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. 2024 Jan 11;12(1):147.
doi: 10.3390/microorganisms12010147.

Diversity of Microbial Mats in the Makgadikgadi Salt Pans, Botswana

Sevasti Filippidou  1   2 , Alex Price  1 , Charlotte Spencer-Jones  1   3 , Anthony Scales  1 , Michael C Macey  1 , Fulvio Franchi  4   5 , Lesedi Lebogang  6 , Barbara Cavalazzi  7   8 , Susanne P Schwenzer  1 , Karen Olsson-Francis  1
Affiliations

Diversity of Microbial Mats in the Makgadikgadi Salt Pans, Botswana

Sevasti Filippidou et al. Microorganisms. .

Abstract

The Makgadikgadi Salt Pans are the remnants of a mega paleo-lake system in the central Kalahari, Botswana. Today, the Makgadikgadi Basin is an arid to semi-arid area receiving water of meteoric origin during the short, wet season. Large microbial mats, which support primary production, are formed due to desiccation during the dry season. This study aimed to characterise the microbial diversity of the microbial mats and the underlying sediment. The focus was the Ntwetwe Pan, located west of the Makgadikgadi Basin. Metagenomic analyses demonstrated that the mats consisted of a high relative abundance of Cyanobacteriota (synonym Cyanobacteria) (20.50-41.47%), Pseudomonadota (synonym Proteobacteria) (15.71 to 32.18%), and Actinomycetota (synonym Actinobacteria) (8.53-32.56%). In the underlying sediments, Pseudomonadota, Actinomycetota, and Euryarchaeota represented over 70% of the community. Localised fluctuations in water content and pH did not significantly affect the microbial diversity of the sediment or the mats.

Keywords: Makgadikgadi Basin; metagenomics; microbial mats; salt pans.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
(A) Location of the Makgadikgadi salt pans in southern Africa. The red box outlines the area shown in (C) (modified from [6]). (B) Schematic view of the main basins in northern Botswana, showing the main affluent to the Makgadikgadi Pans and relevant geomorphic features. Ma—Makalamabedi Basin; G.R.—Gidikwe ridge; M.D.—Mababe Depression. (D) Satellite image of the Makgadikgadi Pans showing the sampling site (yellow) in the northern Ntwetwe Pan. Source Google Earth, Image Landsat/Copernicus, US Department of State Geographer, 2021.
Figure 2
Figure 2
(A) The sampling site located in the Ntwetwe Pan. The red arrows show the microbial mats and the black arrow shows the sediment. (B–D) demonstrate the variation between the water content of the samples and are representative of samples MMA, MMB and MMC, respectively.
Figure 3
Figure 3
The water content (%) of the underlying sediment. The values reported are the means of three independent measurements, and the standard error associated with these determinations is shown.
Figure 4
Figure 4
Electron microscopy observations of the microbial mats using a SEM with EDS (A) and TEM (B). Potential Extracellular Polysaccharide Substrate was observed using TEM (demonstrated by the arrow in (C)).
Figure 5
Figure 5
Microbial community composition at the Phylum level of the Microbial Mats (MM), Underlying Sediments (US) and the surface sediment (SS). The Phylum were assigned based on conserved genes in the metagenomic sequencing data set.
Figure 6
Figure 6
Shannon index (A), α-diversity (B), and Simpson index (C) for the microbial mats, their underlying sediment, and the surface sediment. (D) Sørensen index for the similarity between the mats and their underlying sediment. (E) Ordination plot using NMDA showing the distribution of the microbial mats (open circles) and the underlying sediment (open triangles).
See this image and copyright information in PMC

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