We assessed soil fungal diversity at two sites on Deception Island, South Shetland Islands, Antarctica using DNA metabarcoding analysis. The first site was a relatively undisturbed area, and the second was much more heavily impacted by research and tourism. We detected 346 fungal amplicon sequence variants dominated by the phyla Ascomycota, Basidiomycota, Mortierellomycota and Chytridiomycota. We also detected taxa belonging to the rare phyla Mucoromycota and Rozellomycota, which have been difficult to detect in Antarctica by traditional isolation methods. Cladosporium sp., Pseudogymnoascus roseus, Leotiomycetes sp. 2, Penicillium sp., Mortierella sp. 1, Mortierella sp. 2, Pseudogymnoascus appendiculatus and Pseudogymnoascus sp. were the most dominant fungi. In addition, 440,153 of the total of 1,214,875 reads detected could be classified only at the level of Fungi. In both sampling areas the DNA of opportunistic, phytopathogenic and symbiotic fungi were detected, which might have been introduced by human activities, transported by birds or wind, and/or represent resident fungi not previously reported from Antarctica. Further long-term studies are required to elucidate how biological colonization in the island may be affected by climatic changes and/or other anthropogenic influences.

In the current study, a total of 135 enterococci strains from different sources were screened for the presence of the enterocin-encoding genes entA, entP, entB, entL50A, and entL50B. The enterocin genes were present at different frequencies, with entA occurring the most frequently, followed by entP and entB; entL50A and L50B were not detected. The occurrence of single enterocin genes was higher than the occurrence of multiple enterocin gene combinations. The 80 isolates that harbor at least one enterocin-encoding gene (denoted "Gene(+) strains") were screened for antimicrobial activity. A total of 82.5% of the Gene(+) strains inhibited at least one of the indicator strains, and the isolates harboring multiple enterocin-encoding genes inhibited a larger number of indicator strains than isolates harboring a single gene. The indicator strains that exhibited growth inhibition included Listeria innocua strain CLIP 12612 (ATCC BAA-680), Listeria monocytogenes strain CDC 4555, Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, S. aureus ATCC 29213, S. aureus ATCC 6538, Salmonella enteritidis ATCC 13076, Salmonella typhimurium strain UK-1 (ATCC 68169), and Escherichia coli BAC 49LT ETEC. Inhibition due to either bacteriophage lysis or cytolysin activity was excluded. The growth inhibition of antilisterial Gene+ strains was further tested under different culture conditions. Among the culture media formulations, the MRS agar medium supplemented with 2% (w/v) yeast extract was the best solidified medium for enterocin production. Our findings extend the current knowledge of enterocin-producing enterococci, which may have potential applications as biopreservatives in the food industry due to their capability of controlling food spoilage pathogens.

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ResumoBacteriocinas são peptídeos antimicrobianos sintetizados nos ribossomos, tendo sido descrita uma grande diversidade de bacteriocinas, as quais diferem entre si quanto a composição de aminoácidos, biossíntese, transporte e modo de ação. Nos alimentos, as bacteriocinas podem ser encontradas naturalmente como produtos da microbiota normal ou introduzida (cultura starter ou probióticos). Devido às suas aplicabilidades frente a organismos patogênicos contaminantes em alimentos, vários estudos têm sido publicados, tornando o uso destes peptídeos uma alternativa aos conservantes químicos tradicionais. Considerando-se as propriedades das bacteriocinas e sua potencial aplicação como bioconservadores de alimentos e alternativa aos antibióticos, o presente estudo busca acercar-se de uma visão geral das bacteriocinas quanto aos aspectos históricos, sistemas de classificação, biossíntese e transporte, modo de ação, abordando também algumas de suas aplicações na indústria de alimentos. Palavras-chave: Bacteriocinas; Peptídeos antimicrobianos; Aplicações industriais; Bioconservantes. SummaryBacteriocins are antimicrobial peptides synthesized in the ribosomes. A wide variety of bacteriocins have been described, which differ in their amino acid composition, biosynthesis, transport and mode of action. Bacteriocins can be found naturally in foods as products of normal or added (starters or probiotics) microbiota in several preparations. Due to their applicability against pathogenic contaminants in food, various studies have been published making the use of these peptides an alternative to traditional chemical preservatives. Considering the properties of bacteriocins and their potential application as bio-preservatives in foods and alternatives to antibiotics, this study presents an overview of bacteriocins with respect to their historical aspects, classification systems, biosynthesis and transport and mode of action, also presenting some applications in food industries.

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