Which one of the following options correctly matches the organism to the pollutant it most commonly degrades?
(1) 1- (ii); II – (iv); III – (i); IV – (iii)
(2) 1- (iii); II – (iv); III – (ii); IV – (i)
(3) 1- (iii); II – (i); III – (iv); IV – (ii)
(4) 1- (iv); II – (iii); III – (i); IV – (ii)

Column A and Column B

Column A
I. Pseudomonas putida
II. Methylibium petroleiphilum
III. Alcanivorax borkumensis
IV. Deinococcus radiodurans

Column B
i. Methyl tert‑butyl ether (MTBE)
ii. Heavy metal detoxification
iii. Toluene, naphthalene
iv. Fuel hydrocarbon

Correct matching:

• I → iii

• II → i

• III → iv

• IV → ii

This corresponds to option (3).

Why each match is correct

• I. Pseudomonas putida → iii. Toluene, naphthalene

  • P. putida strains are classic degraders of aromatic hydrocarbons, especially toluene and naphthalene, via dioxygenase pathways.​

• II. Methylibium petroleiphilum → i. Methyl tert‑butyl ether

  • M. petroleiphilum is well known as a specialist in degrading MTBE, a gasoline oxygenate contaminant.​

• III. Alcanivorax borkumensis → iv. Fuel hydrocarbon

  • A. borkumensis is a dominant marine oil‑degrading bacterium, using fuel hydrocarbons (alkanes in crude oil and spills) as carbon sources.​

• IV. Deinococcus radiodurans → ii. Heavy metal detoxification

  • Radiation‑resistant D. radiodurans has been engineered for bioremediation of radioactive wastes, including mercury and other heavy metals.​

Why the other options are wrong (briefly)

• Option (1) links Pseudomonas to MTBE and Methylibium to fuel hydrocarbons, which swaps their main specializations.

• Option (2) mixes Pseudomonas with toluene correctly but mismatches the others.

• Option (4) assigns Pseudomonas to fuel hydrocarbons and Alcanivorax to MTBE, both incorrect.

Hence, the only fully correct combination is option (3).