IJUP08 - Universidade do Porto

Ultrastructural characterisation of Pirellula sp. OJF20
R. Abreu 1 , F. Viana 1 , J. Torres 1 , J. Bondoso 1,2 , A. Lobo-da-Cunha 2,3 and O.M. Lage 1,2
1 Departamento de Botânica, Faculdade de Ciências, Universidade do Porto
2 CIIMAR, Centro Interdisciplinar de Investigação Marinha e Ambiental
3 Instituto de Ciências Biomédicas Abel Salazar
Planctomycetes are a phylum of the domain Bacteria with particular morphologic and
structural characteristics, as peptidoglycan-less wall and intracellular compartmentalisation
(1, 2). These characteristics make them an important object of study for the clarification of
the phylogenetic relationships between microorganisms (the construction of the tree-oflife)
as well as prokaryotic and eukaryotic differentiation.
Pirellula sp. OJF20 (GenBank accession number-EF589346) was isolated from the surface
of macroalgae Corallina sp., sampled in a rocky beach in Foz, Porto, and belongs to a new
independent cluster close to the Rhodopirellula genus (94% similarity in the 16S rRNA
gene). Electron microscopy techniques such as negative staining, ultrathin section analysis
and ultracytochemistry were used to characterise this strain. Results showed that cell
organisation and life cycle is similar to that of R. baltica (3). They cells usually present an
ovoid shape, although polymorphism can be found especially in older cultures. Ultrathin
sectionsl revealed the presence of a paracrystaline structure well evident in the cytoplasm.
Probably this structure is a virus but new studies are now being performed to confirm its
nature.
1. Fuerst JA. 1995. The planctomycetes: Emerging models for microbial ecology, evolution
and cell biology. Microbiology 141: 1493-506
2. Fuerst JA. 2005. Intracellular compartmentation in planctomycetes. Annual Review of
Microbiology 59: 299-328
3. Gade, D, Stührmann, T, Reinhardt, R & Rabus, R. 2005. Growth phase dependent
regulation of protein composition in Rhodopirellula baltica. Environ. Microbiol. 7: 1074-
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