April 2017

Event Date: 
Wednesday, April 26, 2017 - 18:00 - 18:15
Institution: 
The University of Sydney
Title: 

FRES(H): Fruit ripeness ethylene biosensor (hopefully)

Abstract: 

Biosensors utilise the genetic circuits found in nature for sensing of particular substrates. In our case, we turned to ethylene-metabolising bacteria, specifically a local Australian strain of Mycobacterium known as Mycobacterium NBB4.
SENSE: The regulatory genes behind ethylene metabolism in NBB4 are almost completely novel . Based on sequence homology and structural protein analysis, we've come up with two strong candidates - genes called EtnR1 and EtnR2, which may interact with a putative promoter EtnP. Therefore, we had to check expression and characterise these regulatory components first!
EXPRESS: If we want to use the regulatory aspects of NBB4 ethylene metabolism in a biosensor, we need to incorporate a reporter gene with strong, detectable output into our circuit. Generating such a reporter gene was the focus of EXPRESS, where we used error prone PCR on an existing blue iGEM chromoprotein amilCP to generate amilCP mutants with altered spectral characteristics.
KEEP FRESH: Putting SENSE and EXPRESS biocircuitry together, we can construct a usable biosensor with applications in cold shipping containers, supermarket store rooms and storage warehouses. We focused on the physical design aspects of a biosensor to bring to market, and performed detailed costings in a business plan for our biosensor.

Event Date: 
Wednesday, April 26, 2017 - 18:15 - 18:30
Institution: 
The University of Sydney
Title: 

Divergent roles of β- and γ-actin isoforms during spread of vaccinia virus

Abstract: 

Actin is a major component of the cytoskeleton and is present as two isoforms in non-muscle cells: β- and γ-cytoplasmic actin. These isoforms are strikingly conserved, differing by only four N-terminal amino acids. During spread from infected cells, vaccinia virus (VACV) particles induce localized actin nucleation that propel virus to surrounding cells and facilitate cell-to-cell spread of infection. Here we show that virus-tipped actin comets are composed of β- and γ-actin. We employed isoform-specific siRNA knockdown to examine the role of the two isoforms in VACV-induced actin comets. Despite the high level of similarity between the actin isoforms, and their colocalization, VACV-induced actin nucleation was dependent exclusively on β-actin. Knockdown of β-actin led to a reduction in the release of virus from infected cells, a phenotype dependent on virus-induced Arp2/3 complex activity. We suggest that local concentrations of actin isoforms may regulate the activity of cellular actin nucleator complexes.

 

Event Date: 
Wednesday, April 26, 2017 - 19:00 - 19:30
Institution: 
ithree Institute, University of Technology Sydney
Title: 

Deciphering chlamydial disease and host/pathogen interactions by genome scale biology

Abstract: 

Chlamydia are widespread bacterial pathogens that cause a range of mammalian diseases. The primary human chlamydial pathogen is C. trachomatis. It causes ocular and genital disease in mucosal epithelia across all socioeconomic groups, and is the most common human sexually transmitted infection (STI). Human disease is a consequence of inflammation and scarring from untreated or asymptomatic infections, and/or reinfections, and constitutes the largest economic burden of all bacterial sexually transmitted infections (STIs). We have applied whole genome sequencing across the Order Chlamydiales to show that the two major chlamydial pathogens that infect humans are lapsed zoonoses, with significant implications for therapeutic and vaccine design.
Bacterial pathogens subvert host cells by manipulating cellular pathways for survival and replication; in turn, host cells respond to invading pathogens through cascading changes in gene expression. Deciphering this complex temporal and spatial interplay is crucial for improved diagnostics and therapeutics, as well as understanding fundamental biology. C. trachomatis has a profound effect on human mucosal epithelial cells, actively altering them to secure an intracellular niche. We developed the dual RNA-Seq approach to simultaneously capture prokaryotic and eukaryotic expression profiles of bacteria-infected cells, using C. trachomatis-infected cells as proof of principle. We have significantly extended these results by performing dual RNA-Seq and time-matched miRNA-Seq to characterize the early infected host transcriptomes at 0.5, 1.5, 3, 6, and 12 hours post-infection in response to both C. trachomatis and C. psittaci infections. This dataset also includes time matched controls of mock-infected cells, UV-inactivated Chlamydia and opsonized latex beads for both RNA-Seq and miRNA-Seq data. With these data, we have examined host cell differential mRNA and non-coding RNA expression, and patterns of alternate splicing, allowing a comprehensive definition of the host response to two chlamydial pathogens.
We define a series of positive feedback mechanisms for Chlamydia-induced fibrotic scarring, the major disease outcome for C. trachomatis ocular and STD infections. In addition, despite the high degree of genomic similarity and phylogenetic relatedness of C. trachomatis and C. psittaci, the host response to each is dramatic and distinct, providing insight into the different disease outcomes of a mucosally-restricted STD and ocular pathogen versus a respiratory zoonotic pathogen.

Hi All
For clarity the next monthly JAMS meeting will be held on Wednesday the 26th of April at Harpoon Harry's (the day after Anzac Day).
Some people thought it was on 18th April. Feel free to go to the pub and talk microbiology anyway.