- Ultramicrobacteria
Ultramicrobacteria are
bacteria that are considerably smaller than normal bacterial cells and are 0.3 to 0.2micrometre s in diameter. This term was first used in 1981, to refer to cocci in seawater that were less than 0.3 μm in diameter. [cite journal |author=Torrella F, Morita RY |title=Microcultural Study of Bacterial Size Changes and Microcolony and Ultramicrocolony Formation by Heterotrophic Bacteria in Seawater |journal=Appl. Environ. Microbiol. |volume=41 |issue=2 |pages=518–527 |year=1981 |month=February |pmid=16345721 |pmc=243725 |url=http://aem.asm.org/cgi/pmidlookup?view=long&pmid=16345721] These cells have also been recovered from soil and appeared to be a mixture of Gram-positive and negative species. [cite journal |author=Iizuka T, Yamanaka S, Nishiyama T, Hiraishi A |title=Isolation and phylogenetic analysis of aerobic copiotrophic ultramicrobacteria from urban soil |journal=J. Gen. Appl. Microbiol. |volume=44 |issue=1 |pages=75–84 |year=1998 |month=February |pmid=12501296 |url=http://joi.jlc.jst.go.jp/JST.JSTAGE/jgam/44.75?from=PubMed] Many, if not all, these small bacteria are dormant forms of larger cells that allow survival under starvation conditions.cite journal | author = Velimirov, B. | year = 2001 | title = Nanobacteria, Ultramicrobacteria and Starvation Forms: A Search for the Smallest Metabolizing Bacterium | journal = Microbes and Environments | volume = 16 | issue = 2 | pages = 67-77 | url = http://www.jstage.jst.go.jp/article/jsme2/16/2/67/_pdf | accessdate = 2008-06-23] In this process cells downregulate their metabolism, stop growing and stabilize their DNA, creating dormant non-growing cells that can remain viable for many years. [cite journal |author=Costerton JW, Lewandowski Z, Caldwell DE, Korber DR, Lappin-Scott HM |title=Microbial biofilms |journal=Annu. Rev. Microbiol. |volume=49 |issue= |pages=711–45 |year=1995 |pmid=8561477 |doi=10.1146/annurev.mi.49.100195.003431] These starvation forms may be the most common type of ultramicrobacteria in seawater. [cite journal |author=Haller CM, Rölleke S, Vybiral D, Witte A, Velimirov B |title=Investigation of 0.2 µm filterable bacteria from the Western Mediterranean Sea using a molecular approach: dominance of potential starvation forms |journal=FEMS Microbiol. Ecol. |volume=31 |issue=2 |pages=153–161 |year=2000 |month=February |pmid=10640668]These small living bacterial cells are distinct from the purported "
nanobacteria " or "calcifying nanoparticles", which were proposed to be living organisms that were 0.1 μm in diameter. [cite journal |author=Urbano P, Urbano F |title=Nanobacteria: facts or fancies? |journal=PLoS Pathog. |volume=3 |issue=5 |pages=e55 |year=2007 |month=May |pmid=17530922 |pmc=1876495 |doi=10.1371/journal.ppat.0030055 |url=http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0030055] These structures are now thought to be non-living, [cite journal |author=Kajander EO |title=Nanobacteria--propagating calcifying nanoparticles |journal=Lett. Appl. Microbiol. |volume=42 |issue=6 |pages=549–52 |year=2006 |month=June |pmid=16706890 |doi=10.1111/j.1472-765X.2006.01945.x] and are probably precipitated particles of inorganic material. [cite journal |author=Raoult D, Drancourt M, Azza S, "et al" |title=Nanobacteria are mineralo fetuin complexes |journal=PLoS Pathog. |volume=4 |issue=2 |pages=e41 |year=2008 |month=February |pmid=18282102 |pmc=2242841 |doi=10.1371/journal.ppat.0040041 |url=http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0040041] [cite journal |author=Martel J, Young JD |title=Purported nanobacteria in human blood as calcium carbonate nanoparticles |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=105 |issue=14 |pages=5549–54 |year=2008 |month=April |pmid=18385376 |doi=10.1073/pnas.0711744105 |url=http://www.pnas.org/cgi/pmidlookup?view=long&pmid=18385376]References
External links
* [http://www.erc.montana.edu/MultiCellStrat/01-Waiting_UMB/default.htm Microbial biofilms: Waiting game for ultramicrobacteria]
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