The role of phosphorus as a regulator of bloom-forming diazotrophic cyanobacteria in the Baltic Sea

Eutrophication favours harmful algal blooms worldwide. The blooms cause toxic outbreaks and deteriorated recreational and aesthetic values, causing both economic loss and illness or death of humans and animals. The Baltic Sea is the world s only large brackish water habitat with recurrent blooms of toxic cyanobacteria capable of biological fixation of atmospheric nitrogen gas. Phosphorus is assumed to be the main limiting factor, along with temperature and light, for the growth of these cyanobacteria. This thesis evaluated the role of phosphorus nutrition as a regulating factor for the occurrence of nitrogen-fixing cyanobacteria blooms in the Baltic Sea, utilising experimental laboratory and field studies and surveys on varying spatial scales. Cellular phosphorus sources were found to be able to support substantial growth of the two main bloom forming species Aphanizomenon sp. and Nodularia spumigena. However, N. spumigena growth seemed independent of phosphorus source, whereas, Aphanizomenon sp. grew best in a phosphate enriched environment. Apparent discrepancies with field observations and experiments are explained by the typical seasonal temperature dependent development of Aphanizomenon sp. and N. spumigena biomass allowing the two species to store ambient pre-bloom excess phosphorus in different ways. Field experiments revealed natural cyanobacteria bloom communities to be predominantly phosphorus deficient during blooms. Phosphate additions were found to increase the accumulation of phosphorus relatively most in the planktonic size fraction dominated by the nitrogen-fixing cyanobacteria. Aphanizomenon sp. responded to phosphate additions whereas the phosphorus nutritive status of N. spumigena seemed independent of phosphate addition. The seasonal development of phosphorus deficiency is different for the two species with N. spumigena showing indications of phosphorus deficiency during a longer time period in the open sea. Coastal upwelling introduces phosphorus to the surface layer during nutrient deficient conditions in summer. The species-specific ability of Aphanizomenon sp. and N. spumigena to utilise phosphate enrichment of the surface layer caused by coastal upwelling was clarified. Typical bloom time vertical distributions of biomass maxima were found to render N. spumigena more susceptible to advection by surface currents caused by coastal upwellings. Aphanizomenon sp. populations residing in the seasonal thermocline were observed to be able to utilise the phosphate enrichment and a bloom was produced with a two to three week time lag subsequent to the relaxation of upwelling. Consistent high concentrations of dissolved inorganic phosphorus, caused by persistent internal loading of phosphorus, was found to be the main source of phosphorus for large-scale pelagic blooms. External loads were estimated to contribute with only a fraction of available phosphorus for open sea blooms. Remineralization of organic forms of phosphorus along with vertical mixing to the permanent halocline during winter set the level of available phosphorus for the next growth season. Events such as upwelling are important in replenishing phosphate concentrations during the nutrient deplete growth season. Autecological characteristics of the two main bloom forming species favour Aphanizomenon sp. populations in utilising the abundant excess phosphate concentrations and phosphate pulses mediated through upwelling. Whilst, N. spumigena displays predominant phosphorus limited growth mode and relies on more scarce cellular phosphorus stores and presumably dissolved organic phosphorus compounds for growth. The Baltic Sea is hypothesised to be in an inhibited state of recovery due to the extensive historical external nutrient loading, extensive internal phosphorus loading and the substantial nitrogen load caused by cyanobacteria nitrogen fixation. This state of the sea is characterised as a vicious circle .

MECHANISMS AND EFFECTS OF MITOCHONDRIAL DNA INSTABILITY AND COPY NUMBER MANIPULATION

Defects in mitochondrial DNA (mtDNA) maintenance cause a range of human diseases, including autosomal dominant progressive external ophthalmoplegia (adPEO). This study aimed to clarify the molecular background of adPEO. We discovered that deoxynucleoside triphosphate (dNTP) metabolism plays a crucial in mtDNA maintenance and were thus prompted to search for therapeutic strategies based on the modulation of cellular dNTP pools or mtDNA copy number. Human mtDNA is a 16.6 kb circular molecule present in hundreds to thousands of copies per cell. mtDNA is compacted into nucleoprotein clusters called nucleoids. mtDNA maintenance diseases result from defects in nuclear encoded proteins that maintain the mtDNA. These syndromes typically afflict highly differentiated, post-mitotic tissues such as muscle and nerve, but virtually any organ can be affected. adPEO is a disease where mtDNA molecules with large-scale deletions accumulate in patients tissues, particularly in skeletal muscle. Mutations in five nuclear genes, encoding the proteins ANT1, Twinkle, POLG, POLG2 and OPA1, have previously been shown to cause adPEO. Here, we studied a large North American pedigree with adPEO, and identified a novel heterozygous mutation in the gene RRM2B, which encodes the p53R2 subunit of the enzyme ribonucleotide reductase (RNR). RNR is the rate-limiting enzyme in dNTP biosynthesis, and is required both for nuclear and mitochondrial DNA replication. The mutation results in the expression of a truncated form of p53R2, which is likely to compete with the wild-type allele. A change in enzyme function leads to defective mtDNA replication due to altered dNTP pools. Therefore, RRM2B is a novel adPEO disease gene. The importance of adequate dNTP pools and RNR function for mtDNA maintenance has been established in many organisms. In yeast, induction of RNR has previously been shown to increase mtDNA copy number, and to rescue the phenotype caused by mutations in the yeast mtDNA polymerase. To further study the role of RNR in mammalian mtDNA maintenance, we used mice that broadly overexpress the RNR subunits Rrm1, Rrm2 or p53R2. Active RNR is a heterotetramer consisting of two large subunits (Rrm1) and two small subunits (either Rrm2 or p53R2). We also created bitransgenic mice that overexpress Rrm1 together with either Rrm2 or p53R2. In contrast to the previous findings in yeast, bitransgenic RNR overexpression led to mtDNA depletion in mouse skeletal muscle, without mtDNA deletions or point mutations. The mtDNA depletion was associated with imbalanced dNTP pools. Furthermore, the mRNA expression levels of Rrm1 and p53R2 were found to correlate with mtDNA copy number in two independent mouse models, suggesting nuclear-mitochondrial cross talk with regard to mtDNA copy number. We conclude that tight regulation of RNR is needed to prevent harmful alterations in the dNTP pool balance, which can lead to disordered mtDNA maintenance. Increasing the copy number of wild-type mtDNA has been suggested as a strategy for treating PEO and other mitochondrial diseases. Only two proteins are known to cause a robust increase in mtDNA copy number when overexpressed in mice; the mitochondrial transcription factor A (TFAM), and the mitochondrial replicative helicase Twinkle. We studied the mechanisms by which Twinkle and TFAM elevate mtDNA levels, and showed that Twinkle specifically implements mtDNA synthesis. Furthermore, both Twinkle and TFAM were found to increase mtDNA content per nucleoid. Increased mtDNA content in mouse tissues correlated with an age-related accumulation of mtDNA deletions, depletion of mitochondrial transcripts, and progressive respiratory dysfunction. Simultaneous overexpression of Twinkle and TFAM led to a further increase in the mtDNA content of nucleoids, and aggravated the respiratory deficiency. These results suggested that high mtDNA levels have detrimental long-term effects in mice. These data have to be considered when developing and evaluating treatment strategies for elevating mtDNA copy number.

Method-MS, final report 2010

Radiometric determination methods, such as alpha spectrometry require long counting times when low activities are to be determined. Mass spectrometric techniques as Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Thermal Ionisation Mass Spectrometry (TIMS) and Accelerator Mass Spectrometry (AMS) have shown several advantages compared to traditional methods when measuring long-lived radionuclides. Mass spectrometric methods for determination of very low concentrations of elemental isotopes, and thereby isotopic ratios, have been developed using a variety of ion sources. Although primarily applied to the determination of the lighter stable element isotopes and radioactive isotopes in geological studies, the techniques can equally well be applied to the measurement of activity concentrations of long-lived low-level radionuclides in various samples using “isotope dilution” methods such as those applied in inductively coupled plasma mass spectrometry (ICP-MS). Due to the low specific activity of long-lived radionuclides, many of these are more conveniently detected using mass spectrometric techniques. Mass spectrometry also enables the individual determination of Pu-239 and Pu-240, which cannot be obtained by alpha spectrometry. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) are rapidly growing techniques for the ultra-trace analytical determination of stable and long-lived isotopes and have a wide potential within environmental science, including ecosystem tracers and radio ecological studies. Such instrumentation, of course needs good radiochemical separation, to give best performance. The objectives of the project is to identify current needs and problems within low-level determination of long-lived radioisotopes by ICP-MS, to perform intercalibration and development and improvement of ICP-MS methods for the measurement of radionuclides and isotope ratios and to develop new methods based on modified separation chemistry applied to new auxiliary equipment.

Aikapankki - Tutkimus lahjaperustaiseen vaihtoon perustuvasta yhteisöllisyyden rakentamisesta Helsingissä

Pro gradu -tutkielmassani tutkin aikapankkijärjestelmässä tapahtuvaa palveluiden vaihtoa vertaamalla sitä lahjanvaihtoon. Tutkielmassa kuvaan kuinka Kumpulan Vaihtopiirinä toimintansa aloittaneen Stadin Aikapankin aktiiviset jäsenet kokevat toiminnan, kun se on laajennut oman asuinalueen ulkopuolelle. Aikapankin voi mieltää uudenlaiseksi vapaaehtoistyön muodoksi. Aikapankin jäsenet tuottavat toisilleen palveluita ja mittaavat näihin käytettyä aikaa aikapisteillä, jotka toimivat vaihdon välineenä. Aikapankissa kaikkien työ arvotetaan saman arvoiseksi. Tutkielman pääaineistona on kymmenen käyttäjän avohaastattelut. Näitä täydennetään vaihtotilastolla ja osallistuvan havainnoinnin menetelmällä. Tutkimusta varten on kerätty tausta-aineistoa kahdella sähköpostihaastattelulla kahdelta Ruotsissa ja Englannissa toimivien aikapankkien työntekijältä. Merkittävin tutkimusongelma liittyy aikapankin tasa-arvoisen työnarvottamiseen. Kysyn miten ja millä ehdoin aikapankin kaltainen sosiaalinen innovaatio toimii? Lisäksi kysyn, mitä ehtojen täyttymisestä seuraa? Lähestyn kysymystä Emil Durkheimin modernisaatioteoriaan ja Marcel Maussin lahjanvaihtoa käsittelevään teoreettiseen ajatteluun nojaten. Teoreettisessa keskustelussa viitataan myös Karl Polanyin Maussia tukevaan näkemykseen esimodernien vaihtokäytäntöjen ilmenemisestä markkinatalouden rakenteistamassa maailmassa. Lisäksi pohdin tutkielmassani sitä, mitä aikapankissa vaihdettavat aikapisteet tekisivät, mitä oikea raha ei tekisi paremmin. Vastaus on se, että tutkittavani eivät saisi rahalla sitä, mitä he tavoittelevat – yhteisöä. Tutkielman lopussa keskustelen myös sitä, mikä on aikapankin luomien epämarkkinataloussuhteiden taloudellinen konteksti. Kontekstiin liittyen voidaan todeta, että tutkittavat eivät pakene rahataloutta. He solmivat perinteisen yhteisöllisen siteen (perheen) mukaista (lahjaperustaista) vaihtoa lähellä asuviin ihmisiin. Tutkielmassa päädytään siihen tulokseen, että aikapankin haasteeksi ei muodostu niinkään markkinoille vieras tasapuolinen työn hinnoittelu, vaan sellaisten yhteisöllisten siteiden heikkous, joiden varaan vaihto leviäisi. Tästä syystä aikapankkia perustettaessa ratkaisevaksi muodostuu se, minkä yhteisöllisen siteen varaan vaihtosuhteet muodostuvat. Tästä syystä tutkielmassa tullaan siihen tulokseen, että aikapankkitoiminta olisi hyvä pitää paikallisena. Sosiaalipoliittisesta näkökulmasta katsottuna tutkimusaihe on merkittävä ja tuore. Aihetta tutkittu jo sosiaalipolitiikan alalla, muttei aikaisemmin Suomessa. Aikaisemman muualla tehdyn tutkimuksen tulokset ovat lähestyneet aihetta muun muassa sosiaalisen pääomaan käsitteen avulla. Tutkittavani vaihtavat myös sellaisia palveluita, joita julkinen sektori tuottaa suomessa, kuten lastenhoitoa. Taustoitan tutkimusta aikaisemmalla tutkimuskirjallisuudella ja kuvaan Suomessakin yleistynyttä vertaistuotantokeskustelua. Vertaistuotanto avaa uuden näkökulman palvelutuotantoon 1990-luvulla jalansijaa saaneiden tilaaja-tuottaja–mallien rinnalle. Tutkielman tarkoitus on tuottaa käytännönläheistä tietoa aikapankkitoiminnasta kiinnostuneille yhteisöille ja organisaatioille. Tämän lisäksi tutkimus täydentää aiempien aikapankkeja käsitelleiden tutkimusten tuloksia tarkastelemalla toiminnan ehtoja, ei ainoastaan sen seurauksia.