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Biosurfactants are considered a possible green alternative to chemical surfactants for countless commercial products including detergents and cleaners, personal care products, cosmetics, pharmaceuticals and therapeutics, food additives, emulsifiers, and dispersants for bioremediation. Organisms from extreme environments are well-adapted to the harsh conditions and represent an exciting avenue of discovery of naturally occurring biosurfactants. In this study, we report the genome analysis of Psychrobacter sp. TAE2020, an aerobic ƴ-proteobacterium isolated from an Antarctic coastal seawater sample collected in the vicinity of the French Antarctic station Dumont d'Urville, Terre Adelie (66°40' S; 140° 01' E) which has been shown to produce biosurfactants. Biochemical assays indicate that Psychrobacter sp. TAE2020 can produce one or more excellent emulsifiers and a biosurfactant which is able to reduce the surface tension of a Gut medium. Next generation sequencing and genome mining allowed the identification of a plethora of biosynthetic gene clusters possibly involved in the production of emulsifying agents, just waiting to be isolated and characterized. This study paves the way for a more thorough investigation into the potential biotechnological applications of this new Antarctic strain.

Antarctic bacteria are able to survive under extreme environmental conditions and have adapted to exploit some of the most ephemeral nutrient pockets. Importantly, such strains have been often shown to be capable of synthesizing compounds of valuable biotechnological importance. Here we show that Pseudomonas sp. TAE6080, a possibly new bacterium isolated in 1994 during water column samplings near the French Antarctic station Dumont d'Urville, is capable of inhibiting the formation of Staphylococcus epidermidis biofilm, known to be an important opportunistic pathogen in infections associated to medical devices. A better understanding of this bacterium can therefore provide useful insight on new bioactive molecules that could play a role against chronic infections. To this end, the anti-biofilm effect of cell-free supernatant of Pseudomonas sp. TAE6080 was evaluated on S. epidermidis RP62A biofilm formation, demonstrating that it significantly reduced its aggregation. Furthermore, genome sequencing, assembly and mining revealed a plethora of putative biosynthetic gene clusters that might be involved in biofilm disruption. The experimental and genomic data presented here open the venue to further investigations on the molecular basis underlying biofilm inhibition.

The ability to form biofilms is a common feature of microorganisms, which can colonize a variety of surfaces, such as host tissues and medical devices, resulting in infections highly resistant to conventional drugs. This aspect is particularly critical in polymicrobial biofilms involving both fungi and bacteria, therefore, to eradicate such severe infections, new and effective anti-biofilm strategies are needed. The efficacy of pentadecanal and pentadecanoic acid as anti-biofilm agents has been recently reported against different bacterial strains. Their chemical similarity with diffusible signal factors (DSFs), plus the already known ability of fatty acids to act as anti-biofilm agents, suggested to explore their use against Candida albicans and Klebsiella pneumoniae mixed biofilm. In this work, we demonstrated the ability of both molecules to prevent the formation and destabilize the structure of the dual-species biofilm. Moreover, the pentadecanoic acid anti-biofilm coating, previously developed through the adsorption of the fatty acid on polydimethylsiloxane, was proved to prevent the polymicrobial biofilm formation in dynamic conditions by confocal laser scanning microscopy analysis. Finally, the evaluation of the expression levels of some biofilm-related genes of Candida albicans and Klebsiella pneumoniae treated with pentadecanoic acid provided some insights into the molecular mechanisms underpinning its anti-biofilm effect.

Staphylococcus epidermidis is well known to be one of the major causes of infections related to medical devices, mostly due to its strong capacity to form device-associated biofilms. Nowadays, these infections represent a severe burden to the public health system and the necessity of novel antibacterial strategies for the treatment of these difficult-to-eradicate infections is urgent. The Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125 was found to be able to produce an anti-biofilm molecule, the pentadecanal, active against S. epidermidis. In this work, we modified one of the most widely used silicone-based polymers, polydimethylsiloxane (PDMS), by adsorption of pentadecanal and its most promising derivative, pentadecanoic acid, on the PDMS surface. The biofilm formation of S. epidermidis RP62A on both untreated and modified PDMS was performed in a parallel plate flow chamber system, demonstrating the capability of the proposed anti-biofilm coatings to strongly reduce the biofilm formation. Furthermore, drug-release capacity and long-term efficacy (21 days) were also proven for the pentadecanoic acid coating.

Pseudomonas aeruginosa is an opportunistic pathogen often involved in airway infections of cystic fibrosis (CF) patients. Its pathogenicity is related to several virulence factors, such as biofilm formation, motility and production of toxins and proteases. The expression of these virulence factors is controlled by quorum sensing (QS). Thus, QS inhibition is considered a novel strategy for the development of antipathogenic compounds acting on specific bacterial virulence programs without affecting bacterial vitality. In this context, cold-adapted marine bacteria living in polar regions represent an untapped reservoir of biodiversity endowed with an interesting chemical repertoire. In this paper, we investigated the biological activity of a supernatant derived from a novel Antarctic bacterium (SN_TAE2020) against specific virulence factors produced by P. aeruginosa strains isolated from FC patients. Our results clearly show a reduction in pyocyanin and protease production in the presence of SN_TAE2020. Finally, SN_TAE2020 was also able to strongly affect swarming and swimming motility for almost all tested strains. Furthermore, the effect of SN_TAE2020 was investigated on biofilm growth and texture, captured by SEM analysis. In consideration of the novel results obtained on clinical strains, polar bacteria might represent potential candidates for the discovery of new compounds limiting P. aeruginosa virulence in CF patients.

In this paper, the structure of the capsular polysaccharide isolated from the psychrotolerant bacterium Psychrobacter arcticus 273-4 is reported. The polymer was purified by gel filtration chromatography and the structure was elucidated by means of one- and two-dimensional NMR spectroscopy, in combination with chemical analyses. The polysaccharide consists of a trisaccharidic repeating unit containing two residues of glucose and a residue of a N,N-diacetyl-pseudaminic acid.

Lipopolysaccharides (LPSs) are the main components of the external leaflet of the outer membrane of Gram-negative bacteria. Microorganisms that colonize permanently or transiently cold habitats have evolved an array of structural adaptations, some of which involve components of bacterial membranes. These adaptations assure the perfect functionality of the membrane even at freezing or sub-freezing growth temperatures. This review summarizes the state-of-the-art information concerning the structural features of the LPSs produced by cold-adapted bacteria. The LPS structure has recently been elucidated from species mainly belonging to Gammaproteobacteria and Flavobacteriaceae. Although the reported structural heterogeneity may arise from the phylogenetic diversity of the analyzed source strains, some generalized trends can be deduced. For instance, it is clear that only a small portion of LPSs displays the O-chain. In addition, the biological activity of the lipid A portion from several cold-adapted strains is reported.

Secretion of cold-adapted α-amylase from Pseudoalteromonas haloplanktis TAB23 was studied in three Antarctic bacteria. We demonstrated that the enzyme is specifically secreted in the psychrophilic hosts even in the absence of a protein domain that has been previously reported to be necessary for α-amylase secretion in Escherichia coli . The occurrence of two different secretion pathways in different hosts is proposed.