I completed my PhD at the ithree institute. My research looked at investigating the players involved during a bacterial infection with human host. I have a huge interest in science communication and love nothing more than talking about my research or microbiology in general.
I have had the opportunity to present at a wide variety of conferences both on the international and national setting.
I am also a NSW semi-finalist for FameLab (British Council) and NSW finalist for FreshScience (Science in Public), both which are science communication workshops and events. I have also had the opportunity to speak at public events such as ‘Speed Meet a Scientist’ during Science Week and at Nerd Nite.
My research interests lies in microbiology. For my PhD, I studied a bacteria called Mycoplasma pneumoniae and looked at how it interacts with the human host on the protein level.
Mycoplasma pneumoniae is a tiny “simple” bacteria that causes pneumonia in humans. I looked at what proteins (think of them as tools) does this bacteria use to infect the human epithelium and cause disease.
I have taught a wide range of topics across different subjects.
- Casual lecturer for Metabolic Biochemistry, Molecular Biology 1, and was a guest lecturer for General Microbiology and Molecular Biology 2
- Tutor for Molecular Biology, Analytical Biochemistry, and Pathophysiology and Pharmacology 3
- Teaching assiciate for Molecular Biology 1, Moleculary Biology 2, Analytical Biochemistry, Metabolic Biochemistry, and Pathophysiology and Pharmacology 3.
Jarocki, VM, Steele, JR, Widjaja, M, Tacchi, JL, Padula, MP & Djordjevic, SP 2019, 'Formylated N-terminal methionine is absent from the Mycoplasma hyopneumoniae proteome: Implications for translation initiation.', International journal of medical microbiology : IJMM, vol. 309, no. 5, pp. 288-298.View/Download from: UTS OPUS or Publisher's site
N-terminal methionine excision (NME) is a proteolytic pathway that cleaves the N-termini of proteins, a process that influences where proteins localise in the cell and their turnover rates. In bacteria, protein biosynthesis is initiated by formylated methionine start tRNA (fMet-tRNAfMet). The formyl group is attached by formyltransferase (FMT) and is subsequently removed by peptide deformylase (PDF) in most but not all proteins. Methionine aminopeptidase then cleaves deformylated methionine to complete the process. Components of NME, particularly PDF, are promising therapeutic targets for bacterial pathogens. In Mycoplasma hyopneumoniae, a genome-reduced, major respiratory pathogen of swine, pdf and fmt are absent from its genome. Our bioinformatic analysis uncovered additional enzymes involved in formylated N-terminal methionine (fnMet) processing missing in fourteen mycoplasma species, including M. hyopneumoniae but not in Mycoplasma pneumoniae, a major respiratory pathogen of humans. Consistent with our bioinformatic studies, an analysis of in-house tryptic peptide libraries confirmed the absence of fnMet in M. hyopneumoniae proteins but, as expected fnMet peptides were detected in the proteome of M. pneumoniae. Additionally, computational molecular modelling of M. hyopneumoniae translation initiation factors reveal structural and sequence differences in areas known to interact with fMet-tRNAfMet. Our data suggests that some mycoplasmas have evolved a translation process that does not require fnMet.
Trussart, M, Yus, E, Martinez, S, Baù, D, Tahara, YO, Pengo, T, Widjaja, M, Kretschmer, S, Swoger, J, Djordjevic, S, Turnbull, L, Whitchurch, C, Miyata, M, Marti-Renom, MA, Lluch-Senar, M & Serrano, L 2017, 'Defined chromosome structure in the genome-reduced bacterium Mycoplasma pneumoniae.', Nature Communications, vol. 8.View/Download from: UTS OPUS or Publisher's site
DNA-binding proteins are central regulators of chromosome organization; however, in genome-reduced bacteria their diversity is largely diminished. Whether the chromosomes of such bacteria adopt defined three-dimensional structures remains unexplored. Here we combine Hi-C and super-resolution microscopy to determine the structure of the Mycoplasma pneumoniae chromosome at a 10 kb resolution. We find a defined structure, with a global symmetry between two arms that connect opposite poles, one bearing the chromosomal Ori and the other the midpoint. Analysis of local structures at a 3 kb resolution indicates that the chromosome is organized into domains ranging from 15 to 33 kb. We provide evidence that genes within the same domain tend to be co-regulated, suggesting that chromosome organization influences transcriptional regulation, and that supercoiling regulates local organization. This study extends the current understanding of bacterial genome organization and demonstrates that a defined chromosomal structure is a universal feature of living systems.
Berry, IJ, Jarocki, VM, Tacchi, JL, Raymond, BBA, Widjaja, M, Padula, MP & Djordjevic, SP 2017, 'N-terminomics identifies widespread endoproteolysis and novel methionine excision in a genome-reduced bacterial pathogen.', Scientific Reports, vol. 7, no. 1, pp. 1-17.View/Download from: UTS OPUS or Publisher's site
Proteolytic processing alters protein function. Here we present the first systems-wide analysis of endoproteolysis in the genome-reduced pathogen Mycoplasma hyopneumoniae. 669 N-terminal peptides from 164 proteins were identified, demonstrating that functionally diverse proteins are processed, more than half of which 75 (53%) were accessible on the cell surface. Multiple cleavage sites were characterised, but cleavage with arginine in P1 predominated. Putative functions for a subset of cleaved fragments were assigned by affinity chromatography using heparin, actin, plasminogen and fibronectin as bait. Binding affinity was correlated with the number of cleavages in a protein, indicating that novel binding motifs are exposed, and protein disorder increases, after a cleavage event. Glyceraldehyde 3-phosphate dehydrogenase was used as a model protein to demonstrate this. We define the rules governing methionine excision, show that several aminopeptidases are involved, and propose that through processing, genome-reduced organisms can expand protein function.
Widjaja, M, Harvey, KL, Hagemann, L, Berry, IJ, Jarocki, V, Raymond, BBA, Tacchi, JL, Gründel, A, Steele, JR, Padula, MP, Charles, IG, Dumke, R & Djordjevic, SP 2017, 'Elongation factor Tu is a multifunctional and processed moonlighting protein.', Scientific Reports, vol. 7, no. 1, pp. 1-17.View/Download from: UTS OPUS or Publisher's site
Many bacterial moonlighting proteins were originally described in medically, agriculturally, and commercially important members of the low G + C Firmicutes. We show Elongation factor Tu (Ef-Tu) moonlights on the surface of the human pathogens Staphylococcus aureus (SaEf-Tu) and Mycoplasma pneumoniae (MpnEf-Tu), and the porcine pathogen Mycoplasma hyopneumoniae (MhpEf-Tu). Ef-Tu is also a target of multiple processing events on the cell surface and these were characterised using an N-terminomics pipeline. Recombinant MpnEf-Tu bound strongly to a diverse range of host molecules, and when bound to plasminogen, was able to convert plasminogen to plasmin in the presence of plasminogen activators. Fragments of Ef-Tu retain binding capabilities to host proteins. Bioinformatics and structural modelling studies indicate that the accumulation of positively charged amino acids in short linear motifs (SLiMs), and protein processing promote multifunctional behaviour. Codon bias engendered by an A + T rich genome may influence how positively-charged residues accumulate in SLiMs.
Tacchi, JL, Raymond, BBA, Haynes, PA, Berry, IJ, Widjaja, M, Bogema, DR, Woolley, LK, Jenkins, C, Minion, FC, Padula, MP & Djordjevic, SP 2016, 'Post-translational processing targets functionally diverse proteins in Mycoplasma hyopneumoniae', OPEN BIOLOGY, vol. 6, no. 2.View/Download from: UTS OPUS or Publisher's site
Raymond, BBA, Jenkins, C, Seymour, LM, Tacchi, JL, Widjaja, M, Jarocki, VM, Deutscher, AT, Turnbull, L, Whitchurch, CB, Padula, MP & Djordjevic, SP 2015, 'Proteolytic processing of the cilium adhesin MHJ_0194 (P123(J)) in Mycoplasma hyopneumoniae generates a functionally diverse array of cleavage fragments that bind multiple host molecules', CELLULAR MICROBIOLOGY, vol. 17, no. 3, pp. 425-444.View/Download from: UTS OPUS or Publisher's site
Widjaja, M, Berry, I, Pont, E, Padula, M & Djordjevic, S 2015, 'P40 and P90 from Mpn142 are Targets of Multiple Processing Events on the Surface of Mycoplasma pneumoniae', Proteomes, vol. 3, no. 4, pp. 512-537.View/Download from: UTS OPUS or Publisher's site
Mycoplasma pneumoniae is a significant cause of community acquired pneumonia globally. Despite having a genome less than 1 Mb in size, M. pneumoniae presents a structurally sophisticated attachment organelle that (i) provides cell polarity, (ii) directs adherence to receptors presented on respiratory epithelium, and (iii) plays a major role in cell motility. The major adhesins, P1 (Mpn141) and P30 (Mpn453), are localised to the tip of the attachment organelle by the surface accessible cleavage fragments P90 and P40 derived from Mpn142. Two events play a defining role in the formation of P90 and P40; removal of a leader peptide at position 26 (23SLA↓NTY28) during secretion to the cell surface and cleavage at amino acid 455 (452GPL↓RAG457) generating P40 and P90. Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) analysis of tryptic peptides generated by digesting size-fractionated cell lysates of M. pneumoniae identified 15 cleavage fragments of Mpn142 ranging in mass from 9–84 kDa. Further evidence for the existence of cleavage fragments of Mpn142 was generated by mapping tryptic peptides to proteins recovered from size fractionated eluents from affinity columns loaded with heparin, fibronectin, fetuin, actin, plasminogen and A549 surface proteins as bait. To define the sites of cleavage in Mpn142, neo-N-termini in cell lysates of M. pneumoniae were dimethyl-labelled and characterised by LC-MS/MS. Our data suggests that Mpn142 is cleaved to generate adhesins that are auxiliary to P1 and P30.