Journal of Microbiology

Journal Article

PprM is necessary for up-regulation of katE1, encoding the major catalase of Deinococcus radiodurans, under unstressed culture conditions: Sun-Wook Jeong , Ho Seong Seo , Min-Kyu Kim , Jong-Il Choi , Heon-Man Lim , Sangyong Lim; J. Microbiol. 2016;54(6):426-431. Published online May 27, 2016; DOI: https://doi.org/10.1007/s12275-016-6175-8

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Abstract: Deinococcus radiodurans is a poly-extremophilic organism, capable of tolerating a wide variety of different stresses, such as gamma/ultraviolet radiation, desiccation, and oxidative stress. PprM, a cold shock protein homolog, is involved in the radiation resistance of D. radiodurans, but its role in the oxidative stress response has not been investigated. In this study, we investigated the effect of pprM mutation on catalase gene expression. pprM disruption decreased the mRNA and protein levels of KatE1, which is the major catalase in D. radiodurans, under normal culture conditions. A pprM mutant strain (pprMMT) exhibited decreased catalase activity, and its resistance to hydrogen peroxide (H2O2) decreased accordingly compared with that of the wild-type strain. We confirmed that RecG helicase negatively regulates katE1 under normal culture conditions. Among katE1 transcriptional regulators, the positive regulator drRRA was not altered in pprM-, while the negative regulators perR, dtxR, and recG were activated more than 2.5-fold in pprMMT. These findings suggest that PprM is necessary for KatE1 production under normal culture conditions by down-regulation of katE1 negative regulators.

Research Support, Non-U.S. Gov'ts

Heat- and Cold-Shock Responses in Fusarium graminearum 3 Acetyl- and 15 Acetyl-Deoxynivalenol Chemotypes: Vladimir Vujanovic , Yit Kheng Goh , Prasad Daida; J. Microbiol. 2012;50(1):97-102. Published online February 27, 2012; DOI: https://doi.org/10.1007/s12275-012-1381-5

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Abstract: Fusarium graminearum Schwabe is the primary cause of Fusarium head blight (FHB) in North America. Chemically distinct F. graminearum sub-populations can be identified based on the type or composition of deoxynivalenol (DON) mycotoxin derivatives, including 3-acetyl (3-ADON) and 15-acetyl (15-ADON). The evaluation of randomly selected 3-ADON and 15-ADON isolates, collected from spring wheat throughout Canada, was performed using thin layer chromatography (TLC), high-performance liquid chromatography (HPLC), ice-nucleation activity (INA), and heat and cold tolerance tests conducted within a temperature range of -70°C to 65°C. The results indicated that the 3-ADON sub-population, which is responsible for the highest disease severity and has rapidly displaced the 15-ADON sub-population, produces more DON and zearalenone (ZEA) than the 15-ADON sub-population when exposed to heat and cold. Following exposures (1 and 2 h) to extremely high or low temperatures, 3-ADON isolates exhibited faster mycelial growth than 15-ADON isolates. In addition, the warmest temperature at which INA activity occurred was in 3-ADON (-3.6°C) vs. 15-ADON (-5.1°C). Taken together, these features suggest that the newly emerging 3-ADON sub-population is more resilient than the resident 15-ADON sub-population. Overall, the differences between the two sub-populations could provide new insights into FHB epidemiology and if validated under field conditions, may provide important information for predicting future FHB epidemics.

Rescue of a Cold-Sensitive Mutant at Low Temperatures by Cold Shock Proteins from Polaribacter irgensii KOPRI 22228: Ji-hyun Uh , Youn Hong Jung , Yoo Kyung Lee , Hong Kum Lee , Hana Im; J. Microbiol. 2010;48(6):798-802. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0402-5

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Abstract: Exposure to low temperatures induces the biosynthesis of specific sets of proteins, including cold shock proteins (Csps). Since many of the specific functions of pychrophilic Csps are unknown, the roles of Csps from an Arctic bacterium, Polaribacter irgensii KOPRI 22228, were examined. The genes encoding CspA and CspC of P. irgensii were cloned in this study. Sequence analysis showed that these proteins have cold shock domains containing two RNA-binding motifs, RNP1 and RNP2. Both proteins bound oligo(dT)-cellulose resins, suggesting single-stranded nucleic acid-binding activity. When the P. irgensii Csps were overexpressed in Escherichia coli, the cold-resistance of the host was increased by more than five-fold. The P. irgensii Csps also rescued a cold-sensitive E. coli csp-quadruple deletion strain, BX04, at low temperatures. These results suggest that Csps from P. irgensii play a role in survival in polar environments.

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