Which of the following is a property of salmonellae?

• A. They are non-motile.
• B. They are Gram-negative rods.
• C. They are obligate anaerobes.
• D. They form endospores.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the characteristics of Salmonella species by reviewing their morphology, staining properties, oxygen requirements, motility, and ability to form endospores.
2. Step 2: Recall that Salmonella are classified as Gram-negative bacteria, which means they do not retain the crystal violet stain and appear pink/red after Gram staining due to their thin peptidoglycan layer and outer membrane.
3. Step 3: Consider motility: Salmonella species are generally motile due to the presence of flagella, so the statement 'They are non-motile' is incorrect.
4. Step 4: Evaluate oxygen requirements: Salmonella are facultative anaerobes, meaning they can grow in both the presence and absence of oxygen, so they are not obligate anaerobes.
5. Step 5: Assess endospore formation: Salmonella do not form endospores, which are a feature of certain Gram-positive genera like Bacillus and Clostridium.