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SpeakerChapter 1: What is your research question?
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SpeakerEvery year in spring you have massive algae blooms in the temperate and polar oceans, which vanish after two to three weeks of blooming.
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Speaker The mechanism of this degradation was completely unknown so far and we asked ourselves, who is degrading it?
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Speaker We focused on the bacterial part of it and the second question was, how are they doing it?
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SpeakerChapter 2: Which method did you employ?
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Speaker For tackling the research questions, we have chosen a suite of methods.
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Speaker The first one is based on the ribosomal RNA.
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Speaker This gives you the phylogenetic distribution of the different bacterial organisms and the nature of the bacterial organisms.
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Speaker This is actually addressing the first research question, who is there and how abundant are they?
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SpeakerThe ribosomal RNA is a universal marker, gives you the phylogenetic relation of the different organisms present in the water sample.
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SpeakerAnd the fluorescent in-situ hybridization is a method which you can stain the bacteria in a specific manner
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Speakeron the genus level or on the family level and you really can enumerate the different bacterial genera, families in the water sample.
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Speaker The second question was what are they doing and this is currently the method of choice is metagenome sequencing.
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Speaker You extract the bulk of DNA, sequence it, assemble it into larger pieces and do a gene prediction on these larger pieces.
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SpeakerWith a comparison of the different databases, you can then get a hint on what the gene is coding for
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Speakerand what functions they have in nature, basically, and this is exactly what we want to find out.
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SpeakerChapter 3: What are your findings?
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SpeakerWhat we found out was, for us, quite surprising that not a huge diversity reacted
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Speakerto the phytoplankton biomass, but rather a limited number of organisms, of bacteria.
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Speaker They all belonged to the flavobacterial group.
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SpeakerOne of the earlier responders which reacted first to the algae biomass was a group called Formosa.
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SpeakerThey reacted within a week's time and they increased in their numbers to make up 20% of the whole entire community, which was really a lot,
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Speakerand then vanished within a week, only giving rise to another bacterial group, which is called Polaribacter.
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SpeakerThey come later and so there were another three, four of different groups responding in tight succession
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Speakerand also in abundances from maybe 1 to 2 percent, up to 20 percent.
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Speaker And that was really very surprising for us.
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SpeakerIf we look then into the genomes, the metagenomes, of these organisms
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Speakerwe could see that there's a clear pattern from the beginning of the bacterial bloom, which responded to the phytoplankton bloom basically, that the substrates get more and more complicated.
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SpeakerFor example, earlier responders had degradation potential for laminarin,
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Speakerwhich is a relatively simple polysaccharide of alpha-1,3-connected glucose,
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Speakerto later organisms like Polaribacter, they had repertoires for many different polysaccharides like chondroitin sulfate, mannan, or xylan.
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SpeakerAnd that was for us also a clear hint that they are distinct ecological niches,
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Speaker that they partition the polysaccharides among them and that each has a certain specialization for a certain group of polysaccharides.
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SpeakerChapter 4: What is the relevance of your findings?
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SpeakerOur findings were surprising in that respect that we have found not zillions of different bacterial organisms and groups,
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Speakerbut that we have found a limited number of genera and families which were obviously solely responsible for the degradation of the algae biomass.
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SpeakerThey were in the flavobacteria group.
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SpeakerThat was something new, what was always postulated that it's a rather stochastic process, that who is there first wins.
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Speaker Actually, what we've shown in several years now, that it's a deterministic process, that always the same organisms come up and bloom.
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SpeakerAnd this is actually reasoned in the second finding what we found,
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Speakerthat these organisms have a fixed set of polysaccharide degradation enzymes, so-called glycosidases.
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SpeakerThey are organized in pools, these are large gene sets.
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SpeakerThey are specific for degradation of a type of polysaccharides.
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SpeakerAnd these polysaccharides were also limited in diversity, so always the same sets came up.
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SpeakerSo we had the beginning of the bloom was laminarine important, and the end of the blooms were the more complicated polysaccharides, the branch polysaccharides important.
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SpeakerWe have 10 to 15 types which are important and there are thousands.
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SpeakerIf you look now in new organisms which we are unknown and we find these gene sets for polysaccharide degradation,
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Speakerwe could immediately refer them to this function and say, okay, this bacterium must be specific growing on laminarine, for example,
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Speakeror on xylan, or on mannan, depending on the repertoire what we showed.
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Speaker And this is for us an exciting tool as ecologists that we can predict the ecological role of these bacteria in the environment.
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Speaker This is absolutely novel and gives us really new clues on their role.
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SpeakerChapter 5: Your outlook for the future?
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Speaker So the next steps what we are currently doing in the lab is to verify the function of the predicted enzymes, what we have from the different organisms.
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Speaker For now it's only a comparison to databases and the function is predicted based on bioinformatics measures.
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Speaker But we are more and more now cloning these enzymes and verifying the functions down to even the crystal structure of the individual enzymes.
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Speaker As ultimate goal we want also to show the function in the environment, in the natural environments, to sort out specific organisms and see what they are currently expressing.
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Speaker And if they are really working on one or the other polysaccharide and put this together to a bigger picture.