Alibe Wasa1, Rukmini Gorthy2, Johann Land2, Susan Krumdieck2, Catherine Bishop2, William Godsoe3, Jack Heinemann1
1Biological Sciences, University of Canterbury
2Mechanical Engineering, University of Canterbury
3BioProtection Research Centre, Lincoln University
Superbugs are resistant to critical, often last resort, antibiotics. They transfer from person to person and are difficult to control using even hospital-grade hygiene, products and practices. They are a serious public health issue that causes an increase in medical costs, morbidity and mortality. Photo-activated titania (TiO2) is an antimicrobial agent with self-cleaning properties and could be used to coat door handles and similar surfaces. This coating can reduce viability, spread and colonization of the surface by pathogens. Nanostructured anatase rutile and carbon (NsARC), a TiO2 formulation was tested for antimicrobial (AMA) and antibiofilm (ABA) activity under a variety of light wavelengths and intensities (high intensity visible, UV and ambient light). There was a significant reduction in survival of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Saccharomyces cerevisiae on NsARC coated coupons than on uncoated coupons. A similar pattern of AMA was also observed when some E. coli strains isolated from the environment were tested on NsARC.
An important materials advancement is AMA of NsARC in the dark. To investigate the role of the co-deposited carbon in AMA of the composite coatings, a set of NsARC coating was heat-treated in air to remove the co-deposited amorphous carbon. There was a marginal increase in performance upon heat treatment.
Bacteria that harbour plasmids with multiple antibiotic genes are usually resistant to the AMA of biocides. Investigating how bacteria that carry a plasmid with antibiotic-resistant genes would respond to the AMA of NsARC. I observed an increase in the survival of two E. coli strains that were transformed using a plasmid construct that express fluorescent proteins with multiple antibiotic resistance genes. The increase in survival of the strains harbouring the plasmid construct on NsARC was hypothesised to be due to the expression of the fluorescent proteins.
Anusree Anil1, Laura Domigan2, Christopher Squire1, Juliet Gerrard1
1School of Biological Sciences, University of Auckland
2Chemical & Materials Engineering, University of Auckland
Proteins are versatile building blocks (tectons) in bionanotechnology for simple and cost-effective synthesis of complex structures. Ideally, tectons should form controllable, ordered arrays, which are well defined and stable in all conditions encountered during synthesis and in application. Stable protein 1 (SP1) demonstrates an exceptionally stable, stress tolerant structure, making it an ideal tecton for building nanomaterials.
This study developed SP1 tectons incorporating the unnatural amino acid, p-azido-l-phenylalanine (pAzF) into the protein ring assembly in both lateral and vertical ring orientations; click chemistry by site-specific biorthogonal conjugation then allowed functionalisation of the ring structures. Bacterial cellular machinery was exploited to co-translationally encode pAzF using the amber codon suppression technique. Strain-promoted azide-alkyne cycloaddition (SPAAC) was established at the azide sites, simply by mixing modified SP1 with alkyne-functionalised dyes, proteins or nanoparticles.
Electrospray-ionisation ion trap mass spectrometry confirmed the successful incorporation of pAzF with a calculated efficiency of greater than 70% for both lateral and vertical tectons. Conjugation of the dye molecule Cyanine 5 further verified the incorporation by fluorescence imaging of the SP1 assemblies. Subsequently, a range of functionalities including green fluorescent protein, glucose oxidase (GOX), horse radish peroxidase (HRP), and gold nanoparticles, were selectively attached onto the SP1 tectons. Successful functionalisation was revealed by size exclusion chromatography and transmission electron microscopy.
The Langmuir Blodgett technique was used to assemble vertically-conjugated SP1-GOX and SP1-HRP into functionalised nanosheets. This enzyme cascade nanosheet incorporating the two redox enzymes GOX and HRP was characterised by atomic force microscopy. Electrochemical studies will investigate these sheets for enhanced enzymatic activity associated with co-localisation of the enzyme pair.
Our studies introduce new SP1 tectons as robust scaffolds to build functional nanomaterials as components of future nanodevices.
Sabai Saw Shwe1, David Leung1
1Biological Sciences, University of Canterbury
Eucalyptus species are useful for durable hardwood production due to their abilities of good adaptation to different environments, rapid growth and producing high quality hardwood (Nakhooda and Mandiri, 2016). After banning CCA (copper chrome arsenic) treatment in USA and Europe, these hardwood eucalyptus species are becoming popular as a source of preservative-free, high-grade timber to substitute for the chemical-treated pine wood (Millen, 2009). Eucalyptus bosistoana has been recognised as the best species of special interest to the New Zealand Dryland Forests Initiative (NZDFI) project. E. bosistoana is also known as the Coast Grey Box or Gippsland Grey Box. It has a Class 1 durable hardwood which is resistant to termite damage and highly durable in underground conditions for up to 25 years (Nicolas and Milllen, 2012). Therefore, NZDFI conducted varietal trials and developmental research on these economically important hardwood trees. In vitro methods are useful tools for mass propagation of plant species in a short period of time and to assist further genetic improvement of plants. In this study, different combinations of plant growth regulators including α-naphthalene acetic acid (NAA), benzyladenine (BA) and gibberellic acid (GA3) were trailed for callus induction, shoot regeneration, shoot elongation and root formation. Finally, 100% of the micropropagated plantlets were acclimatised successfully and grown under glasshouse conditions. The protocols for the effective use of plant growth regulators in mass production of E. bosistoana plants in a short period of time will be presented in this talk.
Tonny Miiro1, David Leung1, Georgina Addae Boamponsem1
1Biological Sciences, University of Canterbury
Seed priming is a pre-sowing treatment of seeds which enables uptake of a solution or solvent into a seed during imbibition to a level which allows metabolic reactions to take place without allowing radicle protrusion through the seed coat. There are several methods of seed priming including hydro-, osmo-, chemical, hormonal, biological, redox and solid matrix priming. After seed priming, many studies have shown the following seed priming benefits: significant reduction in radicle emergence time, more uniform seedling emergence, and improved seedling establishment. Moreover, plant growth and crop yield may be protected or enhanced under stressful environmental conditions. Seed priming has, therefore, been suggested as a low cost, simple and practical approach to improve plant tolerance to various abiotic stress conditions. Seed priming triggers a series of biochemical reactions within treated seeds giving them a competitive advantage over the non-treated seeds when the seedlings developed from the seeds are grown under stressful growth conditions. In this talk, an overview of the relevant literature and the possibility of some new seed priming materials will be discussed.