Many bacterial species are motile by means of flagella. The structure and implantation of flagella seems related to the specific environments the cells live in. In some cases, the bacteria even adapt their flagellation pattern in response to the environmental conditions they encounter. Swarming cell differentiation is a remarkable example of this phenomenon. Flagella seem to have more functions than providing motility alone. For many pathogenic species, studies have been performed on the contribution of flagella to the virulence, but the result is not clear in all cases. Flagella are generally accepted as being important virulence factors, and expression and repression of flagellation and virulence have in several cases been shown to be linked. Providing motility is always an important feature of flagella of pathogenic bacteria, but adhesive and other properties also have been attributed to these flagella. In nonpathogenic bacterial colonization, flagella are important locomotive and adhesive organelles as well. In several cases where competition between several bacterial species exists, motility by means of flagella is shown to provide a specific advantage for a bacterium. This review gives an overview of studies that have been performed on the significance of flagellation in a wide variety of processes where flagellated bacteria are involved.

Rather recently it has become clear that prokaryotes (Archaea and Bacteria) are able to glycosylate proteins. A literature survey revealed the different types of glycoproteins. They include mainly surface layer (S-layer) proteins, flagellins, and polysaccharide-degrading enzymes. Only in a few cases is structural information available. Many different structures have been observed that display much more variation than that observed in eukaryotes. A few studies have given evidence for the function of the prokaryotic glycoprotein glycans. Also from the biosynthetic point of view, information is rather scarce. Due to their different cell structure, prokaryotes have to use mechanisms different from those found in eukaryotes to glycosylate proteins. However, from the fragmented data available for the prokaryotic glycoproteins, similarities with the eukaryotic system can be noticed.

Azospirilkcm bnrsilense in a motile Gram-negative bacterium that can adapt its flagellation to different environments. Cells growing in a liquid culture possess only a single polar flagellum; growth on a solid surface additionally induces multiple lateral flagella. The polar flagellum is primarily used for swimming, i.e. locomotion of the bacterium in a liquid environment, whereas the lateral flagella allow the bacteria to swarm over a solid surface. We have previously described a completely non-motile A. brasifense mutant (Sp7 p90DO84), and shown that this mutant has a drastically reduced adsorption capacity to wheat roots. In the present work, we present several lines of evidence demonstrating that adsorption to wheat roots is mediated by the polar flagellum of A. bradense. First, the non-adsorbing mutant Sp7 p9ODO84 forms no polar and no lateral flagella, but is otherwise undistinguishable from wild-type A. brasilense. Second, disintegration of the flagella by heat or acid eliminates adsorption. Third, using a polyclonal antiserum against the polar flagellum filament protein (Flal), we have isolated out of a collection of 3000 TnS-B30-hduced mutants, three additional and genetically different nonflagellate mutants. Like Sp7 p90DOS4, these mutants show a severely reduced adsorption capacity to wheat roots. Finally, purified polar flagella bind to wheat roots in vitvo.