Bacterial genomic DNA is highly organized into one or few compacted bodies known as nucleoid, which is composed of DNA, RNA and several DNA-binding proteins. These DNA-binding proteins require essential alterations in...Bacterial genomic DNA is highly organized into one or few compacted bodies known as nucleoid, which is composed of DNA, RNA and several DNA-binding proteins. These DNA-binding proteins require essential alterations in their expression during stationary phase of growth in order to re-spond to stressful environmental conditions. Dps (DNA-binding protein from starved cells) is one of such DNA-binding proteins, which accumulates most when E. coli cells reach to the stationary phase. Here, we have characterized Dps protein under various growth phases. Immunofluorescent microscopic observation reveals that Dps plays a key role in final round of genome compaction during the stationary phase. Similar results are also obtained by Western immunoblot analysis, after quantification of Dps protein from the exponential phase and early stationary phase nucleoid bound fractions, separated by sucrose density gradient centrifugation. Our results support the conclusion that Dps occupies more than half of the stationary phase nucleoid in E. coli.展开更多
The genomic DNA of bacteria is highly compacted in one or a few bodies known as nucleoids. In order to understand the overall configuration and physiological activities of the cyanobacterial nucleoid under various gro...The genomic DNA of bacteria is highly compacted in one or a few bodies known as nucleoids. In order to understand the overall configuration and physiological activities of the cyanobacterial nucleoid under various growth conditions and the role(s) of each nucleoid protein in clock function, thylakoid membrane-associated nucleoids from the Synechococcus elongatus (se) PCC 7942 strain were isolated and purified in presence of spermidine at low salt concentrations by sucrose density gradient centrifugation. The sedimentation rates, protein/DNA composition and microscopic appearances as well as variation in structural components of clock proteins from the isolated nucleoids were compared under identical conditions. Microscopic appearances of the nucleoids were consistent with the sedimentation profiles. The nucleoid structure in the wild type was more tightly compacted than that in the KaiABC mutant strain. Western immunoblot analyses revealed that the KaiC was associated with the nucleoid fraction whereas maximum KaiA was localized in the cytosolic fraction, supposedly in association with the translation machinery.展开更多
文摘Bacterial genomic DNA is highly organized into one or few compacted bodies known as nucleoid, which is composed of DNA, RNA and several DNA-binding proteins. These DNA-binding proteins require essential alterations in their expression during stationary phase of growth in order to re-spond to stressful environmental conditions. Dps (DNA-binding protein from starved cells) is one of such DNA-binding proteins, which accumulates most when E. coli cells reach to the stationary phase. Here, we have characterized Dps protein under various growth phases. Immunofluorescent microscopic observation reveals that Dps plays a key role in final round of genome compaction during the stationary phase. Similar results are also obtained by Western immunoblot analysis, after quantification of Dps protein from the exponential phase and early stationary phase nucleoid bound fractions, separated by sucrose density gradient centrifugation. Our results support the conclusion that Dps occupies more than half of the stationary phase nucleoid in E. coli.
文摘The genomic DNA of bacteria is highly compacted in one or a few bodies known as nucleoids. In order to understand the overall configuration and physiological activities of the cyanobacterial nucleoid under various growth conditions and the role(s) of each nucleoid protein in clock function, thylakoid membrane-associated nucleoids from the Synechococcus elongatus (se) PCC 7942 strain were isolated and purified in presence of spermidine at low salt concentrations by sucrose density gradient centrifugation. The sedimentation rates, protein/DNA composition and microscopic appearances as well as variation in structural components of clock proteins from the isolated nucleoids were compared under identical conditions. Microscopic appearances of the nucleoids were consistent with the sedimentation profiles. The nucleoid structure in the wild type was more tightly compacted than that in the KaiABC mutant strain. Western immunoblot analyses revealed that the KaiC was associated with the nucleoid fraction whereas maximum KaiA was localized in the cytosolic fraction, supposedly in association with the translation machinery.
