Desiccation sensitivity: which bacterium listed is notably fragile and dies quickly after drying (loss of moisture)?

Introduction / Context:
Survival in the environment varies between species. Understanding which pathogens are labile versus hardy guides infection control, transmission risk, and sample handling.

Given Data / Assumptions:

• Treponema pallidum (syphilis agent) is an extremely fragile spirochete; it does not survive drying, heat, or disinfectants well.
• Mycobacterium tuberculosis has a waxy, mycolic acid–rich wall that confers environmental persistence.
• Staphylococcus aureus survives well on dry surfaces for days to weeks.
• Pseudomonas aeruginosa is resilient in moist environments and forms biofilms, though less tolerant of dryness than staphylococci.

Concept / Approach:
Identify the species known for marked sensitivity to desiccation: Treponema pallidum. Its fragile outer membrane and metabolic requirements limit survival outside the host, explaining sexual and vertical transmission patterns rather than fomite-borne spread.

Step-by-Step Solution:

Verification / Alternative check:
Public health guidance emphasizes that syphilis transmission requires close contact; the organism dies rapidly when dried or heated, supporting limited environmental transmission.

Why Other Options Are Wrong:
M. tuberculosis: Highly resilient due to lipid-rich wall. S. aureus: Tolerates drying, persists on fomites. P. aeruginosa: Environmentally robust in moist niches.

Common Pitfalls:
Assuming all pathogens persist on surfaces; in reality, survival varies dramatically by envelope composition.

Final Answer:
Treponema pallidium