The first three volumes of the "Pseudomonas" series covered the biology of pseudomonads in a wide context, including the niches they inhabit, the taxonomic relations among members of this group, the molecular biology of gene expression in different niches and under different environmental conditions, the analysis of virulence traits in plants, animals and human pathogens as well as the determinants that make some strains useful for biotechnological applications and promotion of plant growth. "Pseudomonas, Volume 4" is intended to collect some of the most relevant new emerging issues in the field of Pseudomonas that were not assembled in the three previous volumes. This fourth volume covers the following topics: Virulence and Pathogens; Genomics and Proteomics; Physiology, Metabolism and Biotechnology. "Pseudomonas, Volume 4" will be of use to researchers working on these bacteria, particularly those studying virulence, genomics, physiology, biotechnology, etc. Advanced students in biology, medicine and agronomy will also find this volume a valuable reference during their studies.