Planctomycetes

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Planctomycetes
Scientific classification
Domain: Bacteria
Phylum: Planctomycetes
Garrity & Holt 2001
Classes
Synonyms
  • Planctomycetaeota Oren et al. 2015

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, at the tip of a thin cylindrical extension from the cell body 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[edit]

For a long time bacteria belonging to this group were considered to 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. It was thought that instead their walls were made up of glycoprotein which is rich in glutamate. Recently, however, representatives of all three clades within the Planctomycetes were found to possess peptidoglycan containing cell walls.[1][2]

Planctomycetes have a distinctive morphology with the appearance of membrane-bound internal compartments, often referred to as the paryphoplasm (ribosome-free space), pirellulosome (ribosome-containing space) and nucleoid (condensed nucleic acid region, in these species surrounded by a double membrane).[3][4] Until the discovery of the Poribacteria, planctomycetes were the only bacteria known with these apparent internal compartments.[5] Three-dimensional electron tomography reconstruction of a representative species, Gemmata obscuriglobus, has yielded varying interpretations of this observation. One 2013 study found the appearance of internal compartments to be due to a densely invaginated but continuous single membrane, concluding that only the two compartments typical of Gram-negative bacteria - the cytoplasm and periplasm - are present. However, the excess membrane triples the surface area of the cell relative to its volume, which may be related to Gemmata's sterol biosynthesis abilities.[6] A 2014 study using similar methods reported confirmation of the earlier enclosed compartment hypothesis.[7]

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.[8][9]

Molecular Signatures[edit]

Although the Planctomycetes are renowned for their unusual cellular characteristics, their distinctness from all other bacteria is additionally supported by the shared presence of two conserved signature indels (CSIs).[10] These CSIs demarcate the group from neighboring phyla within the PVC group.[11] An additional CSI has been found that is shared by all Planctomycetes species, with the exception of Kuenenia stuttgartiensis, which is in line with the observation that K. stuttgartiensis forms a deep branch within the phylum.

A conserved signature indel has also been found to be shared by the entire PVC group, including Planctomycetes.[10][11] Planctomycetes also harbours an important conserved signature protein that has been characterized to play an important housekeeping function that is exclusive to members belonging to the PVC clade.[12]

Life cycle[edit]

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[edit]

The phylogeny based on the work of the All-Species Living Tree Project.[13]



Phycisphaerae

Phycisphaera mikrensis



Tepidisphaera mucosa



"Planctomycetia"



Planctopirus limnophila



Schlesneria paludicola





Gimesia maris




Planctomicrobium piriforme



Rubinisphaera brasiliensis







Rhodopirellula

R. rosea




R. baltica




R. rubra



R. lusitana







Pirellula staleyi


Blastopirellula

B. cremea



B. marina








Gemmata obscuriglobus




Telmatocola sphagniphila



Zavarzinella formosa






Isosphaera pallida




Aquisphaera giovannonii


Singulisphaera

S. acidiphila



S. rosea










Taxonomy[edit]

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LSPN)[14] and the National Center for Biotechnology Information (NCBI).[15]

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

See also[edit]

References[edit]

  1. ^ Jeske, O., Schueler, M., Schumann, P., Schneider, A., Boedeker, C., Jogler, M., Bollschweiler, D., Rohde, M., Mayer, C., Engelhardt, H., Spring, S. & Jogler, C. (2015). "Planctomycetes do possess a peptidoglycan cell wall". Nature Communications. 6: 7116. doi:10.1038/ncomms8116. PMC 4432640Freely accessible. PMID 25964217. 
  2. ^ van Teeseling, M.C.F., Mesman, R.J., Kuru, E., Espaillat, A., Cava, F., Brun, Y.V., VanNieuwenhze, M.S., Kartal, B & van Niftrik, L. (2015). "Anammox Planctomycetes have a peptidoglycan cell wall". Nature Communications. 6: 6878. doi:10.1038/ncomms7878. PMC 4432595Freely accessible. PMID 25962786. 
  3. ^ Lindsay, M. R.; Webb, R. I.; Strous, M; Jetten, M. S.; Butler, M. K.; Forde, R. J.; Fuerst, J. A. (2001). "Cell compartmentalisation in planctomycetes: Novel types of structural organisation for the bacterial cell". Archives of microbiology. 175 (6): 413–29. doi:10.1007/s002030100280. PMID 11491082. 
  4. ^ Glöckner, F. O.; Kube, M; Bauer, M; Teeling, H; Lombardot, T; Ludwig, W; Gade, D; Beck, A; Borzym, K; Heitmann, K; Rabus, R; Schlesner, H; Amann, R; Reinhardt, R (2003). "Complete genome sequence of the marine planctomycete Pirellula sp. Strain 1". Proceedings of the National Academy of Sciences. 100 (14): 8298–303. doi:10.1073/pnas.1431443100. PMC 166223Freely accessible. PMID 12835416. 
  5. ^ Fieseler, L; Horn, M; Wagner, M; Hentschel, U (June 2004). "Discovery of the novel candidate phylum "Poribacteria" in marine sponges.". Applied and Environmental Microbiology. 70 (6): 3724–32. doi:10.1128/aem.70.6.3724-3732.2004. PMC 427773Freely accessible. PMID 15184179. 
  6. ^ Santarella-Mellwig, R., Pruggnaller, S., Roos, N., Mattaj, I., & Devos, D. (2013). "Three-Dimensional Reconstruction of Bacteria with a Complex Endomembrane System". PLoS Biology. 11: e1001565. doi:10.1371/journal.pbio.1001565. PMC 3660258Freely accessible. PMID 23700385. 
  7. ^ Sagulenko, E; Morgan, G. P.; Webb, R. I.; Yee, B; Lee, K. C.; Fuerst, J. A. (2014). "Structural studies of planctomycete Gemmata obscuriglobus support cell compartmentalisation in a bacterium". PLoS ONE. 9 (3): e91344. doi:10.1371/journal.pone.0091344. PMC 3954628Freely accessible. PMID 24632833. 
  8. ^ Lonhienne, Thierry G. A.; Sagulenko, Evgeny; Webb, Richard I.; Lee, Kuo-Chang; Franke, Josef; Devos, Damien P.; Nouwens, Amanda; Carroll, Bernard J. & Fuerst, John A. (2010). "Endocytosis-like protein uptake in the bacterium Gemmata obscuriglobus". Proceedings of the National Academy of Sciences. 107 (29): 12883–12888. doi:10.1073/pnas.1001085107. PMC 2919973Freely accessible. PMID 20566852. 
  9. ^ Williams, Caroline (2011). "Who are you calling simple?". New Scientist. 211 (2821): 38–41. doi:10.1016/S0262-4079(11)61709-0 
  10. ^ a b Gupta RS, Bhandari V, Naushad HS (2012). "Molecular Signatures for the PVC Clade (Planctomycetes, Verrucomicrobia, Chlamydiae, and Lentisphaerae) of Bacteria Provide Insights into Their Evolutionary Relationships". Front Microbiol. 3: 327. doi:10.3389/fmicb.2012.00327. PMC 3444138Freely accessible. PMID 23060863. 
  11. ^ a b Gupta RS (2016). "Impact of genomics on the understanding of microbial evolution and classification: the importance of Darwin's views on classification". FEMS Microbiol Rev. 40 (4): 520–53. doi:10.1093/femsre/fuw011. PMID 27279642. 
  12. ^ Lagkouvardos I, Jehl MA, Rattei T, Horn M (2014). "Signature protein of the PVC superphylum". Appl Environ Microbiol. 80 (2): 440–445. doi:10.1128/AEM.02655-13. PMC 3911108Freely accessible. PMID 24185849. 
  13. ^ "16S rRNA-based LTP release 123 (full tree)" (PDF). Silva Comprehensive Ribosomal RNA Database. Retrieved 2016-03-20. 
  14. ^ J.P. Euzéby. "Planctomycetes". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2016-03-20. 
  15. ^ Sayers; et al. "Planctomycetes". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2016-03-20. 

External links[edit]