Scientists Uncover the Mechanism: Bacterial Protein Revealed to be Key Player in Phage Infection and Resistance

Antibacterial resistance has led to the development of alternative treatments for bacterial infections, including the use of bacteriophages, which are viruses that can kill bacteria. Graham Hatfull, a professor of Biotechnology at the University of Pittsburgh, has been at the forefront of phage therapy, particularly for the treatment of chronic diseases such as cystic fibrosis. While phage therapy offers hope for treating bacterial infections, it is essential to understand how bacteria become resistant to phages, as resistance can limit the efficacy of this therapy.

Recently, Hatfull's team discovered how a specific mutation in a bacterium, Mycobacterium smegmatis, results in phage resistance. The team isolated a mutant form of the bacterium that was resistant to infection by a phage called Fionnbharth and identified how the specific mutation in the lsr2 gene helped these resistant bacteria fight off a phage.

To understand how phages kill bacteria without the relevant mutation, Carlos Guerrero-Bustamante, a graduate student in Hatfull's lab, genetically engineered two types of phages. One produced red fluorescence upon entering a bacterial cell aka reporter phage, while the other had segments of DNA that stuck to fluorescent molecules, allowing phage DNA to light up in an infected cell. This method enabled the team to watch, in unprecedented detail, as a phage attacked a bacterium.

a The histograms in the flow cytometry data display the fluorescent signals at the population level for M smegmatis cells labeled with SYTOX Orange stained mycobacteriophages MOI of 100 N QTF 500 nM and BPs Fionnbharth BPs and N QTF data are presented on the left in the middle and on the right respectively b The plaque assay shows the fluorescent plaques and the 100 mm agarose plate containing WT M smegmatis cells infected with 100 phage particles of Fionnbharth mCherry reporter phage The plate and fluorescent plaques are visible in the transmitted light mCherry and merged channels
a The histograms in the flow cytometry data display the fluorescent signals at the population level for M smegmatis cells labeled with SYTOX Orange stained mycobacteriophages MOI of 100 N QTF 500 nM and BPs Fionnbharth BPs and N QTF data are presented on the left in the middle and on the right respectively b The plaque assay shows the fluorescent plaques and the 100 mm agarose plate containing WT M smegmatis cells infected with 100 phage particles of Fionnbharth mCherry reporter phage The plate and fluorescent plaques are visible in the transmitted light mCherry and merged channels

The team saw how phages bound to cells and injected their DNA into the bacteria. They then applied this knowledge to study the effect of removing the Lsr2 protein, which was critical in phage resistance. The link between Lsr2 and phage resistance was not previously known, but the team's new methodology and tools made it clear that Lsr2 played a critical role in the replication of phage DNA.

Lsr2 typically helps bacteria replicate their own DNA. When a phage attacks, the virus co-opts the protein, using it to replicate phage DNA and overwhelm the bacteria. When the lsr2 gene is missing or defective, as in phage-resistant Mycobacterium smegmatis, the bacteria does not produce the protein, and phages do not replicate enough to take over the bacterial cell. The team's discovery of the link between Lsr2 and phage resistance is a significant breakthrough that could help in the development of better phage therapies.

Hatfull emphasizes that this study focused on one bacterial protein and its resistance to just one phage. However, it has far-reaching implications, as there are numerous phages and proteins to study. The team's new tools and methodology offer insights into how different mutations protect bacteria against invasion by phages. As phage therapy expands, these tools could help others better understand phages' abilities while avoiding the missteps that led to antibiotic resistance.

The N QTF Probe in action
The N QTF Probe A Turn On Fluorescent Tool for Real Time Monitoring of Mycolic Acid Membrane Biosynthesis in Mycobacteria Scientists have developed a new tool for visualizing mycolic acid membrane biosynthesis in mycobacteria in real time The N QTF probe contains a fluorophore and a quencher that is integrated into the mycobacterial outer membrane via Ag85 mycolyltransferase The probes turn on feature allows continuous live cell labeling and does not require washing out steps This tool offers improved stability brightness and membrane integrating properties compared to previous probes and its co localization with phages highlights the distinctive growth strategy of mycobacteriaimage title

The discovery of the link between Lsr2 and phage resistance is a significant step forward in understanding the mechanisms of bacterial resistance to phages. This knowledge could help in the development of more effective phage therapies to treat bacterial infections, including chronic diseases. It also highlights the importance of studying phages and their interactions with bacteria to identify new therapeutic options for antibiotic-resistant infections.

The new methodology and tools developed by Hatfull's team offer an unprecedented level of detail into the interaction between phages and bacteria. This discovery of the link between Lsr2 and phage resistance is just one of the many possibilities that these tools offer. With the continued rise of antibiotic-resistant infections, phage therapy offers a promising alternative, and understanding bacterial resistance to phages is crucial in developing effective therapies.

This research has been published in a peer-reviewed journal and can be accessed via Charles L. Dulberger et al, Mycobacterial nucleoid-associated protein Lsr2 is required for productive mycobacteriophage infection, Nature Microbiology (2023). DOI: 10.1038/s41564-023-01333-x.

All photos used in this article are available on original published research work and all the credit goes to the researchers. Part of the conversation interview has been obtained from Phys.org

About the author

Hello there!
I'm Raphael Hans Lwesya, My true passion lies in the world of phage research and science communication. As a diligent phage researcher and an enthusiastic science communicator, I've founded "www.thephage.xyz," a platform dedicated to unraveling the fascinating universe of bacteriophages – viruses that specifically target microbes. My ultimate mission is to bridge the communication gap between the general public and the often intricate world of scientific concepts. I take pride in simplifying complex ideas, breaking them down into easily understandable pieces, and making cutting-edge phage-related research accessible to a wide audience. Thank you for visiting The Phage blog. If you have got any question or suggestion please drop it as a comment or via [email protected]

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