Functional Gene Expression in Shark Bay Hypersaline Microbial Mats: Adaptive Responses

Abstract

Microbial mat communities possess extensive taxonomic and functional diversity, which drive high metabolic rates and rapid cycling of major elements. Modern microbial mats occurring in hypersaline environments are considered as analogs to extinct geobiological formations dating back to ∼ 3.5 Gyr ago. Despite efforts to understand the diversity and metabolic potential of hypersaline microbial mats in Shark Bay, Western Australia, there has yet to be molecular analyses at the transcriptional level in these microbial communities. In this study, we generated metatranscriptomes for the first time from actively growing mats comparing the type of mat, as well as the influence of diel and seasonal cycles. We observed that the overall gene transcription is strongly influenced by microbial community structure and seasonality. The most transcribed genes were associated with tackling the low nutrient conditions by the uptake of fatty acids, phosphorus, iron, and nickel from the environment as well as with protective mechanisms against elevated salinity conditions and to prevent build-up of ammonium produced by nitrate reducing microorganisms. A range of pathways involved in carbon, nitrogen, and sulfur cycles were identified in mat metatranscriptomes, with anoxygenic photosynthesis and chemoautotrophy using the Arnon–Buchanan cycle inferred as major pathways involved in the carbon cycle. Furthermore, enrichment of active anaerobic pathways (e.g., sulfate reduction, methanogenesis, Wood–Ljungdahl) in smooth mats corroborates previous metagenomic studies and further advocates the potential of these communities as modern analogs of ancient microbialites.

Structure and function of Shark Bay microbial communities following tropical cyclone Olwyn: A metatranscriptomic and organic geochemical perspective

“…Taxonomic analysis of the microbiota was based on 16S rRNA transcripts, followed by functional and taxonomic annotation of transcripts derived from the mRNA fraction (Campbell et al, 2020). Bushnell, 2018).…”

“…These values were visualized using pheatmap and PCA (ggfortify and ggplot2) in R. Relative abundance of compound groups and isotopic distributions were visualized with scatter or bar plots in OriginPro (Seifert, 2014). Additionally, for downstream functional and biomarker analyses, samples were grouped based off taxonomic similarity (Campbell et al, 2020).…”

Modern microbial mats from the Chihuahuan Desert provide insights into ecological stability throughout Earth’s history

“…As stated previously, the Archean Domes microbial system is constantly subject to environmental stress, which could be arguably compared to those experienced by the Shark Bay microbial mats, a recognized terrestrial analog (Wong, White, et al, 2018;Campbell et al, 2020). Therefore, the Archean Domes site is potentially a promising analog for early Earth, and (plausibly) early Mars, just as other potential analogs found in the Cuatro Ciénegas Basin (López-Lozano et al, 2012;Moreno-Letelier et al, 2012;Souza et al, 2012).…”

Functional gene analysis and cultivation experiments predict the degradation of diverse extracellular polysaccharides by ubiquitous taxa in pustular microbial mats from Shark Bay, Western Australia

“…Previous work suggests a tight link between cyanobacterial EPS production and degradation by Bacteroidetes. Earlier studies identified co-enrichments of Bacteroidetes and Cyanobacteria in the same regions of pustular mats (14) and suggested that Bacteroidetes and Alphaproteobacteria most actively produce mRNA transcripts during the day, when Cyanobacteria photosynthesize (68). The extensive functional potential of Bacteroidetes to perform the first steps in degrading fresh cyanobacterial EPS may explain these trends and link Bacteroidetes to other important metabolic guilds in mats.…”