Datensatz

Zusammenfassung

Prokaryotes possess various kinds of cell surface organelles serving versatile biological roles depending on the environmental niche of the organism. The formation of these structures involves fascinating machineries, as not only do the protein components need to travel across the cytoplasmic membrane like all secreted proteins, but they also need to do so in a precisely coordinated manner for proper assembly. Most commonly found on the surface of bacteria are flagella used for swimming (47); the type III secretion injectisome (needle structure) (21), which is used to deliver effector molecules from pathogenic organisms into host cells; and a wide variety of thinner organelles that fall under the broad designation of pili (13, 33, 58, 64, 69, 78). Different classes of these structures (type I pili, type IV pili, sex pili, etc.) which differ significantly in their structure, assembly, and function have been identified. Their many roles include adhesion, twitching (or surface) motility, and delivery of DNA and toxins, as well as functioning as electrically conductive “nanowires.” Other, less commonly studied appendages have also been reported, such as spinae (9).