Prokaryotes chemotaxis

Phosphorylation. In recent years, protein phosphorylation/dephosphoryla-tion catalyzed by protein kinases and phosphatases has been revealed to be widespread among prokaryotes. Many of the purposes of these reactions remain unclear. However, roles for transient phosphorylation have been identified in chemotaxis and nitrogen metabolism regulation. 

Table 2 summarizes the behavioral mechanisms of chemotaxis in the systems reviewed in this book. If these systems faithfully represent the mechanisms of chemotaxis in nature, it appears that prokaryotes mainly employ trial-and-error chemotaxis mechanisms— the phobic response and klinokinesis, defined in Table 2 and, in more detail, in Chapter 1. In contrast, eukaryotes appear to primarily employ the more direct mechanism—modulation of the direction of movement according to the stimulant gradient. A number of non-mutually-exclusive reasons may account for this difference. First, the mechanisms employed by bacteria... 

Beyond this universal, general framework, the molecular mechanisms of chemotaxis involve both commonalities and diversities. Generally speaking, the molecular mechanisms of prokaryotes and eukaryotes are different. Within the prokaryotes, however, commonality seems to govern. Within the eukaryotes, both commonality and diversity appear to dominate (Table 3). 

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