Abstrait

Characterization of chromatin (nucleoid) from extreme halophilic archaeon Halobacterium salinarium H3 shows no nucleosomal organization

Ramaprasadarao Kotipatruni, Tangirala Suryanarayana

Halobacterium salinarium, a euryarchaeote, is a member of haloarchaea requiring at least 3.5MNaCl for optimal growth.We intended to biochemically analyze the chromatin from this organism because of the reported nucleosomal structure of the chromatin. Chromatin (nucleoid) was isolated fromH. salinariumH3. Nucleoid fractions isolated fromthemid logarithmic and late logarithmic phase cells were separated into two peaks (peaks I and II) by sucrose density gradient centrifugation. Growth cycle dependent variation in the two chromatin Peakswas observed as reported earlier. DNA and protein compositions were determined for the isolated chromatin factions frombothmid logarithmic and late logarithmic cells.Micrococcal nuclease digestion and agarose gel electrophoresis of the different chromatin factions showed absence of repeating units (nucleosome-like) of DNA protein complexes and DNA fragments did not resolve into DNA ladder pattern up on gel electrophoresis. Our results suggest that the chromatin of H. salinarium is more like bacterial and crenarchaeal chromatin and unlike that of other euryarchaeal chromatin fromthermophilic methanogens which is organized like mini nucleosomes with the help of histone fold proteins (e.g. HMf).