User:Smanzano1999/Arbitrium

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Recently, in Bacillus phages, a peptide communication system named the arbitrium system was identified that plays an essential role in lysis–lysogeny decisions during infection of Bacillus host cells11–14. This system requires the arbitrium hexapeptide to bind to its cellular receptor AimR to regulate transcription of the lysogeny negative regulator gene aimX. After infecting Bacillus host cells, the phage produces the precursors of signal peptides encoded by the aimP gene. The premature peptides are secreted to the extracellular environment and cleaved by bacterial extracellular proteases to generate the mature hexapeptide. The secreted peptides are imported into the host cell through an oligopeptide permease transporter and then bind to the AimR receptor, which functions as a transcription factor. Consequently, peptide-bound AimR loses its DNA-binding activity. This signal enables phage integration into the Bacillus genome as a prophage (what I'm paraphrasing)

In Bacillus
Arbitrium is a peptide communication system used by bacterial phages, like Bacillus. It plays a key role during infection of the Bacillus host cells11-14 since is it necessary during the lysis-lysogeny decisions. Due to arbitrium being the communication system of this process. In order to successfully transcribe the lysogeny negative regulator gene aimX, arbitriums hexapeptide,6 amino acids, must bind to the AimR receptor. When the Bacillus host cells are infected, precursors are produced to signal the peptides which are encoded by the gene aimP. The hexapeptide, 6 amino acids, must mature by secreting the premature peptides to the outside environment and cleaved by the bacterial outside proteases. The secreted premature peptides are now peptides and secreted into the host cell by a transporter called oligopeptide permease. They then bind to the AimR receptor which happens to function as a transcription factor. As a result, DNA-binding activity is lost in the AimR peptide-bound. Consequently, this sends a signal tot he phage integration in the Bacillus genome in form of a prophage.

'''The arbitrium system is composed of three genes: aimP, which encodes the arbitrium peptide; aimR,encoding a transcriptional factor that binds to AimP; and aimX, which produces a small non-coding RNA that exerts a negative regulatory effect on lysogeny, inducing lysis by a mechanism that has not been deciphered yet. 2 AimP is produced as a 43- aa pro-peptide that is released from the bacterial cell into the'''

surrounding medium. The pro-peptide is then processed into the mature 6-aa AimP before it is imported into neighboring bac-

teria via the oligopeptide permease (OPP) transporter channel.Once internalized, the mature AimP binds to the AimR receptor

and controls its DNA regulatory activity .2 AimR is a transcriptional factor and, in its apo peptide-free form, promotes aimX expression. During the initial stages of infection, when the number of active phages is low, the arbitrium peptide is absent and AimR activates aimX expression, promoting the lytic cycle of the phage (Figure S1). After intense phage replication, AimP will accumulate in the medium, increasing the intracellular concentration of the mature AimP peptide '''until it reaches the threshold level required to bind to its cognate AimR receptor. When this occurs, AimR cannot activate aimX expression. This promotes the lysogenic cycle and the integration of the pro- phage into the bacterial chromosome, thus preventing eradication of the entire bacterial population by the phage (Figure S1)'''.2 This simple and elegant communication system allows infecting phages to ‘‘decide’’ between lytic and lysogenic life cycles.

Arbitrium is made up of three genes which are: aimP, it is responsible for encoding the arbitrium peptide. There is also aimR, it is responsible for encoding transcription factors that happen to bind to aimP. Then theres aimX, it is responsible for producing non-coding RNA which brings to bear a negative regulatory effect on lysogeny. As a result lysis is induced by a mechanism that we still are unaware of. The AimP is made up into 43 amino acid(aa) peptide which is a product of the bacterial cell and goes into the medium. Evidently the peptide of 43 amino acids(aa) matures into a 6 amino acid(aa) AimP. The mature AimP is transported to neighboring bacteria using the oligopeptide permease (OPP) transporter channel. Once inside, the mature AimP binds to the AimR, specifically the AimP to the AimR receptor. Once bound the DNA regulatory activity is being controlled. AimX expression is promoted to AimR since they are transcriptional factors and in their apo peptide-free form. Before complete infection the number of active phages is at a minimum. Due to the fact that the arbitrium peptide isn't present and AimR is needed in order to activate aimX expression. This would then promote the lytic cycle of the phage. Once phage has replicated multiple times AimP builds up in the medium. This increases the concentration inside of the mature AimP peptide. The intracellular concentration stops increasing once it reaches the threshold level which is required to bind to it's cognate AimR receptor. If and when this occurs AimR wont activate aimX expression causing the stimulation of the lysogenic cycle as well as the integration of the prophage into the bacterial chromosome. This then keeps eradication of the bacterial population by the phage from occurring. The arbitrium communication system is what allows infecting phages to decide the cell fate of either lytic or lysogenic cycle.