Please answer this passionately and with full detail! I need the help big time. Question: There are pathogenic strains of E coli that attach to epithelial cells in the bladder and cause disease there. Some of these strains possess three different kinds of protein appendages: fimbriae, conjugation pili, and flagella. What are the functions of each of these appendages? Which is the most important for infecting the bladder? Why do you think that? Which is least important for infecting the bladder? Why do you think that? Solution Although E.coli reside in the gut as normal flora, but some strains of this microbe can be infectious in nature. An example of this strain is E. coli O157:H7. This strain of E. coli contains infectious elements which can be easily transmitted to host and cause disease. One of the most common type of infection occuring due to E. coli is renal and urinary tract infection. In this kind of infection, the E. coli releases toxins in the body of the host and causes disease. Some of the infectious strains possess different kinds of appendages like fimbriae, pili and flagella. Their unique functions are discussed as below: Fimbriae: Fimbriae are appendages which help in attachment of the bacteria on the surface of attachment. This helps the bacteria to reside and colonize at a place and undergo infectious cycle. Fimbriae can be found all over the surface. Conjugation pili: These are hollow membranous extensions which help in transfer of genetic material from one microbe to another. The pili help in transfer of plasmids and thus bring about sexual reproduction in bacteria. Flagella: Flagella represents the appendage of motion and movement in bacteria. A typical movement of flagella is important to modulate forward, reverse or tangling motion of the bacteria. Which is the most important for infecting the bladder? As described above, it is most important for a bacteria to attach to the surface and colonize over there to cause any infection. It should be noted here that a few bacteria are not sufficient enough to cause an infection. A large colony is required to induce a diseased state. For that to be accomplished, the bacteria must attach to the surface firmly. This can be brought about only if they have fimbriae. Thus, fimbriae are most important for infection to occur. Which is least important for infecting the bladder? As it can be observed from the above explanation, pili are the structural appendages required for transmission of genetic material from one bacteria to another. These are also responsible for generation of virulence in non-virulent strains by transmission of virulent plasmid. However, they are not directly related with causing infection in bladder since their presene is meant for transfer of information among bacteria only..