Q.9 Which microbe is not capable of degrading petroleum hydrocarbons:
(1)Candida
(2) Achromobacter
(3)Pseudomonas
(4) Aspergillus
Aspergillus is not capable of degrading petroleum hydrocarbons among the given options. While Candida, Achromobacter, and Pseudomonas are well-documented for breaking down petroleum hydrocarbons via specific enzymes like alkane hydroxylases and P450 systems, Aspergillus lacks this capability in standard contexts, making it the exception.
Option Analysis
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(1) Candida: Yeast genus (e.g., C. tropicalis, C. maltosa) with eukaryotic P450 enzymes that degrade C10-C16 alkanes and other hydrocarbons effectively in bioremediation.
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(2) Achromobacter: Gram-negative bacteria (now often Alcaligenes) producing dioxygenases and P450 systems; degrades C5-C16 alkanes and complex petroleum fractions.
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(3) Pseudomonas: Prominent hydrocarbonoclastic bacterium with AlkB hydroxylases; rapidly mineralizes alkanes, aromatics, and crude oil components under aerobic conditions.
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(4) Aspergillus: Fungus mainly degrading simple sugars/cellulose via extracellular enzymes; lacks specialized alkane/P450 systems for petroleum hydrocarbons, unlike other microbes.
The correct answer is (4) Aspergillus.
Introduction to Petroleum Hydrocarbon Degradation
Petroleum hydrocarbon degradation relies on specialized microbes like bacteria and yeasts using oxygenases to break down alkanes and aromatics in oil spills. Which microbe is not capable of degrading petroleum hydrocarbons? This MCQ highlights key players in environmental microbiology for GATE Life Sciences.
Key Degraders Explained
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Candida yeasts employ cytochrome P450 for mid-chain alkanes.
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Achromobacter uses bacterial P450/dioxygenases for diverse hydrocarbons.
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Pseudomonas excels with AlkB systems, degrading up to 70-90% of crude oil.
Why Aspergillus Doesn’t Qualify
Aspergillus fungi focus on lignocellulose via amylases/cellulases, not the alkane hydroxylases needed for petroleum hydrocarbons, limiting its bioremediation role.
GATE Exam Insights
Memorize Pseudomonas/Candida as top degraders; Aspergillus tests exceptions in hydrocarbonoclastic microbes for microbiology sections.
