Macquarie University

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.

 

Event Date: 
Wednesday, May 27, 2015 - 18:15 - 18:30
Institution: 
University of Western Sydney & Macquarie University
Title: 

Structure, diel functional cycling and viral ecological filtering in the microbiome of a pristine coral atoll in the Indian Ocean

Abstract: 

Given the role of microbes as both indicators and drivers of ecosystem health, establishing baselines in pristine environments is crucial to predicting the response of marine habitats to environmental change.  Here we describe a survey of microbial community composition and metatranscriptomic gene expression across the Indian Ocean, encompassing the first samples from the pristine Salomon Atoll in the Chagos Archipeligo.  We observed strong patterns in beta-diversty  which reflected  Longhurst biogeographical  provinces established  using primary productivity and thermohaline properties of ocean currents.  Samples from within Salomon Atoll showed a highly unique community which was remarkably different even from adjacent samples despite constant water exchange.  This pattern was driven by the dominance of the photosynthetic cyanobacterium Synechococcus within the lagoon, the diel activity of which was responsible for driving shifts in the transcriptional profile of samples.  Inside the lagoon, increases in the expression of genes related to photosynthesis and nutrient cycling associated with the bottom-up control of bacterial populations, however the expression of viral proteins increased five-fold within the lagoon during the day, indicating a concomitant top-down control of bacterial dynamics byphage.  Indeed, genome recruitment against Synechococcus reference genomes suggested  viruses  provide  an  ecological filter for determining the diversity patterns in this system. This study also represented a proof of concept for  using a ‘citizen oceanography’ approach utilzing tools that may easily be adapted to deployment on any ocean going yacht, greatly expanding the scale and outreach of marine microbiology studies. 
 

Thanks to the JAMS faithful for coming out to the Australian Museum last night. The ranks were slightly depleted given the large contingents that are at the ISME conference in Korea this week. No matter, more pizza for all. In the short presentations Robert Moran gave a great account of his work on plasmid and resistance determinants in E. coli lineages in the human gut and Igy Pang from UNSW presented his work on gene co-expression networks underlying synergistic antifungal treatments. In the long presentation by Michael Gillings from Macquarie University results were presented that send an ominous warning of how global antibiotic use is affecting evolution. Michael gave a rivetting account of how microbiology is fused with the Anthropocene. FInally a massive congratulations to JAMS co-founder Professer Ian Paulson from Macquarie University for being awarded an Australian Laureate Fellowship. Our very own home grown legend.

Event Date: 
Wednesday, August 27, 2014 - 19:00 - 20:00
Institution: 
Macquarie University
Title: 

"Xenbiotics and Xenogenetics: Human Influence over Microbial Evolution"

Abstract: 

The extent of human effects on planetary and biological processes means that we are now the world’s greatest evolutionary force. Perhaps the best example of human driven selection is the rapid evolution of antibiotic resistance in a wide range of bacterial pathogens. Continued antibiotic use has resulted in the assembly of complex DNA molecules composed of diverse resistance determinants and mobile elements, each with independent phylogenetic origins. These novel plasmids, transposons, integrons and genomic islands are xenogenetic, in that they have arisen in human-dominated ecosystems as a direct result of human activity. Xenogenetic elements are being released via human waste streams along with significant quantities of selective agents and other xenobiotic compounds, creating environmental reactors that foster even more complex interactions between genes, mobile elements and diverse bacterial species. Saturation of the environment with selective agents is also likely to increase the basal rates of mutation, recombination and lateral gene transfer in all bacterial species. Consequently, the antibiotic revolution may now be having unintended, second order consequences that will affect the entire microbial biosphere.

Event Date: 
Wednesday, July 30, 2014 - 18:15 - 18:30
Institution: 
Macquarie University
Title: 

Effect of Low Temperature on Tropical and Temperate Isolates of Marine Synechococcus.

Abstract: 

An abundant and globally occurring marine picocyanobacterium, the genus Synechococcus is an important player in oceanic primary production and global carbon cycling. In the complex marine environment, this widespread organism has evolved to successfully colonize and inhabit different environmental niches. Their biogeographic distribution suggests that Synechococcus ecotypes exhibit thermal niche preferences. Temperature is a key environmental variable and the elucidation of the temperature stress acclimation in members of this genus can shed light on the molecular mechanisms involved in their adaptive capability. The growth of four representative Synechococcus isolates of various ecotypes from tropical and temperate regions were monitored under various temperature conditions. This revealed drastic differences in growth rates in correlation with their thermal niche preferences. The temperate strains CC9311 and BL107 displayed higher growth rates at lower temperatures while tropical strains WH8102 and WH8109 grew better at higher temperatures. In order to further elucidate their thermal niche preference, the molecular factors influencing the temperature-related growth patterns were explored through global proteomic analysis of WH8102 and BL107. Whole cell lysates of the strains grown at different temperature conditions were fractionated using 1D SDS-PAGE and analysed using label-free quantitative proteomics. Protein identifications provided 27% and 40% coverage of the whole genome for WH8102 and BL107, respectively. Quantitation of protein expression revealed 22% and 20% of the identified proteins were differentially expressed in WH8102 and BL107, respectively. The results were further investigated using qRT-PCR and PAM fluorometry. Differential expression revealed that low temperature appeared to have a significant effect on the photosynthetic machinery. The light harvesting components, phycobilisomes exhibited a reduced expression which could be the result of protein degradation due to photo-oxidative damage and/or as a mechanism to restore the energy balance disturbed as a consequence of low temperature. The lowered phycobilisome expression is found to be a common low temperature-related response between the tropical and temperate isolates. Within the photosynthetic reaction centres, differences in the expression of some core proteins were observed between the two isolates. The expression of core proteins could correlate with the efficiency of repair mechanisms involved in the replacement of photo-damaged core proteins. This differential expression sheds light on the underlying factors which potentially influence the differences in the thermal ranges of tropical and temperate isolates.

Event Date: 
Wednesday, February 26, 2014 - 18:00 - 18:30
Institution: 
Macquarie University
Title: 

Building Virtual Cyanobacteria: To Metagenomics and Beyond!

Event Date: 
Wednesday, May 29, 2013 - 18:15 - 18:30
Institution: 
Macquarie University
Title: 

Dissemination of antibiotic resistance determinants via sewage discharge from Davis Station, Antarctica

Abstract: 

Discharge of untreated or macerated sewage presents a significant risk to Antarctic marine ecosystems by introducing non-native microorganisms that potentially impact microbial communities and threaten health of Antarctic wildlife. Despite these risks, disposal of essentially untreated sewage continues in the Antarctic and sub-Antarctic. As part of an environmental impact assessment of the Davis Station, we investigated carriage of antibiotic resistance determinants in Escherichia coli isolates from marine water and sediments, marine invertebrates (Laturnula and Abatus), birds and mammals within 10 km of the Davis sewage outfall. Class 1 integrons typical of human pathogens and commensals were detected in 12% of E. coli isolates. E. coli carrying these integrons were primarily isolated from the near shore marine water column and the filter feeding mollusc Laturnula. Class 1 integrons were not detected in E. coli isolated from seal (Miroungaleonina, Leptonychotes weddellii) or penguin (Pygoscelis adeliae) feces. However, isolation of E. coli from these vertebrates’ faeces was also low. Consequently, sewage disposal is introducing non-native microorganisms and associated resistance genes into the Antarctic environment. The impact of this “gene pollution” on the diversity and evolution of native Antarctic microbial communities is unknown. 

 

Event Date: 
Wednesday, September 26, 2012 - 18:00 - 18:15
Institution: 
Macquarie University
Title: 

Disruption of transporter genes in the enantio-pyochelin biosynthesis gene cluster of Pseudomonas protegens Pf-5 has pleitropic phenotypic effects

Abstract: 

 
Pseudomonas protegens Pf-5 is a biocontrol bacterium that produces the siderophore enantio-pyochelin under conditions of iron starvation which has the function of scavenging iron. In addition, biosynthetic intermediates of salicylic acid and dihydroaeruginoic acid are usually secreted as well. In this study, we tried to elucidate the roles of three putative transporters that are encoded by the genes PFL_3495, PFL_3503 and PFL_3504 via gene truncation experiments. Out of expectation, truncation of these genes resulted in increased secretion of these products in the culture supernatants. Transcriptional profiling revealed altered expression of the biosynthetic gene cluster by PFL_3504 mutant but not by the PFL_3495 and PFL_3503 mutants. Phenotype microarray revealed that these mutants have different stress and chemical resistance profile when compared to the wild-type. 

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