There is no differentiation of cells and tissues into various specialized structures because there are no tissues and only one cell, that of the organism itself. Nearly all bacteria can be divided into two groups depending on their ability or inability to retain a crystal violet-iodine complex when exposed to an organic solvent such as acetone or alcohol. Although the Gram reaction is not completely understood, it is intimately related to the structure of the bacterial cell wall, a rigid structure that encloses the bacterial organism, and which has known differences in chemical composition between the two types of Gram-reactive bacteria.
Some pili contain a single type of pilin, while others contain more than one type.
Minor proteins, located at the tips of the pili, are responsible for attachment properties of the pili and play a role in the adherence of bacteria to host cells. In fact, the virulence of certain pathogenic bacteria is now recognized to depend not only on toxins secreted by the bacteria, but also on the adherent properties of their pili. We now know that there are more than 20 families of molecular chaperones that assist in the noncovalent assembly of protein structures. Furthermore, there are many cases where interaction of a protein molecule with another of its kind influences the structure of both. It has always been assumed that the main function of molecular chaperones is to somehow protect folding proteins from associating prematurely and forming insoluble aggregates.