50 million tons of the plastic debris annually all across the globe (1). Additionally, many believe that the research done to understand this new classification of bacteria will make it simpler to identify other microbes that possess similar plastic degrading characteristics.
(1) Yoshida, S.; Hiraga, K.; Takehana, T.; Taniguchi, I.; Yamaji, H.; Maeda, Y.; Toyohara, K.; Miyamoto, K.; Kimura, Y.; Oda, K. (11 March 2016). “A bacterium that degrades and assimilates poly(ethylene terephthalate).” Science 351 (6278): 1196–1199.
(2) Tanasupawat, S.; Takehana, T.; Yoshida, S.; Hiraga, K.; Oda, K. (5 Apr 2016). “Ideonella sakaiensis sp. nov., isolated from a microbial consortium that degrades PET.” Int J Syst Evol Microbiol. [published online ahead of print].