Kan oppblomstringer av Gonyostomum semen føre til utslipp av metaller fra innsjøsedimenter?

I løpet av de siste tiårene har det blitt observert en økning i forekomsten av algeoppblomstringer. Dette fenomenet kan påvirke økosystemet i innsjøer ved å forårsake endringer i de kjemiske, fysiske og biologiske forholdene. Gonyostomum semen er en encellet nåleflagellat som har en rekke egenskaper som gjør den i stand til å danne omfattende oppblomstringer. I denne oppgaven undersøkes det om oppblomstringene fra Gonyostomum semen er i stand til å påvirke de abiotiske forholdene i en innsjø så mye at tidligere sedimenterte metaller mobiliseres. Dette innebærer at algeoppblomstringen fører til endringer i blant annet redokspotensialet og vannets pH-verdi. I dette studiet ble det gjennomført et feltforsøk over perioden 23. mai til 22. september 2022 der en rekke parametere ble målt in situ, deriblant redokspotensiale, pH, oksygenkonsentrasjon og lysintensitet. Det ble tatt vannprøver som ble analysert for metaller, næringsstoffer, mengden av Gonyostomum Semen (estimert ved å bruke pigmentet Heteroxanthin som biomarkør) og andre pigmenter. Prøvetakingen ble gjennomført i Glennetjern i Nordre Follo kommune, hvor det tidligere år har blitt påvist gjentagende oppblomstringer av Gonyostomum semen. Det ble funnet en oppblomstring av Gonyostomum semen i Glennetjern som varte fra 10. juni til 2. september. Det inntraff også tidlig en temperatursjiktning i innsjøen, noe som trolig har vært en fordel for Gonyostomum semen på grunn av algens evne til å drive døgnvandringer og miksotrofi. I løpet av oppblomstringen ble det observert endringer i pH-verdi, redokspotensialet og oksygenkonsentrasjon, og det antas at dette delvis skyldes aktiviteten til Gonyostomum semen. Resultatene viste tydelige forskjeller mellom epilimnion og hypolimnion for disse parameterne. Det ble registrert varierende konsentrasjoner av de fem undersøkte metallene bly, kobber, jern, mangan og kadmium. Dette skyldes trolig at de anoksiske forholdene i hypolimnion har påvirket oksidasjonstilstanden til metallene. Konsentrasjonene av fire av de undersøkte metallene ble vurdert til å ha lavt potensiale for toksiske effekter. For jern ble det funnet verdier som overskrider anbefalt grenseverdi. Dog er det mye usikkerhet knyttet til potensialet for toksiske effekter. Dette er på grunn av det komplekse samspillet mellom ulike faktorer som kan påvirke oksidasjonstilstanden.During the last decades there has been observed an increase in the occurrence of algal blooms. This phenomenon can affect the ecosystem of lakes by altering the chemical, physical and biological conditions. Gonyostomum semen is a unicellular Raphidophyte that possesses several characteristics that enable extensive blooms. In this thesis, the aim is to investigate whether the blooms of Gonyotomum Semen can influence the abiotic conditions in a lake to the extent that previously sedimented metals are mobilized. This implies that the algal blooms results in changes in, among other things, the redox potential and pH of the water. In this thesis there was conducted a field study from May 23 to September 22, 2022. Several parameters were measured in situ, including redox potential, pH, oxygen concentration and light intensity. Water samples were also collected and analyzed for metals, nutrients, the abundance of Gonyostomum semen (estimated using the pigment Heteroxanthin as a biomarker), and other pigments. The sampling took place in Glennetjern in Nordre Follo municipality, where recurring blooms of Gonyostomum semen have been observed in previous years. A bloom of Gonyostomum semen was found in Glennetjern in this study, lasting from June 10 to September 2. An early thermal stratification occurred in the lake, which likely favored Gonyostomum semen due to the algae’s ability to undergo diel vertical migration and mixotrophy. During the bloom, changes in pH, redox potential and oxygen concentration were observed. It is assumed that this is partly due to the activity of Gonyostomum semen. The results showed distinct differences between the epilimnion and hypolimnion for these parameters. Varying concentrations of the five investigated metals; led, copper, iron, manganese and cadmium were recorded. This is likely due to the anoxic conditions in the hypolimnion affecting the oxidation state of the metals. The concentrations of four of the examined metals were assessed to have low potential for toxic effects. However, iron was found exceed the recommended threshold value. Nevertheless, there is considerable uncertainty regarding the potential for toxic effects. This is because of the complex interplay of various factors that can influence the oxidation state of metals

Temporal Dynamics of Interferon Gamma Responses in Children Evaluated for Tuberculosis

BACKGROUND: Development of T-cells based-Interferon gamma (IFNgamma) assays has offered new possibilities for the diagnosis of latent tuberculosis infection (LTBI) and active disease in adults. Few studies have been performed in children, none in France. With reference to the published data on childhood TB epidemiology in the Paris and Ile de France Region, we considered it important to evaluate the performance of IGRA (QuantiFERON TB Gold In Tube(R), QF-TB-IT) in the diagnosis and the follow-up through treatment of LTBI and active TB in a cohort of French children. METHODOLOGY/PRINCIPAL FINDINGS: 131 children were recruited during a prospective and multicentre study (October 2005 and May 2007; Ethical Committee St Louis Hospital, Paris, study number 2005/32). Children were sampled at day 0, 10, 30, 60 (except Healthy Contacts, HC) and 90 for LTBI and HC, and a further day 120, and day 180 for active TB children. Median age was 7.4 years, with 91% of the children BCG vaccinated. LTBI and active TB children undergoing therapy produced significant higher IFNgamma values after 10 days of treatment (p = 0.035). In addition, IFNgamma values were significantly lower at the end of treatment compared to IFNgamma values at day 0, although the number of positive patients was not significantly different between day 0 and end of treatment. CONCLUSIONS/ SIGNIFICANCE: By following quantitative IFNgamma values in each enrolled child with LTBI or active TB and receiving treatment, we were able to detect an increase in the IFNgamma response at day 10 of treatment which might allow the confirmation of a diagnosis. In addition, a decline in IFNgamma values during treatment makes it possible for clinicians to monitor the effect of preventive or curative therapy

Phylogenetic Analysis and Prevalence of Urosepsis Strains of Escherichia coli Bearing Pathogenicity Island-Like Domains

We characterized 100 Escherichia coli urosepsis isolates from adult patients according to host compromise status by means of ribotyping, PCR phylogenetic grouping, and PCR detection of papG alleles and the virulence-related genes sfa/foc, fyuA, irp-2, aer, hly, cnf-1 and hra. We also tested these strains for copies of pap and hly and their direct physical linkage with other virulence genes in an attempt to look for pathogenicity islands (PAIs) described for the archetypal uropathogenic strains J96, CFT073, and 536. Most of the isolates belonged to E. coli phylogenetic groups B2 and D and bore papG allele II, aer, and fyuA/irp-2. papG allele II-bearing strains were more common in noncompromised patients, while papG allele-negative strains were significantly more frequent in compromised patients. Fifteen ribotypes were identified. The three archetypal strains harbored different ribotypes, and only one-third of our urosepsis strains were genetically related to one of the archetypal strains. Three and 18 strains harbored three and two copies of pap, respectively, and 5 strains harbored two copies of hly. papGIII was physically linked to hly, cnf-1, and hra (reported to be PAI II(J96)-like genetic elements) in 14% of the strains. The PAI II(J96)-like domain was inserted within pheR tRNA in 11 strains and near leuX tRNA in 3 strains. Moreover, the colocalized genes cnf-1, hra, and hly were physically linked to papGII in four strains and to no pap gene in three strains. papGII and hly (reported to be PAI I(CFT073)-like genetic elements) were physically linked in 16 strains, pointing to a PAI I(CFT073)-like domain. Three strains contained both a PAI II(J96)-like domain and a PAI I(CFTO73)-like domain. Forty-two strains harbored papGII but not hly, in keeping with the presence of a PAI II(CFT073)-like domain. Only one strain harbored a PAI I(536)-like domain (hly only), and none harbored a PAI I(J96)-like domain (papGI plus hly) or a PAI II(536)-like domain (papGIII plus hly). This study provides new data on the prevalence and variability of physical genetic linkage between pap and certain virulence-associated genes that are consistent with their colocalization on archetypal PAIs