AUTHOR=Yee Benjamin , Sagulenko Evgeny , Morgan Garry , Webb Richard , Fuerst John A.

TITLE=Electron tomography of the nucleoid of Gemmata obscuriglobus reveals complex liquid crystalline cholesteric structure

JOURNAL=Frontiers in Microbiology

VOLUME=3

YEAR=2012

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2012.00326

DOI=10.3389/fmicb.2012.00326

ISSN=1664-302X

ABSTRACT=<p>The nucleoid of the planctomycete <italic>Gemmata obscuriglobus</italic> is unique within the Bacteria in being both highly condensed and enclosed by a double-membrane nuclear envelope, seemingly analogous to the nucleus of eukaryotes. Here we have applied electron tomography to study high-pressure frozen, cryosubstituted cells of <italic>G. obscuriglobus</italic> and found multiple nested orders of DNA organization within the condensed nucleoid structure. Detailed examination of the nucleoid revealed a series of nested arcs characteristic of liquid crystalline cholesteric DNA structure. The finest fibers were arranged in parallel concentrically in a double-twist organization. At the highest order of nucleoid organization, several of these structures come together to form the core of the <italic>G. obscuriglobus</italic> nucleoid. The complex structure of DNA within this nucleoid may have implications for understanding the evolutionary significance of compartmentalized planctomycete cells.</p>