Efflux

 

In September, JAMS was back into top gear, with a bigger audience, and a room with a view. Kent Lim from Macquarie University led off with a talk on his PhD work on the biocontrol agent Pseudomonas strain Pf5. As is often the case in science, things didn’t work out as expected, and Kent found that knocking out suspected pyochelin transporters led to an increase rather than a decrease in efflux of this siderophore and its metabolic precursors. Kent valiantly soldiered on, applying qRT-PCR and Biolog phenotype microarrays to untangle the problem, but unfortunately, this released even more worms from the seemingly-bottomless can provided by strain Pf5. It seems that these transporters may in fact also be regulatory proteins, explaining the unexpected pleiotropic effects of the knockouts.
 

Event Date: 
Wednesday, September 26, 2012 - 18:15
Institution: 
Macquarie University
Title: 

Defining the effluxome of Acinetobacter baumannii

Abstract: 

 
Acinetobacter baumannii is a Gram-negative opportunistic human pathogen known to cause a range of infections in hospitals. Despite their recent emergence, strains of A. baumannii, resistant to essentially all routinely used antibiotics, have been isolated from clinical settings. Bioinformatic analysis identified more than 50 transporter systems with a putative role in drug efflux in the genome of A. baumannii ATCC17978, representing ~2% of all its protein coding ORFs. Based on an assumption that drug transport is often associated with over-expression of a relevant efflux system in the presence of the substrate, high-throughput quantitative reverse-transcriptase PCR (qRT-PCR) has been performed after shock treatments with sub-inhibitory concentrations of antibiotics and differential expression of genes was assessed. This strategy has led to the discovery of novel drug efflux systems and defined physiological functions for previously characterised and novel pumps in drug resistance.
Efflux systems have evolved for millions of years before bacteria such as A. baumannii entered the hospital environment. Presumably, they have initially developed as mechanisms of resistance against naturally occurring substrates. To further characterize the role of efflux systems, cultures of A. baumannii were treated with bioactive natural compounds found in the environment, i.e. soil. These treatments resulted in significant changes in the transcription of efflux pumps indicating their possible role in the defence against compounds found in nature.
Increased expression of efflux systems was also observed when cells of A. baumannii were grown in biofilms compared to planktonic cultures which could suggest that efflux pumps may also play an important role in the functioning of these bacterial communities.

 

Event Date: 
Wednesday, April 27, 2011 - 18:00 - 18:15
Institution: 
Maquarie University
Title: 

Transcriptome led microbial discovery.

Abstract: 

Using a genome wide transcriptomic approach, Karl was able to unravel the role of the Pseudomonas global
activator system (GacA/GacS) in the regulation of an extremely broad range of functions including iron acquisition, oxidative stress response, secondary metabolism and motility. Similar work in Acinetobacter baumannii, a bacterium that is emerging as a major human pathogen due to multiple drug resistance, has revealed the antibiotic efflux to be major mode of resistance and led to the discovery of novel resistance proteins. Karl is a post-
doctoral fellow at Macquarie University working in Prof. Ian Paulsen’s group.

Syndicate content