Sewerage

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, January 28, 2015 - 18:00 - 18:15
Institution: 
University of New South Wales
Title: 

Biomining and methanogenesis for resource extraction from asteroids

Abstract: 

As spacecraft fuel is a limited resource, creating a readily available source for hydrocarbon-based fuels in space will reduce launch cost and increase operating time of spacecraft. Biomethanation is viable for Earth-based operations, thus applications in space under controlled conditions have potential. This study proposes a sustainable environment for methanogens on Near-Earth Objects. Vacuum and desiccation effects, at 0.025% Earth atmospheric pressure, are conducted on three bacterial and three Archaea strains to test post-exposure viability. Cell degradation and colony size reduction was quantified for aerobic strains. Adverse effects were exhibited more so in gram-negative than gram-positive strains. Archaea showed limited to no cell degradation, providing evidence that vacuum effects, at these pressures, will have minor effects on in-situ biofuel operations. If successful, a sustainable and cost-effective method of metal extraction and producing methane based fuel reservoirs could revolutionise in-situ resource and fuel resupply of spacecraft, thus enhancing spacefaring capabilities.

Event Date: 
Wednesday, September 26, 2012 - 19:00 - 20:00
Institution: 
University of New South Wales
Title: 

Microbial methane formation and oxidation in abandoned coal mines

Abstract: 

 
Worldwide, mine gas is being used increasingly for heat and power production. About 7% of the annual methane emissions originate from coal mining. In abandoned coal mines, stable carbon and hydrogen isotopic signatures of methane indicate a mixed thermogenic and biogenic origin. The thermogenic methane is a reminder of geological processes, but its biogenic formation is still going on. Besides hard coal, possible sources for methane are large amounts of mine timber left behind after the end of mining.
Methanogenic archaea are responsible for the production of substantial amounts of methane. Mine timber and hard coal showed an in situ production of methane with isotopic signatures similar to those of the methane in the mine atmosphere. Long-term incubations of coal and timber as sole carbon sources formed methane over a period of 9 months. We directly unraveled the active methanogens mediating the methane release as well as the active bacteria potentially involved in the trophic network. Furthermore, we proved the presence of an active methanotrophic community. Directed by the methane production and oxidation, respectively, samples for DNA stable-isotope probing (SIP) coupled to subsequent quantitative PCR and DGGE analyses were taken from long term incubations over 6 months. The stable-isotope-labeled precursors of methane, [13C]acetate and H2-13CO2, and 13CH4 were fed to liquid cultures from hard coal and mine timber. Predominantly acetoclastic methanogenesis was stimulated in enrichments containing acetate and H2+CO2. The H2+CO2 was mainly used by acetogens similar to Pelobacter acetylenicus and Clostridium species forming acetate as intermediate and providing it to the methanogens. Active methanogens, closely affiliated to Methanosarcina barkeri, utilized the readily available acetate rather than the thermodynamical more favourable hydrogen. Furthermore, the activity of a distinct methane-oxidizing community is predominated of a member belonging to the type I methanotrophs similar to Methylobacter marinus that assimilated 13CH4 nearly exclusively. Thus, active methanotrophic bacteria are associated with the methanogenic microbial community that is highly adapted to the low H2 conditions found in the coal mines with acetate as the main precursor of the biogenic methane.

Event Date: 
Wednesday, February 29, 2012 - 18:30 - 19:00
Institution: 
CSIRO Livestock Industries, St. Lucia, Australia
Title: 

Differences downunder: macropodids, methane and metagenomics.

Abstract: 

The agricultural sector accounts for a large amount of Australia’s greenhouse gas emissions, and strategies that reduce the production and (or) release of methane from ruminant livestock has resurfaced as a viable research topic. While there has been a relatively intense focus on better understanding how rumen microbiology, nutrition and (or) animal genetics might be targeted and productively altered to reduce these emissions; less attention has been directed towards the comparative study of those native Australian herbivores thought to produce small amounts of methane during feed digestion. These animals include the Australian macropodids (kangaroos and wallabies), which have evolved to retain a foregut microbiota that effectively converts plant biomass into nutrients for the host animal; and appears to do so with much less methane emitted. Our research group in Brisbane has used metagenomics approaches with a view to characterize the foregut microbiota of the Tammar wallaby (Macropus eugenii). There is a reduced number of methanogenic archaea resident in the macropodid foregut compared to ruminants, but the species present appear to have some unique attributes relative to their counterparts from other environments. We have also used a combination of metagenomic data and cultivation-based methods to identify and isolate several “new” bacteria that support feed digestion and fermentation schemes consistent with a low methane emitting phenotype. The structure-function relationships inherent to these interesting gut microbiomes warrant further investigation.

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