Bioremediation of hydrocarbon-contaminated soil from Carlini Station, Antarctica: effectiveness of different nutrient sources as biostimulation agents

Ligilactobacillus-Derived Extracellular Vesicles Inhibit Growth and Virulence of Enteric Pathogens

Bacterial intra-kingdom communication involves the secretion of outer membrane vesicles as signaling carriers to the target cells. However, limited research exists on extracellular vesicles (EVs) from Gram-positive gut bacteria, their interactions with enteric pathogens, and potential inhibitory effects. In this study, we characterized the structure, protein content, and inhibitory effects of EVs from three new potential probiotic gut symbionts, Ligilactobacillus salivarius UO.C109, Ligilactobacillus saerimneri UO.C121, and Ligilactobacillus salivarius UO.C249. EVs were isolated and characterized using three different methods (ultracentrifugation, density gradient purification, and size exclusion chromatography). The purity, dose-dependency, structure, and proteome profiles of the purified EVs were evaluated. Antibacterial and anti-virulence activities of EV subpopulations were assessed against Salmonella enterica serovar Typhimurium and Campylobacter jejuni. EVs from Lg. salivarius UO.C109 and Lg. saerimneri UO.C121 showed inhibitory activity against S. Typhimurium, whereas EVs from Lg. salivarius UO.C249 inhibited the growth of C. jejuni. Notably, purified F3 fraction exhibited the highest inhibitory activity and was enriched in lysin motif (LysM)-containing proteins, peptidoglycan hydrolases, peptidoglycan recognition proteins (PGRPs), and metallopeptidases, which have been shown to play a prominent role in antimicrobial activities against pathogens. F3 had the highest concentration (73.8%) in the 80-90 nm size compared to the other fractions. Gene expression analysis revealed that EVs from Lg. salivarius UO.C109 and Lg. saerimneri UO.C121 downregulated adhesion and invasion factors in S. Typhimurium. Likewise, EVs from Lg. salivarius UO.C249 reduced pathogenicity gene expression in C. jejuni. This study highlighted the potential of gut bacterial EVs as therapeutic agents against enteric pathogens.

Trends in Antarctic soil fungal research in the context of environmental changes

Antarctic soils represent one of the most pristine environments on Earth, where highly adapted and often endemic microbial species withstand multiple extremes. Specifically, fungal diversity is extremely low in Antarctic soils and species distribution and diversity are still not fully characterized in the continent. Despite the unique features of this environment and the international interest in its preservation, several factors pose severe threats to the conservation of inhabiting ecosystems. In this light, we aimed to provide an overview of the effects on fungal communities of the main changes endangering the soils of the continent. Among these, the increasing human presence, both for touristic and scientific purposes, has led to increased use of fuels for transport and energy supply, which has been linked to an increase in unintentional environmental contamination. It has been reported that several fungal species have evolved cellular processes in response to these soil contamination episodes, which may be exploited for restoring contaminated areas at low temperatures. Additionally, the effects of climate change are another significant threat to Antarctic ecosystems, with the expected merging of previously isolated ecosystems and their homogenization. A possible reduction of biodiversity due to the disappearance of well-adapted, often endemic species, as well as an increase of biodiversity, due to the spreading of non-native, more competitive species have been suggested. Despite some studies describing the specialization of fungal communities and their correlation with environmental parameters, our comprehension of how soil communities may respond to these changes remains limited. The majority of studies attempting to precisely define the effects of climate change, including in situ and laboratory simulations, have mainly focused on the bacterial components of these soils, and further studies are necessary, including the other biotic components.

Effect of oil pollution on the ecological condition of soils and bottom sediments of the arctic region (Yakutia)

Oil and petroleum products are known to be among the most widespread soil pollutants. The risk of emergencies is sure to increase greatly in conditions of abnormally low temperatures. Oil and oil products are not only toxic to the environment, but can also have a negative impact on the state of the permafrost zone, accelerating the processes of permafrost degradation. The goal of the research was to study the soils and bottom sediments for oil pollution in the Arctic region of Yakutia. The research was carried out with using the complex of geochemical and microbiological methods of analysis. It had shown that at present oil pollution was mainly concentrated on the objects bearing a high technogenic load. However, some migration of hydrocarbons was observed with melt, seasonal melt and rainwaters, as a result of which the natural background of the nearby territories became technogenic character. In the Arctic conditions for the first time according to the obtained data on geochemical and microbiological studies oxidative destruction of oil pollutants in soil occurred mainly under the influence of physic and chemical environmental factors, not by microbial oxidation. Sluggish processes of mineralization of organic residues and the transformation of oil pollutants by the type of putrefaction led to the colonization of oil-polluted soils of the Arctic with putrefying and pathogenic microorganisms. The purpose of further research will be studying the possibility of intensification of soil remediation processes of technologically disturbed soils at abnormally low temperatures.