Project Leader 

Jolene Ramsey, Ph.D.
past CPT Postdoctoral Research Associate
Contact email: jolenerr@tamu.edu

Bacteriophage lysis mechanisms and novel virus discovery.

Phage exit is a tightly regulated process. In gram-negative bacterial hosts, phage must cross three cell barriers, the inner and outer membrane and the peptidoglycan cell wall, to release phage progeny. To understand the proteins that govern those processes, our team studies lysis proteins in both well-studied canonical phage systems (lambda, Mu) and less known phages as well. Here we apply molecular, biochemical, and genetic approaches to tease out the pathways leading to lysis.

As the Center for Phage Technology mandate states, we are interested in finding and characterizing novel phage from the environment that target relevant bacterial hosts. Our host panel is continuously being updated based on the needs in the community; these are not your garden variety E. coli. These projects could be the seed for industry partnerships and often extend from or flow into the BICH 464 Bacteriophage Genomics course.

Holt, Ashley

Martin, Cody

Awah, Adey

Tomaszewski, Adam

Snowden, Jason

Nittolo, Toni

Corban, James

Torres, Ruben

Sullivan, Teresa

Panin, Nick

Mota, Andrea

Reichert, Dacia

Project Leader

Karthik Chamakura, Ph.D.
CPT Postdoctoral Research Associate
Contact email: krcham02@tamu.edu

Single Gene Lysis Systems

The final step in a bacteriophage infection cycle, lysis and release of progeny virions from the host, requires destruction of the bacterial cell envelope, which in Gram-negative bacteria, includes the cytoplasmic membrane, the cell wall (peptidoglycan), and the outer membrane.  For the simple, ubiquitous lytic single-strand RNA and DNA phages, lysis is effected by the expression of a single gene.  There are three general classes of these phages: the ssDNA microviruses and two classes of ssRNA phages, the leviviruses and the alloleviruses. By studying how these lysis genes make the host undergo lysis, we expect to advance our understanding of how bacteria synthesize and maintain their cell envelope and thus potentially open the way for developing new antibiotic strategies.

Previously, three different single gene lysis systems identified in the well-studied paradigm phages representing the three phage classes:  E of the microvirus fX174, A₂ of the allolevivirus Qb, and L of the levivirus MS2.  Work in done in the Young lab has shown that A₂ and E function as specific inhibitors of enzymes in the pathway for murein precursor biosynthesis, MurA and MraY, respectively.  The third prototypic lysis protein L causes lysis by an unknown mechanism and is currently being investigated by my team.

Recently, we discovered a fourth mode of single gene lysis system, the lysis protein Lys^M from the Escherichia coli phage M. Lys^M was also shown to target peptidoglycan biosynthesis by inhibiting MurJ, the essential lipid II flippase. This recent discovery raises the possibility that ssRNA phages have evolved proteins that target other essential steps in peptidoglycan biosynthesis and maintenance. Thus, understanding the lysis mechanisms of ssRNA phages might facilitate the discovery of novel targets for antibiotic development.

491 Students under Karthik Chamakura (2016- 2021)

Min, Lorna

Tran, Jennifer

Williams, Zachary

Tran, Elizabeth

Painter, Joanie

Richardson, Ted

Patel, Janki

Wang, Nancy

Publications

1. Chamakura, KR, Sham, LT, Davis, RM, Min, L, Cho, H, Ruiz, N et al.. A viral protein antibiotic inhibits lipid II flippase activity. Nat Microbiol. 2017;2 (11):1480-1484. doi: 10.1038/s41564-017-0023-4. PubMed PMID:28894177 PubMed Central PMC5764540.
2. Chamakura, KR, Edwards, GB, Young, R. Mutational analysis of the MS2 lysis protein L. Microbiology (Reading, Engl.). 2017;163 (7):961-969. doi: 10.1099/mic.0.000485. PubMed PMID:28691656 PubMed Central PMC5775895.
3. Chamakura, KR, Tran, JS, Young, R. MS2 Lysis of Escherichia coli Depends on Host Chaperone DnaJ. J. Bacteriol. 2017;199 (12):. doi: 10.1128/JB.00058-17. PubMed PMID:28396351 PubMed Central PMC5446614.