Editing Bacteriophage (section)

=== Attachment and penetration ===

[[File:Phage.jpg|thumb|In this [[electron micrograph]] of bacteriophages attached to a bacterial cell, the viruses are the size and shape of coliphage T1 ]]
<!-- Deleted image removed: [[File:Trialphage.jpg|thumb|A 3D rendering of a T4 type bacteriophage landing on a bacterium to inject genetic material]] -->
Bacterial cells are protected by a cell wall of [[polysaccharide]]s, which are important virulence factors protecting bacterial cells against both immune host defenses and [[antibiotic]]s.<ref>{{cite journal | vauthors = Drulis-Kawa Z, Majkowska-Skrobek G, Maciejewska B | title = Bacteriophages and phage-derived proteins--application approaches | journal = Current Medicinal Chemistry | volume = 22 | issue = 14 | pages = 1757–1773 | year = 2015 | pmid = 25666799 | pmc = 4468916 | doi = 10.2174/0929867322666150209152851 }}</ref> {{citation needed span|date=November 2021|To enter a host cell, bacteriophages bind to specific receptors on the surface of bacteria, including [[lipopolysaccharide]]s, [[teichoic acid]]s, [[protein]]s, or even [[flagella]]. This specificity means a bacteriophage can infect only certain bacteria bearing receptors to which they can bind, which in turn, determines the phage's host range. Polysaccharide-degrading enzymes are virion-associated proteins that enzymatically degrade the capsular outer layer of their hosts at the initial step of a tightly programmed phage infection process.}}
Host growth conditions also influence the ability of the phage to attach and invade them.<ref name="pmid9356254">{{cite journal | vauthors = Gabashvili IS, Khan SA, Hayes SJ, Serwer P | title = Polymorphism of bacteriophage T7 | journal = Journal of Molecular Biology | volume = 273 | issue = 3 | pages = 658–667 | date = October 1997 | pmid = 9356254 | doi = 10.1006/jmbi.1997.1353 }}</ref> As phage virions do not move independently, they must rely on random encounters with the correct receptors when in solution, such as blood, lymphatic circulation, irrigation, soil water, etc.{{citation needed|date=October 2022}}

Myovirus bacteriophages use a [[hypodermic syringe]]-like motion to inject their genetic material into the cell. After contacting the appropriate receptor, the tail fibers flex to bring the base plate closer to the surface of the cell. This is known as reversible binding. Once attached completely, irreversible binding is initiated and the tail contracts, possibly with the help of [[Adenosine triphosphate|ATP]] present in the tail,<ref name="Prescott" /> injecting genetic material through the bacterial membrane.<ref name="Maghsoodi Chatterjee Andricioaei Perkins pp. 25097–25105">{{cite journal | vauthors = Maghsoodi A, Chatterjee A, Andricioaei I, Perkins NC | title = How the phage T4 injection machinery works including energetics, forces, and dynamic pathway | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 116 | issue = 50 | pages = 25097–25105 | date = December 2019 | pmid = 31767752 | pmc = 6911207 | doi = 10.1073/pnas.1909298116 | doi-access = free | bibcode = 2019PNAS..11625097M }}</ref> The injection is accomplished through a sort of bending motion in the shaft by going to the side, contracting closer to the cell and pushing back up. Podoviruses lack an elongated tail sheath like that of a myovirus, so instead, they use their small, tooth-like tail fibers enzymatically to degrade a portion of the cell membrane before inserting their genetic material.