Cariti, F. | Search bioRxiv

bioRxiv2022

Observed Kinetics of Enterovirus Inactivation by Free Chlorine Is Host Cell-Dependent

The virucidal efficacy of disinfectants is typically assessed by infectivity assay utilizing a single type of host cell. Enteroviruses infect multiple host cells via different entry routes, and each entry route may be impaired to a varying extent by a given disinfectant. Yet, it is not known how the choice of host cells for titration affects the observed inactivation kinetics. Here, we evaluated the inactivation kinetics of echovirus 11 (E11) by free chlorine, ultraviolet (UV) irradiation, and heat, using three different host cells (BGMK, RD, and A549). E11 inactivation by free chlorine occurred at a two-fold greater rate when enumerated on BGMK cells compared to RD and A549 cells. Conversely, a comparable inactivation rate was observed for UV and heat independent of the host cell used. Host cell-dependent inactivation kinetics by free chlorine were also observed for echovirus 7, 9 and 13, and coxsackievirus A9, confirming that this phenomenon is not serotype-specific. Inactivation of E11 was partly caused by a loss in host cell attachment, which was most pronounced for BGMK cells, and which may be promoted by a lack of CD55 attachment receptors on this cell type. Additionally, BGMK cells lack a key subunit of the uncoating receptor, {beta}2M, which may further contribute to the differential inactivation kinetic for this cell type. Consequently, inactivation kinetics of enteroviruses should be assessed using host cells with different receptor profiles. This will yield a more complete understanding of the inactivating power of disinfectants targeting the viral attachment and/or uncoating. Graphic for Table of Contents (TOC) O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/509468v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@148461eorg.highwire.dtl.DTLVardef@1f3667corg.highwire.dtl.DTLVardef@cd75a3org.highwire.dtl.DTLVardef@e65616_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2020

Regulation of light harvesting in Chlamydomonas: two protein phosphatases are involved in state transitions

Protein phosphorylation plays important roles in short-term regulation of photosynthetic electron transfer. In a mechanism known as state transitions, the kinase STATE TRANSITION 7 (STT7) of Chlamydomonas reinhardtii phosphorylates components of light-harvesting antenna complex II (LHCII). This reversible phosphorylation governs the dynamic allocation of a part of LHCII to photosystem I or photosystem II, depending on light conditions and metabolic demands. Little is however known in the green alga on the counteracting phosphatase(s). In Arabidopsis, the homologous kinase STN7 is specifically antagonized by PROTEIN PHOSPHATASE 1/THYLAKOID-ASSOCIATED PHOSPHATASE 38 (PPH1/TAP38). Furthermore, the paralogous kinase STN8 and the countering phosphatase PHOTOSYSTEM II PHOSPHATASE (PBCP), which count subunits of PSII amongst their major targets, influence thylakoid architecture and high-light tolerance. Here we analyze state transitions in C. reinhardtii mutants of the two homologous phosphatases, CrPPH1 and CrPBCP. The transition from state 2 to state 1 is retarded in pph1, and surprisingly also in pbcp. However both mutants can eventually return to state 1. In contrast, the double mutant pph1;pbcp appears strongly locked in state 2. The complex phosphorylation patterns of the LHCII trimers and of the monomeric subunits are affected in the phosphatase mutants. Their analysis indicates that the two phosphatases have different yet overlapping sets of protein targets. The dual control of thylakoid protein de-phosphorylation and the more complex antenna phosphorylation patterns in Chlamydomonas compared to Arabidopsis are discussed in the context of the stronger amplitude of state transitions and the more diverse LHCII isoforms in the alga.

plant biology↗