Dissolved organic carbon

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

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


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. 

Maria-Luisa Gutierrez-Zamora

The JAMS rendezvous this October 31st took place in the fourth floor of the Museum with a magnificent view of Sydney, and began with an ad hoc presentation featuring sulphurous scents and sexy fangs. Katherina Petrou (UTS) initiated us in the science of the sulphur cycle in the oceans and how this process is dominated by the production of dimethylsulfoniopropionate (DMSP) by microalgae and its decomposition into dimethylsulphide (DMS), a strong odorous chemoattractant for a range of marine organisms. In tackling the mystery of how harmful algal blooms disappear, Katherina discovered that DMS produced by the dinoflagellate Alexandrium minutum (causative agent of toxic algal blooms) was the chemical cue for the infection of its parasitoid Parvilucifera sinerae.  An elegant video illustrated how DMS at 300 nM was able to activate the parasitoid spores from a dormant state to leave the sporangium (an infected A. minutum cell) in transit to infect other cells and propagate. Activation only occurred in the range of 30 to 300 nM indicating that the effect was dependent on cell density. Thus, Katherina’s work showed that DMS plays an important role in the biological control of toxic algal blooms in the oceans. Her results contribute to the better understanding of marine chemical ecology.

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