Dr Tim R Blower, MA (Cantab) MSci PhD
(email at email@example.com)
Toxin-antitoxin systems and bacteriophage resistance
Whilst bacteria are often thought of as selfish cells out for their own purposes, increasingly, we can observe that they exist as diverse interacting communities. This is reflected in the ubiquitous presence and implementation of "toxin-antitoxin" systems throughout known Bacterial and Archaeal species. Toxin-antitoxin systems are characterised as small genetic loci encoding two parts. The toxin, when free to act, will target the host cell and stall growth, sometimes to the point of cell death. In the presence of the antitoxin, this effect is negated and cells grow freely.
It might appear peculiar that bacterial cells carry toxin-antitoxin systems, until you consider the potential advantages. For instance, if there aren't enough nutrients to go around, one cell activates its internal toxins, allowing it to grow slower or die, so that the population of clonal bacteria around it can survive. Another example would be when a bacterial cell becomes infected by a bacteria-specific virus, called a bacteriophage. Unchecked, the bacteriophage would replicate, burst out, and infect neighbour cells. If the infected cell shuts down quickly, it can stop viral spread. An example of this type of viral defence is the ToxIN toxin-antitoxin system (Figure 1), which is made up of antitoxic RNA (ToxI) bound to a toxic protein (ToxN).
Figure 1. ToxIN toxin-antitoxin and phage resistance system. ToxI RNA (blue), folds into a pseudoknot that binds and inhibits ToxN protein (pink). Bacteriophage infection reduces the levels of ToxI RNA and releases ToxN to kill the host cell. This atomic resolution structure was obtained by X-ray crystallography (see Blower et al. (2011) Nature Structure and Molecular Biology below).
Harnessing molecular tools from bacteriophage-host interactions
Toxin-antitoxin systems are diverse, with a wide range of roles and many targets, which include the ribosome, DNA replication (via topoisomerases) and the cell wall. This list matches the targets of common antibiotics. By understanding how these toxins inhibit bacterial cell growth, we may be able to co-opt this ability to control bacterial species. This is becoming increasingly important in the face of widespread antibiotic resistance.
Furthermore, as the natural predators of bacteria, it is essential to investigate bacteriophage biology and host-interactions, in particular, the many ways bacteriophages can adapt to avoid host bacteriophage-resistance mechanisms.
A range of molecular biology and biochemical techniques are employed in the lab, including protein biochemistry, genomics and structural analysis through X-ray crystallography.
Department of Biosciences
Wolfson Research Institute for Health and Wellbeing
Indicators of Esteem
- Blower, T.R., Bandak, A., Lee, A.S.Y., Austin, C.A., Nitiss, J.L. & Berger, J.M. (2019). A complex suite of loci and elements in eukaryotic type II topoisomerases determine selective sensitivity to distinct poisoning agents. Nucleic Acids Research 47(15): 8163-8179.
- Hampton, H.G., Jackson, S.A., Fagerlund, R.D., Vogel, A.I.M., Dy, R.L., Blower, T.R. & Fineran, P.C. (2018). AbiEi binds cooperatively to the Type IV abiE toxin-antitoxin operator via a positively-charged surface and causes DNA bending and negative autoregulation. Journal of Molecular Biology 430(8): 1141-1156.
- Gibson, E.G., Blower, T.R., Cacho, M., Bax, B., Berger, J.M. & Osheroff, N. (2018). Mechanism of Action of Mycobacterium tuberculosis Gyrase Inhibitors: A Novel Class of Gyrase Poisons. ACS Infectious Diseases 4(8): 1211-1222.
- Blower, T.R., Chai, R., Przybilski, R., Chindhy, S., Fang, X., Kidman, S.E., Tan, H., Luisi, B.F., Fineran, P.C. & Salmond, G.P.C. (2017). Evolution of Pectobacterium bacteriophage ΦM1 to escape two bifunctional Type III toxin-antitoxin and abortive infection systems through mutations in a single viral gene. Applied and Environmental Microbiology 83(8): e03229-16.
- Ashley, R.E., Blower, T.R., Berger, J.M. & Osheroff, N. (2017). Recognition of DNA Supercoil Geometry by Mycobacterium tuberculosis Gyrase. Biochemistry 56(40): 5440-5448.
- Cross, J.M., Blower, T.R., Gallagher, N., Gill, J.H., Rockley, K.L. & Walton, J.W. (2016). Anticancer RuII and RhIII Piano-Stool Complexes that are Histone Deacetylase Inhibitors. ChemPlusChem 81(12): 1276-1280.
- Blower, T.R., Williamson, B.H., Kerns, R.J. & Berger, J.M. (2016). Crystal structure and stability of gyrase–fluoroquinolone cleaved complexes from Mycobacterium tuberculosis. Proceedings of the National Academy of Sciences of the United States of America 113(7): 1706-1713.
- Aldred, K.J., Blower, T.R., Kerns, R.J., Berger, J.M. & Osheroff, N. (2016). Fluoroquinolone interactions with Mycobacterium tuberculosis gyrase: Enhancing drug activity against wild-type and resistant gyrase. Proceedings of the National Academy of Sciences of the United States of America 113(7): E839-E846.
- Rao, F., Short, F.L., Voss, J.E., Blower, T.R., Orme, A.L., Whittaker, T.E., Luisi, B.F. & Salmond, G.P.C. (2015). Co-evolution of quaternary organization and novel RNA tertiary interactions revealed in the crystal structure of a bacterial protein–RNA toxin–antitoxin system. Nucleic Acids Research 43(19): 9529-9540.
- Unwin, R.R., Cabanas, R.A., Yanagishima, T., Blower, T.R., Takahashi, H., Salmond, G.P.C., Edwardson, J.M., Fraden, S. & Eiser, E. (2015). DNA driven self-assembly of micron-sized rods using DNA-grafted bacteriophage fd virions. Physical chemistry chemical physics 17(12): 8194-202.
- Short, F.L., Pei, X.Y., Blower, T.R., Ong, S.L., Fineran, P.C., Luisi, B.F. & Salmond, G.P. (2013). Selectivity and self-assembly in the control of a bacterial toxin by an antitoxic noncoding RNA pseudoknot. Proceedings of the National Academy of Sciences of the United States of America 110(3): E241-9.
- Short, F.L., Blower, T.R. & Salmond, G.P. (2012). A promiscuous antitoxin of bacteriophage T4 ensures successful viral replication. Molecular Microbiology 83(4): 665-668.
- Blower, T.R., Short, F.L., Rao, F., Mizuguchi, K., Pei, X.Y., Fineran, P.C., Luisi, B.F. & Salmond, G.P. (2012). Identification and classification of bacterial Type III toxin-antitoxin systems encoded in chromosomal and plasmid genomes. Nucleic Acids Research 40(13): 6158-6173.
- Blower, T.R., Evans, T.J., Przybilski, R., Fineran, P.C. & Salmond, G.P. (2012). Viral Evasion of a Bacterial Suicide System by RNA-Based Molecular Mimicry Enables Infectious Altruism. PLoS Genetics 8(10): e1003023.
- Blower, T.R., Short, F.L., Fineran, P.C. & Salmond, G.P. (2012). Viral molecular mimicry circumvents abortive infection and suppresses bacterial suicide to make hosts permissive for replication. Bacteriophage 2(4): 234-238.
- Blower, T.R., Pei, X.Y., Short, F.L., Fineran, P.C., Humphreys, D.P., Luisi, B.F. & Salmond, G.P.C. (2011). A processed non-coding RNA regulates an altruistic bacterial antiviral system. Nature Structural and Molecular Biology 18(2): 185-190.
- Blower, T.R., Salmond, G.P.C. & Luisi, B.F. (2011). Balancing at survival's edge: the structure and adaptive benefits of prokaryotic toxin-antitoxin partners. Current Opinion in Structural Biology 21(1): 109-18.
- Blower, T.R., Fineran, P.C., Johnson, M.J., Toth, I.K., Humphreys, D.P. & Salmond, G.P. (2009). Mutagenesis and functional characterisation of the RNA and protein components of the toxIN abortive infection and toxin-antitoxin locus of Erwinia. Journal of Bacteriology 191(19): 6029-6039.
- Fineran, P.C., Blower, T.R., Foulds, I.J., Humphreys, D.P., Lilley, K.S. & Salmond, G.P. (2009). The phage abortive infection system, ToxIN, functions as a protein-RNA toxin-antitoxin pair. Proceedings of the National Academy of Sciences of the United States of America 106(3): 894-899.