Editing Clostridium botulinum (section)

==Microbiology==

''C. botulinum ''is a [[Gram-positive bacteria|Gram-positive]], rod-shaped, spore-forming [[bacterium]].<ref name = "Tiwari_2021" /> It is an [[obligate anaerobe]], requiring an environment that lacks [[oxygen]]. However, ''C. botulinum'' tolerates traces of oxygen due to the enzyme [[superoxide dismutase]], which is an important antioxidant defense in nearly all cells exposed to oxygen.<ref name="Brock">{{cite book | vauthors = Doyle MP | title = Food Microbiology: Fundamentals and Frontiers | publisher = ASM Press| year = 2007 | isbn = 978-1-55581-208-9}}</ref> ''C. botulinum'' is able to produce the neurotoxin only during sporulation, which can happen only in an anaerobic environment.

''C. botulinum'' is divided into four distinct [[phenotypic]] groups (I-IV) and is also classified into seven [[serotype]]s (A–G) based on the [[antigenicity]] of the botulinum toxin produced.<ref>{{cite journal | vauthors = Peck MW, Stringer SC, Carter AT | title = Clostridium botulinum in the post-genomic era | journal = Food Microbiology | volume = 28 | issue = 2 | pages = 183–191 | date = April 2011 | pmid = 21315972 | doi = 10.1016/j.fm.2010.03.005 }}</ref><ref>{{cite journal | vauthors = Shukla HD, Sharma SK | title = Clostridium botulinum: a bug with beauty and weapon | journal = Critical Reviews in Microbiology | volume = 31 | issue = 1 | pages = 11–18 | year = 2005 | pmid = 15839401 | doi = 10.1080/10408410590912952 | s2cid = 2855356 }}</ref> On the level visible to DNA sequences, the phenotypic grouping matches the results of whole-genome and [[rRNA]] analyses,<ref name="ScienceDirect 2003 pp. 1407"/><ref name=Dobritsa18/> and setotype grouping approximates the result of analyses focused specifically on the toxin sequence. The two [[phylogenetic tree]]s do not match because of the ability of the toxin [[gene cluster]] to be horizontally transferred.<ref name=Hill>{{cite book | vauthors = Hill KK, Smith TJ |chapter=Genetic Diversity Within Clostridium botulinum Serotypes, Botulinum Neurotoxin Gene Clusters and Toxin Subtypes |title=Botulinum Neurotoxins |series=Current Topics in Microbiology and Immunology |date=2012 |volume=364 |pages=1–20 |doi=10.1007/978-3-642-33570-9_1|pmid=23239346 |isbn=978-3-642-33569-3 |url=https://www.researchgate.net/publication/233914979}}</ref>

=== Serotypes ===
{{Main|Botulinum toxin}}
[[Botulinum toxin|Botulinum neurotoxin]] (BoNT) production is the unifying feature of the species. Seven [[serotypes]] of [[toxins]] have been identified that are allocated a letter (A–G), several of which can cause disease in humans. They are resistant to degradation by enzymes found in the gastrointestinal tract. This allows for ingested toxins to be absorbed from the intestines into the bloodstream.<ref name="SherrisCh19"/>  Toxins can be further differentiated into subtypes on the bases of smaller variations.<ref>{{cite journal | vauthors = Peck MW, Smith TJ, Anniballi F, Austin JW, Bano L, Bradshaw M, Cuervo P, Cheng LW, Derman Y, Dorner BG, Fisher A, Hill KK, Kalb SR, Korkeala H, Lindström M, Lista F, Lúquez C, Mazuet C, Pirazzini M, Popoff MR, Rossetto O, Rummel A, Sesardic D, Singh BR, Stringer SC | title = Historical Perspectives and Guidelines for Botulinum Neurotoxin Subtype Nomenclature | journal = Toxins | volume = 9 | issue = 1 | page = 38 | date = January 2017 | pmid = 28106761 | pmc = 5308270 | doi = 10.3390/toxins9010038 | doi-access = free }}</ref>
However, all types of botulinum toxin are rapidly destroyed by heating to 100&nbsp;°C for 15 minutes (900 seconds). 80&nbsp;°C for 30 minutes also destroys BoNT.<ref>{{cite journal | doi = 10.1007/BF00395840 | vauthors = Notermans S, Havellar AH | year = 1980 | title = Removal and inactivation of botulinum toxin during production of drinking water from surface water | journal = Antonie van Leeuwenhoek | volume = 46 | issue = 5| pages = 511–514 | s2cid = 21102990}}</ref><ref>{{cite journal | vauthors = Montecucco C, Molgó J | title = Botulinal neurotoxins: revival of an old killer | journal = Current Opinion in Pharmacology | volume = 5 | issue = 3 | pages = 274–279 | date = June 2005 | pmid = 15907915 | doi = 10.1016/j.coph.2004.12.006 }}</ref>

Most strains produce one type of BoNT, but strains producing multiple toxins have been described. ''C. botulinum'' producing B and F toxin types have been isolated from human botulism cases in [[New Mexico]] and [[California]].<ref>{{cite journal | vauthors = Hatheway CL, McCroskey LM | title = Examination of feces and serum for diagnosis of infant botulism in 336 patients | journal = Journal of Clinical Microbiology | volume = 25 | issue = 12 | pages = 2334–2338 | date = December 1987 | pmid = 3323228 | pmc = 269483 | doi = 10.1128/JCM.25.12.2334-2338.1987 }}</ref> The toxin type has been designated Bf as the type B toxin was found in excess to the type F. Similarly, strains producing Ab and Af toxins have been reported.<ref name="Hill" />

Evidence indicates the neurotoxin genes have been the subject of [[horizontal gene transfer]], possibly from a viral ([[bacteriophage]]) source. This theory is supported by the presence of integration sites flanking the toxin in some strains of ''C. botulinum''. However, these integrations sites are degraded (except for the C and D types), indicating that the ''C. botulinum'' acquired the toxin genes quite far in the evolutionary past. Nevertheless, further transfers still happen via the plasmids and other mobile elements the genes are located on.<ref>{{cite journal | vauthors = Poulain B, Popoff MR | title = Why Are Botulinum Neurotoxin-Producing Bacteria So Diverse and Botulinum Neurotoxins So Toxic? | journal = Toxins | volume = 11 | issue = 1 | pages = 34 | date = January 2019 | pmid = 30641949 | pmc = 6357194 | doi = 10.3390/toxins11010034 | doi-access = free }}</ref>

==== Toxin types in disease ====
Only [[botulinum toxin]] types A, B, E, F and H (FA) cause disease in humans.  Types A, B, and E <!--or F?--> are associated with food-borne illness, while type E <!--or F?--> is specifically associated with fish products. Type C produces limber-neck in birds and type D causes botulism in other mammals.<ref>{{cite journal | vauthors = Meurens F, Carlin F, Federighi M, Filippitzi ME, Fournier M, Fravalo P, Ganière JP, Grisot L, Guillier L, Hilaire D, Kooh P, Le Bouquin-Leneveu S, Le Maréchal C, Mazuet C, Morvan H, Petit K, Vaillancourt JP, Woudstra C | title = ''Clostridium botulinum'' type C, D, C/D, and D/C: An update | journal = Frontiers in Microbiology | volume = 13 | pages = 1099184 | date = 2023-01-05 | pmid = 36687640 | pmc = 9849819 | doi = 10.3389/fmicb.2022.1099184 | doi-access = free }}</ref>  No disease is associated with type G.<ref>(2013). Chapter 11. Spore-Forming Gram-Positive Bacilli: ''Bacillus'' and ''Clostridium'' Species. In Brooks G.F., Carroll K.C., Butel J.S., Morse S.A., Mietzner T.A. (Eds), ''Jawetz, Melnick, & Adelberg's Medical Microbiology'', 26th ed. {{ISBN|978-0-07-179031-4}}</ref>  The "gold standard" for determining toxin type is a mouse bioassay, but the genes for types A, B, E, and F can now be readily differentiated using [[quantitative PCR]].<ref name="Satterfield, B. A. 2010">{{cite journal | vauthors = Satterfield BA, Stewart AF, Lew CS, Pickett DO, Cohen MN, Moore EA, Luedtke PF, O'Neill KL, Robison RA | title = A quadruplex real-time PCR assay for rapid detection and differentiation of the Clostridium botulinum toxin genes A, B, E and F | journal = Journal of Medical Microbiology | volume = 59 | issue = Pt 1 | pages = 55–64 | date = January 2010 | pmid = 19779029 | doi = 10.1099/jmm.0.012567-0 | doi-access = free }}</ref> Type "H" is in fact a recombinant toxin from types A and F. It can be neutralized by type A antitoxin and no longer is considered a distinct type.<ref name="pmid26068781">{{cite journal | vauthors = Maslanka SE, Lúquez C, Dykes JK, Tepp WH, Pier CL, Pellett S, Raphael BH, Kalb SR, Barr JR, Rao A, Johnson EA | title = A Novel Botulinum Neurotoxin, Previously Reported as Serotype H, Has a Hybrid-Like Structure With Regions of Similarity to the Structures of Serotypes A and F and Is Neutralized With Serotype A Antitoxin | journal = The Journal of Infectious Diseases | volume = 213 | issue = 3 | pages = 379–385 | date = February 2016 | pmid = 26068781 | pmc = 4704661 | doi = 10.1093/infdis/jiv327 }}</ref>

A few strains from organisms genetically identified as other ''Clostridium'' species have caused human botulism: ''C. butyricum'' has produced type E toxin<ref>{{cite journal | vauthors = Aureli P, Fenicia L, Pasolini B, Gianfranceschi M, McCroskey LM, Hatheway CL | title = Two cases of type E infant botulism caused by neurotoxigenic Clostridium butyricum in Italy | journal = The Journal of Infectious Diseases | volume = 154 | issue = 2 | pages = 207–211 | date = August 1986 | pmid = 3722863 | doi = 10.1093/infdis/154.2.207 }}</ref> and ''C. baratii'' had produced type F toxin.<ref>{{cite journal | vauthors = Hall JD, McCroskey LM, Pincomb BJ, Hatheway CL | title = Isolation of an organism resembling Clostridium barati which produces type F botulinal toxin from an infant with botulism | journal = Journal of Clinical Microbiology | volume = 21 | issue = 4 | pages = 654–655 | date = April 1985 | pmid = 3988908 | pmc = 271744 | doi = 10.1128/JCM.21.4.654-655.1985 }}</ref> The ability of ''C. botulinum'' to naturally transfer neurotoxin genes to other clostridia is concerning, especially in the [[food industry]], where preservation systems are designed to destroy or inhibit only ''C. botulinum'' but not other ''Clostridium'' species.<ref name="Hill" />

=== Metabolism ===
Many ''C. botulinum'' genes play a role in the breakdown of essential carbohydrates and the metabolism of sugars. Chitin is the preferred source of carbon and nitrogen for ''C. botulinum''.<ref name=":3">{{cite journal | vauthors = Sebaihia M, Peck MW, Minton NP, Thomson NR, Holden MT, Mitchell WJ, Carter AT, Bentley SD, Mason DR, Crossman L, Paul CJ, Ivens A, Wells-Bennik MH, Davis IJ, Cerdeño-Tárraga AM, Churcher C, Quail MA, Chillingworth T, Feltwell T, Fraser A, Goodhead I, Hance Z, Jagels K, Larke N, Maddison M, Moule S, Mungall K, Norbertczak H, Rabbinowitsch E, Sanders M, Simmonds M, White B, Whithead S, Parkhill J | title = Genome sequence of a proteolytic (Group I) Clostridium botulinum strain Hall A and comparative analysis of the clostridial genomes | journal = Genome Research | volume = 17 | issue = 7 | pages = 1082–1092 | date = July 2007 | pmid = 17519437 | pmc = 1899119 | doi = 10.1101/gr.6282807 }}</ref> Hall A strain of ''C. botulinum'' has an active chitinolytic system to aid in the breakdown of chitin.<ref name=":3" /> Type A and B of ''C. botulinum'' production of BoNT is affected by nitrogen and carbon nutrition.<ref>{{cite journal | vauthors = Leyer GJ, Johnson EA | title = Repression of toxin production by tryptophan in Clostridium botulinum type E | journal = Archives of Microbiology | volume = 154 | issue = 5 | pages = 443–447 | date = October 1990 | pmid = 2256780 | doi = 10.1007/BF00245225 | bibcode = 1990ArMic.154..443L }}</ref><ref>{{cite journal | vauthors = Patterson-Curtis SI, Johnson EA | title = Regulation of neurotoxin and protease formation in Clostridium botulinum Okra B and Hall A by arginine | journal = Applied and Environmental Microbiology | volume = 55 | issue = 6 | pages = 1544–1548 | date = June 1989 | pmid = 2669631 | pmc = 202901 | doi = 10.1128/aem.55.6.1544-1548.1989 | bibcode = 1989ApEnM..55.1544P }}</ref><ref>{{Cite journal | vauthors = Schantz EJ, Johnson EA |date=1992 |title=Properties and use of botulinum toxin and other microbial neurotoxins in medicine. |url=https://mmbr.asm.org/content/56/1/80 |journal=Microbiological Reviews |language=en |volume=56 |issue=1 |pages=80–99 |doi=10.1128/MMBR.56.1.80-99.1992 |pmid=1579114 |pmc=372855 |issn=0146-0749}}</ref> There is evidence that these processes are also under catabolite repression.<ref>{{cite journal | vauthors = Johnson EA, Bradshaw M | title = Clostridium botulinum and its neurotoxins: a metabolic and cellular perspective | journal = Toxicon | volume = 39 | issue = 11 | pages = 1703–1722 | date = November 2001 | pmid = 11595633 | doi = 10.1016/S0041-0101(01)00157-X | bibcode = 2001Txcn...39.1703J }}</ref>

=== Groups ===
Physiological differences and genome sequencing at 16S [[rRNA]] level support the subdivision of the ''C. botulinum'' species into groups I-IV.<ref name="ScienceDirect 2003 pp. 1407">{{cite book | title=Clostridium | chapter=Clostridium &#124; Occurrence of Clostridium botulinum | date=January 1, 2003 | doi=10.1016/B0-12-227055-X/00255-8 | chapter-url=https://www.sciencedirect.com/science/article/pii/B012227055X002558 | access-date=February 19, 2021 | pages=1407–1413| publisher=Academic Press | isbn=978-0-12-227055-0 | vauthors = Austin JW }}</ref> Some authors have briefly used groups V and VI, corresponding to toxin-producing ''C. baratii'' and ''C. butyricum''. What used to be group IV is now ''C. argentinense''.<ref name=Smith18/>
{| class="wikitable plainlist"
|+Phenotypic groups of toxin-producing ''Clostridium''<ref name=Dobritsa18/><ref name=Smith18/>
! Property
! Group I
! Group II
! Group III
! ''C. argentinense''
! ''C. baratii''
! ''C. butyricum''
|-
! Proteolysis (casein)
| {{yes|+}}
| {{no|-}}
| {{no|-}}
| {{yes|+}}
| {{no|-}}
| {{no|-}}
|-
! Saccharolysis
| {{no|-}}
| {{yes|+}}
| {{no|-}}
| {{no|-}}
|-
! Lipase
| {{yes|+}}
| {{yes|+}}
| {{yes|+}}
| {{no|-}}
| {{no|-}}
| {{no|-}}
|-
! Toxin Types
| A, B, F
| B, E, F
| C, D
| G
| F
| E
|-
! Toxin gene
| chromosome/plasmid
| chromosome/plasmid
| bacteriophage
| plasmid
| chromosome<ref>{{cite journal | vauthors = Mazuet C, Legeay C, Sautereau J, Bouchier C, Criscuolo A, Bouvet P, Trehard H, Jourdan Da Silva N, Popoff M | title = Characterization of Clostridium Baratii Type F Strains Responsible for an Outbreak of Botulism Linked to Beef Meat Consumption in France | journal = PLOS Currents | volume = 9 | date = February 2017 | pmid = 29862134 | pmc = 5959735 | doi = 10.1371/currents.outbreaks.6ed2fe754b58a5c42d0c33d586ffc606 | doi-broken-date = 1 November 2024 | doi-access = free }}</ref>
| chromosome<ref>{{cite journal | vauthors = Hill KK, Xie G, Foley BT, Smith TJ, Munk AC, Bruce D, Smith LA, Brettin TS, Detter JC | title = Recombination and insertion events involving the botulinum neurotoxin complex genes in Clostridium botulinum types A, B, E and F and Clostridium butyricum type E strains | journal = BMC Biology | volume = 7 | issue = 1 | pages = 66 | date = October 2009 | pmid = 19804621 | pmc = 2764570 | doi = 10.1186/1741-7007-7-66 | doi-access = free }}</ref>
|-
! Close relatives
|
{{plainlist|1=
* ''[[Clostridium sporogenes|C. sporogenes]]''
* ''C. combesii''
}}
|
* ''C. beijerinckii''
* ''C. butyricum''
|
* ''[[Clostridium novyi|C. novyi]]'' type A
* ''[[Clostridium haemolyticum|C. haemolyticum]]''
| colspan=3 | N/A (already a species)
|}

Although group II cannot degrade native protein such as [[casein]], coagulated [[egg white]], and cooked meat particles, it is able to degrade [[gelatin]].<ref name="Carter Peck 1957 p."/>

Human [[botulism]] is predominantly caused by group I or II ''C. botulinum''.<ref name="Carter Peck 1957 p.">{{cite journal | vauthors = Carter AT, Peck MW | title = Genomes, neurotoxins and biology of Clostridium botulinum Group I and Group II | journal = Research in Microbiology | volume = 166 | issue = 4 | pages = 303–317 | date = May 2015 | pmid = 25445012 | pmc = 4430135 | doi = 10.1016/j.resmic.2014.10.010 | doi-access = free }}</ref> Group III organisms mainly cause diseases in non-human animals.<ref name="Carter Peck 1957 p."/>

===Laboratory isolation===
In the laboratory, ''C. botulinum'' is usually isolated in tryptose sulfite [[cycloserine]] (TSC) growth medium in an anaerobic environment with less than 2% oxygen. This can be achieved by several [[Oxygen scavenger|commercial kits]] that use a chemical reaction to replace O<sub>2</sub> with CO<sub>2</sub>. ''C. botulinum'' (groups I through III) is a [[lipase]]-positive microorganism that grows between [[pH]] of 4.8 and 7.0 and cannot use [[lactose]] as a primary carbon source, characteristics important for biochemical identification.<ref name="Doyle">{{cite book|title=Brock Biology of Microorganisms|edition=11th| veditors = Madigan MT, Martinko JM |publisher=Prentice Hall|year=2005|isbn=978-0-13-144329-7}}</ref>

=== Transmission and sporulation ===
The exact mechanism behind [[spores|sporulation]] of ''C. botulinum'' is not known. Different strains of ''C. botulinum'' can be divided into three different groups, group I, II, and III, based on environmental conditions like heat resistance, temperature, and biome.<ref name=":0">{{cite journal | vauthors = Portinha IM, Douillard FP, Korkeala H, Lindström M | title = Sporulation Strategies and Potential Role of the Exosporium in Survival and Persistence of ''Clostridium botulinum'' | journal = International Journal of Molecular Sciences | volume = 23 | issue = 2 | page = 754 | date = January 2022 | pmid = 35054941 | pmc = 8775613 | doi = 10.3390/ijms23020754 | doi-access = free }}></ref> Within each group, different strains will use different strategies to adapt to their environment to survive.<ref name=":0" /> Unlike other clostridial species, ''C. botulinum'' spores will sporulate as it enters the stationary phase.<ref name=":1">{{cite journal | vauthors = Shen A, Edwards AN, Sarker MR, Paredes-Sabja D | title = Sporulation and Germination in Clostridial Pathogens | journal = Microbiology Spectrum | volume = 7 | issue = 6 | date = November 2019 | pmid = 31858953 | pmc = 6927485 | doi = 10.1128/microbiolspec.GPP3-0017-2018 | veditors = Fischetti VA, Novick RP, Ferretti JJ, Portnoy DA, Braunstein M, Rood JI }}</ref> ''C. botulinum'' relies on [[Quorum sensing|quorum-sensing]] to initiate the sporulation process.<ref name=":1" />  ''C. botulinum'' spores are not found in human feces unless the individual has contracted botulism,<ref>{{Cite journal |url=https://jamanetwork.com/journals/jama/fullarticle/356218 |title= Coproexamination for Botulinal Toxin and Clostridium botulinum |access-date=2024-04-11 |journal=JAMA |date= 1977 |doi=10.1001/jama.1977.03280180033021 | vauthors = Dowell VR |volume= 238 |issue= 17 |page= 1829 |url-access= subscription }}</ref>  but ''C. botulinum'' cannot spread from person to person.<ref>{{Cite web |title=Botulism |url=https://www.who.int/news-room/fact-sheets/detail/botulism |access-date=2024-04-16 |website=www.who.int |language=en}}</ref>

=== Motility structures ===
The most common motility structure for ''C. botulinum'' is a flagellum. Though this structure is not found in all strains of ''C. botulinum'', most produce  [[peritrichous]] flagella.<ref name=":4">{{Cite journal |last1=Paul |first1=Catherine J. |last2=Twine |first2=Susan M. |last3=Tam |first3=Kevin J. |last4=Mullen |first4=James A. |last5=Kelly |first5=John F. |last6=Austin |first6=John W. |last7=Logan |first7=Susan M. |date=May 2007 |title=Flagellin Diversity in Clostridium botulinum Groups I and II: a New Strategy for Strain Identification |journal=Applied and Environmental Microbiology |language=en |volume=73 |issue=9 |pages=2963–2975 |doi=10.1128/AEM.02623-06 |issn=0099-2240 |pmc=1892883 |pmid=17351097|bibcode=2007ApEnM..73.2963P }}</ref> When comparing the different strains, there is also differences in the length of the flagella and how many are present on the cell.<ref name=":4" />