Microbiology

Event Date: 
Wednesday, February 25, 2015 - 17:00 - 17:30
Institution: 
University of Southern Maine
Title: 

Prochlorococcus: the “invisible forest” in the ocean’s Outback.

Abstract: 

The smallest, most abundant phototroph in the world, Prochlorococcus, dominates the base of the food web in the “Outback” of the world’s oceans, the nutrient-depleted ocean gyres. This unicellular, marine cyanobacterium, unknown only 30 years ago, is an oligotrophic specialist with a streamlined genome and reduced cellular requirement for the limited resources available in this environment. Based on physiological and molecular analyses of isolated strains from different oceans and depths, two broad groupings of Prochlorococcus were characterized: high- and low-light adapted “ecotypes”. Within these broad groupings are many subclades, some of which have been shown to dominate under certain temperature and light conditions. Through additional culture-based studies, my lab has been exploring nutrient physiology and other physiological characteristics that may contribute to the ecology and evolution of other Prochlorococcus subgroups. Some subgroups have the capacity to utilize nitrate, which was not the case for the initial isolates of Prochlorococcus, and others differ in their pigmentation. We have also found that Prochlorococcus regulates its uptake velocity and specific affinity for inorganic and organic phosphorus under P stress conditions. Examining the physiology, ecology and genomics of Prochlorococcus isolates and natural populations is providing insights into how these tiny photosynthesizing cells create a stable, yet invisible forest in the deserts of the world’s oceans.

Event Date: 
Wednesday, January 28, 2015 - 18:00 - 18:15
Institution: 
University of New South Wales
Title: 

Biomining and methanogenesis for resource extraction from asteroids

Abstract: 

As spacecraft fuel is a limited resource, creating a readily available source for hydrocarbon-based fuels in space will reduce launch cost and increase operating time of spacecraft. Biomethanation is viable for Earth-based operations, thus applications in space under controlled conditions have potential. This study proposes a sustainable environment for methanogens on Near-Earth Objects. Vacuum and desiccation effects, at 0.025% Earth atmospheric pressure, are conducted on three bacterial and three Archaea strains to test post-exposure viability. Cell degradation and colony size reduction was quantified for aerobic strains. Adverse effects were exhibited more so in gram-negative than gram-positive strains. Archaea showed limited to no cell degradation, providing evidence that vacuum effects, at these pressures, will have minor effects on in-situ biofuel operations. If successful, a sustainable and cost-effective method of metal extraction and producing methane based fuel reservoirs could revolutionise in-situ resource and fuel resupply of spacecraft, thus enhancing spacefaring capabilities.

Event Date: 
Wednesday, November 26, 2014 - 19:00 - 19:45
Institution: 
UNSW
Title: 

“The microbial friends and foes of seaweeds”

Abstract: 

 

Seaweeds (macroalgae) form a diverse and ubiquitous group of photosynthetic organisms that play an essential role in many aquatic ecosystems, yet till recently very little was understood with respect to their associated microbiota. We now know that macroalgae are home to a diverse community of microorganisms, that display both temporal and spatial variation yet remain distinct from the surrounding seawater. Symbiotic interactions between marine microorganisms and macroalgae can have both positive (e.g. providing nutrients and morphogenic cues or protection from biofouling) and negative (e.g. disease) outcomes for the host. This talk will give an overview of the microorganisms typically associated with macroalgae with a focus on the bacterial symbionts. Details of how bacteria successfully colonize macroalgal hosts will be discussed with specific examples of the functional role of microbial epiphytes in macroalgal health (including disease) highlighted from a “holobiont” perspective.

 

Event Date: 
Wednesday, November 26, 2014 - 18:15 - 18:30
Institution: 
QAAFI
Title: 

Plant Cell Wall Breakdown in Complex Ecosystems

Abstract: 

Plant cell walls in e.g. whole grains, fruits and vegetables are a major source of dietary fibre (DF) in human diets. Cellulose is a key DF component, and its fermentation in the large intestine also contributes to the extent of nutritional benefits to the host. However our understanding of which microbes actively ferment cellulose in the complex gut environment is minimal. Here we report on the use of isotopically-labelled cellulose as a route to defining microbial fermentation in a complex ecosystem. The ability of the Gram-negative, obligately aerobic, rod-shaped bacteriumGluconacetobacter xylinus, to produce extracellular cellulose in simple fermentation experiments, in the presence of a 13C-labelled carbon source, was exploited to make isotopically labelled cellulose. Scanning electron microscopy (SEM) and nuclear magnetic resonance spectroscopy (NMR) showed no differences in micro-architecture and crystallinity between native and isotopically labelled bacterial cellulose. Fermentability was assessed by an in vitro batch culture system, where anaerobic fermentations with either a pig faecal slurry or minimal medium with a 1: 5 diluted pig faecal inoculum were carried out.  The gas production kinetics was recorded and end-products were analysed. Results indicated that 13C did not alter the fermentability of bacterial cellulose. We are now carrying out DNA-stable isotope probing coupled with high-throughput sequencing, to provide direct information on which microbes from the porcine faecal inoculum actively ferment the substrates. Ultimately, combining such studies will identify mechanisms of plant cell wall breakdown in the human nutritional context and allow for the understanding of gut microbiota responses to molecularly-defined dietary changes.

Event Date: 
Wednesday, October 29, 2014 - 18:15 - 18:30
Institution: 
UTS
Title: 

Stigmergic social behaviours facilitate the active expansion of Pseudomonas aeruginosa interstitial biofilms.

Abstract: 

Erin S. Gloag1, Awais Javed2, Huabin Wang3, Michelle L. Gee3, Scott A. Wade2, Lynne Turnbull1, Cynthia B. Whitchurch1*
1 The ithree institute, University of Technology Sydney, Ultimo, NSW, 2007, Australia.
2 Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, VIC, 3122, Australia
3 School of Chemistry, University of Melbourne, Parkville, VIC, 3010, Australia.
 
Biofilms are often found associated with infections of implantable medical devices; accounting for approximately half of all nosocomial infections. Biofilms are often thought of as sessile surface-attached communities that are embedded in a protective slimy matrix. However, many bacterial pathogens also have the capacity to actively expand their biofilm communities via complex multi-cellular behaviours. We have observed that when P. aeruginosa is cultured at the interstitial surface between a coverslip and solidified nutrient media the resulting biofilm actively expands via twitching motility and is characterised by the formation of an extensive pattern of interconnected trails.
We set out to identify the factors governing pattern formation and coordinated movement during P. aeruginosa interstitial biofilm expansion. Our observations have revealed that during biofilm migration the cells at the advancing edge create furrows as they migrate across the semi-solid media The following cells are preferentially confined to these furrows, resulting in the emergence of an interconnected furrow network and the subsequent extensive large scale-patterning characteristic of these biofilms.
Stigmergy is a concept which describes self-organisation processes observed in higher organisms and abiotic systems through indirect communication via persistent cues in the environment left by individuals that influence the behavior of other individuals of the group at a later point in time. Our observations indicate that self-organised pattern formation in P. aeruginosa interstitial biofilms is also a stigmergic phenomenon. To our knowledge this is the first time that stigmergy has been identified as a mechanism of self-organisation of bacterial biofilms and propose that the concept of stigmergy can be included in the repertoire of systems used by bacteria to co-ordinate complex multicellular behaviours. We are currently exploring the development of novel antimicrobial strategies aimed at controlling and inhibiting biofilm expansion in medical settings via exploiting our new understanding of biofilm expansion.

Event Date: 
Wednesday, October 29, 2014 - 18:00 - 18:15
Institution: 
UNSW
Title: 

Ammonia-oxidizing bacteria play redundant roles with ammonia-oxidizing archeae in acidic soil

Abstract: 

 
It is widely accepted that ammonia-oxidizing achaea (AOA) dominates ammonia oxidization, the rate-limiting step in the nitrification process, in acidic soils, but their counterpart ammonia-oxidizing bacteria (AOB) which are ubiquitous in acidic soils should not be neglected. Researches about the functions of AOB in acidic soils are very few. Here, we investigated the abundance and community of AOA and AOB in acidic soils (pH 3.35 ~ 4.46) with nine different treatments (Ctrol, N, NK, NP, NPK, N+CaO, NK+CaO, NP+CaO, NPK+CaO) and found that significant positive correlations between potential nitrification rate (PNR) with the total amoA gene copy numbers of AOA and AOB. The community of AOB but not of AOA responded to CaO significantly. Moreover, microcosms incubation with different concentration CaO (N+0, 500, 1000, 2000 ppm CaO, pH 3.42 ~ 4.37) showed that the abundance of AOB amoA gene significantly increased in N+1000 and N+2000 treatments at day 7 while the abundance of AOA amoA gene significantly increased in N and N+500 treatments at day 60. The community of AOA and AOB changed significantly during the incubation. Phylogenetic analysis of bacterial and archaeal amoA gene in treatment N+1000 revealed that AOA belonged to group 1.1a-associated increased whereas that belonged to group 1.1b decreased significantly during the incubation.  AOB belonged to Cluster 10 increased significantly at day 7 but decreased during the last incubation while AOB belonged to Cluster 3a.1 and 3a.2 showed reverse trends during the incubation. Additionally, AOB belonged to Cluster 7 were obligately observed at day 7. Moreover, we studied the activity of ammonia oxidizers in treatments N, N+1000 and N+CaO with 13CO2-DNA-stable isotope probing incubation for 30 days. Interestingly, 13C-labeled carbon source was significantly assimilated into the amoA gene of AOB but not AOA at day 7 and the reverse result was observed at day 30 in treatment N+1000 though it was acidic soil. Significant assimilation of 13C-labeled carbon source was detected in AOA amoA gene in treatments N and N+CaO during the incubation. Taken together, these results suggested that AOB responded to the disturbance significantly then drove the ammonia oxidization in acidic soils, meaning that AOB played redundant roles with AOA in acidic soils though the two groups of ammonia oxidizers had special niches.

Event Date: 
Wednesday, September 24, 2014 - 19:00 - 19:15
Institution: 
CSIRO
Title: 

Animating the Gut Microbiome

Abstract: 

Animation can be a powerful way to inspire and educate people with science. Creating biomedical animations which depict advanced scientific concepts in a clear way requires 2 main considerations, 1) rigorous investigation of the underlying science, and 2) careful development of the story to express the ideas in a meaningful way.

In this talk Christopher Hammang will present his first biomedical animation “The Hungry Microbiome”. He will explore the challenges involved in animating the human gut microbiome and the unique insight gained from creating an animation about resistant starch. The talk will also explore the workflow and technology which can be used to create these biomedical animations, as well as a brief review of the science underlying resistant starch research.

 

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