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Event Date: 
Wednesday, October 28, 2015 - 18:15 - 18:30
Institution: 
UTS
Title: 

Heterogeneity in diazotroph diversity and activity within a putative hotspot for marine nitrogen fixation

Abstract: 

Australia’s tropical waters represent predicted “hotspots” for nitrogen (N2) fixation based on empirical and modelled data. However, the identity, activity and ecology of N2 fixing bacteria (diazotrophs) within this region are virtually unknown. By coupling DNA and cDNA sequencing of nitrogenase genes (nifH) with size fractionated N2 fixation rate measurements, we elucidated diazotroph dynamics across the shelf region of the Arafura and Timor Seas (ATS) and oceanic Coral Sea during Austral spring and winter. During spring, Trichodesmium dominated ATS assemblages, comprising 60% of nifH DNA sequences, while Candidatus Atelocyanobacterium thalassa (UCYN-A) comprised 42% in the Coral Sea. In contrast, during winter the relative abundance of heterotrophic unicellular diazotrophs (∂-proteobacteria and gamma-24774A11) increased in both regions, concomitant with a marked decline in UCYN-A sequences, whereby this clade effectively disappeared in the Coral Sea. Conservative estimates of N2 fixation rates ranged from < 1 to 91 nmol L-1 d-1, and size fractionation indicated that unicellular organisms dominated N2 fixation during both spring and winter, but average unicellular rates were up to 10-fold higher in winter than spring. Relative abundances of UCYN-A1 and gamma-24774A11 nifH transcripts negatively correlated to silicate and phosphate, suggesting an affinity for oligotrophy. Our results indicate that Australia’s tropical waters are indeed hotspots for N2 fixation, and that regional physicochemical characteristics drive differential contributions of cyanobacterial and heterotrophic phylotypes to N2 fixation.

Event Date: 
Wednesday, October 28, 2015 - 18:00 - 18:15
Institution: 
UNSW
Title: 

Key to living in the extreme desert soils of eastern Antarctica: a chemolithotrophic lifestyle

Abstract: 

Mitchell Peninsula is located at the south of the Windmill Islands, Eastern Antarctica. It is described as a nutrient poor, extreme polar desert and limited knowledge on the microbial diversity of  the soils in this area exists. We examined the microbial taxonomic composition and metabolic potential of Mitchell Peninsula soils  using 16S metagenomics and shotgun metagenomics. We found the site to be a potential biodiversity hotspot, containing a high abundance of Candidate Phyla WPS2 and AD3. Subsequently, differential binning was used to recover 23 draft genomes, including 3 genomes from WPS-2 and two from AD3.  Further analysis of the metagenome revealed a novel Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) gene to be abundant in the bacterial community, despite a lack of evidence for photosynthesis related genes. We believe that unlike many other Antarctic regions, chemolithautrophic carbon fixation via CBB cycle is the dominant carbon fixation pathway, hence this pathway is providing the key to survival is this very dry, hostile environment. 

Reference: JOB474
Application deadline: CLOSED



The Centre for Systems Genomics is holding a 1-day symposium on metagenomics and microbiome research, Tuesday November 17 at Bio21. 

Interested in presenting? Register now! and complete the abstract section.

This free event will feature talks on a range of microbiome-related topics including new computational and lab methods, covering a range of application areas including the human microbiome in health and disease, environmental metagenomics, ecology, agriculture and ancient DNA.

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Event Date: 
Wednesday, September 30, 2015 - 18:15 - 18:30
Institution: 
UTS
Title: 

Divergence in temperature stress management between coastal and East Australian current (EAC) phytoplankton populations.

Abstract: 

In June 2015, 27 scientists took part in a 3 week ocean voyage aboard the brand new Australian research vessel, the RV Investigator. The main objective of the expedition was to study sub-mesoscale processes - billows and eddies - along the productive shelf influenced by the East Australian Current. Dr Olivier Laczka is presenting the results obtained for one of the multiple projects conducted during this voyage. Microbial communities from the EAC and a coastal site (north of Smokey Cape) were incubated along a temperature gradient (spanning 32 to 15.5 °C) to examine their capacity to deal with departures from in situ temperature (~22 °C). Intracellular stress within picoeukaryote populations was examined using a fluorescent stain targeting Reactive Oxygen Species (ROS). Stained samples were examined with a flow cytometer (excitation wavelength 488 nm). The goal of this study was to assess whether EAC microbial communities are more thermally tolerant than coastal microbial communities and determine whether general oxidative stress patterns could be used as a signature of water mass origins.

Event Date: 
Thursday, October 8, 2015 - 15:00 - 19:00

 

JAMS will be presenting a seminar series at the Westmead Millennium Institute, held 3-7pm Thrusday October 8th.

Registration is free, please RVSP.
Afternoon tea and dinner with drinks will be provided.

Seminar Speakers:

Dr Cameron Webb – Plenary

Mosquito‐borne disease in Australia: emerging threats and novel solutions

Prof Shari Forbes

Profiling breath samples for detection of volatile bacterial ‘fingerprints’ in lung infections

Dr Carola Venturini

Gut microbial ecology: the side‐effects of antibiotic treatment

Dr Gurjeet Kohli

Hunt for toxin biosynthesis genes in dinoflagellates

Dr Matthew O’Sullivan

Managing healthcare workers with suspected Ebola in Sierra Leone

Connie Ha

The guts of lifestyle disease management: targeting host‐microbiome interactions for optimal intervention

Event Date: 
Wednesday, September 30, 2015 - 18:00 - 18:15
Institution: 
Macquarie University
Title: 

Aquifer microbial community assembly: do neutral processes dominate?

Abstract: 

Community assembly processes can be condensed into four categories: dispersal, selection, drift and speciation. We tested aquifer communities (of Archaea, Bacteria, Fungi, and Eukarya generally) for evidence that dispersal limitation and environmental selection play a role in determining community biodiversity and composition. We found only weak evidence for these processes at a regional scale of up to 250 km and spanning several significant dispersal barriers. I discuss the possibility that neutral (i.e. non-deterministic, non-selective) processes dominate in groundwater ecosystems, and the spatial scaling of these processes.

 

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