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Ideonella sakaiensis

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From Wikipedia, the free encyclopedia

Species of bacterium

Ideonella sakaiensis

Scientific classification

Domain:

Bacteria

Kingdom:

Pseudomonadati

Phylum:

Pseudomonadota

Class:

Betaproteobacteria

Order:

Burkholderiales

Family:

Comamonadaceae

Genus:

Ideonella

Species:

I. sakaiensis

Binomial name

Ideonella sakaiensis<br>Yoshida et al. 2016[1]

Ideonella sakaiensis is a bacterium from the genus Ideonella and family Comamonadaceae capable of breaking down and consuming the plastic polyethylene terephthalate (PET), using it as both a carbon and energy source. The bacterium was originally isolated from a sediment sample taken outside of a plastic bottle recycling facility in Sakai City, Japan.[1][2]

Discovery<br>[edit]

Ideonella sakaiensis was first identified in 2016 by a team of researchers led by Kohei Oda of Kyoto Institute of Technology and Kenji Miyamoto of Keio University after collecting a sample of PET-contaminated sediment at a plastic bottle recycling facility in Sakai, Japan.[1][3] The bacteria was first isolated from a consortium of microorganisms in the sediment sample, which included protozoa and yeast-like cells. The entire microbial community was shown to mineralize 75% of the degraded PET into carbon dioxide once it had been initially degraded and assimilated by Ideonella sakaiensis.[1]

Characterization<br>[edit]

Physical attributes<br>[edit]

Ideonella sakaiensis is gram-negative, aerobic, and rod-shaped. Cells are motile and have a single flagellum. Colonies of I. sakaiensis are colorless, smooth, and circular. Its size varies from 0.6 to 0.8 μm in width and 1.2-1.5 μm in length.[1]

Chemical attributes<br>[edit]

I. sakaiensis also tests positive for oxidase and catalase. The bacterium grows at a pH range of 5.5 to 9.0 (optimally at 7 to 7.5) and a temperature of 15–42 °C (59–108 °F) (optimally at 30–37 °C (86–99 °F)).

Ideonella sakaiensis adhering to PET plastic with its thin flagellum & delivering PET-degrading enzymes to the plastic's surface<br>Use of characteristics<br>[edit]

This bacterium's gram negativity gives it resistant abilities and genes; this could include antibiotic resistance. The negativity also means that it has a thin cell wall and a high lipid content.[citation needed]

The aerobic aspect of this bacterium means that it can grow and thrive only in an environment that contains oxygen. Ideonella sakaiensis and other aerobic bacteria therefore survive in oxygen-rich soil that is moist and aerated.[citation needed]

The flagellum attached to this bacterium are used as motile organelles and are able to rotate and thrust the cell throughout its environment by creating motion. The bacterium was also shown to grow on the surface of polyethylene terephthalate (PET), a type of plastic, adhering with its thin flagellum. This is shown in the image to the right. The flagellum may also secrete PET-degrading enzymes onto the PET surface known as PETases.[citation needed]

Through phylogenetic analysis, the species was shown to be a part of the genus Ideonella, but possessed a significantly different genome than other known species in the genus, including Ideonella dechloratans and Ideonella azotifigens, thus justifying its classification as a new species.[1]

Degradation and assimilation of PET<br>[edit]

I. sakaiensis PETase enzyme chemical mechanism<br>Ideonella sakaiensis adhere to PET surface and use a secreted PET hydrolase, or PETase, to degrade the PET into mono(2-hydroxyethyl)terephthalic acid (MHET), a heterodimer composed of terephthalic acid (TPA) and ethylene glycol. The PETase also degrades PET into another intermediate known as Bis-(2-hydroxyethyl) terephthalate (BHET), BHET can be converted into MHET after PET hydrolysis.[4] The I. sakaiensis PETase functions by hydrolyzing the ester bonds present in PET with high specificity. The resulting MHET is then degraded into its two monomeric constituents by a lipid-anchored MHET hydrolase enzyme, or MHETase, on the cell's outer membrane.[1] The overall mechanism of the PET plastic being broken down is exhibited in the image above. The monomeric constituents such as ethylene glycol is then taken up and used by I. sakaiensis and many other bacteria.[1][5] The other constituent; terephthalic acid, a more recalcitrant compound, is imported into the I. sakaiensis cell via the terephthalic acid transporter protein. Once in the cell, the aromatic terephthalic acid molecule is oxidized by terephthalic acid-1,2-dioxygenase and 1,2-dihydroxy-3,5-cyclohexadiene-1,4-dicarboxylate dehydrogenase into a catechol intermediate. The catechol ring is then cleaved by PCA...