Fungus

Event Date: 
Wednesday, November 26, 2014 - 18:00 - 18:15
Institution: 
UWS
Title: 

Clues of sexual reproduction in the Arbuscular Mycorrhizal Fungi: a putatively ancient asexual land-plant symbiont

Abstract: 

Arbuscular Mycorrhizal Fungi (AMF) are an ancient group of obligate land-plant symbionts which form a mutualistic symbiosis with the roots of over 80% of land plants  and are found in the majority of terrestrial ecosystems. The filamentous hyphae of these fungi grow throughout the soil, scavanging for water and nutrients and transfer these to the plant in exchange for plant produced sugars.  As a result, extensive underground networks can form where multiple fungal individuals can be connected to a single plant and a single fungus can be connected to multiple plants simultaneously.  AMF do not have cells, rather nuclei flow freely through a common cytoplasm and genetically distinct individuals of a species are capable of anastomosis – or hyphal fusion – where cytoplasmic and nuclear exchange may occur. Curiously, these fungi have been once classified as ‘ancient asexuals’ due the lack of any observable sexual structures and an assumed purely clonal life-style. I present recent insights from the genome of the model AMFRhizophagus irregularis which contains evidence of a genetic tool kit which looks more like that of a sexually reproducing organism. I highlight the extreme expansion of a group of MATA-HMG genes which normally act as master- regulators of sex in fungi and present insights into the structure and function of these genes from a survey of local and global populations of R. irregularis individuals along with transcriptional evidence via QRT-PCR that a subset of these genes have a functional involvement in AMF partner recognition and possibly sexual reproduction.

Event Date: 
Wednesday, February 27, 2013 - 15:15 - 15:45
Institution: 
University of Western Sydney
Title: 

Responses of soil fungi to global change: effects of elevated atmospheric CO2, temperature and drought

Abstract: 

Fungi are central to forest carbon and nutrient cycles in Australian sclerophyll forest soils, but little is known about how they will respond to future global change. Our recent research has used a combination of controlled environment glasshouse and field experimentation to investigate the interactive effects of elevated atmospheric CO2 concentration [CO2], increased temperature and drought on Australian eucalypt soil fungal biodiversity.
 
In a glasshouse experiment, seedlings of two eucalypt species (Eucalyptus saligna and E. sideroxylon) were grown in field soil for 5 months under sub-ambient (290 µl l-1), ambient (400 µl l-1) and elevated (650 µl l-1) atmospheric CO2 conditions at both ambient (26°C) and elevated temperature (30°C). Multivariate analyses conducted on molecular data generated from soil and hyphal ingrowth bags (which select for mycorrhizal fungal mycelia) showed a significant (P < 0.035) separation between fungal communities associated with the two different tree species. While there was an effect of [CO2] and temperature, the response was plant species dependent with the exception of the combined elevated [CO2] and elevated temperature treatment (650 µl l-1 CO2 and 30oC) which clustered together regardless of tree species.
 
In the field experiment, E. saligna trees were grown in 12 whole tree chambers for three years under controlled temperature conditions and exposed to either ambient (ca. 380 µl l-1) or elevated (ca. 640 µl l-1) atmospheric [CO2] and different watering regimes to simulate drought. Multivariate analyses of molecular data showed that elevated [CO2] intensified the effect of drought stress by significantly altering fungal community composition.
 
Collectively, our data demonstrate that alterations to atmospheric [CO2], temperature and drought conditions modify soil fungal communities associated with Australian eucalypts. We are currently investigating the knock-on effects of these changes for fungal driven soil processes given the potential for soil microorganisms to significantly influence the direction and magnitude of terrestrial ecosystem/atmosphere feedbacks that regulate global change.

Event Date: 
Wednesday, August 29, 2012 - 18:00 - 18:15
Institution: 
University of Western Sydney
Title: 

Beware the mulch! Adaptation to its natural habitat makes Aspergillus fumigatus a formidable human pathogen.

Abstract: 

 
The fungus Aspergillus fumigatus can be found in decaying organic matter such as compost.  As an adaptable environmental microbe it can survive in a wide range of habitats including the lungs of birds and mammals.  It has become the most important cause of morbidity and mortality in immunosuppressed patients undergoing stem cell transplantation.  The success of A. fumigatus as a pathogen can be attributed to its ability to cope with environmental stresses that are similar to the conditions encountered by microbes in the human body.  In particular the fungus can survive interactions with host immune cells such as dendritic cells.  In this talk the interaction of the fungus with human dendritic cells will be explored along with the usefulness of protozoan models to examine the pathogenicity of A. fumigatus.
 

Event Date: 
Wednesday, March 28, 2012 - 18:00 - 18:15
Institution: 
University of Sydney
Title: 

Genetically controlled network architecture in the filamentous fungus Neurospora crassa constrains amino acid translocation

Abstract: 

Effective nutrient translocation in fungi is essential for nutrient cycling, mycorrhizal symbioses, virulence and substrate utilization. An interconnected mycelial network is proposed to influence resource translocation, but has not been empirically tested. By comparing amino acid translocation in Neurospora crassa colonies defective in network formation and translocation between wild type colonies of different developmental ages, we can gain insight into the influence of network formation on nutrient translocation.

Event Date: 
Wednesday, November 30, 2011 - 18:15 - 18:30
Institution: 
University of Sydney
Title: 

The fungal secretome and virulence: analysis of the proteins secreted by Cryptococcus gattii strains with different virulence profiles.

Abstract: 
Cryptococcus gattii is a ubiquitous environmental yeast-like fungus capable of causing disease in a wide range of animal hosts. In humans, disease progression begins after inhalation of the infectious propagule leading to infection of the lung. The infective yeast cells can then disseminate to the central nervous system, resulting in meningoencephalitis, which can be fatal if left untreated.

Closely related strains of C. gattii exhibit significantly different degrees of virulence in the mammalian host. Fungi utilize absorbtive nutrition and produce a range of secreted degrative enzymes, and as these may invoke a host response, the fungal secretome is likely to be very important in modulating the host-pathogen interaction. In this study, we compare the secretomes of two C. gattii strains, one categorized as hypervirulent (R265) and the other exhibiting low-level virulence (R272). C. gattii was grown under conditions designed to be as similar as possible to those encountered in vivo. Secreted proteins were captured from the culture supernatant by re-circulating across ProteominerTM beads using a closed peristaltic pump system. Concentrated protein was analysed via 1D nanoLC-MS/MS. A total of 27 proteins were identified with only four protein identifications being shared by both strains. The secretome of R265 primarily included uncharacterized proteins containing catalytic cores with roles in carbohydrate degradation as well as the antioxidant superoxide dismutase and a GTPase. R272 secreted a more diverse set of proteins including enolase and transaldolase, enzymes canonically involved in glycolysis and the pentose phosphate pathway respectively, but both also described as fungal allergens that bind IgE.

This work indicates that very different cohorts of proteins are secreted by closely related strains of C. gattii exhibiting different levels of virulence. By enhancing our understanding of the fungal secretome and unraveling these differences it may suggest novel therapeutic strategies or help devise diagnostic markers predicting for disease progression.
Event Date: 
Wednesday, August 31, 2011 - 19:15 - 20:00
Institution: 
Oregon State University
Title: 

Genomics-guided discovery of novel traits in Pseudomonas fluorescens

Abstract: 

Pseudomonas fluorescens is a diverse bacterial species known for its ubiquity in natural habitats and the production of structurally diverse, bioactive secondary metabolites. The high degree of ecological and metabolic diversity represented in P. fluorescens is reflected in the genomic diversity displayed among strains. Certain strains, such as the biological control bacterium P. fluorescens Pf-5, live in association with plants, protecting them from infection by plant pathogens. Strain Pf-5 produces an array of structurally-characterized secondary metabolites that are toxic to plant pathogenic bacteria, fungi and Oomycetes. Biosynthetic gene clusters for many of these metabolites are located in lineage-specific regions absent from the genomes of other strains of P. fluorescens. Orphan gene clusters, which encode for the biosynthesis of unknown natural products, have also been identified in lineage-specific regions of the Pf-5 genome and the following products identified through combined bioinformatic and chemical analyses. The novel cyclic lipopeptide orfamide A lyses zoospores produced by phytopathogenic Phytophthora spp. The FitD insect toxin contributes to the newly-discovered insecticidal activity of Pf-5, and several analogs of rhizoxin, a macrocyclic lactone, exhibit antifungal activity. Recently, orphan gene clusters expressed under the control of global regulators such as GacA have been identified via transcriptome analysis of Pf-5, demonstrating the value of global-regulator-based genome mining as an approach to decipher the secondary metabolome of Pseudomonas spp. We are also employing microarrays to gain a holistic view of genome expression profiles of Pf-5 living on seed surfaces, the environment where the bacterium interacts with seed-infecting fungi and Oomycetes to affect biocontrol. A series of Pf-5 mutants having deletions in one or many (up to seven) known or orphan gene clusters have been derived and are being tested in a series of bioassays. These approaches are providing new insights into the metabolic capacity of this bacterium, its activity on plant surfaces, and its interactions with plants, insects and other microorganisms.

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