Planctomycetales

Planctomycetales

Planctomycetes
Scientific classification
Domain: Bacteria
Phylum: Planctomycetes
Families & Genera
  • Phycisphaerae Fukunaga et al. 2010
    • Phycisphaerales Fukunaga et al. 2010
      • Phycisphaeraceae Fukunaga et al. 2010
        • Phycisphaera Fukunaga et al. 2010
  • Planctomycetacia Cavalier-Smith 2002
    • Planctomycetales Schlesner and Stackebrandt 1987
      •  ?Candidatus Nostocoida limicola III
      • Brocadiaceae
        • Candidatus Brocadia Jetten et al. 2001
        • Candidatus Kuenenia Schmid et al. 2000
        • Candidatus Scalindua Schmid et al. 2003
        • Candidatus Anammoxoglobus Kartal et al. 2006
        • Candidatus Jettenia Quan et al. 2008
      • Planctomycetaceae Schlesner and Stackebrandt 1987
        • Aquisphaera Bondoso et al. 2011
        • Blastopirellula Schlesner et al. 2004
        • Gemmata Franzmann and Skerman 1985
        • Isosphaera Giovannoni et al. 1995
        • Pirellula Schlesner and Hirsch 1987 emend. Schlesner et al. 2004
        • Planctomyces Gimesi 1924
        • Rhodopirellula Schlesner et al. 2004
        • Schlesneria Kulichevskaya et al. 2007
        • Singulisphaera Kulichevskaya et al. 2008 emend. Kulichevskaya et al. 2012
        • Telmatocola Kulichevskaya et al. 2012
        • Zavarzinella Kulichevskaya et al. 2009

Planctomycetes are a phylum of aquatic bacteria and are found in samples of brackish, and marine and fresh water. They reproduce by budding. In structure, the organisms of this group are ovoid and have a holdfast, called the stalk, at the nonreproductive end that helps them to attach to each other during budding.

Cavalier-Smith has postulated that the Planctomycetes are within the clade Planctobacteria in the larger clade Gracilicutes, but this is not generally accepted.

Structure

The bacteria belonging to this group lack peptidoglycan, (also called murein) in their cell walls, which is an important heteropolymer present in most bacterial cell walls that serves as a protective component. Instead their walls are made up of glycoprotein which is rich in glutamate. For a long time Planctomycetes were thought to be unique in that, unlike other prokaryotes, they contained intracellular compartments separated by membranes. Compartments that were often quoted in literature were paryphoplasm (ribosome-free space), pirellulosome (ribosome-containing space) and even a nucleoid surrounded by a double membrane.[1] However, Santarella-Mellwig et al have recently shown (2013), that the apparent internal compartments seen in microscope images of Gemmata obscuriglobus (a Planctomycetes species) are in fact interconnected and are surrounded by only a single highly convoluted membrane. Therefore, like other gram-negative bacteria Gemmata has only 2 compartments present, namely cytoplasm and periplasm. The authors calculated that excess of membrane triplicates the surface area of the cell relative to its volume and they suggest that this might have enabled Gemmata to retain an ancient pathway of sterol synthesis.[2]

It has recently been shown that Gemmata obscuriglobus is able to take in large molecules via a process which in some ways resembles endocytosis, the process used by eukaryotic cells to engulf external items.[3][4]

Genome

RNA sequencing shows that the planctomycetes are related to the Verrucomicrobia and possibly the Chlamydiae.[5] A number of essential pathways are not organised as operons, which is unusual for bacteria.[6] A number of genes have been found (through sequence comparisons) that are similar to genes found in eukaryotes. One such example is a gene sequence (in Gemmata obscuriglobus) that was found to have significant homology to the integrin alpha-V, a protein that is important in transmembrane signal transduction in eukaryotes.[7]

Life cycle

The life cycle of many planctomycetes involves alternation between sessile cells and flagellated swarmer cells. The sessile cells bud to form the flagellated swarmer cells which swim for a while before settling down to attach and begin reproduction.

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LSPN) [8] and the phylogeny is based on 16S rRNA-based LTP release 111 by The All-Species Living Tree Project [9]



Phycisphaera mikrensis Fukunaga et al. 2010


Planctomycetales

?Candidatus Nostocoida limicola III


Brocadiaceae
Candidatus Scalindua

?Candidatus S. arabica Woebken et al. 2008



?Candidatus S. marina Van de Vossenberg et al. 2007



?Candidatus S. profunda Van De Vossenberg et al. 2008



?Candidatus S. richardsii Fuchsman et al. 2012



Candidatus S. wagneri Schmid et al. 2003




Candidatus S. sorokinii Kuypers et al. 2003



Candidatus S. brodae Schmid et al. 2003






Candidatus Kuenenia stuttgartiensis Schmid et al. 2000



Candidatus Brocadia

Candidatus B. anammoxidans Jetten et al. 2001



Candidatus B. brasiliensis Araujo et al. 2011



Candidatus B. caroliniensis



Candidatus B. fulgida Kartal et al. 2004



Candidatus B. sinica Hu et al. 2010





Candidatus Anammoxoglobus propionicus Kartal et al. 2006



Candidatus Jettenia asiatica Quan et al. 2008






Planctomycetaceae
Planctomyces


?P. bekefiiGimesi 1924 (type sp.)



?P. guttaeformis(ex Hortobágyi 1965) Starr and Schmidt 1984



?P. stranskae(ex Wawrik 1952) Starr and Schmidt 1984




P. brasiliensis Schlesner 1990



P. maris (ex Bauld and Staley 1976) Bauld and Staley 1980





P. limnophilus Hirsch and Müller 1986



Schlesneria paludicola Kulichevskaya et al. 2007







Rhodopirellula

R. baltica Schlesner et al. 2004 (type sp.)



R. europaeaFrank 2011



R. maioricaFrank 2011



R. sallentinaFrank 2011





Blastopirellula marina (Schlesner 1987) Schlesner et al. 2004



Pirellula staleyi Schlesner and Hirsch 1987







Gemmata obscuriglobus Franzmann and Skerman 1985




Telmatocola sphagniphila Kulichevskaya et al. 2012



Zavarzinella formosa Kulichevskaya et al. 2009






Isosphaera pallida (ex Woronichin 1927) Giovannoni et al. 1995




Aquisphaera giovannonii Bondoso et al. 2011


Singulisphaera

?S. mucilaginosaZaicnikova et al. 2011



S. acidiphila Kulichevskaya et al. 2008 (type sp.)



S. rosea Kulichevskaya et al. 2012










Notes:
♠ Strains found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LSPN)
♪ Prokaryotes where no pure (axenic) cultures are isolated or available, i. e. not cultivated or can not be sustained in culture for more than a few serial passages

References

External links

  • Beyond Prokaryotes and Eukaryotes : Planctomycetes and Cell Organization.
  • Gemmata at Microbewiki