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18 pages, 6 figures, supplementary material https://www.frontiersin.org/articles/10.3389/fmicb.2020.584222/full#supplementary-material.-- The datasets generated in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found below: https://www.ebi.ac.uk/ena, PRJEB38662, Marine snow is an important habitat for microbes, characterized by chemical and physical properties contrasting those of the ambient water. The higher nutrient concentrations in marine snow lead to compositional differences between the ambient water and the marine snow-associated prokaryotic community. Whether these compositional differences vary due to seasonal environmental changes, however, remains unclear. Thus, we investigated the seasonal patterns of the free-living and marine snow-associated microbial community composition and their functional potential in the northern Adriatic Sea. Our data revealed seasonal patterns in both, the free-living and marine snow-associated prokaryotes. The two assemblages were more similar to each other in spring and fall than in winter and summer. The taxonomic distinctness resulted in a contrasting functional potential. Motility and adaptations to low temperature in winter and partly anaerobic metabolism in summer characterized the marine snow-associated prokaryotes. Free-living prokaryotes were enriched in genes indicative for functions related to phosphorus limitation in winter and in genes tentatively supplementing heterotrophic growth with proteorhodopsins and CO-oxidation in summer. Taken together, the results suggest a strong influence of environmental parameters on both free-living and marine snow-associated prokaryotic communities in spring and fall leading to higher similarity between the communities, while the marine snow habitat in winter and summer leads to a specific prokaryotic community in marine snow in these two seasons, This study was funded by the Wittgenstein prize (Austrian Science Fund, FWF, Z194-B1) to GH and the projects ARTEMIS (P28781-B21) and DK microbial nitrogen cycling (W1257-B20) to GH, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Messenger RNA can provide valuable insights into the variability of metabolic processes of microorganisms. However, due to uncertainties that include the stability of RNA, its application for activity profiling of environmental samples is questionable. We explored different factors affecting the decay rate of transcripts of three marine bacterial isolates using qPCR and determined mRNA half‐life time of specific bacterial taxa and of functional genes by metatranscriptomics of a coastal environmental prokaryotic community. The half‐life time of transcripts from 11 genes from bacterial isolates ranged from 1 to 46 min. About 80% of the analysed transcripts exhibited half‐live times shorter than 10 min. Significant differences were found in the half‐life time between mRNA and rRNA. The half‐life time of mRNA obtained from a coastal metatranscriptome ranged from 9 to 400 min. The shortest half‐life times of the metatranscriptome corresponded to transcripts from the same clusters of orthologous groups (COGs) in all bacterial classes. The prevalence of short mRNA half‐life time in genes related to defence mechanisms and motility indicate a tight connection of RNA decay rate to environmental stressors. The short half‐life time of RNA and its high variability needs to be considered when assessing metatranscriptomes especially in environmental samples.

Messenger RNA can provide valuable insights into the variability of metabolic processes of microorganisms. However, due to uncertainties that include the stability of RNA, its application for activity profiling of environmental samples is questionable. We explored different factors affecting the decay rate of transcripts of three marine bacterial isolates using qPCR and determined mRNA half-life time of specific bacterial taxa and of functional genes by metatranscriptomics of a coastal environmental prokaryotic community. The half-life time of transcripts from 11 genes from bacterial isolates ranged from 1 to 46 min. About 80% of the analysed transcripts exhibited half-live times shorter than 10 min. Significant differences were found in the half-life time between mRNA and rRNA. The halflife time of mRNA obtained from a coastal metatranscriptome ranged from 9 to 400 min. The shortest half-life times of the metatranscriptome corresponded to transcripts from the same clusters of orthologous groups (COGs) in all bacterial classes. The prevalence of short mRNA half-life time in genes related to defence mechanisms and motility indicate a tight connection of RNA decay rate to environmental stressors. The short half-life time of RNA and its high variability needs to be considered when assessing metatranscriptomes especially in environmental samples.

This project is a study of the optimization of a ring resonator filter situated after a DML semiconductor laser in a global short-range optical link system. The main purpose is to optimize the optical filter performing matlab simulations in order to find the parameters of the transfer function of the filter that we may tune to achieve an error-free transmission. From a theoretical point of view, this project will give the knowledge of the optical direct modulation operation where the chirp is an evitable factor that we have to minimize to achieve good performance in our global system. Also a high extinction ratio over this low chirp will be an interesting parameter to take into account. Combining the theoretical background of DML and ring resonators of terms such as FSR, internal losses, finesse…with the experimental work, the goal of the project will be achieved concluding that there is some intervals in which the parameters can oscillate in order to obtain the fewer errors in the system. Ingeniería de Telecomunicación