Philip Bell

Viral eukaryogenesis: was the ancestor of the nucleus a complex DNA virus?

In the theory of viral eukaryogenesis I propose here, the eukaryotic nucleus evolved from a complex DNA virus. It is proposed that the virus established a persistent presence in the cytoplasm of a methanogenic mycoplasma and evolved into the eukaryotic nucleus by acquiring a set of essential genes from the host genome and eventually usurping its role. It is proposed that several characteristic features of the eukaryotic nucleus derive from its viral ancestry. These include mRNA capping, linear chromosomes, and separation of transcription from translation. In the model, phagocytosis and other membrane fusion-based processes are derived from viral membrane fusion processes and evolved in concert with the nucleus. The coevolution of phagocytosis and the nucleus rendered much of the host archaeal genome redundant since the protoeukaryote could obtain raw materials and energy by engulfing bacterial syntrophs/prey. This redundancy allowed loss of the archaeal chromosome, generating an organism with eukaryotic features. The evolution of phagocytosis allowed the eukaryotes to be the first organisms to occupy the niche of predator.Abstract. In the theory of viral eukaryogenesis I propose here, the eukaryotic nucleus evolved from a complex DNA virus. It is proposed that the virus established a persistent presence in the cytoplasm of a methanogenic mycoplasma and evolved into the eukaryotic nucleus by acquiring a set of essential genes from the host genome and eventually usurping its role. It is proposed that several characteristic features of the eukaryotic nucleus derive from its viral ancestry. These include mRNA capping, linear chromosomes, and separation of transcription from translation. In the model, phagocytosis and other membrane fusion-based processes are derived from viral membrane fusion processes and evolved in concert with the nucleus. The coevolution of phagocytosis and the nucleus rendered much of the host archaeal genome redundant since the protoeukaryote could obtain raw materials and energy by engulfing bacterial syntrophs/prey. This redundancy allowed loss of the archaeal chromosome, generating an organism with eukaryotic features. The evolution of phagocytosis allowed the eukaryotes to be the first organisms to occupy the niche of predator.

Flow Cytometry and Cell Sorting for Yeast Viability Assessment and Cell Selection

Yeast suspensions were analysed by flow cytometry after dye staining for determination of total and viable cell densities. Results were comparable to traditional colony counting and, in addition, provided further information on the percentage of total cells that were viable. The flow cytometric methods provided results within 20 min whereas colony counts were not available until 36 h. We evaluated a number of fluorescent dyes: ChemChrome Y (CY), oxonol (Ox), propidium iodide (PI), Fungolight and rhodamine 123, for accurate determination of viability of industrial yeast cultures and freshly re‐hydrated high activity dried yeast (HADY). PI, Ox and CY gave the most conclusive live/dead discrimination and were the simplest to use. Culturing after dye staining and cell sorting demonstrated that the yeast remained viable after cell sorting and incubation with PI, CY or Ox. The methods, therefore, permit physical selection of individual yeast cells from populations of mixed viability. Sorting demonstrated that PI stained non‐culturable cells whilst CY stained culturable cells. Analysis of yeast stained simultaneously with CY and PI or with Ox and PI demonstrated that PI and CY assays were in mutual agreement with respect to viability assessments. The Ox assay was in agreement with CY and PI for live/heat‐killed mixtures. However, for re‐hydrated HADY, Ox stained a significantly (P⩽0·05) higher proportion of cells than did PI.

Prospecting for novel lipase genes using PCR

A PCR method suitable for the isolation of lipase genes directly from environmental DNA is described. The problems associated with the low levels of similarity between lipase genes were overcome by extensive analysis of conserved regions and careful primer design. Using this method, a lipase gene (oli-lipase) was isolated directly from environmental DNA. This lipase showed less than 20% similarity with other known lipases at the amino acid level. The study also revealed that distantly related members of the alpha/beta hydrolase superfamily share similar conserved motifs with the lipases, thus making these genes targets for gene prospecting by PCR.

Comparison of fermentative capacities of industrial baking and wild-type yeasts of the species Saccharomyces cerevisiae in different sugar media

Aims: To compare the fermentative capacity of wild and domesticated isolates of the genus Saccharomyces.

Goffman’s Gender Advertisements revisited: combining content analysis with semiotic analysis

An analysis of 827 advertisements from a representative sample of magazines demonstrates that an abstract framework from Systemic Functional Analysis can be used to identify the semiotic resources which are the basis for gender stereotypes. Resources such as perspectival angle, plane of composition and gaze are used to investigate stereotyped portrayals of males and females. Goffman’s work, Gender Advertisements, forms the basis for hypotheses about how male and female participants would be represented in terms of eight dimensions of visual structure, derived from Kress and Van Leeuwen’s system of analysis. Hypotheses were largely confirmed, indicating that gender stereotyping was still significant in the sample of Australian magazines analysed more than two decades after Goffman’s analysis was first published. However, several results did not confirm the hypotheses or were contrary to the direction of differences predicted. Three types of explanations for exceptions to the hypotheses are discussed: first, the need for some degree of supplementary macrocosmic or contextual analysis; second, the possibility of socially determined changes in some features of stereotyped portrayals; and third, limitations in the functional semiotic framework of analysis adopted in this study.

Heterogeneity of stress gene expression and stress resistance among individual cells of Saccharomyces cerevisiae

Knowledge of gene expression and cellular responses in microorganisms is derived from analyses of populations consisting of millions of cells. Analytical techniques that provide data as population averages fail to inform of culture heterogeneity. Flow cytometry and fluorescence techniques were used to provide information on the heterogeneity of stress‐responsive gene expression and stress tolerance in individual cells within populations. A sequence of DNA encoding the heat shock and stress response elements of the Saccharomyces cerevisiae HSP104 gene was used to express enhanced green fluorescent protein (EGFP). When integrated into the genome of yeast strain W303‐1A, intrinsic expression of EGFP increased about twofold as cells progressed from growth on glucose to ethanol utilization in aerobic batch cultures. Staining of cells with orange/red fluorescent propidium iodide (PI), which only enters cells that have compromised membrane integrity, revealed that the population became more tolerant to 52°C heat stress as it progressed from growth on glucose and through the ethanol utilization phase of aerobic batch culture. Exposure of cultures growing on glucose to a mild heat shock (shift from 25°C to 37°C) resulted in significantly increased expression of EGFP in the population. However, there was heterogeneity in the intensity of fluorescence of individual cells from heat‐shocked cultures, indicating variability in the strength of stress response in the clonal population. Detailed analysis of the heterogeneity showed a clear positive trend between intensity of stress response and individual cell resistance, measured in terms of PI exclusion, to heat stress at 52°C. Further experiments indicated that, although the mean gene expression by a population is influenced by the genetic background, the heterogeneity among individual cells in clonal populations is largely physiologically based.

Generation of a Novel Saccharomyces cerevisiae Strain That Exhibits Strong Maltose Utilization and Hyperosmotic Resistance Using Nonrecombinant Techniques

ABSTRACT A yeast strain capable of leavening both unsugared and sweet bread dough efficiently would reduce the necessity of carrying out the expensive procedure of producing multiple bakers yeast strains. But issues involving the use of genetically modified foods have rendered the use of recombinant techniques for developing yeast strains controversial. Therefore, we used strong selection and screening systems in conjunction with traditional mass mating techniques to develop a strain of Saccharomyces cerevisiaethat efficiently leavens both types of dough.

Drugs and the Media

“Drugs” are extremely newsworthy: each year they are the subject of literally thousands of items produced by the Australian media. Most of these items are repetitious, stereotypical and narrowly focused on crime, deviance and rectification. Illegal drug consumption by individuals and the efforts of medical and social welfare professionals to eradicate the “problem” so defined are the twin foci of the press and television. Legal substances (including tobacco and alcohol) are interpreted much more ambiguously, and are relatively infrequently the subject of journalistic analysis.The media systematically ignore the historical, economic and industrial aspects of drug production and consumption.“Drugs”, although habitually construed as the cause of “human” and “social” problems (and hence as necessitating administrative attention), seem strangely divorced from real political economic determinations. They serve as inexhaustabled pretexts for the proliferation of television current affairs items and newspaper fea...

A two-reporter gene system for the analysis of bi-directional transcription from the divergent MAL6T-MAL6S promoter in Saccharomyces cerevisiae.

Many sets of genes in Saccharomyces cerevisiae are divergently transcribed, but at present there are no vectors generally available for the simultaneous analysis of divergent transcription from these promoters. In the present study MEL1 and lacZ were used to construct a vector capable of measuring the divergent expression initiated by the MAL6T-MAL6S bi-directional promoter. Our observations demonstrate that the expression of both reporter genes was regulated in a similar fashion to the native MAL6T and MAL6S genes, and that induction was dependent upon the presence of a functional MALR activator gene. The results confirmed that the MAL6T-MAL6S promoter was co-ordinately regulated, repressed by glucose, induced by maltose, and that basal expression was more active in the MAL6S direction than in the MAL6T direction.

Rapid cloning of thermoalkalophilic lipases from Bacillus spp. using PCR

A lipase gene from a thermophilic Bacillus sp. TG43, whose product showed optimal activity at alkaline pH, was cloned using a lambda expression library. Consensus PCR primers were designed based on a DNA sequence alignment of the cloned lipase with two other homologous lipases reported in the literature. The consensus primers allowed rapid cloning and expression of several novel lipases from DNA of both pure cultures of Bacillus and biomass from thermophilic environmental samples.