The gyrB gene, coding for the B subunit of DNA gyrase (a protein belonging to topoisomerases) has been recently studied as a potential marker for identification and genetic diversity determination of bacteria. Due to its high diversity the gryB gene is a very good candidate for an evolutionary marker of the relationship between closely related bacteria. Moreover, results obtained from sequence analyses of housekeeping genes to which gyrB belongs, correspond to those of time consuming conventional methods used for identification of bacteria and studies of their phylogeny and genetic diversity. The objective of this paper was to review the recent knowledge regarding the gyrB gene in plant pathogenic bacteria, such as: Pseudomonas aeruginosa, R syringae, R viridiflava, Xylella fastidiosa and some other bacteria from Enterobacteriaceae family and Actinomycetales order.