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- Ahlinder, Jon, et al.
(författare)
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Oligotyping reveals divergent responses of predation resistant bacteria to aquatic productivity and plankton composition
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Predation-resistance has been suggested to be a key for persistence of pathogenic bacteria in aquatic environments. Little is known about driving factors for different types of protozoa resistant bacteria (PRB). We studied if presence of PRB is linked to specific plankton taxa, the aquatic nutrient state, or predation pressure on bacteria. Nineteen freshwater systems were sampled and analyzed for PRB, plankton composition and physicochemical variables. Three PRB genera were identified; Pseudomonas, Mycobacterium and Rickettsia. Use of minimum entropy decomposition algorithm and phylogenetic analysis showed that different nodes (representing OTUs of high taxonomic resolution) matched to environmental isolates of the three genera. Links between the PRB genera and specific plankton taxa were found, but showed different relationships depending on if 18S rRNA OTU or microscopy data were used in the analysis. Mycobacterium spp. was negatively correlated to aquatic nutrient state, while Pseudomonas showed the opposite pattern. Rickettsia spp. was positively related to predation pressure on bacteria. Both Mycobacterium and Rickettsia were more abundant in systems with high eukaryotic diversity, while Pseudomonas occurred abundantly in waters with low prokaryotic diversity. The different drivers may be explained by varying ecological strategies, where Mycobacterium and Rickettsia are slow growing and have an intracellular life style, while Pseudomonas is fast growing and opportunistic. Here we give an insight to the possibilities of newly advanced methods such as sequencing and oligotyping to link potential pathogens with biomarkers. This as a tool to assist predictions of the occurrence and persistence of environmental pathogens.
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| 2. |
- Allington, Megan, et al.
(författare)
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New Archaeointensity Results from the Iron Age in Southern Africa
- 2023
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Abstract In this study we present new palaeointensity measurements on Iron Age (200 AD – 1840 AD) pottery from the southern Africa region, where there is only limited data available at present. Many sites only produce a single accepted palaeointensity result and we have therefore opted to focus on analysis at sample level as opposed to site level, which is more common in traditional archaeomagnetic investigations. This strategy allows a large number of locations to be included and, as we demonstrate, a chance to evaluate regional and global geomagnetic field model predictions. Some of the initial palaeointensity estimates are anomalously low (< 10 µT), but after adding more strict criteria that relate to direction statistics, the intensity estimates that are accepted fall into a narrower range consistent with geomagnetic field model predictions. Overall, we find that the new data are consistent with the limited regional data and available secular variation curves. An archaeomagnetic dating example is presented following established procedures adapted for sample level data by considering that the real uncertainty of the palaeointensity estimate is largely unknown. The modified dating approach is applied to a Botswanan site from thisstudy, which is dated to the mid- to late- Iron Age.
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| 3. |
- Andersson, Agneta, et al.
(författare)
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Aquatic ecosystems at risk for occurrence of pathogenic bacteria
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Pathogenic bacteria occur naturally in aquatic systems. Co-existence of bacteria and protozoa has led to development of predation resistance strategies, which is suggested to serve as a driver for evolution of pathogenic bacteria. However, the ecological mechanisms for selection for different types of predation resistant and pathogenic bacteria are poorly known. To disentangle effects from nutrient availability and protozoan predation pressure on the occurrence of varying predation resistant bacterial genera, an enrichment-dilution experiment was performed where an aquatic bacterial community was exposed to protozoa. Operational taxonomical units, specific for three predation resistant bacterial genera were identified; Pseudomonas, Rickettsia and Mycobacterium. These genera are also known to harbor species that are potentially pathogenic to mammals. Rickettsia and Mycobacterium were promoted where protozoa were abundant and the predation pressure high, while Pseudomonas dominated the bacterial community at the highest nutrient level where the predation pressure on bacteria were low. Our study thus indicates that waters of all nutrient states can harbor pathogenic bacteria, but that bacteria with different ecological strategies occur depending on nutrient level and perturbation. The generative model approach presented here provide a possibility to integrate environmental data in prediction models of pathogens in complex environments.
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| 5. |
- Bergh, Andreas, et al.
(författare)
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More Open – Better Governed? Evidence from High- and Low-income Countries
- 2013
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Using World Bank data on institutional quality and the KOF Globalization Index, we examine over 100 countries from 1992 to 2010 to analyze the relationship between economic and social globalization and six measures of institutional quality. Theoretically, the incentives of elites to respond to globalization by improving institutions should differ between low-income and high-income countries. Empirically, increasing economic flows and social globalization are followed by improving institutions in rich countries, while the effect is the opposite for low-income countries. Previous findings of positive effects of trade on institutional quality are likely driven by rich countries.
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