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- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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- Marques, Wesley Leoricy, et al.
(author)
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Laboratory evolution and physiological analysis of Saccharomyces cerevisiae strains dependent on sucrose uptake via the Phaseolus vulgaris Suf1 transporter
- 2018
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In: Yeast. - : Wiley. - 0749-503X .- 1097-0061. ; 35:12, s. 639-652
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Journal article (peer-reviewed)abstract
- Knowledge on the genetic factors important for the efficient expression of plant transporters in yeast is still very limited. Phaseolus vulgaris sucrose facilitator 1 (PvSuf1), a presumable uniporter, was an essential component in a previously published strategy aimed at increasing ATP yield in Saccharomyces cerevisiae. However, attempts to construct yeast strains in which sucrose metabolism was dependent on PvSUF1 led to slow sucrose uptake. Here, PvSUF1-dependent S. cerevisiae strains were evolved for faster growth. Of five independently evolved strains, two showed an approximately twofold higher anaerobic growth rate on sucrose than the parental strain (mu = 0.19 h(-1) and mu = 0.08 h(-1), respectively). All five mutants displayed sucrose-induced proton uptake (13-50 mu mol H+ (g biomass)(-1) min(-1)). Their ATP yield from sucrose dissimilation, as estimated from biomass yields in anaerobic chemostat cultures, was the same as that of a congenic strain expressing the native sucrose symporter Mal11p. Four out of six observed amino acid substitutions encoded by evolved PvSUF1 alleles removed or introduced a cysteine residue and may be involved in transporter folding and/or oligomerization. Expression of one of the evolved PvSUF1 alleles (PvSUF1(I209F C265F G326C)) in an unevolved strain enabled it to grow on sucrose at the same rate (0.19 h(-1)) as the corresponding evolved strain. This study shows how laboratory evolution may improve sucrose uptake in yeast via heterologous plant transporters, highlights the importance of cysteine residues for their efficient expression, and warrants reinvestigation of PvSuf1's transport mechanism.
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- Nijenhuis, N, et al.
(author)
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The Use of Audio and Video in Synchronous Computer-Supported Collaborative Writing
- 2005
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Conference paper (peer-reviewed)abstract
- In this study the use of audio and video and the support of common ground was investigated in the context of the planning stage in the writing process. The esearch question for this study was: “Compared to the use of an audio communication modality, how is common ground supported by a video communication modality when people are planning a document together with the use of a collaborative writing tool?” To study how common ground was supported by an audio and video communication modality, the following definition of common ground was used: For a conversation to be effective the communicators need to understand each other, that means they are noticing and hearing each other, they understand what was said and what was meant. In total 45 participants took part in this study. The task was to make an outline about Sweden. A questionnaire was used to measure the support for common ground, satisfaction with the interaction and satisfaction with the outcome. Task performance was measured with the quality of the outlines. The outlines were reviewed and sorted on quality. The results for this study show that common ground is well supported by both communication modalities, but differences in support for common ground do exist. It is argued that video supports the creation and maintenance of common ground better in complex situations, which demand intensive collaboration, especially for non-native speakers of English.
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- Ortiz Catalan, Max Jair, 1982, et al.
(author)
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Virtual Reality
- 2014
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In: Biosystems and Biorobotics. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 2195-3570 .- 2195-3562. - 9783642385551 ; 4, s. 249-265
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Book chapter (other academic/artistic)abstract
- This chapter provides an overview on the use of Virtual Reality (VR) in rehabilitation with respect to recent neuroscience and physical therapy reviews of individuals with motor impairments. A wide range of technologies have been employed to provide rehabilitation supported by VR. Several studies have found evidence of the benefits of VR rehabilitation technologies. However, support for their efficacy is still limited due the lack of generalizable results and the uncoordinated effort of many individual, heterogeneous studies that have been conducted. Although VR has clear potential as a rehabilitation tool to improve treatment outcomes, future trials need to take into account the individual perspective of each patient group and consolidate research methodologies across trials to allow for stronger conclusions across the heterogeneous field of neurorehabilitation. Interventions must be designed with a strong focus on the patient’s needs and clinical outcomes, rather than on the technology available to the clinician.
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