Microorganism motile at 25 degree Celsius but non-motile at 37 degree Celsius and shows actin binding polymerization to escape is:

Ans. is 'a' i.e., Listeria monocytogenes L. monocytogenes is a short, gram positive, non-spore forming rod. The motility test rapidly differentiates listeria from diphtheroids that are members of the normal microbiota of the skin. The organism has several adhesion proteins (Ami, Fbp A, and flagellin proteins) that facilitate bacterial binding to the host cells and that contribute to virulence.It has cell wall surface proteins called internalins A and B that interact with E-cadherin, a receptor on epithelial cells, promoting phagocytosis into the epithelial cells. After phagocytosis, the bacterium is enclosed in a phagolysosome, where the low pH activates the bacterium to produce listeriolysin.This enzyme, along with two phospholipases, lyses the membrane of the phagolysosome and allows the listeriae to escape into the cytoplasm of the epithelial cell. The organism proliferates, and ActA, another listerial surface protein, induces host cell actin polymerization, which propels them to the cell membrane. Pushing against the host cell membrane, they cause formation of elongated protrusions called filopods. These filopods are ingested by adjacent epithelial cells, macrophages, and hepatocytes, the listeriae are released, and the cycle begins again. L monocytogenes move from cell to cell without being exposed to antibodies, complement, or polymorphonuclear cells.