Andrew FentonDr Andrew Fenton

Research Fellow

Room: F15b
Tel:0114 222 2832


Research Precis

Fig1Work in my lab focuses on molecular mechanisms governing bacterial cell growth and division within the host environment. We study the ellipsoid-shaped model organism and human pathogen Streptococcus pneumoniae.

Pneumonia and meningitis are leading causes of death in the world. These diseases are caused by a variety of bacteria but are commonly caused by invasive S. pneumoniae. How these bacteria grow and divide inside their hosts is fundamental to our understanding of these conditions. My lab focuses on S. pneumoniae growth and division processes. Specifically, how the process of cell wall biosynthesis is governed and coordinated to maintain the cell shape and integrity as the cells grow and divide.

As S. pneumoniae cell growth takes place exclusively within the human host, we study the cell host-cell interactions to provide context of cell growth processes. We study how S. pneumoniae cells adapt to environmental changes within hosts, resist clearance by the immune system and cope with antibiotic challenges.

We use genetic screens, biochemical assays and epifluorescence microscopy to advance our understanding of the molecular mechanisms behind these processes.

Identification of a new cell wall biogenesis factor CozE using Tn-seq

Our recent work has utilised a genetic screening technique called Tn-seq 1-3 to identify a new cell wall assembly factor: CozE. Broadly, the Tn-seq technique starts out with large populations of bacteria, each containing an individual gene inactivation. A selective pressure is applied to this population killing some of the more sensitised members. Next, all surviving members are sequenced and their individual gene inactivation is identified (Figure 1A). In this study, we exploited a known genetic relationship between two cell wall biosynthetic factors, PBP1a and PBP2a, to screen for new genes involved in the regulation of these enzymes. Examples of Tn-seq insertion profiles generated from this work are shown in Figure 1B. These insertion profiles revealed a novel cell wall biogenesis regulator in bacteria, which we named CozE for Coordinator Of Zonal Elongation.

Tn-seq can reveal novel genetic relationships. Fig 1A. First, a large population of bacteria each containing a unique gene inactivation is generated (represented by different coloured cells). These populations, or libraries, are subjected to a selection pressure which kills sensitive cells removing them from the culture. Genomic DNA is prepared from each library and each gene inactivation mapped onto the genome. Individual inactivations are represented by a line at the point of interruption, the height of which represents the number of times each insertion was sequenced.  Fig 1B. In this case the selection pressure on the library is applied through gene inactivation. The two libraries were generated: wild-type (wt) and a strain lacking the pbp1a gene (Δpbp1a). Each library was: sequenced, compared, and three regions of the genome representing different Tn-seq insertion profiles selected. The figure shows the gene cozE can be interrupted by multiple transposon insertions in the Δpbp1a library but not in the wt background. This suggests pbp1a disruption suppresses cozE essentiality ‘synthetic viable’. The figure also shows examples of insertion profiles for a gene now essential in the Δpbp1a background (pbp2a) and a gene not-essential in either library (SPD_1516). The ‘synthetic lethal’ pbp2a gene has no apparent transposon insertions in the Δpbp1a strain, whereas SPD_1516 has multiple insertions in each strain background. Figure adapted from reference 4.

Fig2CozE is essential for coordinated cell wall synthesis

Most bacterial cells are surrounded by a cellular exoskeleton called the cell wall. This structure gives the cells their shape and protects them from osmotic lysis. Our Tn-seq study identified the membrane protein CozE, which is essential for coordinated cell wall synthesis in S. pneumoniae (Figure 2A). The cell wall of S. pneumoniae is synthesised in a highly regulated manner involving the action of many enzymes. Removing CozE from S. pneumoniae cells effectively shatters this machinery into its composite pieces, dispersing them throughout the cell surface. Surprisingly, the PBP1a component of the machine appears to keep on working. Like an assembly line out of control, PBP1a synthesises new cell wall seemingly all over the place, inserting new material in inappropriate places. The cells are unable to cope with the aberrant synthesis, which makes them swell and eventually lyse (Figure 2B). Our current work focuses on understanding this rogue cell wall synthesis activity further to see if we can ultimately exploit it for future therapies.

For more information on CozE, please read our paper CozE is a member of the MreCD complex that directs cell elongation in Streptococcus pneumoniae.

Research Keywords

Pneumonia, Streptococcus pneumoniae, host-pathogen interactions, antibiotic resistance, deep sequencing, cell division, cell wall, genetics, epifluorescence microscopy, time-lapse microscopy.


1. van Opijnen, T., Bodi, K. L. & Camilli, A. Tn-seq: high-throughput parallel sequencing for fitness and genetic interaction studies in microorganisms. Nat. Methods 6, 767–72 (2009).
2. Gawronski, J. D., Wong, S. M. S., Giannoukos, G., Ward, D. V & Akerley, B. J. Tracking insertion mutants within libraries by deep sequencing and a genome-wide screen for Haemophilus genes required in the lung. Proc. Natl. Acad. Sci. U. S. A. 106, 16422–16427 (2009)
3. Langridge, G. C. et al. Simultaneous assay of every Salmonella typhi gene using one million transposon mutants. Genome Res. 19, 2308–2316 (2009).
4. Fenton, A. K., El Mortaji, L., Lau, D. T. C., Rudner, D. Z. &Bernhardt, T.G. CozE is a member of the MreCD complex that directs cell elongation in Streptococcus pneumoniae. Nat. Microbiol. 2, 16237 (2016).

If you are interested in joining the team, please contact me at:

Postdoctoral Fellowships

Postdocs who wish to apply for fellowships to join the team are welcome. Please contact me to discuss project ideas.

Project students and Internships

Students wishing to apply for summer internships are welcome and should send me a CV and a letter describing their interests, motivations and research experience.

Career History

Career History

  • 2016 - present: Florey Institute Research Fellow, Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK.
  • 2013 – 2016: Postdoctoral Fellow, Harvard Medical School, Boston, USA.
  • 2010 – 2013: Research Associate, Centre for Bacterial Cell Biology, Newcastle University, Newcastle, UK.
  • 2006 – 2010: PhD, Institute of Genetics, The University of Nottingham, Nottingham, UK.


Journal articles