摘要:Microcoleus vaginatus has been proclaimed to be a cosmopolitan species. However, morphological studies performed on natural populations of cyanobacterial crusts in a region with a particular geological history at the southern part of the Baja California Peninsula, Mexico, called Sierra de la Laguna (SL), do not support the last assertion. We compared the community structure of cyanobacteria, with emphasis in the genus Microcoleus, in biological desert crusts from 10 different localities along the Baja California Peninsula. We analyzed natural cyanobacterial populations and matched them with type cultures from public collections: Microcoleus sociatus (Sammlung von Algenkulturen Germany- SAG 26.92), M. paludosus (SAG 1445. 1a), M. vaginatus (Pasteur Culture Collection-PCC 9802), and M. chthonoplastes (PCC 7420). Microscopy and cluster analysis of band patterns of 16S rRNA sequences from denaturing gradient gel electrophoresis (DGGE) were applied. The microscopic analysis of natural samples resulted in the undetection of morphotypes of M. vaginatus in 6 of the 10 localities, 4 or them from the SL. Comparison of band profiles from denaturing gradient gel electrophoresis showed signifi cant differences in the natural cyanobacterial community structure and the absence of the band that matches with that of M. vaginatus (PCC 9802) in all of the SL localities.