Fig 1.
Illustration (from 2013) of Nadine dune, Lat 24.904496° Lon 51.549534.
Table 1.
Average on-grain cell counts per gram of sand (± Standard Error) retrieved from floor, base, mid and crest of Nadine (column 2).
Column 3 shows the percentage of colony forming grains (of 504 grains tested) for various dune locations, as well as estimated colony forming grains per gram of sand. Column 4 shows the number of CFUs in sand extracts. Column 5 shows the moisture content per gram of sand.
Fig 2.
Heatmap showing the most abundant OTUs in all samples.
OTU names are given at the lowest available taxonomic level; OTUs that could not be classified below the level of order are termed Unclassified. Dendrograms were generated using hierarchical clustering with complete linkage. Plot indicates the relative fraction of sequences in each sample that were classified as Gammaproteobacteria at the level of class. Sample key: dune name; location on dune face (C = crest, M = middle, B = base); sample number.
Fig 3.
A. Alpha diversity, as measured by the Shannon diversity index at genus-level resolution. Samples were grouped according to their dune of origin. B. Linear regression of alpha diversity by the proportion of sequences classified as Gammaproteobacteria out of the total number of sequences in each sample.
Table 2.
Results of ANOVA and PERMANOVA analyses.
P values less than 0.05 are bolded.
Fig 4.
A. NMDS ordination of 16S rRNA gene-derived microbial community structure. Similarity profile analysis, an a priori statistical approach that uses permutation to identify groups of communities that are more dissimilar than expected by chance, identified two distinct clusters of communities. Ellipses represent the 95% confidence intervals around the centroid for each cluster (the spatial mean in NMDS space of the communities belonging to each cluster). Lines emanating from the centroids indicate to which cluster each community belongs. Bacterial families well-correlated with the ordination (r2 > 0.40) are displayed; vector length is proportional to the Pearson correlation coefficient for each family and vector direction corresponds to the direction of increasing abundance relative to the ordinated communities. Legend indicates the dune from which each ordinated community originated. Final 2-dimensional stress of the ordination is 0.12. B. Linear discriminant analysis (LDA) of bacterial classes indicates that the two clusters of microbial communities identified by similarity profile analysis are driven by the disparity between a high abundance of Gammaproteobacteria in one set of communities and more diverse population in the other set of communities. Only classes with effect size > 2.0 are displayed. C. NMDS ordination is based only on samples for which environmental parameters were measured. Parameters with r2 > 0.1 are displayed. Final 2-dimensional stress of the ordination is 0.07.
Table 3.
Comparison of filter-based epifluorescent direct counts from Qatari dune (this work) with those of Middle Eastern and North African soils [16].
Table 4.
Comparison of the relative abundance of phyla between cultivation, deep 16S rRNA gene amplicon sequencing and metagenomics.
Fig 5.
Relative abundance of domain-level sequences in the metagenomes of Nadine and Michel as compared with selected soil samples from Fierer et al., [15].
Fig 6.
A. The relative abundance (based on Representative Hit Analysis in MG-RAST) of dominant bacterial phyla and B. MG-RAST Subsystems analysis (Level 1) of Nadine and Michel dunes, versus desert soils and non-desert soils studied by Fierer et al. [15]).