Browsing publications of the department Central Unit of Microscopy [ZEIM] by Subjects
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IL-1β Promotes Biofilms on Implants .Implant associated infections represent a serious health burden in clinics since some microorganisms are able to colonize biological surfaces or surfaces of indwelling medical devices and form biofilms. Biofilms represent communities of microorganisms attached to hydrated surfaces and enclosed in self-produced extracellular matrix. This renders them resistant to exogenous assaults like antibiotics or immune effector mechanisms. Little is known regarding the role of the immune system in the formation of biofilms during implant associated infections, largely due to the lack of suitable mouse models. Here we use colonized osmotic pumps in mice to study the interaction of an activated immune system with biofilm-forming Staphylococcus aureus encoding Gaussia luciferase. This approach permits biofilm formation on the osmotic pumps in living animals. It also allows the continuous supply of soluble immune cell activating agents, such as cytokines to study their effect on biofilm formation in vivo. Using non-invasive imaging of the bioluminescent signal emitted by the lux expressing bacteria for quantification of bacterial load in conjunction with light and electron microscopy, we observed that pump-supplied pro-inflammatory cytokine IL-1β strongly increased biofilm formation along with a massive influx of neutrophils adjacent to the biofilm-coated pumps. Thus, our data demonstrate that immune defense mechanisms can augment biofilm formation.
Sulfate-Reducing Bacteria That Produce Exopolymers Thrive in the Calcifying Zone of a Hypersaline Cyanobacterial Mat.Calcifying microbial mats in hypersaline environments are important model systems for the study of the earliest ecosystems on Earth that started to appear more than three billion years ago and have been preserved in the fossil record as laminated lithified structures known as stromatolites. It is believed that sulfate-reducing bacteria play a pivotal role in the lithification process by increasing the saturation index of calcium minerals within the mat. Strain L21-Syr-ABT was isolated from anoxic samples of a several centimeters-thick microbialite-forming cyanobacterial mat of a hypersaline lake on the Kiritimati Atoll (Kiribati, Central Pacific). The novel isolate was assigned to the family Desulfovibrionaceae within the Deltaproteobacteria. Available 16S rRNA-based population surveys obtained from discrete layers of the mat indicate that the occurrence of a species-level clade represented by strain L21-Syr-ABT is restricted to a specific layer of the suboxic zone, which is characterized by the presence of aragonitic spherulites. To elucidate a possible function of this sulfate-reducing bacterium in the mineral formation within the mat a comprehensive phenotypic characterization was combined with the results of a comparative genome analysis. Among the determined traits of strain L21-Syr-ABT, several features were identified that could play a role in the precipitation of calcium carbonate: (i) the potential deacetylation of polysaccharides and consumption of substrates such as lactate and sulfate could mobilize free calcium; (ii) under conditions that favor the utilization of formate and hydrogen, the alkalinity engine within the mat is stimulated, thereby increasing the availability of carbonate; (iii) the production of extracellular polysaccharides could provide nucleation sites for calcium mineralization. In addition, our data suggest the proposal of the novel species and genus Desulfohalovibrio reitneri represented by the type strain L21-Syr-ABT (=DSM 26903T = JCM 18662T).