Beneficial Bacteria -- Plant-associated bacteria: survey, molecular phylogeny, genomics and recent advances -- Rhizobium-legume symbioses: molecular signals elaborated by rhizobia that are important for nodulati -- Nitrogen-fixing bacteria in non-legumes -- Epiphytic bacteria, their ecology and functions -- Bacterial endophytes: The endophytic niche, its occupants, and its utility -- Rhizosphere Bacteria -- Plant growth-promoting rhizobacteria -- Contribution of studies on suppressive soils to the identification of bacterial biocontrol agents and to the knowledge of their modes of action -- Root-associated bacteria inducing systemic resistance -- Rhizosphere competence and the role of root colonization in biocontrol -- Deleterious Rhizobacteria -- Plant Pathogenic Bacteria -- Agrobacterium biology and crown gall disease -- Clavibacter michiganensis, a group of gram-positive phytopathogenic bacteria -- The soft rot Erwinia -- Plant pathogenic Pseudomonas species -- Virulence functions of xanthomonads -- Plant pathogenic Ralstonia species -- Burkholderia -- Plant pathogenic members of the genera Acidovorax and Herbaspirillum.