The nature of parasite specialization in the fungus-growing ant symbiosis

textHost-parasite coevolution is intricately coupled with parasite specialization. As hosts become resistant, parasites may adapt and overcome that resistance or may become specialized on a narrow range of susceptible hosts. Ultimately, a parasite’s host range will dictate ecological host-parasite dynamics and host-parasite coevolution. Here, I use the system of fungus-growing ants and their symbionts to study host-specialization by Escovopsis, a parasite of the ants’ cultivated fungus. In recent years, the fungus-growing ant symbiosis has emerged as a model system for studying coevolution, speciation, cooperation and conflict between the ants and their fungal cultivars. In chapter one, I outline how this system has also proven to be an easily tractable system for studying the ecological and evolutionary dynamics of hosts and parasites. In chapters two and five, I combine molecular analysis of phylogenetic relationships of host and parasites with finer analysis of population differences within species to identify specialization by parasites on particular host-species and host-genotypes. At the host-species level, Escovopsis that attack gardens of Cyphomyrmex ants are specific to a narrow range of fungal cultivars propagated by the ants. At the host-genotype level, however, there is little evidence that genotypically similar strains of Escovopsis that attack Apterostigma dentigerum gardens are specialized on within-species host cultivar genotypes. In chapters three and four, knowledge of such patterns of specialization is used as a foundation for experiments in which the host fungi and the parasitic fungi are confronted to determine patterns of host resistance and parasite infectivity. I demonstrate that host cultivars can chemically defend themselves against some Escovopsis spp., but Escovopsis spp. can overcome the defenses of host-species on which they are specialized and can efficiently recognize and be attracted to these susceptible hosts. These host and parasite adaptations are consistent with patterns of parasite specialization and host-switching in the Apterostigma ant symbiosis. Thus, this comprehensive approach reveals both process and pattern, demonstrating how mechanisms of resistance and infectivity shape parasite hostspecialization and ultimately population dynamics of interacting organisms.Biological Sciences, School o

Aphid reproductive investment in response to mortality risks

<p>Abstract</p> <p>Background</p> <p>Aphids are striking in their prodigious reproductive capacity and reliance on microbial endosymbionts, which provision their hosts with necessary amino acids and provide protection against parasites and heat stress. Perhaps as a result of this bacterial dependence, aphids have limited immune function that may leave them vulnerable to bacterial pathogens. An alternative, non-immunological response that may be available to infected aphids is to increase reproduction, thereby ameliorating fitness loss from infection. Such a response would reduce the need to mount a potentially energetically costly immune response, and would parallel that of other hosts that alter life-history traits when there is a risk of infection. Here we examined whether pea aphids (<it>Acyrthosiphon pisum</it>) respond to immunological challenges by increasing reproduction. As a comparison to the response to the internal cue of risk elicited by immunological challenge, we also exposed pea aphids to an external cue of risk - the aphid alarm pheromone (<it>E</it>)-<it>β</it>-farnesene (EBF), which is released in the presence of predators. For each challenge, we also examined whether the presence of symbionts modified the host response, as maintaining host fitness in the face of challenge would benefit both the host and its dependent bacteria.</p> <p>Results</p> <p>We found that aphids stabbed abdominally with a sterile needle had reduced fecundity relative to control aphids but that aphids stabbed with a needle bearing heat-killed bacteria had reproduction intermediate, and statistically indistinguishable, to the aphids stabbed with a sterile needle and the controls. Aphids with different species of facultative symbiotic bacteria had different reproductive patterns overall, but symbionts in general did not alter aphid reproduction in response to bacterial exposure. However, in response to exposure to alarm pheromone, aphids with <it>Hamiltonella defensa </it>or <it>Serratia symbiotica </it>symbiotic infections increased reproduction but those without a facultative symbiont or with <it>Regiella insecticola </it>did not.</p> <p>Conclusions</p> <p>Overall, our results suggest that pea aphids are able to increase their reproduction in response to specific cues and that symbiont presence sometimes moderates this response. Such increased reproduction in response to risk of death increases the fitness of both aphids and their vertically transmitted symbionts, and since these organisms have high reproductive capacity, slight increases in reproduction could lead to a very large numerical advantage later in the season. Thus both symbiotic partners can benefit by increasing host fecundity under dangerous conditions.</p

Complex host-pathogen coevolution in the Apterostigma fungus-growing ant-microbe symbiosis

BACKGROUND: The fungus-growing ant-microbe symbiosis consists of coevolving microbial mutualists and pathogens. The diverse fungal lineages that these ants cultivate are attacked by parasitic microfungi of the genus Escovopsis. Previous molecular analyses have demonstrated strong phylogenetic congruence between the ants, the ants-cultivated fungi and the garden pathogen Escovopsis at ancient phylogenetic levels, suggesting coevolution of these symbionts. However, few studies have explored cophylogenetic patterns between these symbionts at the recent phylogenetic levels necessary to address whether these parasites are occasionally switching to novel hosts or whether they are diversifying with their hosts as a consequence of long-term host fidelity. RESULTS: Here, a more extensive phylogenetic analysis of Escovopsis lineages infecting the gardens of Apterostigma ants demonstrates that these pathogens display patterns of phylogenetic congruence with their fungal hosts. Particular clades of Escovopsis track particular clades of cultivated fungi, and closely-related Escovopsis generally infect closely-related hosts. Discordance between host and parasite phylogenies, however, provides the first evidence for occasional host-switches or acquisitions of novel infections from the environment. CONCLUSION: The fungus-growing ant-microbe association has a complex coevolutionary history. Though there is clear evidence of host-specificity on the part of diverse Escovopsis lineages, these pathogens have switched occasionally to novel host fungi. Such switching is likely to have profound effects on how these host and parasites adapt to one another over evolutionary time scales and may impact how disease spreads over ecological time scales

Elaboración de un glosario terminológico médico inglés-español sobre fisiología humana, Lima, 2022

El presente trabajo de investigación titulado Elaboración de un glosario terminológico médico inglés-español sobre fisiología humana, Lima, 2022 tuvo como objetivo elaborar un glosario terminológico inglés-español sobre fisiología humana. La investigación cuenta con un enfoque cualitativo, de tipo básico, nivel descriptivo y un diseño de estudio de casos. Se aplicó la técnica de análisis de contenido y se elaboró una ficha terminológica bilingüe como instrumento. El corpus fue el libro Textbook of Medical Physiology, del cual se seleccionaron 80 términos. Como resultado, la categoría del término origen más común fue el léxico específico del texto especializado; en cuanto al equivalente el más común fue el absoluto; en la categoría gramatical tanto de origen como equivalente se obtuvo solo sustantivos. En cuanto a la definición del equivalente la única encontrada fue la intensional, en las fuentes del término origen la más común fue el artículo y finalmente en la ejemplificación contextual tanto de origen como de equivalente se obtuvieron del corpus. Por último, se concluyó que la extracción del término origen, identificar el equivalente, la búsqueda de las definiciones y la identificación de la categoría gramatical, las fuentes y el contexto hacen factible la elaboración de un glosario

Identification of Heart Failure Events in Medicare Claims: The Atherosclerosis Risk in Communities (ARIC) Study

We examined the accuracy of CMS Medicare HF diagnostic codes in the identification of acute decompensated and chronic stable HF (ADHF and CSHF)

Mucins trigger dispersal of Pseudomonas aeruginosa biofilms

Mucus is a biological gel that lines all wet epithelia in the body, including the mouth, lungs, and digestive tract, and has evolved to protect the body from pathogenic infection. However, microbial pathogenesis is often studied in mucus-free environments that lack the geometric constraints and microbial interactions in physiological three-dimensional mucus gels. We developed fluid-flow and static test systems based on purified mucin polymers, the major gel-forming constituents of the mucus barrier, to understand how the mucus barrier influences bacterial virulence, particularly the integrity of Pseudomonas aeruginosa biofilms, which can become resistant to immune clearance and antimicrobial agents. We found that mucins separate the cells in P. aeruginosa biofilms and disperse them into suspension. Other viscous polymer solutions did not match the biofilm disruption caused by mucins, suggesting that mucin-specific properties mediate the phenomenon. Cellular dispersion depended on functional flagella, indicating a role for swimming motility. Taken together, our observations support a model in which host mucins are key players in the regulation of microbial virulence. These mucins should be considered in studies of mucosal pathogenesis and during the development of novel strategies to treat biofilms