| Congresso Brasileiro de Microbiologia 2023 | Resumo: 1501-1 | ||||
Resumo:The framework of microbial ecological succession is an interplay of natural selection mechanisms, resource availability, and microbial growth strategies, as elucidated by the r/K selection theory. Due to the ongoing effects of climate change, glaciers worldwide are melting, exposing subglacial soil to the atmosphere by a process known as glacial retreat. These newly exposed soils, identified as chronosequences, provide crucial sites for studying microbial succession and r/K selection patterns. We aimed to evaluate these patterns in Antarctic chronosequences through an opportunism index obtained from the ratio of culturable to total cells (C:T ratio). Soil samples were collected at 0, 50, 100, 200, 300, and 400 meters from the fronts of Baranowski and Collins Glacier, with respective retreating times of around 40 and 2000 years. Viable cell count was accomplished in each soil sample using 1% Nutrient Agar medium (w/v) incubated at 20 °C for 14 days. Colony-forming units (CFU) emerging within 48 hours were designated as r-strategists, whereas CFUs emerged after 48 hours as K-strategists. Representative CFUs of each sample were isolated and distributed in eco-collections sorted by the growth strategy and distance from the glacier. Total cell count was achieved by fluorescence microscopy using DAPI stain. Colony accumulation curves (CFCs) showed differences in r/K selection patterns, depending on soil age. The faster retreat of Baranowski glacier showed a trend of increasing viable cells along the chronosequence. The slower retreating Collins glacier showed a decrease in viable cells up to 200 m, and the ratio increased beyond this distance. The viable cell count revealed that subglacial soils are dominated by K-strategists, suggesting that the soil microbial community was already at an advanced stage of development when the glacier formed, preserving populations in a state of dormancy or under a low metabolic rate. R-strategist populations increased in the first years after the retreat (50 m), as expected by ecological succession theory for newly exposed environments, where the interactions and biodiversity increase as the ecosystem undergoes development. The farthest soils (400 m) also presented an increase of r-strategists, indicating a new environmental disturbance and the formation of novel ecological niches for a fast-growing population. The opportunism index revealed a non-linearity trend in the C:T ratio for both chronosequences, since the C:T ratio decreased between (200-300 m) for Baranowski and (300-400 m) for Collins. Thus, we hypothesize that in Antarctica, microbial succession occurs in stages of development: the pre-established community in the subglacial soil and the pioneer communities at 50 m and 400 m from the glaciers.
Palavras-chave: Chronosequence, ecological succession, glacier retreat, r/K selection, opportunism index Agência de fomento:CNPq | |||||