Jellyfish Modulate Bacterial Dynamic and Community Structure

Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom - forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish - enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to ‘jellyfish - associated’ and ‘free - living’ bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into possible changes in bacterial population dynamics and nutrient pathways following jellyfish blooms which have important implications for ecology of coastal waters

Climate Change and the Potential Spreading of Marine Mucilage and Microbial Pathogens in the Mediterranean Sea

Background: Marine snow (small amorphous aggregates with colloidal properties) is present in all oceans of the world. Surface water warming and the consequent increase of water column stability can favour the coalescence of marine snow into marine mucilage, large marine aggregates representing an ephemeral and extreme habitat. Marine mucilage characterize aquatic systems with altered environmental conditions. Methodology/Principal Findings: We investigated, by means of molecular techniques, viruses and prokaryotes within the mucilage and in surrounding seawater to examine the potential of mucilage to host new microbial diversity and/or spread marine diseases. We found that marine mucilage contained a large and unexpectedly exclusive microbial biodiversity and hosted pathogenic species that were absent in surrounding seawater. We also investigated the relationship between climate change and the frequency of mucilage in the Mediterranean Sea over the last 200 years and found that the number of mucilage outbreaks increased almost exponentially in the last 20 years. The increasing frequency of mucilage outbreaks is closely associated with the temperature anomalies. Conclusions/Significance: We conclude that the spreading of mucilage in the Mediterranean Sea is linked to climate-driven sea surface warming. The mucilage can act as a controlling factor of microbial diversity across wide oceanic regions and could have the potential to act as a carrier of specific microorganisms, thereby increasing the spread of pathogenic bacteria

Microstructure development in deformed nickel alloy 625

Glavni cilj doktorske disertacije je raziskava vpliva deformacije in toplotne obdelave na izločanje sekundarnih faz nikljeve zlitine 625 z različno kemijsko sestavo. V vroče deformiranih ploščah, ki imajo pozitivne segregacije z niobijem smo opazovali izločanje sekundarnih faz po staranju na temperaturi 750 °C. Ker se je povprečni delež niobija spreminjal čez segregacijski pas, smo spremljali izločanje sekundarnih faz pri različnem povprečnem deležu niobija. Pri majhnem povprečnem deležu niobija ( 4 mas.% Nb) je izločanje večjega števila finih izločkov ?\u27\u27 potekalo v deformiranih in rekristaliziranih zrnih. Na deformacijskem dilatometru smo spreminjali temperaturo deformacije in jo povezali z izločanjem ?\u27\u27-faze s pomočjo EBSD-analiz. Temperatura deformacije (950, 1050 in 1150 °C) ima vpliv na porazdelitev faze ?\u27\u27 in je povezana z lokalno razliko v orientaciji. V zadnjem delu disertacije smo raziskovali vpliv žarjenih in deformiranih vzorcev na utrjevanje z izločanjem ?\u27\u27 v homogeniziranih ploščah z različnim dodatkom titana in aluminija. Na osnovi meritev trdot in mikrostrukturnih preiskav, ima dodatek titana (0,36 mas.%) in aluminija (0,35 mas.%) majhen vpliv na izločanje ?\u27\u27 faze. Trdota deformiranih vzorcev se je po staranju na temperaturah 700 in 750 °C zaradi izločanja ?\u27\u27, bolj povečala v primerjavi z žarjenimi vzorci. Majhno povečanje v natezni trdnosti pa je bilo povezano z deležem niobija (~ 3,3 mas%).The main objective of doctoral thesis was to research the influence of the deformation and heat treatment on the precipitation of secondary phases in chemically modified Inconel 625. The precipitation of secondary phases during aging at 750°C was researched in hot rolled plates containing positive segregations with niobium. Due to segregations the fraction of niobium changed acros the segregation band. The deformed grains enabled precipitation of large number of fine ?\u27\u27 (Ni3Nb) precipitates when fraction of niobium was low ( 4 wt.%). The precipitation of ?\u27\u27 in samples hot compressed at different temperature was researched with EBSD-analyis. The local change in orientation of hot-deformed samples at different temperature (950, 1050 in 1150°C) had influence on the distribution of the ?\u27\u27-phase. In the last part the influence of deformed and annealed samples was researched, on precipitation hardening by ?\u27\u27 in homogenized plates with different addition of titanium and aluminium. The increased content of aluminium (0,36 wt.%) and titanium (0,35 wt. %) had small influence on the precipitation of the ?\u27\u27. The hardness of deformed plates after aging at 700 and 750°C increased more than in annealed plates. Small increase in tensile strength was conected with low content of niobium (~ 3,3 wt.%)