In this issue


Microbiology Australia Microbiology Australia
Issue 2

Vertical Transmission, May 2007

As you read this column, I along with two members of the society, Liz Harry and Belinda Ferrari, will have taken part in Science Meets Parliament. This annual event, organised by the Federation of Australian Scientific and Technological Societies (FASTS), provides the opportunity for scientists to understand political processes and for members of parliament to gain insight into how science contributes to Australia?s environmental, social and economic development. It is important that microbiological issues are raised and the that the society is...

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Yeasts: Products and Discovery (YPD) in Australia

'Consider life without chocolate or good quality coffee' (see Graham Fleet and Hugh Dircks paper, ?Yeast, Cocoa Beans and Chocolate?, in this Yeast Special Edition of Microbiology Australia). And one can add to their list: wine (see papers from Sakkie Pretorius? and Vladimir Jiranek?s groups), beer (Vince Higgin?s paper) and leavened breads. All require the action of yeasts for their production, and yeasts are of enormous value as hosts for the expression and production of many proteins, including pharmaceuticals (see Ian Macreadie?s paper). Cl...

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It is well known that brewers yeast can grow by fermentation but it can also respire using mitochondria. However, damage to mitochondria can permanently block respiration. Such damaged or mutant cells can still grow, although more slowly than the wild-type, producing ?petite colonie? forms on agar plates. Remarkably, these small colonies appear spontaneously at the high frequency of 1% per generation. Indeed, petite colonie forms had frequently been observed in plated cultures of brewers or bakers yeast Saccharomyces cerevisiae by a number of g...

Yeast, cocoa beans and chocolate

Yeast play a key role in the fermentation of many foods andbeverages. The best known examples are bread, beer and wine, where understanding of the ecology, biochemistry, physiology and genomics of the yeast contribution is well advanced. Yeast also have prominent roles in the production of other well-known commodities, such as cheeses, salami-style meat sausages, and soy sauce, where their activities in the fermentation and maturation processes are attracting increasing research. Still, there are many other products where yeast have a significa...

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Functional genomics in yeast

Completion of the Saccharomyces cerevisiae genome sequencing project in 1996 led to an incredible explosion of research on basic cellular processes and has provided the opportunity to determine how genes and their products are regulated and function on a genome-wide scale. The technologies that were developed from this provided an incredible array of tools to study cellular processes in great detail and were a paradigm for developments from subsequent sequencing projects.

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Not all wine yeast are equal

It may come as a surprise to learn that there are over 200 commercial strains of Saccharomyces cerevisiae available for winemakers to work their magic on grape juice. Why so many? Surely one or two reliable workhorse strains should suffice; after all, don?t they just make ethanol from sugar? The answer to this is an emphatic no; the more we look at the role(s) of yeast in winemaking, the more we are learning about their influences on appearance, aroma, flavour, mouthfeel and final ethanol concentration. And different yeast are more or less robu...

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Host factors in virus budding ? Insights from yeast

The budding yeast, Saccharomyces cerevisiae, is an excellentmodel organism for the study of eukaryotic cellular processes such as endocytosis 1. Like other eukaryotic cells, yeast take up extracellular material by invagination of the plasma membraneto form a vesicle. The internalised material is transported to a membrane-bound compartment, the early endosome. As the early endosome matures, internal vesicles form within the lumen giving it the appearance of a multivesicular body (vesicles enclosed by a membrane). The machinery required for endos...

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Optimisation of industrial strains of Saccharomyces cerevisiae using recombinant and non-recombinant methods

The production of fermented beverages such as beer and wine is typically achieved using strains of Saccharomyces cerevisiae, which have been selected for their reliable fermentative properties and desirable sensory contribution to the end product. Even so, these strains are not without shortcomings and new strains are constantly being sought. In aiming to provide such strains, working with industrial isolates has its own set of challenges. Wine strains of S. cerevisiae are typically of higher ploidy or aneuploid, frequently lack convenient sele...

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Compartmentation of cellular activities

In the yeast Saccharomyces cerevisiae, almost one third of cellular function is concerned with maintaining the compartmentation of cellular activities. From classic studies in yeast genetics we have come to understand a great deal of the processes driving the delivery of proteins into these compartments and the metabolic advantages that this provides. With the publication of the yeast genome sequence, ?-omics? level studies began to provide further detail on the compartmentation of yeast cells. Very recent technological advances, including new ...

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Organelle turnover by autophagy

All eukaryotic cells turn over (degrade) parts of their internal structure, including organelles, by autophagy (?self eating?), a process that utilises a specialised compartment of cells; the vacuole in yeast and the lysosome in mammals. Defects in autophagy are increasingly being linked to pathological conditions, including neurodegenerative and muscle diseases and some forms of cancer. In addition, several studies report a role for autophagy as a mechanism for the removal of invading bacteria (e.g. Streptococcus pyogenes, Mycobacterium tuberc...

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The emergence of Cryptococcus gattii VGII as a super killer?

Members of the Cryptococcus neoformans (C.n.) species complex are basidiomycetous yeast, which cause the second most common life-threatening invasive fungal disease (cryptococcosis) in humans and animals worldwide. The C.n. species complex has spawned the recent global emergence of highly virulent strains and is comprised of two closely related species.

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Saccharomyces cerevisiae as a conduit to providing insights into cellular responses using hypothesis-generating technology

In the post-genomic era, hypothesis-generating methods of data collection have facilitated rapid advances in many areas of research. Using Saccharomyces cerevisiae in conjunction with these methods we have been able to gain insight into the ?bigger picture? of our particular research fields. This has provided the means of generating more ?informed? hypotheses that have subsequently been used in traditional hypothesis-driven research. As a result, important issues have been elucidated in the areas of flavour profile management in industrial ferm...

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Yeast DNA damage response pathways and human disease

All living organisms are constantly subjected to a diverse range of environmental genotoxins such as ultraviolet radiation, but even in a perfect environment, DNA damage would be unavoidable; DNA polymerases inevitably make errors, spontaneously stalled replication forks are at high risk to collapse into DNA double strand breaks and free radicals generated during normal cellular metabolism damage thousands of bases per cell per day. DNA damage that is not appropriately repaired leads to accumulating genome instability, which we now know is a ma...

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Molecular characterisation of the wine spoilage yeast ? Dekkera (Brettanomyces) bruxellensis

How would you react if, upon opening that expensive bottle of red wine you had been saving for a special occasion, all you could smell was a box of Band-aid medical plasters. ?Band-aid?, or ?medicinal? aroma in red wine is but one spectrum of the (generally) negative sensory characteristics that have become synonymous with wine ?spoiled? by the yeast species Dekkera bruxellensis, and its non-sporulating form Brettanomyces bruxellensis.

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Regulating the transition between the two major fungal cell types; yeast cells and filamentous hyphal cells

Fungi are a large group of eukaryotic microorganisms that are of medical, agricultural and biotechnological importance. They are a diverse group, occupying their own kingdom, and range from single cells to what is arguably the largest mutlicellular organism on earth. Despite this diversity, fungi exhibit two predominant growth forms; unicellular yeast and multicellular filamentous hyphae. Some fungi can alternate between these two forms in response to an intrinsic or extrinsic stimulus, a process known as dimorphic switching.

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Therapeutic products from yeast

Over the past three decades recombinant DNA methodologies for yeast have opened a plethora of new biotechnology opportunities for biotechnology?s oldest organism. It is now possible to introduce foreign genes that are capable of encoding rare proteins or new pathways that could lead to the production of rare or novel biological or chemical entities (NBEs or NCEs).

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?Cradle?to?grave? regulation of mRNA fate

Microarray studies in Saccharomyces cerevisiae have set the benchmark for genome-wide analyses, available data-sets covering practically every stage of gene expression from DNA-binding by transcription factors to mRNA export, sub-cellular localisation, translation and decay. A theme to emerge from such data has been the prevalence of coordinate gene regulation. Thus, gene modules or ?regulons? are well recognised at the level of gene transcription and the activity of transcription factors provides an obvious molecular explanation for such coord...

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Alcohol, stress and working with yeast

Ethanologenic fermentation is traditionally associated with beverage production. However, more recently it has become increasingly important in the biofuel sector. Although the harnessing of yeast for societal outcomes has resulted in many improvements to the fermentation process, there are still considerable gains to be made in this area. In this regard, microbial sensitivity to ethanol toxicity is a major factor affecting fermentation productivity, its impact causing lower fermentation rates, reduced ethanol yields and decreased microbial lif...

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ASM Affairs, May 2007

ASM new members; ASM sustaining members

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