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Marine sponges commonly host a repertoire of bacterial-associated organisms, which significantly contribute to their health and survival by producing several anti-predatory molecules. Many of these compounds are produced by sponge-associated bacteria and represent an incredible source of novel bioactive metabolites with biotechnological relevance. Although most investigations are focused on tropical and temperate species, to date, few studies have described the composition of microbiota hosted by Antarctic sponges and the secondary metabolites that they produce. The investigation was conducted on four sponges collected from two different sites in the framework of the XXXIV Italian National Antarctic Research Program (PNRA) in November-December 2018. Collected species were characterized as Mycale ( Oxymycale ) acerata , Haliclona ( Rhizoniera ) dancoi, Hemigellius pilosus and Microxina sarai by morphological analysis of spicules and amplification of four molecular markers. Metataxonomic analysis of these four Antarctic sponges revealed a considerable abundance of Amplicon Sequence Variants (ASVs) belonging to the phyla Proteobacteria, Bacteroidetes, Actinobacteria and Verrucomicrobia. In particular, M . ( Oxymycale ) acerata, displayed several genera of great interest, such as Endozoicomonas , Rubritalea , Ulvibacter , Fulvivirga and Colwellia . On the other hand, the sponges H. pilosus and H. ( Rhizoniera ) dancoi hosted bacteria belonging to the genera Pseudhongella , Roseobacter and Bdellovibrio , whereas M. sarai was the sole species showing some strains affiliated to the genus Polaribacter . Considering that most of the bacteria identified in the present study are known to produce valuable secondary metabolites, the four Antarctic sponges could be proposed as potential tools for the discovery of novel pharmacologically active compounds.

Antarctica is an untapped reservoir of bacterial communities, which are able to adapt to a huge variety of strategies to cope with extreme conditions and, therefore, are capable of producing potentially valuable compounds for biotechnological applications. In this study, 31 UV-resistant bacteria collected from different Antarctic aquatic environments (surface sea waters/ice and shallow lake sediments) were isolated by UV-C assay and subsequently identified. A phylogenetic analysis based on 16S rRNA gene sequence similarities showed that the isolates were affiliated with Proteobacteria, Actinobacteria and Firmicutes phyla, and they were clustered into 15 bacterial genera, 5 of which were Gram negative (Brevundimonas, Qipengyuania, Sphingorhabdus, Sphingobium, and Psychrobacter) and 10 of which were Gram positive (Staphylococcus, Bacillus, Mesobacillus, Kocuria, Gordonia, Rhodococcus, Micrococcus, Arthrobacter, Agrococcus, and Salinibacterium). Strains belonging to Proteobacteria and Actinobacteria phyla were the most abundant species in all environments. The genus Psychrobacter was dominant in all collection sites, whereas bacteria belonging to Actinobacteria appeared to be the most diverse and rich in terms of species among the investigated sites. Many of these isolates (20 of 31 isolates) were pigmented. Bacterial pigments, which are generally carotenoid-type compounds, are often involved in the protection of cells against the negative effects of UV radiation. For this reason, these pigments may help bacteria to successfully tolerate Antarctic extreme conditions of low temperature and harmful levels of UV radiation. [ABSTRACT FROM AUTHOR]

This review is an overview on marine bioactive peptides with promising activities for the development of alternative drugs to fight human pathologies. In particular, we focus on potentially prolific producers of peptides in microorganisms, including sponge-associated bacteria and marine photoautotrophs such as microalgae and cyanobacteria. Microorganisms are still poorly explored for drug discovery, even if they are highly metabolically plastic and potentially amenable to culturing. This offers the possibility of obtaining a continuous source of bioactive compounds to satisfy the challenging demands of pharmaceutical industries. This review targets peptides because of the variety of potent biological activities demonstrated by these molecules, including antiviral, antimicrobial, antifungal, antioxidant, anticoagulant, antihypertensive, anticancer, antidiabetic, antiobesity, and calcium-binding bioactivities. Several of these peptides have already gained recognition as effective drug agents in recent years. We also focus on cutting-edge omic approaches for the discovery of novel compounds for pharmacological applications. With rapid depletion of natural resources, omic technologies may be the solution to efficiently produce a vast variety of novel peptides with unique pharmacological potential. [ABSTRACT FROM AUTHOR]

Despite the large number of globins recently discovered in bacteria, our knowledge of their physiological functions is restricted to only a few examples. In the microbial world, globins appear to perform multiple roles in addition to the reversible binding of oxygen; all these functions are attributable to the heme pocket that dominates functional properties. Resistance to nitrosative stress and involvement in oxygen chemistry seem to be the most prevalent functions for bacterial globins, although the number of globins for which functional roles have been studied via mutation and genetic complementation is very limited. The acquisition of structural information has considerably outpaced the physiological and molecular characterisation of these proteins. The genome of the Antarctic cold-adapted bacterium Pseudoalteromonas haloplanktis TAC125 ( Ph TAC125) contains genes encoding three distinct single-chain 2/2 globins, supporting the hypothesis of their crucial involvement in a number of functions, including protection against oxidative and nitrosative stress in the cold and O 2 -rich environment. In the genome of Ph TAC125, the genes encoding 2/2 globins are constitutively transcribed, thus suggesting that these globins are not functionally redundant in their physiological function in Ph TAC125. In the present study, the physiological role of one of the 2/2 globins, Ph -2/2HbO-2217, was investigated by integrating in vivo and in vitro results. This role includes the involvement in the detoxification of reactive nitrogen and O 2 species including NO by developing two in vivo and in vitro models to highlight the protective role of Ph -2/2HbO-2217 against reactive nitrogen species. The PSHAa2217 gene was cloned and over-expressed in the flavohemoglobin-deficient mutant of Escherichia coli and the growth properties and O 2 uptake in the presence of NO of the mutant carrying the PSHAa2217 gene were analysed. The ferric form of Ph -2/2HbO-2217 is able to catalyse peroxynitrite isomerisation in vitro , indicating its potential role in the scavenging of reactive nitrogen species. Here we present in vitro evidence for the detoxification of NO by Ph -2/2HbO-2217. [ABSTRACT FROM AUTHOR]