One of the first users of Diamond Light Source’s new cryo-electron microscope (cryo-EM) has elucidated the structure of the hair-like appendages found on Escherichia coli (E.coli). The remarkable atomic model generated from a 3.8 Å resolution cryo-EM reconstruction has recently been published in the high-profile journal, Cell (Fig. 1).
Bacteria, such as E.coli, naturally possess hair-like structures exposed at the cell surface, which are known as pili. The pili play an essential role in infection as they are responsible for seeking out and latching onto specific host tissues. By fully understanding the structure and function of these unassuming bacterial appendages, it is thought that new medicines could be developed to prevent infection.
A team of scientists from University College London (UCL) and Birkbeck, University of London, the University of Washington, and the University of Virginia, took on the challenge to delve into the inner workings of the pili. By using the cutting edge cryo-EM facility at Diamond, the group discovered that the pili were shaped like springs, which allowed the bacteria to cling on to host tissues even in adverse environments.
Figure 1. A) Surface diagram of the pilus in its coiled state, showing each subunit in a different colour. The subunit coloured cyan is the reference subunit and is numbered ‘0’. Subunits above or below this reference are numbered accordingly. B) Surface diagram of the pilus in its uncoiled state, showing only the N-terminal extension sections to clearly illustrate the helical organisation of the pilus.
Hospenthal MK, Redzej A, Dodson K, Ukleja M, Frenz B, Rodrigues C, Hultgre SJ, DiMaio F, Egelman EH & Waksman G. Structure of a chaperone-usher pilus reveals the molecular basis of rod uncoiling. Cell 164, 1–10. (2016) doi:10.1016/j.cell.2015.11.049
Watch the University of Virginia's video with Professor Edward H. Egelman describing how the research team explored the structure of the bacterial pili.
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