Effect of experimentally increased nutrient availability on the structure, metabolic activities, and potential microbial functions of a maritime Antarctic microbial mat

• Published in: Frontiers in Microbiology
• Main Authors: Antonio Camacho, Carlos Rochera, Antonio Picazo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2022
• Subjects: microbial mats; Antarctica; inorganic nutrients (N and P); community structural and functional effects; metabarcoding and functional prediction; Microbiology; QR1-502; Antarctic; Byers; Byers peninsula; Antarc*
• Online Access: https://doi.org/10.3389/fmicb.2022.900158; https://doaj.org/article/8ee53aac84ab45489b9f0ec115144049

The role of competitive interactions based on resource utilisation was explored in a phototrophic microbial mat from Byers Peninsula (Maritime Antarctica). Shotgun metagenomic profiling of the mat showed a taxonomic and functionally diverse microbial community. The heterotrophic bacterial community was dominated by Proteobacteria, where genera typically found in polar habitats, such as Janthinobacterium, Pseudomonas, and Polaromonas, were highly prevalent. Cyanobacteria played the main role as primary producers, accompanied by diatoms and chlorophytes. To test the potential effects of the inorganic nutrient (N and P) availability on this community, a fully factorial nitrate and phosphorus addition experiment was conducted in situ. The mat exhibited a functional and structural response to the nutrient amendments. Compared to the undisturbed mat, phosphorus fertilisation favoured the growth of (non-heterocystous) cyanobacteria relative to that of diatoms, as indicated by changes in the carotenoid pigment biomarkers. Although no mat accretion was visible, fertilisation improved the phototrophic activity, and, mainly, when P was amended, the production of exopolymeric substances was favoured, whereas further changes in the vertical distribution of primary production activity were observed as well. Illumina amplicon sequencing of the 16S rRNA gene also demonstrated changes in the relative abundance of heterotrophic prokaryotes, which were detectable from the phylum to the genus level and mainly related to the amendment of nitrogen. Predictions made on the functional skills of these shifted prokaryotic communities indicated changes in abundance selecting taxa with a metabolic adaptation to the new nutrient scenarios. They mainly consisted of the enhancement of ecological strategies and metabolic regulatory mechanisms related to the uptake and metabolising of either nitrogen or phosphorus, regulated by its availability whether in a balanced way or not. This study is a pioneer in demonstrating how shifts in the regional ...