Differences

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--- bacteria_defences [2025/01/11 09:26] – [Formation of biofilms] gary1
+++ bacteria_defences [2026/10/16 11:42] (current) – [Cell death when infected by phages] gary1
@@ Line 22: / Line 22: @@
 =====Cell death when infected by phages=====
-  *SIR2 protein normally acts as a nuclease in digesting nucleic acids to maintain proper cell functions, however it also has affinity for binding to the protein HerA and then in the presence of a phage, becomes a NADase causing depletion of NAD+ which results in cell death and reduced transmissions of the phage to other bacteria in the colony (([[https://www.cell.com/molecular-cell/fulltext/S1097-2765(23)00949-8|The Cell Dec 2023. Assembly-mediated activation of the SIR2-HerA supramolecular complex for anti-phage defense]]))
+  ***retron systems**
+    * sense when a specific strain of phage has attacked the bacterial cell, and they then unleash a toxic protein to kill the cell which stops the phage before it has a chance to multiply and spread to neighboring cells in the same colony
+    *most retron systems produce a toxin that, in uninfected cells, is constantly present but deliberately repressed by small, single-stranded DNA molecules which become perturbed when a phage infects the cells allowing the toxin to be released
+    *type VI retrons act in reverse, they do not produce noticeable levels of single-stranded DNA nor toxin in an uninfected cell, and instead when a phage infects the cell, it starts producing single-stranded DNA which when it builds up interacts with an RNA that has been blocking production of the toxin and thereby allowing toxin production to ramp up - the toxin appears to be a tiny protein that embeds itself into the membrane surrounding the cell, which destabilizes the cells and kills it(([[https://www.news-medical.net/news/20261013/Scientists-find-strange-bacterial-immune-system-that-works-backward.aspx]]))
+  ***SIR2-mediated cell death:**
+    *SIR2 protein normally acts as a nuclease in digesting nucleic acids to maintain proper cell functions, however it also has affinity for binding to the protein HerA and then in the presence of a phage, becomes a NADase causing depletion of NAD+ which results in cell death and reduced transmissions of the phage to other bacteria in the colony (([[https://www.cell.com/molecular-cell/fulltext/S1097-2765(23)00949-8|The Cell Dec 2023. Assembly-mediated activation of the SIR2-HerA supramolecular complex for anti-phage defense]]))
 =====Formation of biofilms=====