Salt flat microbial diversity and dynamics across salinity gradient

High-quality genome assembly and annotation of five bacteria isolated from the Abu Dhabi sabkha-shore region

OBJECTIVES

Sabkhas represent polyextreme environments characterized by elevated salinity levels, intense ultraviolet (UV) radiation exposure, and extreme temperature fluctuations. In this study, we present the complete genomes of five bacterial isolates isolated from the sabkha-shore region and investigate their genomic organization and gene annotations. A better understanding of the bacterial genomic organization and genetic adaptations of these bacteria holds promise for engineering microbes with tailored functionalities for diverse industrial and agricultural applications, including bioremediation and promotion of plant growth under salinity stress conditions.

DATA DESCRIPTION

We present a comprehensive genome sequencing and annotation of five bacteria (kcgeb_sa, kcgeb_sc, kcgeb_sd, kcgeb_S4, and kcgeb_S11) obtained from the shores of the Abu Dhabi Sabkha region. Initial bacterial identification was conducted through 16 S rDNA amplification and sequencing. Employing a hybrid genome assembly technique combining Illumina short reads (NovaSeq 6000) and Oxford Nanopore long reads (MinION), we obtained complete annotated high-quality gap-free genome sequences. The genome sizes of the kcgeb_sa, kcgeb_sc, kcgeb_sd, kcgeb_S4, and kcgeb_S11 isolates were determined to be 2.4 Mb, 4.1 Mb, 2.9 Mb, 5.05 Mb, and 4.1 Mb, respectively. Our analysis conclusively assigned the bacterial isolates as Staphylococcus capitis (kcgeb_sa), Bacillus spizizenii (kcgeb_sc and kcgeb_S11), Pelagerythrobacter marensis (kcgeb_sd), and Priestia aryabhattai (kcgeb_S4).

Assessing the Influence of HGT on the Evolution of Stress Responses in Microbial Communities from Shark Bay, Western Australia

Pustular microbial mats in Shark Bay, Western Australia, are modern analogs of microbial systems that colonized peritidal environments before the evolution of complex life. To understand how these microbial communities evolved to grow and metabolize in the presence of various environmental stresses, the horizontal gene transfer (HGT) detection tool, MetaCHIP, was used to identify the horizontal transfer of genes related to stress response in 83 metagenome-assembled genomes from a Shark Bay pustular mat. Subsequently, maximum-likelihood phylogenies were constructed using these genes and their most closely related homologs from other environments in order to determine the likelihood of these HGT events occurring within the pustular mat. Phylogenies of several stress-related genes-including those involved in response to osmotic stress, oxidative stress and arsenic toxicity-indicate a potentially long history of HGT events and are consistent with these transfers occurring outside of modern pustular mats. The phylogeny of a particular osmoprotectant transport gene reveals relatively recent adaptations and suggests interactions between Planctomycetota and Myxococcota within these pustular mats. Overall, HGT phylogenies support a potentially broad distribution in the relative timing of the HGT events of stress-related genes and demonstrate ongoing microbial adaptations and evolution in these pustular mat communities.

Study of diversity of mineral-forming bacteria in sabkha mats and sediments of mangrove forest in Qatar

The involvement of microorganisms in carbonate minerals and modern dolomite formation in evaporitic environments occupied with microbial mats (i.e., sabkha) and in mangrove forests is evidenced, while its potential diversity requires further elucidation. Microorganisms can create supersaturated microenvironments facilitating the formation of various carbonate minerals through specific metabolic pathways. This is particularly important in arid environments, where deposition and sedimentary structures can occur. This study investigated the biodiversity of halophilic, heterotrophic, and aerobic mineral-forming bacteria in mangrove forests and living and decaying mats of Qatari sabkha. The diversity study was performed at the protein level using MALDI-TOF mass spectrometry protein profiles combined with principal component analysis (PCA), which revealed a high diversity of isolated strains at the taxonomy and protein profile levels. The diversity of the minerals formed in pure cultures was evidenced by SEM/EDS and XRD analysis. Different types of carbonate minerals (calcium carbonate, magnesium carbonates, and high-magnesium calcites) were formed in pure cultures of the studied strains, which might explain their occurrence in the bulk composition of the sediments from where the strains were isolated. These results illuminate the diversity of biological mineral-formation processes in the extreme environments of Qatari sabkhas and mangroves, explaining the high diversity of minerals in these environments.

Variability of blue carbon storage in arid evaporitic environment of two coastal Sabkhas or mudflats

Coastal Sabkhas are mudflats found in arid coastal regions that are located within the supratidal zone when high rates of evaporation lead to high salinity. While evaporitic minerals often accumulate underneath the surface, the microbial mats are present on the surface of Sabkhas. Coastal Sabkha, an under-studied ecosystem in Qatar, has the potential to store blue carbon. In the present study, we investigated the carbon storage capacity of two Sabkhas from contrasting geological backgrounds. The spatial and temporal variabilities of the carbon stocks were examined. The results showed that both studied Sabkhas exhibit a considerable potential for soil carbon storage with carbon stocks of 109.11 ± 7.07 Mg C ha-1 and 67.77 ± 18.10 Mg C ha-1 in Dohat Faishakh and Khor al Adaid Sabkha respectively. These values fall within the reported range for carbon stocks in coastal Sabkhas in the region (51-194 Mg C ha-1). Interestingly, the carbon stocks in the sediments of the Sabkhas were higher than those in the sediments of Qatari mangroves (50.17 ± 6.27 Mg C ha-1). These finding suggest that coastal Sabkhas can serve as blue carbon ecosystems in arid environments.