Editing Mesosome

{{Short description|Structures in bacteria}}
{{For|the arthropod anatomical term|mesosoma}}
[[File:Mesosome formation.svg|thumb|right|250px|Mesosomes form in bacterial cells prepared for [[electron microscopy]] by chemical fixation, but not by freeze-fracture fixation.<ref>{{cite journal |author=Nanninga N |title=The mesosome of Bacillus subtilis as affected by chemical and physical fixation |journal=J. Cell Biol. |volume=48 |issue=1 |pages=219–24 |year=1971 |pmid=4993484 |doi=10.1083/jcb.48.1.219 |pmc=2108225}}</ref>]]

'''Mesosomes''' or chondrioids are folded [[invagination]]s in the [[plasma membrane]] of [[bacteria]] that are produced by the chemical [[Fixation (histology)|fixation]] techniques used to prepare samples for [[electron microscopy]]. Although several functions were proposed for these structures in the 1960s, they were recognized as [[Artifact (error)|artifacts]] by the late 1970s and are no longer considered to be part of the normal structure of bacterial cells. These extensions are in the form of vesicles, tubules and lamellae.

==Initial observations==
These structures are invaginations of the plasma membrane observed in [[gram-positive]] bacteria that have been chemically [[Fixation (histology)|fixed]] to prepare them for electron microscopy.<ref name=Silva/> They were first observed in 1953 by George B. Chapman and James Hillier,<ref name=Chapman1953>{{cite journal|author1=Chapman, George B. |author2=Hillier, James  |name-list-style=amp | year = 1953 | title = Electron microscopy of ultra-thin sections of bacteria I. Cellular division in Bacillus cereus | journal = J. Bacteriol. |volume=66 |issue=3 | pages = 362–373|doi=10.1128/JB.66.3.362-373.1953 |pmid=13096487 |pmc=357155 }}</ref> who referred to them as "peripheral bodies." They were termed "mesosomes" by Fitz-James in 1960.<ref name=Robertson1959>{{cite journal | author = Robertson, J.D. | year = 1959 | title = The ultra structure of cell membranes and their derivatives, Biochem | journal = Soc. Syrup | pages = 3}}</ref>

Initially, it was thought that mesosomes might play a role in several cellular processes, such as [[cell wall]] formation during [[cell division]], [[chromosome]] replication, or as a site for [[oxidative phosphorylation]].<ref>{{cite journal |author=Suganuma A |title=Studies on the fine structure of Staphylococcus aureus |journal=J Electron Microsc (Tokyo) |volume=15 |issue=4 |pages=257–61 |year=1966 |pmid=5984369}}</ref><ref>{{cite journal |vauthors=Pontefract RD, Bergeron G, Thatcher FS |title=Mesosomes in Escherichia coli |journal=J. Bacteriol. |volume=97 |issue=1 |pages=367–75 |year=1969 |pmid=4884819 |url= |doi=10.1002/path.1710970223 |pmc=249612}}</ref> The mesosome was thought to increase the surface area of the cell, aiding the cell in cellular respiration. This is analogous to [[cristae]] in the [[mitochondrion]] in eukaryotic cells, which are finger-like projections and help eukaryotic cells undergo cellular respiration. Mesosomes were also hypothesized to aid in photosynthesis, cell division, DNA replication, and cell compartmentalisation.

==Disproof of hypothesis==
These models were called into question during the late 1970s when data accumulated suggesting that mesosomes are artifacts formed through damage to the membrane during the process of chemical fixation, and do not occur in cells that have not been chemically fixed.<ref name=Silva>{{cite journal |vauthors=Silva MT, Sousa JC, Polónia JJ, Macedo MA, Parente AM |title=Bacterial mesosomes. Real structures or artifacts? |journal=Biochim. Biophys. Acta |volume=443 |issue=1 |pages=92–105 |year=1976 |pmid=821538 |doi=10.1016/0005-2736(76)90493-4}}</ref><ref>{{cite journal |vauthors=Ebersold HR, Cordier JL, Lüthy P |title=Bacterial mesosomes: method dependent artifacts |journal=Arch. Microbiol. |volume=130 |issue=1 |pages=19–22 |year=1981 |pmid=6796029 |doi=10.1007/BF00527066|bibcode=1981ArMic.130...19E |s2cid=4430755 }}</ref><ref>{{cite journal |vauthors=Higgins ML, Tsien HC, Daneo-Moore L |title=Organization of mesosomes in fixed and unfixed cells |journal=J. Bacteriol. |volume=127 |issue=3 |pages=1519–23 |year=1976 |doi=10.1128/JB.127.3.1519-1523.1976 |pmid=821934 |pmc=232947}}</ref> By the mid to late 1980s, with advances in cryofixation and freeze substitution methods for electron microscopy, it was generally concluded that mesosomes do not exist in living cells.<ref>{{cite journal |author=Ryter A |title=Contribution of new cryomethods to a better knowledge of bacterial anatomy |journal=Ann. Inst. Pasteur Microbiol. |volume=139 |issue=1 |pages=33–44 |year=1988 |pmid=3289587 |doi=10.1016/0769-2609(88)90095-6}}</ref><ref>{{cite journal |vauthors=Nanninga N, Brakenhoff GJ, Meijer M, Woldringh CL |title=Bacterial anatomy in retrospect and prospect |journal=Antonie van Leeuwenhoek |volume=50 |issue=5–6 |pages=433–60 |year=1984 |pmid=6442119 |doi=10.1007/BF02386219|s2cid=7015394 }}</ref><ref>{{cite journal |vauthors=Dubochet J, McDowall AW, Menge B, Schmid EN, Lickfeld KG |title=Electron microscopy of frozen-hydrated bacteria |journal=J. Bacteriol. |volume=155 |issue=1 |pages=381–90 |date=1 July 1983|doi=10.1128/JB.155.1.381-390.1983 |pmid=6408064 |pmc=217690 }}</ref> However, a few researchers continue to argue that the evidence remains inconclusive, and that mesosomes might not be artifacts in all cases.<ref>John F. Stolz (1991) [https://books.google.com/books?id=Ly0OnkNJu00C "Structure of Phototrophic Prokaryotes"] CRC Press {{ISBN|0-8493-4814-5}}</ref><ref name=Murata2008>{{cite journal | author = Murata, K. |author2=Kawai, S. |author3=Mikami, B. |author4=Hashimoto, W. | year = 2008 | title = Superchannel of Bacteria: Biological Significance and New Horizons | journal = Bioscience, Biotechnology, and Biochemistry | pages = 265–277 | volume = 72 |issue=2 | doi = 10.1271/bbb.70635 | pmid=18256495|s2cid=33051803 | doi-access = free }}</ref>

Recently, similar folds in the membrane have been observed in bacteria that have been exposed to some classes of [[antibiotic]]s,<ref>{{cite journal  |vauthors=Santhana Raj L, Hing HL, Baharudin O, etal |title=Mesosomes are a definite event in antibiotic-treated Staphylococcus aureus ATCC 25923 |journal=Trop Biomed |volume=24 |issue=1 |pages=105–9 |year=2007 |pmid=17568383}}</ref> and antibacterial peptides ([[defensin]]s).<ref>{{cite journal |vauthors=Friedrich CL, Moyles D, Beveridge TJ, Hancock RE |title=Antibacterial action of structurally diverse cationic peptides on gram-positive bacteria |journal=Antimicrob. Agents Chemother. |volume=44 |issue=8 |pages=2086–92 |year=2000 |pmid=10898680 |doi=10.1128/AAC.44.8.2086-2092.2000 |pmc=90018}}</ref> The appearance of these mesosome-like structures may be the result of these chemicals damaging the plasma membrane and/or cell wall.<ref>{{cite journal |vauthors=Balkwill DL, Stevens SE |title=Effects of penicillin G on mesosome-like structures in Agmenellum quadruplicatum |journal=Antimicrob. Agents Chemother. |volume=17 |issue=3 |pages=506–9 |year=1980 |pmid=6775592 |doi= 10.1128/aac.17.3.506|pmc=283817}}</ref>

The case of the proposal and then disproof of the mesosome [[hypothesis]] has been discussed from the viewpoint of the [[philosophy of science]] as an example of how a scientific idea can be [[falsifiability|falsified]] and the hypothesis then rejected, and analyzed to explore how the [[scientific community]] carries out this testing process.<ref name=Culp1994>{{cite journal | author = Culp, S. | year = 1994 | title = Defending Robustness: The Bacterial Mesosome as a Test Case | journal = PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association | volume = 1994 | pages = 46–57 | jstor=193010| doi = 10.1086/psaprocbienmeetp.1994.1.193010 | s2cid = 112215147 }}</ref><ref name=Rasmussen2001>{{cite journal | author = Rasmussen, N. | year = 2001 | title = Evolving Scientific Epistemologies and the Artifacts of Empirical Philosophy of Science: A Reply Concerning Mesosomes | journal = Biology and Philosophy | volume = 16 | issue = 5 | pages = 627–652 | doi = 10.1023/A:1012038815107| s2cid = 142344737 }}</ref><ref name=Allchin2000>{{cite journal | author = Allchin, D. | year = 2000 | title = The Epistemology of Error | journal = Philosophy of Science Association Meetings, Vancouver, November | url = http://cbe.ivic.ve/mic250/pdf/epist-of.pdf | accessdate = 2008-03-08 | url-status = dead | archiveurl = https://web.archive.org/web/20081217143936/http://cbe.ivic.ve/mic250/pdf/epist-of.pdf | archivedate = 2008-12-17 }}</ref>

==See also==
*[[Cell membrane]]
*[[Organelle]]
*[[Lysosome]]

== References ==
{{Reflist|2}}

==Further reading==
*{{cite journal |author = Fritz H. Kayser, M.D. | year = 2005 | title = Color Atlas of Medical Microbiology.Kayser, Medical Microbiology © 2005 Thieme}}

[[Category:Membrane biology]]
[[Category:Organelles]]
[[Category:Prokaryotic cell anatomy]]