| Congresso Brasileiro de Microbiologia 2023 | Resumo: 1501-2 | ||||
Resumo:Over the last half-century, the Antarctic Peninsula has undergone significant warming, which is usually associated with the retreat of 87% of glacier fronts in this area. Glacial retreat leads to the exposure of subglacial soil containing inactive microbial communities for hundreds or thousands of years. The glacier soil forefields (known as “chronosequences”) represent an opportunity to investigate changes in microbial community structure and biogeochemical processes over time. Also, chronosequences are unique systems to understand how microorganisms respond to climate change and how they could be used as monitoring agents. The goal of this study was to evaluate microbial succession in two Antarctic chronosequences. Soil samples were collected from Baranowski Glacier and Collins Glacier on a 0-400 m transect in front of each glacier. A 16S rRNA sequencing (metabarcoding) approach was used to characterize the prokaryotic community. The photoautotrophic cells were quantified using the most probable number (MPN) method, and the soil respiration rate was determined for basal and C-induced microcosms. Soils were characterized as basaltic/andesitic, with sandy loam texture. The pH was relatively acidic for both Baranowski (pH 6,2-6,7) and Collins (pH 5,6-6,1), with low total organic Carbon (3,5 g.dm-3 for Baranowski; 4,0-6,0 g.dm-3 for Collins). Alpha-diversity analysis showed that Baranowski soils have a rapid turnover rate, with trend to increase both richness and diversity over time. On the other hand, Collins exhibits declining soil richness and diversity, particularly in older soils. Both glacier forefields showed a similar microbial community composition, with a dominance of Bacteroidetes (45.1%), Proteobacteria (15.8%) and Actinobacteria (10.3%). Other Phyla with > 1% relative abundance were Acidobacteria (6.8%), Patescibacteria (5.3%), Verrucomicrobia (5.0%), Cyanobacteria (3.6%), Chloroflexi (2.6%), Firmicutes (1.5%), Gemmatimonadetes (1.4%) and Planctomycetes (1.1%). Collins soils showed a gradual transition of organisms as succession advances, whereas Baranowski exhibits a more chaotic ecological pattern as detected by higher turnover rate. Subglacial soils initially rely on existing organic carbon, later transitioning to photoautotrophic microorganisms contributing to the carbon pool. The number of photoautotroph cells varied along the chronosequence, showing a trend to increase on Baranowski (from 7.8 to 92 photoautotrophic cells.g-1 soil) and decrease on Collins (from 660 to 163 cells.g-1). Basal respiration rates were low for both Baranowski (0.172±0.07 mg CO2.h-1) and Collins (0.182±0.05 mg CO2.h-1). A non-linear correlation between respiration rates and soil distance was found. CO2 flux increased in early stages (0 to 100-200 m), followed by a decrease towards older soils (400 m). For both glaciers, qCO2 was low in recently exposed soils (0 to 50 m), increased and reached a peak at 200 m, followed by a decrease towards older exposed soils (400 m). C-induced respiration rates showed that both glacier soils presented the maximum respiration rates at a distance of 100 m. This study reveals the dynamics of microbial succession on Antarctic soils, highlighting the protagonism of microbes in nutrient cycling and soil formation. Palavras-chave: Antarctica, chronosequence, microbial succession, metagenomics, respiration Agência de fomento:CNPq, CAPES | |||||