Phylogenetic and Morphological Diversity of Cyanobacteria in Soil Desert Crusts from the Colorado Plateau

Abstract

We compared the community structures of cyanobacteria in four biological desert crusts from Utah's Colorado Plateau developing on different substrata. We analyzed natural samples, cultures, and cyanobacterial filaments or colonies retrieved by micromanipulation from field samples using microscopy, denaturing gradient gel electrophoresis, and sequencing of 16S rRNA genes. While microscopic analyses apparently underestimated the biodiversity of thin filamentous cyanobacteria, molecular analyses failed to retrieve signals for otherwise conspicuous heterocystous cyanobacteria with thick sheaths. The diversity found in desert crusts was underrepresented in currently available nucleotide sequence databases, and several novel phylogenetic clusters could be identified. Morphotypes fitting the description of Microcoleus vaginatus Gomont, dominant in most samples, corresponded to a tight phylogenetic cluster of probable cosmopolitan distribution, which was well differentiated from other cyanobacteria traditionally classified within the same genus. A new, diverse phylogenetic cluster, named "Xeronema," grouped a series of thin filamentous Phormidium-like cyanobacteria. These were also ubiquitous in our samples and probably correspond to various botanical Phormidium and Schizothrix spp., but they are phylogenetically distant from thin filamentous cyanobacteria from other environments. Significant differences in community structure were found among soil types, indicating that soil characteristics may select for specific cyanobacteria. Gypsum crusts were most deviant from the rest, while sandy, silt, and shale crusts were relatively more similar among themselves.

Hydrotaxis of Cyanobacteria in Desert Crusts

“…2). 16S rRNA analyses of field samples and cultures from this cyanobacterium demonstrated its relatedness to filamentous oscillatorian cyanobacteria of marine origin, which is somewhat unusual for a desert crust organism [9]. This was probably a result of selection due to the presence of sulfate in the soils.…”

“…obtained from Las Bárdenas samples. The inset is a neighbor-joining distance tree based on 16S rRNA gene sequences showing the phylogenetic relationship of this isolate (in bold) to its most closely related cyanobacterium (simplified from [9]). Its closest known relative is a marine Oscillatoria isolate.…”

Heterotrophic Pioneers Facilitate Phototrophic Biofilm Development

“…During the exponential phase, thick dominant bands appeared at similar positions in the DGGE profiles of the PFD 60 and PFD 120 biofilms. These bands represented DNA sequences affiliated to the filamentous cyanobacterium Microcoleus vaginatus, a known inhabitant of desert soil crusts [10] (Fig. 2, bands 8, 12, 13, and 17, and Fig.…”

Did Smoke from the Kuwait Oil Well Fires Affect Iranian Archaeological Heritage?

“…Microbiotic crusts are desert communities composed of diverse photosynthetic and non-photosynthetic organisms, including cyanobacteria and other prokaryotes, algae, lichens, non-lichenized fungi, etc (39). Desert crusts from the Colorado Plateau comprise a diverse, polyphyletic array of cyanobacteria, but no microscopic or molecular evidence for the presence of significant populations of eukaryotic algae have been obtained (40).…”