Ideonella sakaiensis (plastic-eating bacteria)

A new species of the genus Ideonella called Ideonella sakaiensis is a rod-shaped, gram-negative aerobic bacteria. It is also known as bacterium that consumes plastic.

• Plastic may serve as a key source of carbon and energy for growth for bacteria that consume it.
• With Leo Baekeland's invention of Bakelite in 1907, the era of plastics began. The creation of a broad variety of synthetic polymers has led to their widespread use and need in both everyday life and, tragically, the environment.
• In 2015, there was 5,000 Mt of plastic garbage in landfills and other places. That amount might increase to 12,000 Mt by 2050.
• Numerous hydrolytic enzymes may hydrolyze the ester bonds that bind the monomers of poly (ethylene terephthalate). Because there are no known enzymes that may directly break their C-C bonds, PET is potentially more prone to spontaneous deterioration than polyolefin.
• The genome of I. sakaiensis was sequenced, and this led to the discovery of an enzyme that hydrolyzes PET.
• The hydrolysis products are discharged into the aqueous environment, and the surface of an amorphous PET film develops pitting that resembles craters.
• The I. sakaiensis enzyme was given the name PET hydrolase because, when compared to other known PHEs, it displays the greatest catalytic preference for PET at ambient temperature (PETase).
• This bacteria converts PET into CO2 and water, using it as a main source of carbon and energy.

Table of Contents

Ideonella sakaiensis Discovery

Ideonella sakaiensis Classification

Habitat of Ideonella sakaiensis

Morphology of Ideonella sakaiensis

Cultural characteristics of Ideonella sakaiensis

NBRC no.802 agar

Biochemical characteristics of Ideonella sakaiensis

Mode of action of Ideonella sakaiensis

1) PETase enzyme

2) MHET hydrolase

Lab Diagnosis of Ideonella sakaiensis

Potent applications of Ideonella sakaiensis

Discovery of Ideonella sakaiensis

• A team of researchers led by Kohei Oda of Kyoto Institute of Technology and Kenji Miyamoto of Keio University reported that they had isolated a novel bacterium, Ideonella sakaiensis 201-F6, from the environment among 250 samples from a PET-contaminated environment, including sediment, soil, wastewater, and activated sludge close to a plastic bottle recycling site.
• Using these samples, they searched for bacteria that could thrive preferentially on low-crystallinity (1.9%) PET film.
• After being cultivated in one sediment sample, a separate microbial consortia formed on the PET film, resulting in morphological changes.
• Ideonella sakaiensis is a species that belongs to the Ideonella genus.
• The bacteria got its name since it was found in Sakai, a Japanese city.
• A collection of microorganisms in the soil sample, which also included protozoa and cells that resembled yeast, led to the first isolation of the bacterium.
• On the film and in the culture fluid, appendages connecting the cells were visible.
• There were shorter appendages that may have assisted in delivering secreted enzymes to the film between the cells and the film.
• The PET film had undergone substantial deterioration and was almost destroyed after six weeks at 30°C.

Ideonella sakaiensis Classification

• Ideonella sakaiensis, a member of the genus Ideonella of the family Comamonadaceae, was discovered to degrade plastic in response to the hunt for a biological system that could degrade plastic waste.
• In the Betaproteobacteria 16S rRNA phylogeny, members of the Comamonadaceae family are found together in a phylogenetic cluster.

Domain	Bacteria
Phylum	Pseudomonadota
Class	Betaproteobacteria
Order	Burkholderiales
Family	Comamonadaceae
Genus	Ideonella
Species	Ideonella sakaiensis

Ideonella sakaiensis's habitat

• Ideonella sakaiensis may be found in a range of both natural and artificial environments, and they don't care if a place is clean or dirty.
• Soil, fresh and groundwater, activated sludge, and water used in industrial processes are a few examples of these ecosystems.
• The physical and physiological traits of the distinct features of the genera vary widely within the species itself as a result of the large diversity of environments.

Ideonella sakaiensis morphology

• Gram-negative, aerobic, and rod-shaped Ideonella sakaiensis.
• They are between 0.6 and 0.8 m wide and between 1.2 and 1.5 m long.
• The cells' polar flagellum enables movement.
• It can thrive in the range of pH 5.5 to 9.0 and temperatures of 15 to 42 °C (28 °C is optimal) (pH 7–7.5 is ideal).
• G+C concentration in genomic DNA was 70.4 mol%.
• Three percent (w/v) NaCl is fatal for this bacteria.
• Ideonella sakaiensis may attach to PET surfaces and grow there by holding on with its delicate tendrils.
• These extensions could provide enzymes to the PET film that degrade PET.

Characteristics of the Ideonella sakaiensis culture

Because it consumes PET as its only source of carbon and energy for development, Ideonella sakaiensis is a great candidate for growth in settings with high concentrations of accumulated plastics.

agar NBRC no. 802

• Colonies were 0.5-1.0 mm in diameter, round, elevated, transparent, with an entire edge, and non-pigmented or cream after two days of incubation at 30°C.

Ideonella sakaiensis's biochemical characteristics

The following table lists Ideonella sakaiensis's biochemical traits:

S.N.	Basic characteristics	Ideonella sakaiensis
1.	Gram staining	Negative (-)
2.	Shape	Rods
3.	Spore	Negative (-)
4.	Motility	Motile
5.	Nitrate reduction	Negative (-)
6.	Catalase	Positive (+)
7.	Oxidase	Positive (+)
8.	Indole formation	Negative (-)
9.	Pigmentation	Negative (-)

Fermentation of 

S.N.	Sugars	Ideonella sakaiensis
1.	Glucose	Negative (-)
2.	Maltose	Positive (+)

Enzymatic reactions

S.N.	Enzymes
1.	Galactosidase

Ideonella sakaiensis's mechanism of action

1) The enzyme PETase

• PET is broken down by the bacterial enzyme PET hydrolase, or PETase, creating mono (2-hydroxyethyl) terephthalic acid (MHET), a heterodimer consisting of terephthalic acid (TPA) and ethylene glycol (EG).
• Inia sakaiensis PETase breaks down the ester linkages in PET by hydrolyzing them.
• MHET hydrolase is a different enzyme that is utilised since I. sakaiensis and many other bacteria cannot use TPA but can readily absorb and use ethylene glycol among the products.
• In other words, both chemicals produced from the PET are used by the cell to create energy and for metabolic functions.
• This system, in particular, ranks among the most effective PET hydrolases known to exist at room temperature in terms of PET breakdown efficiency.
• As carbon is assimilated, it may ultimately mineralize into carbon dioxide and be released into the environment.

2) MHET hydrolase

• The Ideonella sakaiensis genus has another tannase-family enzyme involved in PET metabolism.
• This enzyme hydrolyzes 2-hydroxyethyl terephthalic acid (MHET), the main PET hydrolysis product of PETase, into TPA and EG.
• Due to its strong activity and excellent specificity for mono-(2-hydroxyethyl) terephthalate (MHET), this enzyme was given the name MHET hydrolase (MHETase), but it has a modest hydrolytic impact on bis-(2-hydroxyethyl) TPA (BHET) and a number of other substrates.
• Its consist comprises a lid domain and a hydrolase domain was disclosed by the crystal structure.
• While the hydrolase domain has the amino acid residues required for catalysis, the lid domain provides substrate selectivity.
• This enzyme degrades the resultant MHET into its two monomeric components and is lipid-anchored to the bacterial cell's outer membrane.
• Terephthalic acid (TPA) is more resistant to breakdown in this situation and is transported into the cell through the terephthalic acid transporter protein.
• Once the aromatic terephthalic acid molecule has entered the cell, terephthalic acid-1, 2- dioxygenase and 1, 2-dihydroxy-3, 5-cyclohexadiene-1, 4-dicarboxylate dehydrogenase oxidise it into a catechol intermediate.
• PCA 3, 4-dioxygenase breaks the catechol ring before the chemical reaches other metabolic pathways (like the TCA cycle), ensuring that no dangerous or toxic metabolites are left in the environment.

Ideonella Sakiensis Lab Diagnosis

• We looked at the cell shape, colony appearance, and pigmentation of the cells cultured on NBRC no. 802 agar plate as well as their morphological and cultural properties.
• The existence of flagella in cells cultured in NBRC no. 802 broth at 30 degrees Celsius was examined using transmission electron microscopy.
• Additionally, it was feasible to ascertain the biochemical characteristics of casein, esculin, and starch as well as catalase, oxidase, MR-VP, and other enzymes.
• Polymerase chain reaction (PCR) is further used to confirm species.

Effective uses for Ideonella sakaiensis

• The discovery of Ideonella sakaiensis may have important implications for the degradation of PET polymers. Only a few bacteria and fungi, such Fusarium solani, were previously known PET degraders, and no species were definitively known to utilise PET as their principal source of carbon and energy.
• By using I. sakaiensis directly or its PET-hydrolyzing enzymes through metabolic engineering of other organisms, the discovery of I. sakaiensis and its capacity to assimilate PET through hydrolysis, followed by downstream metabolism of its monomers, may offer a potential remedy for biological recycling of PET.
• A crucial breakthrough technology for a circular economy and the accomplishment of Sustainable Development Goals may be the ongoing biodegradation of PET.
• For the creation of several possible uses, Ideonella sakaiensis and other organisms, together with their hydrolyzing enzymes, would be necessary.

Ideonella sakaiensis's future

• Considering that PET makes up the bulk of water bottles, polyester clothes, and dinner trays, scientists anticipate being able to harness the bacterial species to promote broad biodegradation.
• If used in a commercial setting, the microbe may be able to degrade more than 50 million tonnes of plastic garbage annually worldwide.
• By creating items, you may turn plastic into a resource.
• Many individuals also believe that if more study is done to comprehend this new classification of bacteria, it will be simpler to locate more germs with comparable plastic-degrading characteristics.
• genetic modification The enzyme PETase from Ideonella sakaiensis, which also degrades PEF (polyethylene furanoate) polymers, may be genetically modified and coupled with MHETase to degrade PET more rapidly.