The decay of mitochondrial activity of chlorella after heat stress / Effect of antimicrobial peptides on the growth of Escherichia coli

• Main Author: 白松穎
• Other Authors: Ban-Dar Hsu
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/56866005184286786713

碩士 === 國立清華大學 === 生物資訊與結構生物研究所 === 95 === When cell exposed to extreme environment, both their physiology and morphology change accordingly. In previous studies, we found that Chlorella pyrenoidosa exposed to heat stress (46.5℃) for one hour and cultured again under light or dark environment., their nuclear DNA would be condensed. If recultured under light, both chlorophylls and DNA would degrade. We thus speculated that heat stress plus readtirition might lead chlorella to go through a process of programmed cell death. In order to understand more about this process, we tried to detect the early DNA changes after heat stress by confocal microscopy and measured mitochondrial cell activity by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide (MTT) cell viability assay. Surprisingly, If re-culture was done in the dark, cells’ activity would reduce. Continuously, leading cells to death. On the other hand, under continuous illumination some cell would escape from death, and repaired normal chlorophyll fluorescence and cell activity. This repair system certainly is worthy to study further. Because antibiotic resistances of pathogens are growing worse these day , research about antimicrobial peptides (AMPs) has become more important. Many AMPs have bean discovered in animals and plants, insects. In this study, was focused on magainin 2(MG2), an AMP secreted from African clawed frog Xenopus laevis. We changed MG2’s amino acid sequence or the number of helix number, and tested their effect on Escherichia coli’s growth. Our data indicate no change in E.coli’s growth curve, when MG2 was expressing. However, expression of MG3, which lacked the C-terminal helix of MG2, inhibited the growth of E.coli. The mechanisms behind requires further study.