Friend and foe: factors influencing the movement of the bacterium Helicobacter pylori along the parasitism-mutualism continuum.

Understanding the transition of bacterial species from commensal to pathogen, or vice versa, is a key application of evolutionary theory to preventative medicine. This requires working knowledge of the molecular interaction between hosts and bacteria, ecological interactions among microbes, spatial variation in bacterial prevalence or host life history, and evolution in response to these factors. However, there are very few systems for which such broad datasets are available. One exception is the gram-negative bacterium, Helicobacter pylori, which infects upwards of 50% of the global human population. This bacterium is associated with a wide breadth of human gastrointestinal disease, including numerous cancers, inflammatory disorders, and pathogenic infections, but is also known to confer fitness benefits to its host both indirectly, through interactions with other pathogens, and directly. Outstanding questions are therefore why, when, and how this bacterium transitions along the parasitism-mutualism continuum. We examine known virulence factors, genetic predispositions of the host, and environmental contributors that impact progression of clinical disease and help define geographical trends in disease incidence. We also highlight the complexity of the interaction and discuss future therapeutic strategies for disease management and public health in light of the longstanding evolutionary history between the bacterium and its human host

Phage therapy: An alternative to antibiotics in the age of multi-drug resistance.

The practice of phage therapy, which uses bacterial viruses (phages) to treat bacterial infections, has been around for almost a century. The universal decline in the effectiveness of antibiotics has generated renewed interest in revisiting this practice. Conventionally, phage therapy relies on the use of naturally-occurring phages to infect and lyse bacteria at the site of infection. Biotechnological advances have further expanded the repertoire of potential phage therapeutics to include novel strategies using bioengineered phages and purified phage lytic proteins. Current research on the use of phages and their lytic proteins, specifically against multidrug-resistant bacterial infections, suggests phage therapy has the potential to be used as either an alternative or a supplement to antibiotic treatments. Antibacterial therapies, whether phage- or antibiotic-based, each have relative advantages and disadvantages; accordingly, many considerations must be taken into account when designing novel therapeutic approaches for preventing and treating bacterial infections. Although much is still unknown about the interactions between phage, bacteria, and human host, the time to take phage therapy seriously seems to be rapidly approaching

The cost of phage resistance in a plant pathogenic bacterium is context-dependent.

Parasites are ubiquitous features of living systems and many parasites severely reduce the fecundity or longevity of their hosts. This parasite-imposed selection on host populations should strongly favor the evolution of host resistance, but hosts typically face a trade-off between investment in reproductive fitness and investment in defense against parasites. The magnitude of such a trade-off is likely to be context-dependent, and accordingly costs that are key in shaping evolution in nature may not be easily observable in an artificial environment. We set out to assess the costs of phage resistance for a plant pathogenic bacterium in its natural plant host versus in a nutrient-rich, artificial medium. We demonstrate that mutants of Pseudomonas syringae that have evolved resistance via a single mutational step pay a substantial cost for this resistance when grown on their tomato plant hosts, but do not realize any measurable growth rate costs in nutrient-rich media. This work demonstrates that resistance to phage can significantly alter bacterial growth within plant hosts, and therefore that phage-mediated selection in nature is likely to be an important component of bacterial pathogenicity

Doctor of Philosophy

dissertationArabic historical narratives from fifteenth century Egypt allow a holistic exploration of the parallels and dichotomies inherent in debates regarding plague epidemics and etiology, classical Islamic medicine, and the fluid and yet precarious societal position of the ulama as historians of these epidemics. In a tenuous relationship, the ulama were bound not only to the sultan and his key associates for their livelihood, but also to the general population, over whom they exerted influence. Plague epidemics were recorded in the scholars' narratives, reflecting the narrative voice of the ulama, their varying social networks, the context in which they acted, and the literary traditions of the period. Previous research concerning plague epidemics in Mamluk Egypt has too narrowly focused on a so-called rigid religious orthodoxy, and the rise and decline of the Golden Age of Islam paradigm. However, classical scholars were a loosely formed, but dynamic group of individuals from various walks of life who interpreted their society, and through their written narratives, asserted their independence. These authors worked during difficult times to record plague epidemics and relate events critical for their understanding of Islamic Tradition, classical medicine and people's fear, misery and hope. Previous research has incorrectly portrayed these historical narratives as static and repetitive, confined by both Mamluk patronage and an undefined "Islam.

A survey of physical education programs in small communities

Thesis (Ed.M.)--Boston Universit