The bacteria that have variable shapes (bacteria with changeable shapes) are called?

Appeared in: UPRVUNL - 2021

Explanation

The term 'pleomorphic' literally means 'many shapes' and is used in microbiology to describe bacteria that can exhibit a variety of shapes and sizes.
This variability is often due to the absence of a rigid cell wall, as seen in Mycoplasma, or can be a characteristic feature of certain species like Haemophilus and Proteus.
Pleomorphism is a distinct characteristic related to the cell body, not its appendages.

Option A: Lophotrichous describes a specific arrangement of flagella, where a tuft or cluster of flagella is located at one end (pole) of the bacterial cell. It does not describe the shape of the bacterium itself.
Option B: Monotrichous refers to the presence of a single flagellum at one pole of the bacterium. This term describes motility apparatus, not cell shape.
Option C: Amphitrichous describes bacteria that have a single flagellum at both ends of the cell. Like the other distractors, this term relates to flagellar arrangement, not the variability of the cell's shape.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Bacterial Morphology as background academic context rather than a clinical decision trigger.
Understanding pleomorphism is crucial for antibiotic selection. For instance, Mycoplasma pneumoniae, a common cause of atypical pneumonia, is pleomorphic because it lacks a cell wall. Therefore, antibiotics like penicillin that target the cell wall are ineffective.
A nurse administering antibiotics should be aware of the organism's characteristics. For a Mycoplasma infection, they would anticipate orders for macrolides (e.g., azithromycin) or tetracyclines, not beta-lactams.
What if? If a lab report identifies a 'Gram-negative pleomorphic rod' from a sputum sample, the nurse should consider pathogens like Haemophilus influenzae and ensure appropriate contact or droplet precautions are in place, as this organism can cause respiratory infections.

How to Approach the Question

First, analyze the question's core concept. The question asks for a term describing 'variable shapes' of bacteria.
Next, evaluate each option's meaning. Recognize that 'trichous' is a suffix related to hair or flagella.
Define each term: Lophotrichous (tuft of flagella), Monotrichous (single flagellum), and Amphitrichous (flagella at both ends) all describe flagellar arrangements.
Define the remaining option: 'Pleomorphic' means having many forms or shapes.
Match the definition to the question. 'Pleomorphic' is the only term that describes variable cell shape, making it the correct answer.

Concept Tested & Keywords

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E6 Microbiology Essentials Sastry 4e Part 1 pp. 39-41, 35-37

E6 Microbiology Applied AnjuDhir 3e Part 1 p. 54-56

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