7th joint conference "Joint Microbiology & Infection Conference 2024" of the DGHM and VAAM

<strong>Illuminating the two oscillators of Synechocystis sp. PCC 6803 using backscatter measurements</strong>

Microbial Cell Biology 

Poster Session 2

Poster Presentation

Abstract: Cyanobacteria use a circadian clock to predict environmental daily cycles and organize a multitude of cellular processes in matching daily rhythms. In the clock model organism Synechococcus elongatus PCC 7942 the clock is composed of the three proteins KaiA, KaiB and KaiC. Some cyanobacteria express multiple diverged Kai proteins, which implies that circadian regulation might be more complex in those organisms. In Synechocystis sp. PCC 6803 three KaiB and KaiC proteins are present. We chose it as a representative to study the function and interplay of diverged clock proteins in an otherwise well characterized model organism (1- 4). Based on homology searches, it was believed that all cyanobacteria contain only one copy of KaiA, but we discovered a second KaiA protein (KaiA3) in Synechocystis (5). Only the C-terminal domain of this new chimeric KaiA3 protein resembles a KaiA domain. The N-terminal domain is similar to a NarL-type response regulator receiver domain. Mixing KaiA3, KaiB3 and KaiC3, we could reconstitute low amplitude, temperature compensated ~24h oscillations of KaiC3 phosphorylation in vitro. This demonstrates that KaiA3B3C3 form a bona fide circadian oscillator. In the cell, KaiC3 displayed 24h phosphorylation rhythms that were phase-locked with KaiC1 phosphorylation cycles. Circadian rhythms can be simply read out via online monitoring of the backscatter properties of cells (6). Studies of kai gene deletion strains indicated that the KaiA1B1C1 oscillator and KaiA3B3C3 oscillator are both required to maintain stable backscatter oscillations, which implies that two interconnected oscillators are present in Synechocystis.  We are currently investigating the interplay of these two oscillators. 
 
(1) Wiegard A, Dörrich AK, Deinzer HT, Beck C, Wilde A, Holtzendorff J, Axmann IM. Microbiology (Reading). 2013 May;159(Pt 5):948-958. doi: 10.1099/mic.0.065425-0.  
(2) Beck C, Hertel S, Rediger A, Lehmann R, Wiegard A, Kölsch A, Heilmann B, Georg J, Hess WR, Axmann IM. Appl Environ Microbiol. 2014 Sep;80(17):5195-206. doi: 10.1128/AEM.01086-14.  
(3) Schmelling NM, Lehmann R, Chaudhury P, Beck C, Albers SV, Axmann IM, Wiegard A. BMC Evol Biol. 2017 Jul 21;17(1):169. doi: 10.1186/s12862-017-0999-7. P 
(4) Wiegard A, Köbler C, Oyama K, Dörrich AK, Azai C, Terauchi K, Wilde A, Axmann IM.  J Bacteriol. 2020 Jan 29;202(4):e00478-19. doi: 10.1128/JB.00478-19.  
(5) Köbler , Schmelling NM, Pawlowski A, Spät P, Scheurer NM, Sebastian K, Berwanger LC, Maček B, Wiegard A, Axmann IM, Wilde A. preprint,  bioRxiv 2021.07.20.453058; doi: https://doi.org/10.1101/2021.07.20.453058 
(6) Berwanger LC, Thumm N, Gholamipoor R, Wiegard A, Schlebusch J, Kollmann M, Axmann IM. preprint, bioRxiv 2023.09.26.559469; doi: https://doi.org/10.1101/2023.09.26.559469 

Anika Wiegard

Invited Speaker

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