| 1. |
- Ahmerkamp, Soeren, et al.
(författare)
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Simultaneous visualization of flow fields and oxygen concentrations to unravel transport and metabolic processes in biological systems
- 2022
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Ingår i: CELL REPORTS METHODS. - : Elsevier. - 2667-2375. ; 2:5
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Tidskriftsartikel (refereegranskat)abstract
- From individual cells to whole organisms, O-2 transport unfolds across micrometer- tomillimeter-length scales and can change within milliseconds in response to fluid flows and organismal behavior. The spatiotemporal complexity of these processes makes the accurate assessment of O-2 dynamics via currently availablemethods difficult or unreliable. Here, we present "sensPIV,'' a method to simultaneously measure O-2 concentrations and flow fields. By tracking O-2-sensitive microparticles in flow using imaging technologies that allow for instantaneous referencing, wemeasuredO(2) transportwithin (1) microfluidic devices, (2) sinkingmodel aggregates, and (3) complex colony-forming corals. Through the use of sensPIV, we find that corals use ciliarymovement to link zones of photosynthetic O-2 production to zones of O-2 consumption. SensPIV can potentially be extendable to study flow-organism interactions across many life-science and engineering applications.
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| 2. |
- Alcolombri, Uria, et al.
(författare)
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Sinking enhances the degradation of organic particles by marine bacteria
- 2021
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Ingår i: Nature Geoscience. - : Springer Nature. - 1752-0894 .- 1752-0908. ; 14:10, s. 775-780
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Tidskriftsartikel (refereegranskat)abstract
- The sinking of organic particles in the ocean and their degradation by marine microorganisms is one of the main drivers of the biological pump. Yet, the mechanisms determining the magnitude of the pump remain poorly understood, limiting our ability to predict this carbon flux in future ocean scenarios. Current ocean models assume that the biological pump is governed by the competition between sinking speed and degradation rate, with the two processes independent from one another. Contrary to this paradigm, we show that sinking itself is a primary determinant of the rate at which bacteria degrade particles. Heterotrophic bacterial degradation rates were obtained from a laboratory study on model surface-colonized particles at atmospheric pressure under a range of flow speeds to mimic different sinking velocities. We find that even modest sinking speeds of 8 m day−1 enhance degradation rates more than 10-fold compared with degradation rates of non-sinking particles. We discovered that the molecular mechanism underlying this sinking-enhanced degradation is the flow-induced removal from the particles of the oligomeric breakdown products, which otherwise compete for enzymatic activity. This mechanism applies across several substrates and bacterial strains, suggesting its potentially broad occurrence under natural marine conditions. Integrating our findings into a mathematical model of particulate carbon flux, we propose that the coupling of sinking and degradation may contribute, in conjunction with other processes, to determining the magnitude of the vertical carbon flux in the ocean.
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| 3. |
- Behrendt, Lars, et al.
(författare)
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PhenoChip : A single-cell phenomic platform for high-throughput photophysiological analyses of microalgae
- 2020
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Ingår i: Science Advances. - : AMER ASSOC ADVANCEMENT SCIENCE. - 2375-2548. ; 6:36
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic microorganisms are key players in aquatic ecosystems with strong potential for bioenergy production, yet their systematic selection at the single-cell level for improved productivity or stress resilience ("phenotyping") has remained largely inaccessible. To facilitate the phenotyping of microalgae and cyanobacteria, we developed "PhenoChip," a platform for the multiparametric photophysiological characterization and selection of unicellular phenotypes under user-controlled physicochemical conditions. We used PhenoChip to expose single cells of the coral symbiont Symbiodinium to thermal and chemical treatments and monitor single-cell photophysiology via chlorophyll fluorometry. This revealed strain-specific thermal sensitivity thresholds and distinct pH optima for photosynthetic performance, and permitted the identification of single cells with elevated resilience toward rising temperature. Optical expulsion technology was used to collect single cells from PhenoChip, and their propagation revealed indications of transgenerational preservation of photosynthetic phenotypes. PhenoChip represents a versatile platform for the phenotyping of photosynthetic unicells relevant to biotechnology, ecotoxicology, and assisted evolution.
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| 4. |
- Carrara, Francesco, et al.
(författare)
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Bistability in oxidative stress response determines the migration behavior of phytoplankton in turbulence
- 2021
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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 (PNAS). - 0027-8424 .- 1091-6490. ; 118:5
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Tidskriftsartikel (refereegranskat)abstract
- Turbulence is an important determinant of phytoplankton physiology, often leading to cell stress and damage. Turbulence affects phytoplankton migration both by transporting cells and by triggering switches in migratory behavior, whereby vertically migrating cells can actively invert their direction of migration upon exposure to turbulent cues. However, a mechanistic link between single-cell physiology and vertical migration of phytoplankton in turbulence is currently missing. Here, by combining physiological and behavioral experiments with a mathematical model of stress accumulation and dissipation, we show that the mechanism responsible for the switch in the direction of migration in the marine raphidophyte Heterosigma akashiwo is the integration of reactive oxygen species (ROS) signaling generated by turbulent cues. Within timescales as short as tens of seconds, the emergent downward-migrating subpopulation exhibited a twofold increase in ROS, an indicator of stress, 15% lower photosynthetic efficiency, and 35% lower growth rate over multiple generations compared to the upward-migrating subpopulation. The origin of the behavioral split as a result of a bistable oxidative stress response is corroborated by the observation that exposure of cells to exogenous stressors (H2O2, UV-A radiation, or high irradiance), in lieu of turbulence, caused comparable ROS accumulation and an equivalent split into the two subpopulations. By providing a mechanistic link between the single-cell mechanics of swimming and physiology on the one side and the emergent population-scale migratory response and impact on fitness on the other, the ROS-mediated early warning response we discovered contributes to our understanding of phytoplankton community composition in future ocean conditions.
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| 5. |
- Lee, Kang Soo, et al.
(författare)
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Optofluidic Raman-activated cell sorting for targeted genome retrieval or cultivation of microbial cells with specific functions
- 2021
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Ingår i: Nature Protocols. - : Springer Nature. - 1754-2189 .- 1750-2799. ; 16:2
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotope labeling of microbial taxa of interest and their sorting provide an efficient and direct way to answer the question "who does what?" in complex microbial communities when coupled with fluorescence in situ hybridization or downstream 'omics' analyses. We have developed a platform for automated Raman-based sorting in which optical tweezers and microfluidics are used to sort individual cells of interest from microbial communities on the basis of their Raman spectra. This sorting of cells and their downstream DNA analysis, such as by mini-metagenomics or single-cell genomics, or cultivation permits a direct link to be made between the metabolic roles and the genomes of microbial cells within complex microbial communities, as well as targeted isolation of novel microbes with a specific physiology of interest. We describe a protocol from sample preparation through Raman-activated live cell sorting. Subsequent cultivation of sorted cells is described, whereas downstream DNA analysis involves well-established approaches with abundant methods available in the literature. Compared with manual sorting, this technique provides a substantially higher throughput (up to 500 cells per h). Furthermore, the platform has very high sorting accuracy (98.3 +/- 1.7%) and is fully automated, thus avoiding user biases that might accompany manual sorting. We anticipate that this protocol will empower in particular environmental and host-associated microbiome research with a versatile tool to elucidate the metabolic contributions of microbial taxa within their complex communities. After a 1-d preparation of cells, sorting takes on the order of 4 h, depending on the number of cells required. This protocol describes a microfluidic platform for high-throughput sorting of individual cells from microbial communities. Metabolically active cells are labeled using D2O or C-13, selected by Raman imaging, and sorted on-chip with optical tweezers.
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| 6. |
- Moor, Kathrin, et al.
(författare)
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High-avidity IgA protects the intestine by enchaining growing bacteria
- 2017
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 544:7651, s. 498-
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Tidskriftsartikel (refereegranskat)abstract
- Vaccine-induced high-avidity IgA can protect against bacterial enteropathogens by directly neutralizing virulence factors or by poorly defined mechanisms that physically impede bacterial interactions with the gut tissues ('immune exclusion')(1-3). IgA-mediated cross-linking clumps bacteria in the gut lumen and is critical for protection against infection by non-typhoidal Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium). However, classical agglutination, which was thought to drive this process, is efficient only at high pathogen densities (>= 10(8) non-motile bacteria per gram). In typical infections, much lower densities(4,5) (10(0)-10(7) colony-forming units per gram) of rapidly dividing bacteria are present in the gut lumen. Here we show that a different physical process drives formation of clumps in vivo: IgA-mediated cross-linking enchains daughter cells, preventing their separation after division, and clumping is therefore dependent on growth. Enchained growth is effective at all realistic pathogen densities, and accelerates pathogen clearance from the gut lumen. Furthermore, IgA enchains plasmid-donor and -recipient clones into separate clumps, impeding conjugative plasmid transfer in vivo. Enchained growth is therefore a mechanism by which IgA can disarm and clear potentially invasive species from the intestinal lumen without requiring high pathogen densities, inflammation or bacterial killing. Furthermore, our results reveal an untapped potential for oral vaccines in combating the spread of antimicrobial resistance.
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