Environmental control on the distribution of metabolic strategies of benthic microbial mats in Lake Fryxell, Antarctica

Abstract

Ecological theories posit that heterogeneity in environmental conditions greatly affects community structure and function. However, the degree to which ecological theory developed using plant-and animal-dominated systems applies to microbiomes is unclear. Investigating the metabolic strategies found in microbiomes are particularly informative for testing the universality of ecological theories because microorganisms have far wider metabolic capacity than plants and animals. We used metagenomic analyses to explore the relationships between the energy and physicochemical gradients in Lake Fryxell and the metabolic capacity of its benthic microbiome. Statistical analysis of the relative abundance of metabolic marker genes and gene family diversity shows that oxygenic photosynthesis, carbon fixation, and flavin-based electron bifurcation differentiate mats growing in different environmental conditions. The pattern of gene family diversity points to the likely importance of temporal environmental heterogeneity in addition to resource gradients. Overall, we found that the environmental heterogeneity of photosynthetically active radiation (PAR) and oxygen concentration ([O 2 ]) in Lake Fryxell provide the framework by which metabolic diversity and composition of the community is structured, in accordance with its phylogenetic structure. The organization of the resulting microbial ecosystems are consistent with the maximum power principle and the species sorting model.

Lipid Biomarkers From Microbial Mats on the McMurdo Ice Shelf, Antarctica: Signatures for Life in the Cryosphere

“…Accordingly, the high abundance of BHT-II suggests the presence of an anaerobic bacterial community in the microbial mat from 9.7 m depth in Lake Vanda. This agrees with a recent study that showed a high abundance of genes indicative of anaerobic respiration capacity in microbial mats collected at a depth of 9.8 m in Lake Vanda (Dillon et al, 2020). However, we note that Rush et al (2014) identified BHT-II only in marine and not freshwater anammox bacteria.…”

“…In Lake Vanda, Highborne Cay, and Hamelin Pool, typically, N/P-ratios above 20 have been reported (Atkinson, 1987;Priscu et al, 1989;Jabro, 2008). This suggests that P may be the limiting nutrient compared to the meltwater ponds, as suggested for Lake Vanda (Dillon et al, 2020). A replacement with N-bearing lipids in phospholipid-containing ) shows the results from the three different Antarctic lakes: Lake Joyce (LJ), Lake Fryxell (LF) and Lake Vanda (LV).…”

“…This suggests that the low availability of phosphate in Lake Vanda and the subtropical mats leads to a substitution of phosphatidyl IPLs by aminolipids (Figure 8). Genes for the substitution of nitrogen for phosphorous in membrane lipids have been, for instance, recently detected in microbial mats from Lake Vanda (Dillon et al, 2020).…”

Marine Vertebrates Impact the Bacterial Community Composition and Food Webs of Antarctic Microbial Mats

“…Our analysis revealed that inorganic nitrogen (N-NH 4 + and NO 3 − ) is a key factor in driving bacterial community composition, which agree with previous studies of polar microbial communities from terrestrial ecosystem (Kleinteich et al, 2017;Valdespino-Castillo et al, 2018;Dillon et al, 2020;Jackson et al, 2021). A similar pattern was determined for Antarctic soils (Smith et al, 2010), where NH 3 , NO 3 − , and total N, among other physicochemical parameters, were driving the microbial community composition.…”

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

“…Light availability in microbial mats varies on vertical microscales (Jørgensen et al, 1987) that can influence community composition to an extent comparable to variation across larger geographic spatial scales (Al-Najjar et al, 2014). Ice-covered Antarctic lakes illustrate how variation of light due to ice thickness and water depth shapes which cyanobacteria taxa are present in cyanobacterial mats and their productivity, metabolism, and physical structure (Dillon et al, 2020b;Hawes & Schwarz, 2001;Mackey et al, 2017;Moorhead et al, 1997).…”