a Whole Genome Array Approach - Jacobs University

Background
1.2.1 Rhodopirellula baltica
Pirellula sp. strain 1, which now has been validated as "Rhodopirellula baltica
SH1 T "(Schlesner et al. 2004), is a marine aerobic, heterotrophic representative of the phylum
Planctomycetes. R. baltica was isolated from the
water column in the Kiel fjord which is part of the
Baltic Sea. The whole genome sequence of
R. baltica has been completed and published
(Glöckner et al. 2003) by the REGX project research
group at the Max Planck Institute for Marine
Microbiology, Germany (www.regx.de). With 7,145
Mb and 7,325 open reading frames, the genome of
R. baltica represented one of the largest bacterial
genomes sequenced at that time.
Fig 1 Rhodopirellula baltica EM (Schlesner et al. 2004)
1.2.1.1 Division and cell-cycle
The pear-shaped adult cells of Rhodopirellula baltica are non-motile and display a polar
organisation. From the smaller cell pole a holdfast substance of yet unknown chemical
composition is excreted. It mediates attachment of cells to surfaces or to each other leading to
the formation of rosettes (Fig 2). The broader cell pole is the site of budding. The bud is a
mirror image of the mother cell, except that it is smaller in size and has a single flagellum
inserted in a sub polar position at the proximate pole. At a certain developmental stage the
bud (daughter cell) is released as a motile swarmer. The swarmer cells abort their flagellum,
when differentiating into adult cells. Only these adult cells possess fimbriae that originate
from so-called crateriform structures at the broader (reproductive) cell pole (Olga Lang,
personal. communication). While these crateriform structures are restricted to the broader cell
pole in adult cells, they are observed across the complete cell surface of buds (Gade et al.
2005).
Gade and coworkers (Gade et al. 2005) showed that there is a correlation between distinct
morphotypes and different growth phases of R. baltica cultures based on microscopic
examination and analysis. As illustrated in the growth curve in Fig 2, during early stages of
growth numerous budding mother cells and swarmer cells are present. As growth proceeds,
the number of swarmers decreases, and single cells begin to attach to each other forming
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