Tag Archives: bacteria

Real-time label-free tracking of bacteriophages interacting with bacteria

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(a) Two-dimensional random dynamics (blue line) of a pelp20 bacteriophage monitored for a period of 5 s. Scale bar, 2 µm. (b) A plot of the same dynamics and (c) the mean square displacement (MSD) of the random walk. The MSD of the random walk is represented by square data points, and a linear fit (black line) has been applied to the data.

(a) Two-dimensional random dynamics (blue line) of a pelp20 bacteriophage monitored for a period of 5 s. Scale bar, 2 µm. (b) A plot of the same dynamics and (c) the mean square displacement (MSD) of the random walk. The MSD of the random walk is represented by square data points, and a linear fit (black line) has been applied to the data (Figure 4 from https://royalsocietypublishing.org/view-large/figure/20098614/rsif.2026.0250.f004.tif)

I was excited last month when our latest research on tracking nano-entities was published by the Journal of the Royal Society Interface.  The paper describes the real-time and label-free tracking of bacteriophages, or phages, in an optical microscope using caustics (see right thumbnail).  Phages are of interest due to the potential applications in biotechnology and medicine.  They selectively infect and replicate within bacteria and play an important role in regulating bacterial populations across many ecosystems.  I have written previously about the threat of antimicrobial resistant (AMR) infections and our research on the real-time tracking of individual bacterium that could be responsible for such infections [see ‘Label-free real-time tracking of individual bacterium‘ on January 25th, 2023].  In this newly published paper, we describe tracking phages as they interact with and compromise bacteria (see bottom thumbnail) using the same technique, optical caustics [see ‘Caustics‘ on October 15th, 2024 and application to ‘Nanoparticle motion through heterogeneous hydrogels‘ on November 6th, 2024 and to ‘Corona-induced transition from molecular to particle motion in biological media‘ on December 4th, 2024]. Traditionally, phages have been monitored using fluorescent labelling because their size is nanometric which renders them invisible in a conventional optical microscope.  However, chemically attaching labels to nano entities has been shown to influence their dynamics.  Hence, this new study represents a significant advance that will accelerate the real-time observation of phage-bacteria interactions which will enable the development of phage-based diagnostics and antimicrobial therapies.

Sources:

Francesco Giorgi, Samuel Chenery, Liberty Duignan, Joanne L. Fothergill, Eann Patterson, Judith M. Curran; Elucidating bacteriophage dynamics and interactions with real-time label-free optical imaging. J R Soc Interface 1 May 2026; 23 (238): 20260250. https://doi.org/10.1098/rsif.2026.0250

Details of E. coli bacteria: (a) not exposed (reprinted from [17]) and (b,c) exposed to a population of EcoLiv25 phages in solution. In (b), the arrow points at the supposed presence of a phage attached to the bacterium’s external membrane, while in (c), the arrows point at the compromised sections of the bacterium’s external membrane as a result of phage infection. Scale bars, 2 µm.

Details of E. coli bacteria: (a) not exposed and (b,c) exposed to a population of EcoLiv25 phages in solution. In (b), the arrow points at the supposed presence of a phage attached to the bacterium’s external membrane, while in (c), the arrows point at the compromised sections of the bacterium’s external membrane as a result of phage infection. Scale bars, 2 µm (Figure 6 from https://royalsocietypublishing.org/view-large/figure/20098622/rsif.2026.0250.f006.tif).

Are we individuals?

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It has been estimated that there are 150 species of bacteria in our gut with a megagenome correspondingly larger than the human genome; and that 90% of the cells in our bodies are bacterial [1].  This challenges a simple understanding of individual identity because on one level we are a collection of organisms, mainly bacteria, rather than a single entity.  The complexity is almost incomprehensible with 30 trillion cells in the human body each with about a billion protein molecules [2].  Each cell is apparently autonomous, making decisions about its role in the system based on information acquired through communicating and signalling with its neighbours, the rest of the system and the environment.  Its autonomy would appear to imbue it with a sense of individual identity which is shaped by its relationships within the network of cells [3].  This also holds for human beings within society although you could argue the network is simpler because the global population is only about 8 billion; however the quantity of information being communicated is probably greater than between cells, so perhaps that makes the network more complex.  Networks are horizontal hierarchies with no one or thing in overall control and they can adapt to cope with changes in the environment.  By contrast, vertical hierarchies depend on top-down obedience and tend to eliminate dissent, yet without dissent there is little or no innovation or adaptation.  Hence, vertical hierarchies can appear to be robust but are actually brittle [4].  In a network we can build connections and share knowledge leading to the development of a collective intelligence that enables us to solve otherwise intractable problems.  Our ability to acquire knowledge not just from own our experiences but also from the experience of others, and hence to progressively grow collective intelligence, is one of the secrets of our success as a species [5].  It also underpins the competitive advantage of many successful organisations; however, it needs a horizontal, stable structure with high levels of trust and mutual dependence, in which our sense of individual identity is shaped by our relationships.

References:

  1. Gilbert SF, Sapp J, Tauber AI, A symbiotic view of life: we have never been individuals, Quarterly Review of Biology, 87(4):325-341, 2012.
  2. Ball P, How Life Works, Picador, 2023.
  3. Wheatley M, Leadership and the New Science: Discovering Order in a Chaotic World, 2nd Edition, Berrett-Koehler Publishers Inc, San Francisco, 1999.
  4. McWilliams D, Money – A Story of Humanity, Simon & Schuster, London, 2024.
  5. Henrich J, The secret of our success: how culture is driving human evolution, domesticating our species, and making us smarter, Princeton, NJ: Princeton University Press, 2015.

Reasons I became an engineer: #4

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Images from the optical microscope showing the tracks of bacteria interacting with a surfaceThis is the last in a series of posts reflecting on my steps towards becoming an engineer.  At the end of the previous post, I described how I moved to Canada becoming a biomedical engineer in the Medical School at the University of Calgary.  It was a brief period of my career, because shortly after I started, I was encouraged to apply for a lectureship in mechanical engineering at my alma mater which I did successfully.  So, I returned to the University of Sheffield and started my career as an academic engineer.  I continued to work in biomedical engineering, focussing initially on cardiac mechanics [see ‘Tears in the heart’ on July 20th, 2022], then on osseointegrated prostheses [see ‘Turning the screw in dentistry’ on September 9th, 2020] and, more recently, on computational biology [see ‘Hierarchical modelling in engineering and biology’ on March 14th, 2018] and cellular dynamics [see ‘Label-free real-time tracking of individual bacterium’ on January 25th, 2023].  However, the dominant application area of my research has been aerospace engineering informed by, if not also influenced by, my experiences in the Royal Navy, including flying a jet trainer aircraft shortly before leaving.  In the last decade, I have been introduced to nuclear reactor engineering, both fission and fusion, and have used them as vehicles for developing research in digital engineering [see ‘Thought leadership in fusion engineering’ on October 9th, 2019].  This biographical series of posts has described my evolution as an engineer – it was not an ambition I ever had nor did anyone push me towards engineering but I have found that my way of thinking about problems is well-suited to engineering, or perhaps engineering has taught me a way of thinking.

Image: Figure 4 – Tracks (yellow lines) of the sections (purple circles) of four E. coli bacteria experiencing: (a) random diffusion above the surface; (b) rotary attachment; (c) lateral attachment; (d) static attachment. The dynamics of the four bacteria was monitored for approximately 20 s. The length of the scale bars is 5 μm. From Scientific Reports, 12:18146, 2022.

Label-free real-time tracking of individual bacterium

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Images from the optical microscope showing the tracks of bacteria interacting with a surfaceAntimicrobial resistant (AMR) infections are already the third leading cause of death in the USA and are predicted to kill 50 million people per year by 2050.  It is the next pandemic starting already.  We have been using our capability to track nanoparticles in an optical microscope [see ‘Slow moving nanoparticles‘ on December 13th, 2017 and ‘Nano biomechanical engineering of agent delivery to cells‘ on December 15th, 2021] to track individual bacterium as they interact with surfaces to form biofilms.  Bacterial biofilms are complex colonies of bacteria that are highly resistant to antimicrobial agents and can cause life-threatening infections.  We have used our label-free, real-time tracking capabilities to explore the dynamics and adhesion of bacteria to surfaces and found that viable bacteria adhered to the surface but continue to move with rotary or sliding motions depending on the mechanics of their attachment to the surface.  Bacteria that were killed by contact with the surface did not move once they were attached to the surface.  The image shows examples of these motions from our paper published last month.  Our ability to detect these differences in the dynamics of bacteria will allow us to detect the onset of the formation of biofilms and to quantify the efficacy of antimicrobial surfaces and coatings.

Image: Figure 4 – Tracks (yellow lines) of the sections (purple circles) of four E. coli bacteria experiencing: (a) random diffusion above the surface; (b) rotary attachment; (c) lateral attachment; (d) static attachment. The dynamics of the four bacteria was monitored for approximately 20 s. The length of the scale bars is 5 μm. From Scientific Reports, 12:18146, 2022.

Source:

Giorgi F, Curran JM & Patterson EA, Real-time monitoring of the dynamics and interactions of bacteria and the early-stage formation of biofilms, Scientific Reports, 12:18146, 2022.