Biology

Event Date: 
Wednesday, November 27, 2013 - 18:00 - 18:15
Institution: 
Hawkesbury Institute for the Environment, UWS
Title: 

Organic phosphorus acquisition may be a functional driver of community structure for ectomycorrhizal fungi in a tri-partite symbiosis

Abstract: 

 
Alnus trees associate with ectomycorrhizal (ECM) fungi and nitrogen-fixing Frankia bacteria, and while their ECM fungal communities are uncommonly host specific and species poor, it is unclear whether the functioning of Alnus ECM fungal symbionts differs from that of other ECM hosts. We used exoenzyme root tip assays and molecular identification to test whether ECM fungi on Alnus rubra differed in their ability to access organic phosphorus and nitrogen as compared with ECM fungi on the non-Frankia host Pseudotsuga menziesii. At the community level, potential acid phosphatase (AP) activity of ECM fungal root tips from A. rubra was significantly higher than those from P. menziesii, while potential leucine aminopeptidase (LA) activity was significantly lower for A. rubra root tips at one of the two sites.  At the individual species level, there was no clear relationship between ECM fungal relative root tip abundance and relative AP or LA enzyme activities on either host. Our results are consistent with the hypothesis that ECM fungal communities associated with Alnus trees have enhanced organic phosphorus acquisition abilities relative to non-Frankia ECM hosts.  This shift, in combination with chemical conditions present in Alnus forest soils, may drive the atypical structure of Alnus ECM fungal communities. 

Event Date: 
Wednesday, November 27, 2013 - 19:00 - 20:00
Institution: 
Deptartment of Civil and Environmental Engineering, MIT
Title: 

The Ocean....from the microscale

Abstract: 

At a time when microbial ecology is largely traveling along genomic roads, we cannot forget that the functions and services of microbes depend greatly on their behaviors, encounters, and interactions with their environment. New technologies, including microfluidics, high-speed video-microscopy and image analysis, provide a powerful opportunity to spy on the lives of microbes, directly observing their behaviors at the spatiotemporal resolution most relevant to their ecology. I will illustrate this 'natural history approach to microbial ecology' by focusing on marine bacteria, unveiling striking adaptations in their motility and chemotaxis and describing how these are connected to their incredibly dynamic, gradient-rich microenvironments. Specifically, I will present (i) direct evidence for a diverse gallery of microscale microbial hotspots in the ocean; (ii) a new framework for understanding the evolution of microbial diversity in the ocean; and (iii) microfluidic experiments to capture the dramatic chemotactic abilities of bacterial pathogens towards the roiling surface of coral hosts. Through these examples, I hope to show that direct visualization can foster a new layer of understanding in microbial ecology and can help us unlock the ocean's microscale.

Event Date: 
Wednesday, October 30, 2013 - 18:00 - 18:15
Institution: 
UNSW
Title: 

NO signals for dispersing biofilms in clinical and industrial applications

Abstract: 

A story from science bench to bedside, or at least towards it What started as purely academic studies of the life cycle of bacterial biofilms, addressing the regulation of cell death events during late developmental stages, led to the discovery of a role for nitric oxide (NO) as a key regulator of biofilm dispersal. NO, which is a simple gas and universal biological signal, was found to be produced endogenously in mature biofilms, and trigger a signaling pathway involving the secondary messenger cyclic di-GMP, which in turn activates cellular effectors resulting in dispersal. Add-back of low levels (picomolar to nanomolar range) of NO was able to induce dispersal across various single species and mixed species biofilms. While the biofilm mode of growth confers a high level of resistance to control measures including antibiotics, exposure to NO greatly increases the efficacy of a range of antimicrobial treatments. Therefore the use of low, non-toxic concentrations of NO represents a promising strategy for the management of biofilms in medical and industrial contexts. Several NO-based technologies have been developed to control bacterial biofilms, including: (i) NO-generating compounds with short or long half-lives and safe or inert residues, (ii) novel materials and surface coatings which catalytically produce NO in situ, and (iii) novel compounds for the targeted delivery of NO to infectious biofilms during systemic treatments.

Event Date: 
Wednesday, October 30, 2013 - 19:00 - 20:00
Institution: 
USyd
Title: 

How microbial community structure is shaped

Abstract: 

 
Microbes profoundly influence biological systems. Owing to their small individual size, but extremely large populations, their influence is typically an emergent property of the microbial community.  As such understanding how microbial community structure is shaped is a generic question relevant to almost all biological systems.
A major focus of my research is the interplay between diet, gut microbiota and health. Our health is the product of interplay between many different factors with arguably three of the most important being adequate nutrition, homeostatic regulation and exclusion of foreign cells. Gut functions influence all these, but occur in the immediate proximity of a huge community of microorganisms – our gut microbiome. The gut microbiome profoundly effects our health via its contribution to and influence on gut functions.
Arguably the most significant aspect of our gut microbiome is that differences in composition matter. The contribution of our microbiome to nutrition, metabolism, gut and immune functions varies from person-to-person. Thus the clinical manifestation of many diseases will be influenced by the individual’s microbiome. Secondly, environmental or lifestyle differences such as diet and hygiene may modulate microbiome composition and thus its influence on health. This gives rise to two basic opportunities for improving healthcare. These are, using the microbiome as a metric to improve diagnosis and targeting the microbiome for therapeutic intervention. We are specifically exploring forces that shape microbial community structure in mouse and human models of with a view to developing diagnostic and intervention strategies across a range of health issues. 

Event Date: 
Wednesday, August 28, 2013 - 18:15 - 18:30
Institution: 
CSIRO Canberra
Title: 

Multi-scale spatial patterns of soil microbial communities and biogeochemical processes in three arctic ecosystems

Abstract: 

Microbial communities and their functional role in soil biogeochemical processes vary across spatial scales. Although soil and microbial spatial variability has been studied in various tropical and temperate ecosystems, little information is available from arctic ecosystems. Arctic soils represent a significant proportion of global land mass and contain about one fourth of total soil carbon pool. Soil microbial nitrogen (N) transformations such as nitrification and denitrification have significant implications for N availability and N loss in nutrient-limited arctic ecosystems. This study explored the spatial relationships among microbial communities, functional processes and soil properties in three Canadian arctic ecosystems. Despite adverse climatic conditions and frequent cryopedogenic processes, soil attributes and microbial abundance are highly spatially structured and their spatial autocorrelation is consistent within and between the ecohabitats. However, the zone of spatial autocorrelation is substantially smaller than non-arctic ecosystems. Ammonia-oxidizing and denitrifying communities are spatially structured within 5 m whereas potential nitrification and denitrification are spatially autocorrelated within 40 m in arctic soils. Nitrification activities are driven at small scales (<1 m) by moisture and total organic carbon content whereas gene abundance and other edaphic factors drive at medium (1-10 m) and large (10-100 m) scales. Soil moisture, organic carbon and nitrogen content are the predominant driving factors with nirK abundance also correlated to denitrification across spatial scales. Overall, this study unravels the multi-scale determinants of nitrification and denitrification in Arctic ecosystems.

Event Date: 
Wednesday, August 28, 2013 - 19:00 - 20:00
Institution: 
iThree Institute UTS
Title: 

Genome plasticity in Vibrio species – how lateral gene transfer directs niche specialisation and pathogenicity

Abstract: 

Bacteria of the Vibrio genus are abundant in aquatic environments, fulfil important nutrient cycling roles and are often found in association with marine animals such as corals, molluscs, sponges, crustaceans and fish. This diversity in niche occupation is a feature of Vibrio species and is largely (or at least in significant part) driven by lateral gene transfer (LGT). LGT is a two-step process firstly requiring physical transfer of DNA from one bacterial cell to another followed by subsequent integration of the transferred DNA into the genome thus allowing stable inheritance and expression. Numerous mechanisms for integration exist such as homologous recombination and a wide-range of diverse genetic elements such as transposons, integrative conjugative elements, prophages and integrons. Using two Vibrios species, V. rotiferianus and V. cholerae, research in our laboratory has sought to understand how mobile DNA contributes to vibrio evolution, niche specialisation and pathogenicity. In V. rotiferianus, we have been researching the integron, a genetic element that contributes up to 3% of a vibrios genome in laterally acquired mobile DNA. This region is dynamic and evolves at a faster rate than mutation. Our research has shown that this region provides the organism a mechanism for reworking surface polysaccharide affecting biofilm formation and potentially interactions with higher organisms. Furthermore, we have been researching evolution in V. cholerae isolated from Sydney estuarine waters. These isolates are pathogenic in animal models with all lacking the usual virulence factors of cholera toxin and colonisation factor tcpA and most lacking type III secretion indicating the presence of novel virulence factors. One isolate we are focussing on contains a novel 32-kb mobile element inserted into the indigenous recA but carries a unique recA with only 80% identity to other V. cholerae recA genes. Overall, our research demonstrates the plasticity of vibrio genomes and the significant contribution that LGT makes to the continuing evolution to the Vibrio genus.

REPORT
Mike Manefield

Amazing turn out for JAMS last night at the Australian Museum. Three excellent presentations from Nathan Lo (Blattabacterium genome evolution - USyd), Tom Jeffries (Sydney Harbour Microbiome - UTS) and Yit Heng Chooi (Fungal metabolite genetics and biochemistry - ANU). The audience was also on the money with probing questions reassuring the speakers that their labours are well appreciated by an elite body of microbiology professionals.

The idea of a two day microbial community analysis workshop was also re-introduced and planning for this has commenced. A call is also out for volunteers for the Australian Museum Sciecne Festival (10th August, 13th-15th August and 20th-22nd August).

Please email Mike Manefield if you're interested. As of the 1st of August, we still need around 10 more volunteers.

Event Date: 
Wednesday, July 31, 2013 - 19:00 - 19:45
Institution: 
Australian National University
Title: 

Understanding Secondary Metabolite Biosynthesis as the Key to Unlock New Chemical Diversity in Fungi – from Viridicatumtoxin to the Immunosuppressive Neosartoricin

Abstract: 

The advancement of DNA sequencing technology has unlocked an unprecedented amount of microbial genomic information. These genome sequences also revealed a large number of secondary metabolite (SM) genes in both bacteria and fungi. For filamentous fungi in particular, the number of SM gene clusters encoded in the genome are often beyond the number of compounds that are reported for individual species. This is likely attributed to the tight regulation of the SM genes by the eukaryotic fungi compared to their prokaryotic counterparts, where some SM genes are only expressed in the presence of appropriate environmental signals. Research is currently going on to uncover new methods to activate these "silent" gene clusters. However, at the same time, continuously expanding our understanding of the relationship between SM compounds, the biosynthetic genes and microbial ecology will assists us in navigating the exponentially expanding seas of genomic information in the search for new bioactive compounds. The past four years, I have been involved in the elucidation of the SM pathways for viridicatumtoxin, griseofulvin, tryptoquialanine, cytochalasins, lovastatins, echinocandin, fumagilin and azaphilones. A specific example is given here on how the investigation into the genes and enzymes involved in the biosynthesis of an interesting molecule, viridicatumtoxin, eventually leads to the discovery of a new immunosuppressive compound, neosartoricin, from the human pathogens Aspergillus fumigatus and Neosartorya fischeri.

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