Which of the following organisms are classified as non-motile?

The correct answer identifies Shigella and Klebsiella as non-motile organisms. Shigella, a genus of bacteria known for causing dysentery, is known for not possessing flagella, the structures typically responsible for motility. As a result, Shigella does not move independently and relies on more passive means for transmission. Similarly, Klebsiella is characterized by its non-motility as well; it has a capsule but lacks flagella for self-propulsion.

Other organisms mentioned in the other choices exhibit different motility characteristics. For example, Salmonella and Escherichia species are motile due to the presence of flagella. Bacillus species are generally motile, particularly Bacillus cereus, which can swim due to its flagella. Clostridium species also display motility in some of their members. Proteus is well-known for its swarming motility on solid media due to its flagella, and Pseudomonas aeruginosa also displays significant motility through its flagella.

Thus, the classification of Shigella and Klebsiella as non-motile is accurate and highlights the distinction of these organisms in terms of their movement capabilities compared to other bacterial species.