Bacteria encode sophisticated anti-phage systems that are diverse and versatile and display high genetic mobility. How this variability and mobility occurs remains largely unknown. Here, we demonstrate that a widespread family of pathogenicity islands, the phage-inducible chromosomal islands (PICIs), carry an impressive arsenal of defense mechanisms, which can be disseminated intra- and inter-generically by helper phages. These defense systems provide broad immunity, blocking not only phage reproduction, but also plasmid and non-cognate PICI transfer. Our results demonstrate that phages can mobilize PICI-encoded immunity systems to use them against other mobile genetic elements, which compete with the phages for the same bacterial hosts. Therefore, despite the cost, mobilization of PICIs may be beneficial for phages, PICIs, and bacteria in nature. Our results suggest that PICIs are important players controlling horizontal gene transfer and that PICIs and phages establish mutualistic interactions that drive bacterial ecology and evolution.
PFAM:PF02452
contributors:
-Héloïse Georjon
relevantAbstracts:
-doi:10.1016/j.cell.2022.07.014
-doi:10.1016/j.cell.2022.07.014
---
# FS_Sma
## To do
## Description
SMA (single-protein MazF-like antiphage system) was identified in a phage-inducible chromosomal island (PICI) found in *Staphylococcus aureus* :ref{doi=10.1016/j.cell.2022.07.014}. SMA was shown to inhibit phage infection and to inhibit the formation of new virions after prophage induction.
## Molecular mechanisms
The SMA protein comprises a domain analogous to MazF. MazF a protein that is normally part of the MazEF toxin-antitoxin systems, in which MazF is a toxic endoribonuclease that targets mRNA :ref{doi=10.1016/s1097-2765(03)00402-7}.
As far as we are aware, the precise molecular mechanism of SMA is unknown.
## Example of genomic structure
The FS_Sma is composed of 1 protein: Sma.
The Sma is composed of 1 protein: Sma.
Here is an example found in the RefSeq database:
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The FS_Sma system in *Staphylococcus aureus* (GCF_022869625.1, NZ_CP064365) is composed of 1 protein: Sma (WP_000041883.1)
The Sma system in *Staphylococcus aureus* (GCF_022869625.1, NZ_CP064365) is composed of 1 protein: Sma (WP_000041883.1)
## Distribution of the system among prokaryotes
Among the 22,803 complete genomes of RefSeq, the FS_Sma is detected in 578 genomes (2.53 %).
Among the 22,803 complete genomes of RefSeq, the Sma is detected in 578 genomes (2.53 %).
