Contrasting effects of historical contingency on phenotypic and genomic trajectories during a two-step evolution experiment with bacteria

Background The impact of historical contingency, i.e. the past evolutionary history of a population, on further adaptation is mostly unknown at both the phenotypic and genomic levels. We addressed this question using a two-step evolution experiment. First, replicate populations of Escherichia coli were propagated in four different environmental conditions for 1000 generations. Then, all replicate populations were transferred and propagated for further 1000 generations to a single new environment. Results Using this two-step experimental evolution strategy, we investigated, at both the phenotypic and genomic levels, whether and how adaptation in the initial historical environments impacted evolutionary trajectories in a new environment. We showed that both the growth rate and fitness of the evolved populations obtained after the second step of evolution were contingent upon past evolutionary history. In contrast however, the genes that were modified during the second step of evolution were independent from the previous history of the populations. Conclusions Our work suggests that historical contingency affects phenotypic adaptation to a new environment. This was however not reflected at the genomic level implying complex relationships between environmental factors and the genotype-to-phenotype map.

Production of bioactive metabolites by intestinal bacteria

The adult intestinal microbiota comprises a microbial ecosystem of approximately 100 trillion microorganisms, with specific bacterial communities holding distinct metabolic capabilities. Bacteria produce a range of bioactive compounds to survive unfavourable stimuli and to interact with other organisms, and generate several bioactive products during degradation of dietary constituents the host is not capable of digesting. This thesis addressed the impact of feeding potential probiotic bacteria and other dietary strategies such as pure fatty acids and prebiotics, on gut microbiota composition, short chain fatty acid (SCFA) production and modulation of metabolism in animal models. In the first experimental chapter (Chapter 2) a gas chromatography method for the quantification of SCFA was optimized and applied in the analysis of caecal samples obtained in animal studies described in other chapters of this thesis. In Chapter 3, t10, c12 CLA supplementation was shown to significantly alter murine gut microbiota composition and SCFA production rather than no supplementation. These changes were suggested to be extra factors affecting host lipid metabolism. Chapter 4 described the contrasting effects of CLA-producing strains, Bifidobacterium breve DPC 6330 and B. breve NCIMB 702258, on murine fat distribution/composition and gut microbiota composition, suggesting that these changes were most likely strain-dependent. In Chapter 5, dietary GABA-producing strain Lactobacillus brevis DPC 6108 was shown to significantly increase (p<0.05) serum insulin in healthy rats, leading to a second experiment using a type 1 diabetes rat model. Lb. brevis DPC 6108 administration did not change insulin levels in diabetic rats, but attenuated high levels of glucose when compared to diabetic control. However, an auto-immune-induced diabetes model was suggested as a better model to study GABA-related effects on diabetes. In Chapter 6 bovine milk oligosaccharides, 6’sialyllactose and Beneo Orafti P95 oligofructose supplementations were associated with depletion or reduction of less favourable bacteria, demonstrating that ingestion of these oligosaccharides might be a safe and effective approach to modulate populations of the intestinal microbiota. In Chapter 7 (General discussion) the major findings of all studies were reviewed and discussed.

Predicting behaviour to reduce stroke risk in at-risk populations : the role of beliefs

Aims: Changing behaviour to reduce stroke risk is a difficult prospect made particularly complex because of psychological factors. This study examined predictors of intentions and behaviours to reduce stroke risk in a sample of at-risk individuals, seeking to find how knowledge and health beliefs influenced both intention and actual behaviour to reduce stroke risk. Methods: A repeated measures design was used to assess behavioural intentions at time 1 (T1) and subsequent behaviour (T2). One hundred and twenty six respondents completed an online survey at T1, and behavioural follow-up data were collected from approximately 70 participants 1 month later. Predictors were stroke knowledge, demographic variables, and beliefs about stroke that were derived from an expanded health belief model. Dependent measures were: exercise and weight loss, and intention to engage in these behaviours to reduce stroke risk. Findings: Multiple hierarchical regression analyses showed that, for exercise and weight loss respectively, different health beliefs predicted intention to control stroke risk. The most important exercise-related health beliefs were benefits, susceptibility, and self-efficacy; for weight loss, the most important beliefs were barriers, and to a lesser degree, susceptibility and subjective norm. Conclusions: Health beliefs may play an important role in stroke prevention, particularly beliefs about susceptibility because these emerged for both behaviours. Stroke education and prevention programmes that selectively target the health beliefs relevant to specific behaviours may prove most efficacious.

Cough-generated aerosols of Pseudomonas aeruginosa and other Gram Negative Bacteria from cystic fibrosis patients.

Background: Pseudomonas aeruginosa is the most common bacterial pathogen in cystic fibrosis (CF) patients. Current infection control guidelines aim to prevent transmission via contact and respiratory droplet routes and do not consider the possibility of airborne transmission. We hypothesized that with coughing, CF subjects produce viable, respirable bacterial aerosols. Methods: Cross-sectional study of 15 children and 13 adults with CF, 26 chronically infected with P. aeruginosa. A cough aerosol sampling system enabled fractioning of respiratory particles of different size, and culture of viable Gram negative non-fermentative bacteria. We collected cough aerosols during 5 minutes voluntary coughing and during a sputum induction procedure when tolerated. Standardized quantitative culture and genotyping techniques were used. Results: P. aeruginosa was isolated in cough aerosols of 25 (89%) subjects of whom 22 produced sputum samples. P. aeruginosa from sputum and paired cough aerosols were indistinguishable by molecular typing. In 4 cases the same genotype was isolated from ambient room air. Approximately 70% of viable aerosols collected during voluntary coughing were of particles ≤ 3.3 microns aerodynamic diameter. P. aeruginosa, Burkholderia cenocepacia Stenotrophomonas maltophilia and Achromobacter xylosoxidans were cultivated from respiratory particles in this size range. Positive room air samples were associated with high total counts in cough aerosols (P=0.003). The magnitude of cough aerosols were associated with higher FEV1 (r=0.45, P=0.02) and higher quantitative sputum culture results (r=0.58, P=0.008). Conclusion: During coughing, CF patients produce viable aerosols of P. aeruginosa and other Gram negative bacteria of respirable size range, suggesting the potential for airborne transmission.

Stem cell–related gene expression in clonal populations of mesenchymal stromal cells from bone marrow

Decline in the frequency of potent mesenchymal stem cells (MSCs) has been implicated in ageing and degenerative diseases. Increasing the circulating stem cell population can lead to renewed recruitment of these potent cells at sites of damage. Therefore, identifying the ideal cells for ex vivo expansion will form a major pursuit of clinical applications. This study is a follow-up of previous work that demonstrated the occurrence of fast-growing multipotential cells from the bone marrow samples. To investigate the molecular processes involved in the existence of such varying populations, gene expression studies were performed between fast- and slow-growing clonal populations to identify potential genetic markers associated with stemness using the quantitative real-time polymerase chain reaction comprising a series of 84 genes related to stem cell pathways. A group of 10 genes were commonly overrepresented in the fast-growing stem cell clones. These included genes that encode proteins involved in the maintenance of embryonic and neural stem cell renewal (sex-determining region Y-box 2, notch homolog 1, and delta-like 3), proteins associated with chondrogenesis (aggrecan and collagen 2 A1), growth factors (bone morphogenetic protein 2 and insulin-like growth factor 1), an endodermal organogenesis protein (forkhead box a2), and proteins associated with cell-fate specification (fibroblast growth factor 2 and cell division cycle 2). Expression of diverse differentiation genes in MSC clones suggests that these commonly expressed genes may confer the maintenance of multipotentiality and self-renewal of MSCs.

Posttraumatic growth in Australian populations

It is easy to assume that because Australia and the United States are both predominantly English speaking countries that are relatively young and share many similarities in terms of their historical beginnings, they elicit the same results when investigating psychological constructs. In recent years this has been questioned across a number of domains (e.g., personality and stereotyping) and research has demonstrated that although many constructs are universal, there are differences between these nations; some subtle and others quite stark (McCrae et al., 2005; Terraciano et al., 2005). In this chapter we discuss research that has investigated Posttraumatic Growth (PTG) in various populations in Australia and highlight the similarities and differences that have been found between Australian samples and those published in other countries, especially the US. Data are drawn from quantitative and qualitative investigations conducted with groups who have experienced diverse traumatic events as either direct survivors (e.g., rape, armed hold-up, bereavement) or vicarious survivors (e.g., paramedics). A description of the Australian context sets the scene for the ensuing discussion about PTG in Australian populations.

Implications of faecal indicator bacteria for the microbiological assessment of roof harvested rainwater quality in Southeast Queensland, Australia

The study aimed to evaluate the suitability of Escherichia coli, enterococci and C. perfringens to assess the microbiological quality of roof harvested rainwater, and to assess whether the concentrations of these faecal indicators can be used to predict the presence or absence of specific zoonotic bacterial or protozoan pathogens. From a total of 100 samples tested, respectively 58%, 83% and 46% of samples were found to be positive for E. coli, enterococci and C. perfringens spores, as determined by traditional culture based methods. Additionally, in the samples tested, 7%, 19%, 1%, 8%, 17%, and 15% were PCR positive for A. hydrophila lip, C. coli ceuE, C. jejuni mapA, L. pneumophila mip, Salmonella invA, and G. lamblia β-giardin genes. However, none of the samples was positive for E. coli O157 LPS, VT1, VT2 and C. parvum COWP genes. The presence or absence of these potential pathogens did not correlate with any of the faecal indicator bacterial concentrations as determined by a binary logistic regression model. The roof-harvested rainwater samples tested in this study appear to be of poor microbiological quality and no significant correlation was found between the concentration of faecal indicators and pathogenic microorganisms. The use of faecal indicator bacteria raises questions regarding their reliability in assessing the microbiological quality of water and particularly their poor correlation with pathogenic microorganisms. The presence of one or more zoonotic pathogens suggests that the microbiological analysis of water should be performed, and appropriate treatment measures should be undertaken especially in tanks where the water is used for drinking.