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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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2. |
- Fu, Zhang, 1982, et al.
(author)
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On Communication Effectiveness of DoS-Resilient Adaptive Port Hopping
- 2011
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Reports (other academic/artistic)abstract
- Many network-based applications commonly open some known port(s) to communicate with their users, thus making themselves vulnerable to Denial of Service (DoS) attacks. With the purpose of solving this problem, a ``pseudo-random port-hopping'' approach was suggested by Badishi et al. and extended by Fu et al. to work for multi-peer applications in the presence of clock drifts. The suggested solution gives a synchronization algorithm which enables the clients and servers to communicate via communication ports changing periodically. Complementing the analytical study of the earlier work, here we study experimentally the effect of the combined parameter variations. We study the overhead and the efficiency of the algorithm in the presence of constant and various clock drifts, as well as the communication effectiveness under various attack conditions. We conclude that the algorithm's behavior follows the earlier analysis, even under situations of stress, e.g. large and even varying clock drifts.
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