Vibrio cholerae is a gram negative bacterium with a curved-rod shape that causes cholera in humans and its main portal of entry is oral ingestion of contaminated food or water sources. It is a highly motile bacterium by a single polar flagellum as a locomotion organelle. V. cholerae colonizes the gastrointestinal tract, where it adheres to villous absorptive cells via pilli (TCP) and secretes an enterotoxin (CT). It acts by interfering with G-proteins, thus increasing cAMP levels. This leads to massive electrolyte loss and  watery diarrhea, severe dehydration and, eventually, death. Fluid replacement, intravenous or oral rehydration is necessary to prevent acute dehydration. Motility is thought to be an important factor for the virulence of V. cholerae – motility mutants colonizes poorly the intestine of suckling mouse. In the present work, we describe the characterization of a motility mutant (mot-, WK13) of V. cholerae strain O395. The mutation that caused loss of motility arose during a recombinational process between a mutated copy of phoB gene and a wild type one in the chromosome of the bacterium. In this process, phoB- and phoB+ strains were obtained, however, none was motile. In an attempt to trace the origin of the mutation, we sequenced a strech of DNA 6,6 kb leng, from the WK13 mutant, most probably related to recombination. We compared this sequence to the equivalent one in the wild type strain, O395, and found no difference. A Transmission Electron Microscopy showed that WK13 lacks the polar flagellum and apparantely produces pillus TCP in smaller quantities than O395 under appropriated conditions (LB pH 6,5, 30°C). The reduction in TCP production could explain the diminished ability of WK13 to autoagglutination. To understand the molecular basis of this two processes (autoagglutination and motility), we compared the pattern of proteins expressed by WK13 and O395 grown in LB pH 7,2, 37°C or in LB pH 6,5, 30°C. Two-dimensional gel electrophoresis of whole cell lysates, inner and outer membranes, periplasmic and supernatant fractions showed proteins differentially expressed by the strains. These unique spots are being identified by mass spectrometry.