The prokaryotic community in an extreme Antarctic environment: the brines of Boulder Clay lakes (Northern Victoria Land)

Abstract

During summer 2014, three hypersaline brines were discovered in two frozen lakes of Boulder Clay (Northern Victoria Valley, Antarctica). Ongoing research seeks to gain novel insights on the microbial ecology of such environments, in order to further the understanding of life adaptation to extreme conditions. To this aim, the abundance of prokaryotic cells (including cell morphologies and size for biomass conversion), the amount of viable cells (in terms of membrane-intact cells and respiring cells), the viral count, the physiological profiles at community level and the main microbial enzymatic activities were described. The brines differed each other in terms of prokaryotic cells' abundance, size, and viability as well as viral abundance. Cell morphotypes and metabolic responses also varied among the brine samples. Underground interconnections were likely to occur, with the microbial community becoming more abundant and structured to better exploit the limited resource availability. Overall, complex interactions among multiple environmental factors, including marine water origin, depth horizon, isolation time of the brines, and climatic variations, reflected on the microbial community distribution patterns and highlighted the need to preserve these niches of extreme life.

First Insights into the Microbiology of Three Antarctic Briny Systems of the Northern Victoria Land

“…Overall, the prokaryotic community included methanogens, strictly anaerobes, halophiles, and (hyper)thermophiles [4,12]. Diversification in terms of abundance, metabolic potentials, and enzymatic activities of the prokaryotic assemblages among the examined brines has been highlighted [4,5]. In the Tarn Flat brines, previous analyses have found the presence of proteolytic activity, as well as a comparatively lower alkaline phosphatase activity than in Boulder Clay.…”

“…Conversely, in Boulder Clay, the microbial community was mostly active in the decomposition of organic phosphates and lower proteolytic and glycolytic activity rates were recorded. Moreover, decreasing patterns of aminopeptidase and phosphatase activities were observed with increasing depth of the collection site [5]. These peculiar features were ascribed to a lot of factors including brines' historical origin, depth horizon, and time of segregation.…”

“…The bacterial viable counts (BVC) were determined by spread plating on agar plates [11]. Prokaryotic cell abundances (PA), respiration (CTC), viability (L/D), biomass (PB) (Table S1), and morphometric features (Table S1) were estimated by epiflurescence microscopy, as reported in Papale et al [4] and Azzaro et al [5]. Microbial enzymatic activities on proteinaceous and glucidic organic matter as well as on organic phosphates (i.e., AP, beta-GLU, and LAP) were fluorometrically estimated [4,5] (Table S1).…”

“…Studying briny ecosystems is multifaceted, and assumes special relevance for geological aspects, and also for unravelling the functional potential and roles in biogeochemical cycling of the psychrophilic lifeforms. Microorganisms inhabit extreme environments on Earth [3][4][5] that are also intriguingly similar to other worlds within our Solar system [6]. Current knowledge about the drivers of prokaryotic diversity, distribution, and metabolism in Antarctic briny systems is patchy, and therefore deserves to be deepened.…”

“…The TF and BC areas in the NVL host several small perennially ice-covered lakes [7], and some of them conceal brine lenses [8][9][10]. Recently, brines from three Tarn Flat and the Boulder Clay lakes have been analyzed for the prokaryotic component by culture-dependent and -independent approaches [4,5,11,12]. Overall, the prokaryotic community included methanogens, strictly anaerobes, halophiles, and (hyper)thermophiles [4,12].…”