| 1. |
- Becher, Paul G., et al.
(författare)
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Developmentally regulated volatiles geosmin and 2-methylisoborneol attract a soil arthropod to Streptomyces bacteria promoting spore dispersal
- 2020
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Ingår i: Nature Microbiology. - : Springer Science and Business Media LLC. - 2058-5276.
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Tidskriftsartikel (refereegranskat)abstract
- Volatile compounds emitted by bacteria are often sensed by other organisms as odours, but their ecological roles are poorly understood1,2. Well-known examples are the soil-smelling terpenoids geosmin and 2-methylisoborneol (2-MIB)3,4, which humans and various animals sense at extremely low concentrations5,6. The conservation of geosmin biosynthesis genes among virtually all species of Streptomyces bacteria (and genes for the biosynthesis of 2-MIB in about 50%)7,8, suggests that the volatiles provide a selective advantage for these soil microbes. We show, in the present study, that these volatiles mediate interactions of apparent mutual benefit between streptomycetes and springtails (Collembola). In field experiments, springtails were attracted to odours emitted by Streptomyces colonies. Geosmin and 2-MIB in these odours induce electrophysiological responses in the antennae of the model springtail Folsomia candida, which is also attracted to both compounds. Moreover, the genes for geosmin and 2-MIB synthases are under the direct control of sporulation-specific transcription factors, constraining emission of the odorants to sporulating colonies. F. candida feeds on the Streptomyces colonies and disseminates spores both via faecal pellets and through adherence to its hydrophobic cuticle. The results indicate that geosmin and 2-MIB production is an integral part of the sporulation process, completing the Streptomyces life cycle by facilitating dispersal of spores by soil arthropods.
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| 2. |
- Schlimpert, Susan, et al.
(författare)
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Two dynamin-like proteins stabilize FtsZ rings during Streptomyces sporulation
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 114:30, s. 6176-6183
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Tidskriftsartikel (refereegranskat)abstract
- During sporulation, the filamentous bacteria Streptomyces undergo a massive cell division event in which the synthesis of ladders of sporulation septa convert multigenomic hyphae into chains of unigenomic spores. This process requires cytokinetic Z-rings formed by the bacterial tubulin homolog FtsZ, and the stabilization of the newly formed Z-rings is crucial for completion of septum synthesis. Here we show that two dynamin-like proteins, DynA and DynB, play critical roles in this process. Dynamins are a family of large, multidomain GTPases involved in key cellular processes in eukaryotes, including vesicle trafficking and organelle division. Many bacterial genomes encode dynamin-like proteins, but the biological function of these proteins has remained largely enigmatic. Using a cell biological approach, we show that the two Streptomyces dynamins specifically localize to sporulation septa in an FtsZ-dependent manner. Moreover, dynamin mutants have a cell division defect due to the decreased stability of sporulation-specific Z-rings, as demonstrated by kymographs derived from time-lapse images of FtsZ ladder formation. This defect causes the premature disassembly of individual Z-rings, leading to the frequent abortion of septum synthesis, which in turn results in the production of long spore-like compartments with multiple chromosomes. Two-hybrid analysis revealed that the dynamins are part of the cell division machinery and that they mediate their effects on Z-ring stability during developmentally controlled cell division via a network of protein–protein interactions involving DynA, DynB, FtsZ, SepF, SepF2, and the FtsZ-positioning protein SsgB.
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| 3. |
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| 4. |
- Venkateshvaran, Ashwin, et al.
(författare)
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The impact of arterial load on left ventricular performance : An invasive haemodynamic study in severe mitral stenosis
- 2015
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Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 593:8, s. 1901-1912
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Tidskriftsartikel (refereegranskat)abstract
- Key points: A hallmark of mitral stenosis (MS) is the markedly altered left ventricular (LV) loading. As most of the methods used to determine LV performance in MS patients are influenced by loading conditions, previous studies have shown conflicting results. The present study calculated LV elastance, which is a robust method to quantify LV function. We demonstrate that LV loading in MS patients is elevated but normalizes after valve repair and might be a result of reflex pathways. Additionally, we show that the LV in MS is less compliant than normal due to a combination of right ventricular loading and the valvular disease itself. Immediately after valve dilatation the increase in blood inflow into the LV results in even greater LV stiffness. Our findings enrich our understanding of heart function in MS patients and provide a simple reproducible way of assessing LV performance in MS. Left ventricular (LV) function in rheumatic mitral stenosis (MS) remains an issue of controversy, due to load dependency of previously employed assessment methods. We investigated LV performance in MS employing relatively load-independent indices robust to the altered loading state. We studied 106 subjects (32 ± 8 years, 72% female) with severe MS (0.8 ± 0.2 cm2) and 40 age-matched controls. MS subjects underwent simultaneous bi-ventricular catheterization and transthoracic echocardiography (TTE) before and immediately after percutaneous transvenous mitral commisurotomy (PTMC). Sphygmomanometric brachial artery pressures and TTE recordings were simultaneously acquired in controls. Single-beat LV elastance (Ees) was employed for LV contractility measurements. Effective arterial elastance (Ea) and LV diastolic stiffness were measured. MS patients demonstrated significantly elevated afterload (Ea: 3.0 ± 1.3 vs. 1.5 ± 0.3 mmHg ml-1; P < 0.001) and LV contractility (Ees: 4.1 ± 1.6 vs. 2.4 ± 0.5 mmHg ml-1; P < 0.001) as compared to controls, with higher Ea in subjects with smaller mitral valve area (≤ 0.8 cm2) and pronounced subvalvular fusion. Stroke volume (49 ± 16 to 57 ± 17 ml; P < 0.001) and indexed LV end-diastolic volume (LVEDVindex: 57 ± 16 to 64 ± 16 ml m-2; P < 0.001) increased following PTMC while Ees and Ea returned to more normal levels. Elevated LV stiffness was demonstrated at baseline and increased further following PTMC. Our findings provide evidence of elevated LV contractility, increased arterial load and increased diastolic stiffness in severe MS. Following PTMC, both LV contractility and afterload tend to normalize.
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