Studies on cytokinetic injury caused by high pressure treatment on E.coli and fission yeast

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If post-culture was made on E.coli cells for 90 min after they received high pressure treatment(HPT) at 75MPa for 30 min at 25℃, long filamentous cells of about 8 times longer than normal length were observed predominantly. FtsZ ring formation was greatly reduced in the filamentous cells. We already reported these observations. FtsZ protein has a low level of sequence similarity with tubulin α(or β). It can be said, therefore, that FtsZ is a bacterial cytoskeleton. We aimed to test whether cytoskeletones are also most sensitive to HPT in eukaryotic microorganisms such as fission yeast. Actin was fluorescently stained with rhodamine-phalloidine. Microtubule was visualized with YFP(yellow fluorescent protein) conjugated tubulin α. After HPT (100MPa for 30 min), microtubule, actin cable and contractile ring (constituted with actin and myosin) disappeared due to depolymerization. In the post-growth in a liquid culture medium, microtubule was restored after 6 hours and actin cable and contractile ring reappeared after 18 hours. It was concluded that actin cable and contractile ring were most sensitive to HPT. During the experiment of HPT on fission yeast, we happened to find chromosome condensation induced by HPT when DNA was visualized by DAPI staining. The condensation was relieved after 30 min of post-growth. It is well known that chromosome condensation occurs in the prophase of mitosis. HPT induced chromosome condensation was cell cycle-independent and occurred to higher compactness. Nuclear membrane did not shrink after HPT as confirmed by visualization of nuclear membrane by YFP-linked importin, indicating that chromosomal DNA itself did condense. HPT induced chromosome condensation did not require condensin (Cut3-Cut14 complex) that is necessary for cell cycle dependent one. HPT induced type condensation will be an urgent protective response against high pressure-stress.