The outer membrane vesicles: Secretion system type zero.

Gram-negative bacteria have mechanisms through which they can colonize and survive in different environments, such as the secretion systems types (1-6) that have been widely studied and characterized. Nowadays, some authors have proposed extracellular structures, such as the outer membrane vesicles (OMVs), to be considered as an additional and independent secretion system. The OMVs are spherical particles of 50-250 nm in diameter; they originate in the outer membrane, and therefore they have a very similar composition to the latter.

Active Shiga-Like Toxin Produced by Some spp., Isolated in Mexico City.

Shiga-like toxins (Stx) represent a group of bacterial toxins involved in human and animal diseases. Stx is produced by enterohemorrhagic type 1, , and spp.; Stx is an important cause of bloody diarrhea and hemolytic uremic syndrome (HUS).