Cultivable Bacterial Communities in Brines from Perennially Ice-Covered and Pristine Antarctic Lakes: Ecological and Biotechnological Implications

Carmen Rizzo,Angelina Lo Giudice,Maria Papale,Marco Roman,Alessandro C Rappazzo,Mauro Guglielmin,Antonella Conte,Dario Battistel,Maurizio Azzaro

doi:10.3390/microorganisms8060819

Abstract

The diversity and biotechnological potentialities of bacterial isolates from brines of three Antarctic lakes of the Northern Victoria Land (namely Boulder Clay and Tarn Flat areas) were first explored. Cultivable bacterial communities were analysed mainly in terms of bacterial response to contaminants (i.e., antibiotics and heavy metals) and oxidation of contaminants (i.e., aliphatic and aromatic hydrocarbons and polychlorobiphenyls). Moreover, the biosynthesis of biomolecules (antibiotics, extracellular polymeric substances and enzymes) with applications for human health and environmental protection was assayed. A total of 74 and 141 isolates were retrieved from Boulder Clay and Tarn Flat brines, respectively. Based on 16S rRNA gene sequence similarities, bacterial isolates represented three phyla, namely Proteobacteria (i.e., Gamma- and Alphaproteobacteria), Bacteroidetes and Actinobacteria, with differences encountered among brines. At genus level, Rhodobacter, Pseudomonas, Psychrobacter and Leifsonia members were dominant. Results obtained from this study on the physiological and enzymatic features of cold-adapted isolates from Antarctic lake brines provide interesting prospects for possible applications in the biotechnological field through future targeted surveys. Finally, findings on contaminant occurrence and bacterial response suggest that bacteria might be used as bioindicators for tracking human footprints in these remote polar areas.

Highlights

Brine lenses are small amounts of water that remains unfrozen below 0 ◦C due to its high salt content
We mainly report on (i) the abundance and diversity of bacterial communities recovered from brine lenses, (ii) their tolerance to heavy metals and susceptibility to antibiotics, (iii) their ability to growth in presence of organic contaminants and (iv) their bioprospective potential with regard to cold-active enzymes, antibiotics and extracellular polymeric substances
The bacterial community composition differed between TF4 and TF5 samples, with the Gammaproteobacteria (71.2% vs. 36.0%) that strongly predominated over all other groups in TF4 and Alphaproteobacteria (3.0% vs. 26.7%) and Actinobacteria (12.1% vs. 28%) that occurred at higher percentages in TF5

Summary

Introduction

Brine lenses are small amounts of water that remains unfrozen below 0 ◦C due to its high salt content. By a geophysical point of view, Antarctic subglacial streams connect lakes and ponds with their movements, by making brine systems highly dynamic [5,8,9]. The similarities of brine pockets with conditions retrieved on Mars, inMteircrmoosrgoafnicsmolsd20a2n0,d8,dxrFyOcRliPmEaEtReRs,EtVoIgEeWther with the development of highly saline microhabitat [11,122o]f,28 lead researchers to question the common meaning of limits of life and brines are suggested as a model tolsetauddyreesxetarrac-hteerrrsesttoriqaluleisfetio[6n,1t3h]e. Lakes lying in the Northern Victoria Land, namely in the Boulder Clay [21,22,23] and Tarn Flat [6] areas (Figure 1). Brine lenses from Tarn Flat and Boulder Clay lakes were explored for prokaryotic and eukaryotic diversity and activities by the application of advanced culture-independent methods [13,29,30,31]. Diverse (in terms of both ecophysiology and phylogenetic affiliation)

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Conclusion