Nature

Event Date: 
Wednesday, November 27, 2013 - 18:15 - 18:30
Institution: 
School of Civil and Environmental Engineering, UNSW
Title: 

Metal(loid) bioaccessibility dictates microbial community composition in acid sulfate soil horizons and sulfidic drain sediments

Abstract: 

 
Microbial community compositions were determined for three soil horizons and drain sediments within an anthropogenically-disturbed coastal acid sulfate landscape using 16S rRNA gene tagged 454 pyrosequencing.  Diversity analyses were problematic due to the high microbiological heterogeneity between each geochemical replicate.  Taxonomic analyses combined with measurements of metal(loid) bioaccessibility identified significant correlations to genera (5 % phylogenetic distance) abundances. A number of correlations between genera abundance and bioaccessible Al, Cr, Co, Cu, Mn, Ni, Zn, and As concentrations were observed, indicating that metal(loid) tolerance influences microbial community compositions in these types of landscapes.  Of note, Mn was highly bioaccessible (≤ 24 % total soil Mn); and Mn bioaccessibility positively correlated to Acidobacterium abundance, but negatively correlated to Holophaga abundance and two unidentified archaeal genera belonging to Crenarchaeota were also correlated to bioaccessible Mn concentrations, suggesting these genera can exploit Mn redox chemistry. 

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, June 27, 2012 - 19:15 - 20:00
Institution: 
Faculty of Agriculture & Environment, University of Sydney, Sydney, NSW.
Title: 

Sulfur cycling in the rhizosphere: the role of sulfatase and sulfonatase diversity.

Abstract: 

Growth of healthy, high-yielding crop plants requires a stable input not only of nitrogen and phosphorus, but also of sulfur (S). Although S is naturally present in soils, it is usually bound in organic form as sulfate esters or sulfonates, which are not directly bioavailable to plants. Sulfur can be supplemented by addition of inorganic fertilizer, but most sulfate for plant nutrition is provided by microbial turnover of organically-bound sulfur. To identify the rhizosphere organisms responsible for this turnover, we focused on the key genes atsA, which encodes arylsulfatase, and asfA, which is required for aryldesulfonation. Functional T-RFLP analysis was used to analyse atsA diversity in a range of agricultural and natural soils, and clear atsA community differences associated with land use and soil/bedrock types were observed, which were mirrored in the arylsulfatase activity of the cultivable fraction of the population. Soil arylsulfatase activity is routinely assayed as a measure of soil health, but these data highlight the need for detailed studies on arylsulfatase gene diversity in the soil. Sulfonatase diversity was measured in rhizospheres of field-grown wheat plants and in a sulfate-limited Agrostis-dominated grassland, and the effect of adding sulfate in long-term or short-term treatments was tested. Functional asfA community analysis showed that desulfonation genes from both wheat and Agrostis rhizospheres were dominated by Variovorax and Polaromonas species. This distribution of taxa was also found in a cultivation-dependent analysis, and these genera appear to be key players in rhizosphere sulfonate transformations in several environments. Increasing our understanding of the rhizosphere microbes that catalyse soil organosulfur turnover will allow us to develop management practices to maximize soil sulfur availability, and minimize the costs associated with fertilization.

Last week’s ABC Science Show had a large chunk on microbial ecology, with interviews with Janet Jansson, Jack Gilbert, and Tiffany Nelson from UNSW at the AAAS meeting.
Here’s a link to the podcast

Event Date: 
Wednesday, March 28, 2012 - 18:15 - 18:30
Institution: 
Macquarie University
Title: 

Making and breaking dimethylsulfide in salt marsh sediments

Abstract: 

DMSP (dimethylsulfoniopropionate) is a key organic compound in the sulfur cycle with ~10^9 tons of this anti-stress compatible solute being made each year by marine phytoplankton, macro-algae and some salt marsh plants. The DMSP that is liberated is catabolised in a series of different microbial reactions that comprise a massive set of biotransformations in the global sulfur cycle. Some of the reaction products, such as DMS (dimethylsulfide), have major environmental consequences in their own right, from climate regulation to animal behaviour. Our work investigates microbial populations that cycle DMSP and DMS in coastal intertidal sediments. Combining geochemical and molecular biological approaches, such as stable isotope probing (SIP) and targeted high throughput sequencing, we are identifying the main microbial players that catabolise DMSP and DMS in oxic and anoxic parts of intertidal sediments alongside the key genes and cognate biochemical pathways that contribute to the turnover of these influential molecules. Early work led to the observation of a vertical microbial population structure within the salt marsh sediment, partially linked to the sulfur cycle biochemistry of this ecosystem. SIP experiments are allowing the characterisation of active microbial processing of DMSP and DMS compounds by separate new bacterial groups, closely associated to salt marsh plants and within the oxic sediment layer. This work is filling in major gaps in our knowledge of the global organic S cycle and the role of microbial populations in major environmental biochemical processes.

Event Date: 
Wednesday, February 29, 2012 - 15:15 - 15:45
Institution: 
CSIRO Tasmania
Title: 

Towards a biological Argo float.

Abstract: 

Humans have long known about the physical attributes of the ocean – waves, tides, currents and temperatures. Since the 1800’s, deliberate measurements of depth, temperature and velocity have helped to build a low- resolution picture of the dynamic ocean. Argo is an international, collaborative program started in 2000 in which 3000 depth-profiling floats are deployed worldwide. These floats surface routinely and transmit salinity, temperature and depth data via satellite to data handling stations from where it is available to the global research community within 24 hours. Argo data have revolutionised physical oceanography and climate science.

Marine microbial ecology, in particular, how microbial community composition interacts with biogeochemical function in the ocean, is at the low-resolution phase of its history. With deep sequencing, we have the ability to take individual high-resolution samples but we do not yet have the global coverage required to make the connections between the bio and the geochemical.

We have a long-term goal of developing the microbiological equivalent of the Argo float. This requires a lot of hardware and “software” development. Hardware that can automatically sample, filter and process seawater and “software”, the genomic-based assays of microbial community structure that can be automated and miniaturised to work within the hardware. I will describe the development and rationale behind some of our array-based assays that might satisfy these criteria.

Dear JAMSters,

With the Holiday season well underway I wanted to wish you all lasting health and happiness for the coming new year and thank you for making JAMS such a success this year.

Next year promises to be even better and will start off with a great lineup for our January 25th meeting:

Syndicate content