Q.26 Which one of the following is CORRECT about microbial growth medium?
(A) Luria-Bertani broth is a synthetic medium
(B) Nutrient broth is a defined medium
(C) Sabouraud dextrose agar is a differential medium
(D) Trypticase soy agar is a complex medium
Trypticase soy agar is correctly identified as a complex medium in microbial growth classifications. This multiple-choice question tests understanding of culture media types used in microbiology. The right answer is option (D).
Correct Answer
Trypticase soy agar (TSA) qualifies as a complex medium due to its components like trypticase (casein digest) and soy peptone, which provide undefined mixtures of peptides, amino acids, and nutrients. Complex media contain extracts or digests from yeast, meat, or plants where exact compositions vary. TSA supports broad bacterial growth without precise chemical knowledge of ingredients.
Option Breakdown
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(A) Luria-Bertani broth is a synthetic medium: Incorrect. Luria-Bertani (LB) broth uses tryptone (casein digest) and yeast extract, making it a rich, undefined complex medium, not synthetic (chemically defined with known exact ingredients).
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(B) Nutrient broth is a defined medium: Incorrect. Nutrient broth includes peptone and beef extract, which are complex, variable digests, classifying it as undefined rather than defined.
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(C) Sabouraud dextrose agar is a differential medium: Incorrect. This agar, with peptone, dextrose, and acidified pH, selectively grows fungi but lacks indicators for differentiating reactions like sugar fermentation.
Media Types Overview
Defined (synthetic) media list all exact chemicals, like glucose-salts for minimal growth. Complex media, including LB, nutrient broth, and TSA, use digests for richer, non-precise nutrition supporting fastidious microbes. Selective media like Sabouraud target specific groups via pH or inhibitors, while differential ones show visible distinctions.
