In the unending race against pathogenic bacteria, scientific researchers have unveiled a fascinating discovery involving small RNA viruses, known as bacteriophages. Specifically, Jirapat Thongchol and an international team of researchers have uncovered how a bacteriophage targets a type of bacteria named Pseudomonas aeruginosa, disabling and reducing the bacterium’s ability to infect its host.
Pseudomonas aeruginosa, an opportunistic pathogen with various potential virulence factors, is notorious for its retractable type 4 pilus (T4P), a structure that fuels the bacterial cell’s movement. The study focuses on a Pseudomonas bacteriophage called PP7, which incapacitates its host cell by using a virus protein called Mat that attaches to the bacterium’s pilus. The pilus, consequently, retracts and carries the phage towards the bacterial cell surface where it gains entry to the cell.
What’s remarkable about this process is that, upon the bacteriophage’s entry, the pilus bends and breaks off, inhibiting the bacterium from infecting its own host.
Fluorescence microscopy sessions revealed detachment of Pseudomonas aeruginosa’s T4P during PP7 infection. Notably, the T4P detachment also occurred under infection from ultraviolet-inactivated PP7, a variant of the phage incapable of entering the cell, thereby indicating T4P detachment as an occurring process in the bacterium’s cell envelope during PP7 entry.
Upon further gene examination through single-particle cryo-electron microscopy, the research team discovered that the PP7 bacteriophage comprised two Mat proteins forming a heterotypic dimer, one exposed for T4P interaction and the other internalized within the capsid. This discovery deviates considerably from the single-Mat structure found in canonical Escherichia coli phages and broadens the understanding of ssRNA phage structures.
Moreover, the study reveals that the pilus detachment process is influenced by the retraction speed, the force of the pilus, and the affinity between the phage Mat and its bound pilin.
These findings present a potential game-changer in bacteriology. Broadly, it could pave the way for antimicrobial strategies using bacteriophages to combat bacterial infections, specifically Pseudomonas aeruginosa – a health menace often resistant to antibiotics. With thousands of ssRNA phage genomes identified in recent bioinformatic studies of environmental samples, this new research could serve as a benchmark for investigating other phage and virus organisms.
- Bacteriophages: These are viruses that infect bacteria and have the potential for antimicrobial use.
- Pseudomonas aeruginosa: A widespread opportunistic pathogen known for its resistance to various antibiotics.
- Retractable type 4 pilus (T4P): A prominent virulence factor associated with bacterial motility.
- Maturation Protein: A protein crucial for phage maturity and pilus recognition.
References:
Reference 1: “Removal of Pseudomonas type IV pili by a small RNA virus.” Thongchol, J., et al. (2024). Science, Vol. 384, Issue 6691 DOI: 10.1126/science.adl0635