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Model organism Synechocystis sp. PCC 6803 (cyanobacteria) in the modular laboratory photobioreactor setup
The Heinrich Heine University Düsseldorf (HHU) in cooperation with the University of Bielefeld and Photanol B.V. describes in their publication doi:10.1101/2021.07.26.453758 the experimental setup for research with the model microorganism cyanobacteria Synechocystis sp. PCC 6803. The described photobioreactor is a modular LAMBDA MINIFOR reactor system with peripheral devices and probes already available in the HHU laboratory:
doi.org/10.1101/2021.07.26.453758 Fig S7 of the full text version, picture courtesy of HHU Düsseldorf, Louis Goldschmidt. Uncoupling of the Diurnal Growth Program by Artificial Genome Relaxation in Synechocystis sp. PCC 6803. Anna Behle, Maximilian Dietsch, Louis Goldschmidt, Wandana Murugathas, David Brandt, Tobias Busche, Jörn Kalinowski, Oliver Ebenhöh, Ilka M. Axmann, Rainer Machné. bioRxiv 2021.07.26.453758 .
The species Synechocystis sp. PCC 6803 (S. sp. PCC 6803) belongs to the cyanobacteria and is a very slow-growing, unicellular model microorganism for the study of oxygenic photosynthesis.
The DNA of bacteria is present in vivo as an extremely packed, spiralized double helix - the DNA supercoiling. Due to the space-saving twisting, the DNA double helix fits into the bacteria. The researchers of HHU Düsseldorf manipulated the DNA supercoiling of cyanobacteria Synechocystis sp. PCC 6803 using CRISPRi-based knock-down of key genes involved in supercoiling deformation, gyrase subunits (gene subunits: gyrA and gyrB) and overexpression of topoisomerase I (= TopoI; gene: topA). The phenotypes of the cyanobacteria got characterized:
For studying the growth of the modified cyanobacteria, the researchers used the modular photo-bioreactor LAMBDA MINIFOR 1L PBR with peripheral devices - from third-party suppliers as well as from LAMBDA Laboratory Instruments - for the extended measurement and control systems.
The modular photo-bioreactor LAMBDA MINIFOR PBR was used to control the pH (pH = 8) and the temperature (30 °C) as well as to measure the pO2 and control the stirrer (5 Hz) of the liquid culture (1 litre). DASGIP OD4 device for measuring the optical density got also connected to the modular photo-bioreactor, as well as the mass flow meters for the gas supply (1 L/min with 0.5 % CO2-enriched air) and for the flow measurement of the off-gas in front of the measuring devices for the O2 and CO2 concentrations in the off-gas.
For the continuous culture (φ ≈ 0.24 d-1), LAMBDA feeding & harvest pumps connected to the LAMBDA scale module (for keeping the culture weight constant during chemostat) were used. Liquid media and NaOH consumption were recorded and quantified.
As a light source, a warm-white LED was used. The light intensity was controlled with the LAMBDA LUMO module for photo-bioreactors.
All manipulations to reduce supercoiling resulted in strong pleiotropic phenotype in which cell division has been blocked and cell volume growth continued.
More about cyanobacteria Synechocystis sp. and the photo-bioreactor setup can be found online:
Keywords: photobioreactor, laboratory, Synechocystis sp. PCC 6803, cyanobacteria, growth, model microorganism, DNA supercoiling, artificial genome relaxation, gyrase, topoisomerase I
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