Q.63 Possible sources of contamination of the nutrient medium in plant tissue culture are:
A. the medium itself
B. the culture vessel
C. the explant
D. the environment of the transfer area
E. the operator
Choose the most appropriate answer from the options given below:
(A) A, E only
(B) B, C only
(C) A, B, C, D only
(D) A, B, C, D, E only
The correct answer is (D) A, B, C, D, E only.
Sources Analysis
All listed items are established contamination sources in plant tissue culture:
A. Medium itself: Unsterile media/reagents introduce bacteria/fungi.
B. Culture vessel: Poorly sanitized jars/plates harbor microbes.
C. Explant: Endophytic/epiphytic pathogens resist surface sterilization.
D. Transfer area environment: Airborne spores settle during manipulation.
E. Operator: Hands, hair, breath introduce contaminants without PPE.
Option Breakdown
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(A) A,E only: Misses vessels, explants, environment—major risks.
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(B) B,C only: Ignores medium, operator, air—top causes.
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(C) A,B,C,D only: Excludes operator (human error = 30-50% cases).
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(D) All five: Correct—comprehensive per lab protocols.
Introduction: Plant Tissue Culture Contamination Sources
Plant tissue culture contamination sources include the nutrient medium, culture vessels, explants, transfer area environment, and operators—each posing unique microbial risks. Success rates drop 50-90% with contamination; mastering these is essential for NEET biotech MCQs testing A-E options.
Major Contamination Sources Breakdown
1. Medium/Reagents (A): Non-sterile water, agar, hormones introduce endotoxins/bacteria.
2. Culture Vessels (B): Inadequate autoclaving leaves fungal spores.
3. Explants (C): Endophytes (inside tissues) survive HgCl₂/NaOCl treatment.
4. Transfer Environment (D): Laminar flow hood drafts carry 10³-10⁵ spores/m³.
5. Operator (E): Touching face, improper gowning transfers skin flora.
MCQ Solution: Contamination Sources A B C D E
Question: Sources: A. medium B. vessel C. explant D. environment E. operator.
| Option | Evaluation |
|---|---|
| (A) A,E only | Incomplete; ignores explants/vessels |
| (B) B,C only | Misses top causes (medium/air) |
| (C) A,B,C,D | Excludes human error (critical) |
| (D) All five | Correct; standard lab protocol |
Answer: (D)
Prevention Strategies
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Explant: 0.1% HgCl₂ × 5min + 70% ethanol.
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Medium: 121°C × 20min autoclaving.
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Operator: UV exposure, 70% ethanol sprays, flame loops.
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Monitoring: Spread plate weekly; discard at first sign.
