Browsing by Author "Vincent, Warwick F."
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- Contamination analysis of Arctic ice samples as planetary field analogs and implications for future life-detection missions to Europa and EnceladusPublication . Coelho, Lígia F.; Blais, Marie-Amélie; Matveev, Alex; Keller-Costa, Tina; Vincent, Warwick F.; Da Silva Costa, Rodrigo; Martins, Zita; Canário, JoãoMissions to detect extraterrestrial life are being designed to visit Europa and Enceladus in the next decades. The contact between the mission payload and the habitable subsurface of these satellites involves significant risk of forward contamination. The standardization of protocols to decontaminate ice cores from planetary field analogs of icy moons, and monitor the contamination in downstream analysis, has a direct application for developing clean approaches crucial to life detection missions in these satellites. Here we developed a comprehensive protocol that can be used to monitor and minimize the contamination of Arctic ice cores in processing and downstream analysis. We physically removed the exterior layers of ice cores to minimize bioburden from sampling. To monitor contamination, we constructed artificial controls and applied culture-dependent and culture-independent techniques such as 16S rRNA amplicon sequencing. We identified 13 bacterial contaminants, including a radioresistant species. This protocol decreases the contamination risk, provides quantitative and qualitative information about contamination agents, and allows validation of the results obtained. This study highlights the importance of decreasing and evaluating prokaryotic contamination in the processing of polar ice cores, including in their use as analogs of Europa and Enceladus.
- Structural shifts in sea ice prokaryotic communities across a salinity gradient in the subarcticPublication . Coelho, Lígia Fonseca; Couceiro, Joana Fernandes; Keller-Costa, Tina; Valente, Sara Martinez; Ramalho, Tiago Pereirinha; Carneiro, Joana; Comte, Jérôme; Blais, Marie-Amélie; Vincent, Warwick F.; Martins, Zita; Canário, João; Costa, RodrigoCurrent knowledge of the processes that shape prokaryotic community assembly in sea ice across polar ecosystems is scarce. Here, we coupled culture-dependent (bacterial isolation on R2A medium) and culture-independent (high throughput 16S rRNA gene sequencing) approaches to provide the first comprehensive assessment of prokaryotic communities in the late winter ice and its underlying water along a natural salinity gradient in coastal Hudson Bay, an iconic cryo-environment that marks the ecological transition between Canadian Subarctic and Arctic biomes. We found that prokaryotic community assembly processes in the ice were less selective at low salinity since typical freshwater taxa such as Frankiales, Burkholderiales, and Chitinophagales dominated both the ice and its underlying water. In contrast, there were sharp shifts in community structure between the ice and underlying water samples at sites with higher salinity, with the orders Alteromonadales and Flavobacteriales dominating the ice, while the abovementioned freshwater taxa dominated the underlying water communities. Moreover, primary producers including Cyanobium (Cyanobacteria, Synechococcales) may play a role in shaping the ice communities and were accompanied by known Planctomycetes and Verrucomicrobiae taxa. Culture-dependent analyses showed that the ice contained pigment producing psychrotolerant or psychrophilic bacteria from the phyla Proteobacteria, Actinobacteriota, and Bacteroidota, likely favored by the combination of low temperatures and the seasonal increase in sunlight. Our findings suggest that salinity, photosynthesis and dissolved organic matter are the main drivers of prokaryotic community structure in the late winter ice of coastal Hudson Bay, the ecosystem with the fastest sea ice loss rate in the Canadian North.