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Book of Abstracts: Albany 2005

category image Volume 22
No. 6
June 2005

Structural Organization of Bacterial Nucleoid

During growth bacteria normally pass through two major phases: an active, exponential growth phase and a ?tranquil? stationary phase. In accordance with the structure-function relation, the nucleoid, a bacterial analog of eukaryotic chromatin, is expected to have different structures in the two phases. Several factors seem to influence the nucleoid structure, including DNA supercoiling, macromolecular crowding, cellular polyamines, RNAs, histone-like proteins and specific DNA sequences. Malfunction of even one of the factors, resulting from physiological changes or mutations, leads to restructuring of the nucleoid.

Micrococcal nuclease (MNase) digestion of E.coli nucleoids from exponential and stationary phase cells showed different pattern of DNA fragments, reflecting changes in the structural organization of bacterial DNA during the growth process of E.coli cells. Composition of the fraction of the shortest DNA fragments after MNase digestion of E.coli nucleoids from exponential and stationary phase cells was analyzed. The results imply a relationship between MNase accessibility to DNA and transcriptional profile of the chromosome. We are currently testing whether in the folded chromosome genes with similar functions or regulation, even if they are distally located on the genomic DNA, are spatially close to each other, composing dynamic ?compartments?. Such functional ?compartmentalization? can allow maintaining high local concentration of regulators or enzymes near their ?targets?.

Konstantin Virnik1,*
Michael Tolstorukov2
Victor Zhurkin2
Sankar Adhya1

1Laboratory of Molecular Biology
2Laboratory of Experimental and Computational Biology
National Cancer Institute
Bethesda, MD 20892

*Phone: (301)-451-8803
Fax: (301)-496-2212
E-mail: virnikk@mail.nih.gov