In classic bacterial morphology, the “drumstick” appearance (a terminal, bulging spore giving a stick-with-knob silhouette) is characteristic of which organism? Choose the single best answer used in routine diagnostics.

Introduction:
Some spore-forming bacteria develop distinctive shapes when spores are positioned terminally or subterminally. The classic “drumstick” look is a key morphological clue in Gram-stained smears of pathogenic clostridia.

Given Data / Assumptions:

• The term “drumstick” signifies a terminal, bulging spore that makes the cell resemble a club or drumstick.
• We compare several clostridial names; only one is the standard routine answer.
• Taxonomic synonyms may exist in the literature, but teaching keys emphasize a single species.

Concept / Approach:
Clostridium tetani exhibits a terminal spore that distends the cell, producing the classic drumstick morphology in smears from cultures grown under anaerobic conditions. This feature, together with characteristic motility and colony morphology, aids presumptive identification.

Step-by-Step Solution:
Step 1: Recall which clostridium has a terminal, bulging spore. Step 2: Note that C. tetani is the textbook example of the “drumstick.” Step 3: Select “Clostridium tetani.”

Verification / Alternative check:
In lab guides, C. tetani is repeatedly illustrated with a terminal spore causing cell swelling; other listed species do not present this reliable hallmark in routine culture conditions.

Why Other Options Are Wrong:
C. tetanomorphum – historical/ambiguous naming; not the standard keyed answer.

C. sphenoides – does not characteristically show a drumstick spore.

All of these – incorrect because the feature specifically points to C. tetani.

None of the above – incorrect; C. tetani is correct.

Common Pitfalls:
Overgeneralizing spore position as diagnostic for multiple species; for most clostridia, spore position alone is not distinctive. “Drumstick” is classically reserved for C. tetani in exam settings.

Final Answer:
Clostridium tetani.