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Question 600
Microbiology → General
Classification
Question
SSBAQuestion Header
Which description best defines an obligate anaerobe?
Question Stem
A bacterium thrives without oxygen but may die in the presence of oxygen. How should it be classified?
Options
A
Aerobe
B
Facultative anaerobe
C
Gram-negative coccus
D
Gram-positive bacillus
E
Obligate anaerobe
Explanation
Obligate anaerobes live and thrive without oxygen and may die in the presence of oxygen. Facultative anaerobes instead alter their function according to whether oxygen is present or absent.
Option Validity
A) Aerobic organisms require oxygen.
B) Facultative anaerobes alter function according to oxygen availability.
C) Gram-negative coccus describes staining and morphology rather than oxygen requirement.
D) Gram-positive bacillus describes staining and morphology rather than oxygen requirement.
Further Reading
Saxena R. Textbook for MRCOG-1: Basic Sciences in Obstetrics and Gynaecology. Chapter 6 — Microbiology and Immunology: Bacteria. Printed page 183.