Lack of motility is a characteristic of which genus among Enterobacteriaceae?

Lack of motility is a characteristic of which genus among Enterobacteriaceae?

• A. Enterobacter
• B. Klebsiella
• C. Serratia
• D. Salmonella

Answer: (B)

Motility among Enterobacteriaceae is a common way to differentiate genera, because most members have flagella and can move in motility tests. Klebsiella stands out by being nonmotile — it lacks functional flagella, so it does not show movement in motility assays. This nonmotility aligns with other characteristic Klebsiella traits, such as very mucoid, capsule-rich colonies and strong lactose fermentation. In contrast, Enterobacter, Serratia, and Salmonella are motile, so they demonstrate movement in the same tests. Therefore, a lack of motility points to Klebsiella.

Motility among Enterobacteriaceae is a common way to differentiate genera, because most members have flagella and can move in motility tests. Klebsiella stands out by being nonmotile — it lacks functional flagella, so it does not show movement in motility assays. This nonmotility aligns with other characteristic Klebsiella traits, such as very mucoid, capsule-rich colonies and strong lactose fermentation. In contrast, Enterobacter, Serratia, and Salmonella are motile, so they demonstrate movement in the same tests. Therefore, a lack of motility points to Klebsiella.