Seasonal Shifts in Community Composition and Proteome Expression in a Sulfur-Cycling Cyanobacterial Mat

Abstract

Seasonal changes in light and physicochemical conditions have strong impacts on cyanobacteria, but how they affect community structure, metabolism, and biogeochemistry of cyanobacterial mats remains unclear. Light may be particularly influential for cyanobacterial mats exposed to sulfide by altering the balance of oxygenic photosynthesis and sulfide-driven anoxygenic photosynthesis. We studied temporal shifts in irradiance, water chemistry, and community structure and function of microbial mats in Middle Island Sinkhole (MIS), where anoxic and sulfate-rich groundwater provides habitat for cyanobacteria that conduct both oxygenic and anoxygenic photosynthesis. Seasonal changes in light and groundwater chemistry were accompanied by shifts in bacterial community composition, with a succession of dominant cyanobacteria from Phormidium to Planktothrix, and an increase in diatoms, sulfur-oxidizing bacteria, and sulfate-reducing bacteria from summer to autumn. Differential abundance of cyanobacterial light harvesting proteins likely reflects a physiological response of cyanobacteria to light level. Beggiatoa sulfur oxidation proteins were more abundant in autumn. Correlated abundances of taxa through time suggest interactions between sulfur oxidizers and sulfate reducers, sulfate reducers and heterotrophs, and cyanobacteria and heterotrophs. These results support the conclusion that seasonal change, including light availability, has a strong influence on community composition and biogeochemical cycling of sulfur and O2 in cyanobacterial mats.

Metabarcoding reveals unique microbial mat communities and evidence of biogeographic influence in low‐oxygen, high‐sulfur sinkholes and springs

“…Previous research on microbial mats in these sulfur springs includes molecular surveys of diversity, such as analysis of small subunit ribosomal RNA clone libraries from the MIS and Great Sulfur Spring (GSS) in Michigan (Nold, Pangborn, et al, 2010;Chaudhary et al, 2009, respectively), pyrosequencing at MIS (Voorhies et al, 2012), and high-throughput 16S rRNA sequencing at MIS (Grim et al, 2023;Kinsman-Costello et al, 2017).…”

“…Transcriptomics and proteomics have also been used to assess community composition and processes that community members are undergoing in MIS (Grim et al, 2021(Grim et al, , 2023. Additionally, groundwater analyses have characterized the aquifer sources of MIS (Grim et al, 2023) and GSS (Haack et al, 2005).…”

“…Previous research on microbial mats in these sulfur springs includes molecular surveys of diversity, such as analysis of small subunit ribosomal RNA clone libraries from the MIS and Great Sulfur Spring (GSS) in Michigan (Nold, Pangborn, et al., 2010 ; Nold, Zajack, et al., 2010 ; Chaudhary et al., 2009 , respectively), pyrosequencing at MIS (Voorhies et al., 2012 ), and high‐throughput 16S rRNA sequencing at MIS (Grim et al., 2023 ; Kinsman‐Costello et al., 2017 ). Transcriptomics and proteomics have also been used to assess community composition and processes that community members are undergoing in MIS (Grim et al., 2021 , 2023 ). Additionally, groundwater analyses have characterized the aquifer sources of MIS (Grim et al., 2023 ) and GSS (Haack et al., 2005 ).…”

“…Transcriptomics and proteomics have also been used to assess community composition and processes that community members are undergoing in MIS (Grim et al., 2021 , 2023 ). Additionally, groundwater analyses have characterized the aquifer sources of MIS (Grim et al., 2023 ) and GSS (Haack et al., 2005 ). These studies have revealed the biogeochemical and metabolic processes occurring in these habitats, particularly in MIS, but a deeper look into the taxonomic composition of these sites and exploration of new spring habitats is merited to better describe these communities and factors that influence them.…”