Abstract

The geographical isolation of Antarctic continent as well as extreme environmental conditions (e.g., low temperatures, dry cold weather, high UV radiation, terrain snoww-capped most of the time,) have imposed a selective pressures to all forms of lifes. Environmental constraints and geographycal isolation are responsible for the emergence of different types of microorganisms (mainly, bacteria, fungi, actinomycete) with unique metabolic pathways andhighly adapted to Antarctic environments. In Antarctic marine ecosystems, bacterial community play critical ecological roles in recycling process of nutrients and organic matter. . Target species of bacteria can be found in marine environments displayig a wide range of enzymatic activities, such as polysaccharide hydrolases, able tobreak down complex molecular structures. The specificity of polysaccharide hydrolases varies among target bacteria species and also under environmental conditions. The ability to display a wide range of enzymatic machinery adapted to different environmental conditions and also different substrates could be a competitive advantage in extreme environments important to understand. However, despite of all efforts, still remains some gaps of fundamental knowledge related with the characterization of target species of bacteria and its enzymatic activities. This type of information is important to understand not only the role of bacterial communities in ecosystem process in Antarctica but also to guide bioprespection efforts in the near future. being The aim of this study was characterize an Antarctic Flavobacterium strain (INACH0011.6), using a polyphasic approach and evaluated the ability of the culture cell-free supernatant to hydrolyze phycocolloids at different temperatures under controlled conditions. The strain INACH0011.6, isolated from algae wrack, in King George Island, Antarctica, was identified as member of the genus Flavobacterium through 16S rDNA gene analysis. The phylogenetic analysis using related sequences of the genus Flavobacterium, clustered strain INACH0011.6, F. faecale and F. algicola into a well-supported subclade which was distinguishable from other phylogenetically-related sequences. In agreement with previous report, the morphological characteristics of INACH0011.6, typically rod-shaped cells and yellow-pigmented colonies were similar to Flavobacterium strains isolated from a variety of Antarctic habitats. According to growing parameters, optimum temperature (17 ºC) and maximal temperature (20°C) of growth, INACH0011.6 strain was characterized as psychrotrophic microorganism. Agarase and alginate-lyase displayed enzymatic activities within a range of 10 °C to 50 °C, with differences in the optimal temperature to hydrolyze agar (50 °C), agarose (50 °C) and alginate (30 °C) during the first 30 min. Flavobacterium are recognized for their role in remineralization processes in the ocean due to their ability to decompose dissolved complexes and particulate organic matters, which gives them the versatility to colonize substrates containing different polysaccharides. Some species in the genus Flavobacterium have been previously reported to be able to hydrolyse agar or alginate and recently an Antarctic Flavobacterium was reported as an agarase-producing strain. Strain INACH0011.6 exhibited a higher degree of identity (99.8 %) to F. faecale, however both strains have different carbon source (agar and alginate) utilization patterns.