Our studies of bacteria are focused around a variety of problem. A significant part of them is devoted to issues related to the medical field. Research is centred especially around two major streams: (1) diagnosis and (2) study of mechanisms related to drug resistance. The diagnostic aspect of this project involves the use of Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) for pathogen detection in human body fluids (including – but not limiting to – blood and its derivatives). This research is conducted in collaboration with Monash Health and Alfred Hospital.
Fig 1. 3D representation of AFM-IR signal at 1650 cm-1 in S. aureus.
The second aspect of our research is focused on the study of mechanisms related to drug resistance, with particular emphasis on Methicillin-resistant and vancomycin-resistant Staphylococcus aureus (MRSA and VISA). MRSA is one of the most common organism found in both, hospital and community, infections. Its mechanism is known to a certain degree and the infections with MRSA are treated with vancomycin. However, due to a broad use of vancomycin the incidence of infections with VISA (including non-susceptible S. aureus, low-level vancomycin-resistant S. aureus, vancomycin intermediate S. aureus and heterogeneous vancomycin intermediate S. aureus) is rapidly increasing. The resistance mechanism remains in this cases unclear, although it is undoubtedly related to alteration in cell wall composition.
Fig 2. AFM image (height) of E coli.
Location of these changes within cell wall (with a thickness in the range of dozen nanometres) as well as their possible heterogeneity in the prevalence require the use of powerful imaging techniques, enabling to obtain information on a micro- (Raman, FT-IR) and nanoscale (AFM, AFM-IR). The use of imaging techniques based on vibrational spectroscopy enables to obtain unique chemical information about composition of the material (and its changes) together with the precise spatial localisation. This project includes also chemical imaging at the nanoscale of cell walls of a variety of bacteria (including G(+) and G(-)) and their detailed characteristics. This study is performed in collaboration with Department of Microbiology, Monash University and Khon Kaen University.
Fig 3. 3D representation of AFM - IR signal at 1240 cm-1 for single E coli.
The study of bacteria is not limited to solving medical problems (diagnosis, drug resistance mechanisms), but extends also to a variety of others. One of the broadly studied in CfB bacteria are Filamentous bacteria (from Desulfobulbaceae family), first discovered in Denmark and recently found in high concentrations between the mouth of the Yarra and Dight Rivers in Victoria.
Fig 4. AFM (amplitude and height) measurement of a cable bacteria.
These bacteria, colloquially known as "cable bacteria" have the ability to conduct electrons for distances up to few centimetres. They form a narrow, but long organisms capable of sending electric current between the two ends, where the oxidation and reduction processes occurs.
Fig 5. SEM image of a cable bacteria.
A collection of them can produce enough voltage to power a small LED. The phenomenon of electron transport in these organisms is poorly understood and the electron transporters remain unidentified. One of our major goals in this study is to identify the electron transporter in cable bacteria, providing the essential knowledge for their future practical use as a source of renewable, clean energy. This work is done in collaboration with Water Studies Centre, School of Chemistry at Monash University.
Fig 6. 3D Raman imaging of cable bacteria in fresh water the presence of electron transporting ligands within the ridges of bacteria.