Environmental soil science

Event Date: 
Wednesday, April 29, 2015 - 18:00 - 18:15
Institution: 
University of New South Wales (UNSW)
Title: 

Bacterial secondary metabolite prodigiosin inhibit biofilm development by cleaving extracellular DNA

Abstract: 

Prodigiosin a bacterial secondary metabolite is a heterocyclic compound belongs to the class of tripyrrole, synthesized by various strains of bacteria includes Serratia species. Research on prodigiosin is under limelight for past 10 years from clinical and pharmacological aspects in relevance to its potential to be drug for cancer therapy by inducing apoptosis in several cancer cell lines. Reports suggest that prodigiosin promotes oxidative damage to DNA in presence of copper ion and consequently lead to inhibition of cell-cycle progression and inducing cell death. However, prodigiosin has not been previously implicated in biofilm inhibition. We performed experiments to reveal any link between prodigiosin and biofilm inhibition through degradation of extracellular DNA which plays a major role in biofilm establishment. Our study showed that prodigiosin (extracted from Serratia culture) has strong DNA cleaving property but does not intercalate with nitrogenous bases of DNA. Using P. aeruginosa PA14 wild-type strain as a model organism we showed that bacterial cells treated with prodigiosin showed significant reduction in its cells surface hydrophobicity and consequently affecting surface energies and physico-chemical property essential for bacterial adhesion and aggregation. We also found that prodigiosin did not influence planktonic growth of P. aeruginosa however, was successful in inhibiting the establishment of biofilms includes decrease in biofilm thickness, adhesion to substratum, decrease in biovolume, microcolony formation and also significantly dispersed pre-established biofilm of P. aeruginosa. This novel function on the biofilm inhibition of prodigiosin could be used to interfere with risks associated with bacterial biofilms. 

Event Date: 
Wednesday, February 25, 2015 - 15:30 - 16:00
Institution: 
University of California Davis
Title: 

Stress, function and community dynamics in wastewater bioreactors

Abstract: 

Biological wastewater treatment plants receive a complex mixture of chemicals and are operated based on principles of general microbial growth kinetics. Regulated effluent criteria determine the extent of treatment required to achieve removal of chemical oxygen demand and nutrients like reduced nitrogen and phophate. Plants are, however, not designed to metabolize specific (micro)pollutants, and the factors influencing the emergence of microbial communities that are tolerant of or have evolved to metabolize and remove toxic compounds are poorly understood. Basic questions in wastewater engineering include ‘What affects the dynamics of wastewater microbial communities?’  and ‘Are communities ever stable and if so does this matter for basic processes like removal of organics and nutrients?’.  
We investigated the impact of defined and sustained chemical stress on wastewater microbial communities and their functions, using the highly toxic and recalcitrant compound 3-chloroaniline (3-CA) as model stressor. Experimental design included replicate bioreactors, sterile synthetic feed, ambient levels of 3-CA, and fixed factors like bioaugmentation and temperature. Process outcomes varied from no removal of 3-CA to complete removal within three weeks. Community changes were dramatic and nitrification was a key function affected by the stressor. Finally, microbial diversity indices based on 16S rRNA gene amplicon sequencing or T-RFLP, combined with influent nutrient concentrations, were used to predict effluent concentrations using support vector regression, a machine learning model. Sensitivity analysis of a preliminary dataset for a full-scale water reclamation plant would suggest that evenness is the most significant input variable for the prediction of soluble COD, nitrate and ammonium concentrations in the effluent. Overall, we show that both detailed analysis of taxonomy and gene expression and general indices of diversity are useful for understanding the link between stable process performance and microbial communities.

Event Date: 
Wednesday, October 30, 2013 - 18:00 - 18:15
Institution: 
UNSW
Title: 

NO signals for dispersing biofilms in clinical and industrial applications

Abstract: 

A story from science bench to bedside, or at least towards it What started as purely academic studies of the life cycle of bacterial biofilms, addressing the regulation of cell death events during late developmental stages, led to the discovery of a role for nitric oxide (NO) as a key regulator of biofilm dispersal. NO, which is a simple gas and universal biological signal, was found to be produced endogenously in mature biofilms, and trigger a signaling pathway involving the secondary messenger cyclic di-GMP, which in turn activates cellular effectors resulting in dispersal. Add-back of low levels (picomolar to nanomolar range) of NO was able to induce dispersal across various single species and mixed species biofilms. While the biofilm mode of growth confers a high level of resistance to control measures including antibiotics, exposure to NO greatly increases the efficacy of a range of antimicrobial treatments. Therefore the use of low, non-toxic concentrations of NO represents a promising strategy for the management of biofilms in medical and industrial contexts. Several NO-based technologies have been developed to control bacterial biofilms, including: (i) NO-generating compounds with short or long half-lives and safe or inert residues, (ii) novel materials and surface coatings which catalytically produce NO in situ, and (iii) novel compounds for the targeted delivery of NO to infectious biofilms during systemic treatments.

Event Date: 
Wednesday, November 28, 2012 - 07:00 - 08:00
Institution: 
University of Sydney
Title: 

Biodegradation of dichloroethane by aerobic bacteria at the Botany Industrial Park

Abstract: 

The chlorinated hydrocarbon 1,2-dichloroethane (DCA) is a common pollutant of groundwater, and poses both human and environmental health risks. The Botany Industrial Park in south Sydney is heavily contaminated with DCA and other organochlorines. The main user of the site (Orica Ltd) operates a large groundwater treatment plant (GTP) on site to contain and remediate the DCA-contaminated groundwater. At present, remediation is done by air-stripping and thermal oxidation, but this is very costly and energy-intensive. Orica is interested in alternative technologies for treating the groundwater, including bioremediation. In 2010, a pilot scale membrane bioreactor (MBR) was set up to treat a fraction of the groundwater. The aims of our study were to identify DCA-degrading bacteria and genes in the GTP and on the site at large, define the community structure and ecological successions occurring in the MBR, develop a qPCR for catabolic genes in the DCA biodegradation pathway, and field-test this qPCR assay in the MBR and in a survey of groundwater in monitoring wells on the site. We discovered that DCA-degrading bacteria using a hydrolytic pathway (dhlA/dhlB genes) were widespread and diverse at this site, and that the dhlA gene was carried on a catabolic plasmid. The community in the MBR was dominated by alpha- and beta-proteobacteria, and was highly dynamic, changing dramatically in composition as the percentage of raw groundwater in the feed was increased. By combining dhlA qPCR and 16S pyrosequencing data, we found evidence that thus-far-uncultured species of Azoarcus may play a major role in DCA bioremediation in situ in the MBR.

 
Prepared by Valentina Wong (UNSW PhD student)
On a cold Tuesday night, Adrian Low from University of New South Wales warmed the JAMS audience with his passion on bioremediation of organochlorine contaminated groundwater. Adrian described the discovery of Australia’s first 1,2-dichloroethane (DCA) degrading consortium, AusDCA. His work in the field demonstrated the efficacy and sustainability of using organochlorine respiring bacteria to remediate organochlorine contaminants in situ. He plans to isolate the bacterial species responsible for performing this unique task.

Event Date: 
Tuesday, July 24, 2012 - 18:15 - 18:30
Institution: 
University of NSW
Title: 

Development of an Australian 1,2-Dichloroethane degrading culture

Abstract: 

 
1,2-Dichloroethane (DCA) is one of the most common organochlorine groundwater contaminants worldwide. The successes of bioremediation field studies with organochlorine respiring bacteria have proved the efficacy of the method to degrade such contaminants in situ. The objective of this study was to demonstrate that a DCA degrading consortium, named AusDCA could be used to bioaugment a DCA contaminated acidic aquifer in situ. Functional characterisation experiments of AusDCA in batch cultures showed that the culture could dechlorinate high concentrations of DCA (6.3 mM) to ethene anaerobically at pH 5.5 and pH 6.5 and was not inhibited by approximately 15 µM of chloroform (CF). 

Event Date: 
Wednesday, January 25, 2012 - 18:15 - 18:30
Institution: 
UNSW
Title: 

The impact of petroleum hydrocarbons on microbial diversity in a sub-Antarctic soil; a proxy for soil health

Abstract: 

Anthropogenic sources of contamination remain a legacy throughout the Antarctic Region, with the majority of contamination occurring alongside concentrated human activities at research stations. At Macquarie Island, an Australian Sub-Antarctic territory we have been investigating the impact of petroleum hydrocarbon contamination in the form of Special Antarctic Blend (SAB) diesel fuel on the microbial ecology of sub-Antarctic soils. Whilst bioremediation strategies are currently underway on the Island, there is a lack of petroleum hydrocarbon contamination guidelines specific to Antarctic or sub-Antarctic regions. Additionally, there is insufficient site-specific toxicity data available for remediation end points to be established. Therefore, we have assessed the bacterial and fungal response to increasing concentrations of SAB diesel fuel through a combination of novel culturing methods, flow cytometric analysis of cell numbers and massively paralley pyrosequencing targeting the 16S and ITS genes. Results of this investigation will provide the scientific basis for understanding how much fuel is too much and how clean is clean enough?

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