Editing Pilus (section)

===Type IV pili===
[[File:Type_IV_Pilus_Twitching_Motility_Steps.svg|thumb|353x353px|'''<u>Type IV Pilus Twitching Motility</u>'''
'''1.''' Pre-PilA is made in the cytoplasm and moves into the inner membrane.
'''2.''' Pre-PilA is inserted into the inner membrane.

'''3.''' PilD, a [[Protease|peptidase]], removes a leader sequence, thus making the Pre-PilA shorter and into PilA, the main building-block protein of Pili.

'''4.''' PilF, a [[Nucleoside triphosphate|NTP]]-Binding protein that provides energy for Type IV Pili Assembly.

'''5.''' The secretin protein, PilQ, found on the outer membrane of the cell is necessary for the development/extension of the pilus. PilC is the first proteins to form the pilus and are responsible for overall attachment of the pilus.

'''6.''' Once the Type IV Pilus attaches or interacts with what it needs to, it begins to retract. This occurs with the PilT beginning to degrade the last parts of the PilA in the pilus. The mechanism of PilT is very similar to PilF.

'''7.''' Degradation of the pilus into the components to be utilized and synthesized into PilA again.<ref>{{Cite book|title=Microbiology : an evolving science|last=Joan|first=Slonczewski|publisher=W. W. Norton & Company|others=Foster, John Watkins|year=2017|isbn=9780393614039|edition=Fourth|location=New York|pages=1000–1002|oclc=951925510}}</ref>
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[[File:Type IVa pilus machine architectural model.pdf|thumb|Type IVa pilus machine architectural model]]

Some pili, called '''type IV pili''' (T4P), generate [[motility|motile]] forces.<ref name="pmid12142488">{{cite journal |author=Mattick JS |title=Type IV pili and twitching motility |journal=Annu. Rev. Microbiol. |volume=56 |issue= 1|pages=289–314 |year=2002 |pmid=12142488 |doi=10.1146/annurev.micro.56.012302.160938 }}</ref> The external ends of the pili adhere to a solid substrate, either the surface to which the bacterium is attached or to other bacteria. Then, when the pili contract, they pull the bacterium forward like a grappling hook. Movement produced by type IV pili is typically jerky, so it is called [[twitching motility]], as opposed to other forms of bacterial motility such as that produced by [[Flagellum|flagella]]. However, some bacteria, for example ''[[Myxococcus xanthus]]'', exhibit [[bacterial gliding|gliding motility]]. Bacterial type IV pili are similar in structure to the component proteins of [[archaellum|archaella]] (archaeal flagella), and both are related to the [[Type II secretion system]] (T2SS);<ref name= Jarelletal>{{cite book |author= Jarrell|year=2009|chapter=Archaeal Flagella and Pili|title=Pili and Flagella: Current Research and Future Trends|publisher=Caister Academic Press|isbn= 978-1-904455-48-6|display-authors=etal}}</ref> they are unified by the group of [[Type IV filament]] systems. Besides archaella, many archaea produce adhesive type 4 pili, which enable archaeal cells to adhere to different substrates. The N-terminal alpha-helical portions of the archaeal type 4 pilins and archaellins are homologous to the corresponding regions of bacterial T4P; however, the C-terminal beta-strand-rich domains appear to be unrelated in bacterial and archaeal pilins.<ref>{{cite journal |last1=Wang |first1=F |last2=Cvirkaite-Krupovic |first2=V |last3=Kreutzberger |first3=MAB |last4=Su |first4=Z |last5=de Oliveira |first5=GAP |last6=Osinski |first6=T |last7=Sherman |first7=N |last8=DiMaio |first8=F |last9=Wall |first9=JS |last10=Prangishvili |first10=D |last11=Krupovic |first11=M |last12=Egelman |first12=EH |title=An extensively glycosylated archaeal pilus survives extreme conditions. |journal=Nature Microbiology |date=2019 |volume=4 |issue=8 |pages=1401–1410 |doi=10.1038/s41564-019-0458-x |pmid=31110358|pmc=6656605 }}</ref>

[[Transformation (genetics)|Genetic transformation]] is the process by which a recipient bacterial cell takes up DNA from a neighboring cell and integrates this DNA into its genome by [[homologous recombination]].  In ''[[Neisseria meningitidis]]'' (also called meningococcus),  DNA transformation requires the presence of short [[DNA uptake sequence]]s (DUSs) which are 9-10 monomers residing in [[coding region]]s of the donor DNA.  Specific recognition of DUSs is mediated by a type IV [[pilin]].<ref name="pmid23386723">{{cite journal |vauthors=Cehovin A, Simpson PJ, McDowell MA, Brown DR, Noschese R, Pallett M, Brady J, Baldwin GS, Lea SM, Matthews SJ, Pelicic V |title=Specific DNA recognition mediated by a type IV pilin |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=110 |issue=8 |pages=3065–70 |year=2013 |pmid=23386723 |pmc=3581936 |doi=10.1073/pnas.1218832110 |bibcode=2013PNAS..110.3065C |doi-access=free }}</ref> Menningococcal type IV pili bind DNA through the minor pilin ComP via an electropositive stripe that is predicted to be exposed on the filament's surface.  ComP displays an exquisite binding preference for selective DUSs. The distribution of DUSs within the ''N. meningitides'' genome favors certain genes, suggesting that there is a bias for genes involved in genomic maintenance and repair.<ref name="pmid14960717">{{cite journal |vauthors=Davidsen T, Rødland EA, Lagesen K, Seeberg E, Rognes T, Tønjum T |title=Biased distribution of DNA uptake sequences towards genome maintenance genes |journal=Nucleic Acids Res. |volume=32 |issue=3 |pages=1050–8 |year=2004 |pmid=14960717 |pmc=373393 |doi=10.1093/nar/gkh255 }}</ref><ref name="pmid19464092">{{cite journal |vauthors=Caugant DA, Maiden MC |title=Meningococcal carriage and disease--population biology and evolution |journal=Vaccine |volume=27 Suppl 2 |pages=B64–70 |year=2009 |issue=4 |pmid=19464092 |pmc=2719693 |doi=10.1016/j.vaccine.2009.04.061 }}</ref>

This family was originally identified as "type IV fimbriae" by their appearance under the microscope. This classification survived as it happens to correspond to a clade.<ref name="Nuccio SP et al2007">{{cite journal  |vauthors=Nuccio SP, etal | title=Evolution of the chaperone/usher assembly pathway: fimbrial classification goes Greek | journal=Microbiology and Molecular Biology Reviews | year=2007 | volume=71 | issue=4 | pages=551–575 | doi=10.1128/MMBR.00014-07| pmc=2168650 | pmid=18063717}}</ref> It has been shown that some archaeal type IV pilins can exist in 4 different conformations, yielding two pili with dramatically different structures.<ref name=Liu2024NatCommun>{{cite journal |last1=Liu |first1=J |last2=Eastep |first2=GN |last3=Cvirkaite-Krupovic |first3=V |last4=Rich-New |first4=ST |last5=Kreutzberger |first5=MAB |last6=Egelman |first6=EH |last7=Krupovic |first7=M |last8=Wang |first8=F |title=Two distinct archaeal type IV pili structures formed by proteins with identical sequence. |journal=Nature Communications |date=2024 |volume=15 |issue=1 |pages=5049 |doi=10.1038/s41467-024-45062-z |pmid=38877064 |pmc=11178852 |bibcode=2024NatCo..15.5049L }}</ref> Remarkably, the two pili were produced by the same secretion machinery. However, which of the two pili is formed appears to depend on the growth conditions, suggesting that the two pili are functionally distinct.<ref name=Liu2024NatCommun></ref>