Comparative diversity and composition of cyanobacteria in three predominant soil crusts of the Colorado Plateau

Abstract

Terminal restriction fragment length polymorphism (TRF or T-RFLP) analysis and 16S rDNA sequence analysis from clone libraries were used to examine cyanobacterial diversity in three types of predominant soil crusts in an arid grassland. Total DNA was extracted from cyanobacteria-, lichen-, or moss-dominated crusts that represent different successional stages in crust development, and which contribute different amounts of carbon and nitrogen into the ecosystem. Cyanobacterial 16S rRNA genes were amplified by PCR using cyanobacteria-specific 16S rDNA primers. Both TRF and clone sequence analyses indicated that the cyanobacterial crust type is dominated by strains of Microcoleus vaginatus, but also contains other cyanobacterial genera. In the moss crust, M. vaginatus-related sequences were also the most abundant types, together with sequences from moss chloroplasts. In contrast, sequences obtained from the lichen crust were surprisingly diverse, representing numerous genera, but including only two from M. vaginatus relatives. By obtaining clone sequence information, we were able to infer the composition of many peaks observed in TRF profiles, and all peaks predicted for clone sequences were observed in TRF analysis. This study provides the first TRF analysis of biological soil crusts and the first DNA-based comparison of cyanobacterial diversity between lichen-, cyano- and moss-dominated crusts. Results indicate that for this phylogenetic group, TRF analysis, in conjunction with limited sequence analysis, can provide accurate information about the composition and relative abundance of cyanobacterial types in soil crust communities.

Small-Scale Vertical Distribution of Algae and Structure of Lichen Soil Crusts

“…vaginatus was the dominant species in the ASCs, which was consistent with the results of Redfield et al [11]. The present study found that M. vaginatus was also the dominant species in all of the soil layers in the CLSCs and the soil layers below 1 mm in the GLSCs.…”

“…This result may be attributable to this alga's strong gliding ability and relatively large bodies [22]. Moreover, this result is different from those obtained in the LSCs, in which the dominant species M. vaginatus is replaced by other cyanobacteria [11]. In the GLSCs, S. javanicum dominated the top 1-mm soil layer, which may be closely related to this alga's strong resistance to UV radiance [29] and relative smaller swelling factor of the green algae-lichens, which prevents the thalli from completely covering the cracks between the lichen thalli.…”

“…The present study, however, is not quite consistent with previous studies. Redfield et al [11] reported that LSCs had a higher diversity of cyanobacterial phylotypes than cyanobacterial soil crusts (ASCs dominated by cyanobacteria). This inconsistency may be attributable to the different developmental times for lichen coverage or environmental factors.…”

“…BSCs are the main contributors to water and nutrient cycling [1][2][3][4][5], sand stabilization [1,6], and soil formation [7], playing important roles in the establishment and performance of vascular plants [8,9], and serve as habitats for a dependent food web [10]. According to the different dominant species in different developmental stages, BSCs can be classified into three typical stages: algae soil crusts (ASCs), lichen soil crusts (LSCs), and moss soil crusts [11]. LSCs are the BSCs dominated by lichens, including cyanolichen soil crusts (CLSCs) and green algae-lichen soil crusts (GLSCs), because of the different photobionts in the thalli of the dominant lichens.…”

Analysis of environmental factors determining development and succession in biological soil crusts

“…With crust development and succession, dark-colored lichens or mosses later colonize the soil surface (Lange et al, 1992;Zaady et al, 2000;Lan et al, 2010a). Compared with cyanobacterial crusts, later successional lichen or moss crusts have the higher biological metabolic efficiency and protective ability; hence better topsoil microenvironments are expected in the later BSCs (Castenholz and Garcia-Pichel, 2000;Redfield et al, 2002;Housman et al, 2006).…”