Diversity and Persistence of the Gut Microbiome of the Giant Neotropical Bullet Ant.

Identifying the factors that structure host-associated microbiota is critical to understand the role these microbes may play in host ecology and evolutionary history. To begin to address this question we investigate the diversity and persistence of the bacterial community of the giant Neotropical bullet ant, Paraponera clavata. We included samples from four widely dispersed locations to address the role geography plays in shaping these communities. To understand how the digestive tract can filter bacterial communities, we sampled mouth and gut communities. To investigate the stability of community members we sampled wild caught and individuals kept on a sterile diet. Only a single bacterial taxon in the Firmicutes is consistently present across individuals, indicating a remarkably simple "core" bacterial community for the giant Neotropical bullet ant. Geography did not explain host bacterial diversity, but we did find significant reductions in diversity between the mouth and the gut tract. Lastly, our diet manipulations highlight the importance of controlled experiments to tease apart persistent microbial communities from environmental transients.

Divergence across diet, time and populations rules out parallel evolution in the gut microbiomes of Trinidadian guppies.

Diverse microbial consortia profoundly influence animal biology, necessitating an understanding of microbiome variation in studies of animal adaptation. Yet, little is known about such variability among fish, in spite of their importance in aquatic ecosystems. The Trinidadian guppy, Poecilia reticulata, is an intriguing candidate to test microbiome-related hypotheses on the drivers and consequences of animal adaptation, given the recent parallel origins of a similar ecotype across streams. To assess the relationships between the microbiome and host adaptation, we used 16S rRNA amplicon sequencing to characterize gut bacteria of two guppy ecotypes with known divergence in diet, life history, physiology and morphology collected from low-predation (LP) and high-predation (HP) habitats in four Trinidadian streams. Guts were populated by several recurring, core bacteria that are related to other fish associates and rarely detected in the environment. Although gut communities of lab-reared guppies differed from those in the wild, microbiome divergence between ecotypes from the same stream was evident under identical rearing conditions, suggesting host genetic divergence can affect associations with gut bacteria. In the field, gut communities varied over time, across streams and between ecotypes in a stream-specific manner. This latter finding, along with PICRUSt predictions of metagenome function, argues against strong parallelism of the gut microbiome in association with LP ecotype evolution. Thus, bacteria cannot be invoked in facilitating the heightened reliance of LP guppies on lower-quality diets. We argue that the macroevolutionary microbiome convergence seen across animals with similar diets may be a signature of secondary microbial shifts arising some time after host-driven adaptation.

Idiopathic intracranial hypertension in cystinosis.

OBJECTIVES: To report a high frequency of idiopathic intracranial hypertension (IIH) in patients with cystinosis and to speculate on the relationship between these two disorders. STUDY DESIGN: Retrospective case series and review of the literature regarding risk factors for the development of IIH in cystinosis. RESULTS: Eight patients with cystinosis had documented papilledema, normal neuroimaging of the brain, cerebrospinal fluid (CSF) opening pressure greater than 200 mm of H2O, and normal CSF composition. No common medication, condition, or disease except cystinosis was found in these persons. Six of the patients had received prednisone, growth hormone, cyclosporine, oral contraceptives, vitamin D, or levothyroxine at the time of onset of IIH. Five patients had previous renal transplants. CONCLUSION: No single risk factor for the development of IIH linked IIH to cystinosis in our patients. However, thrombosis susceptibility as a result of renal disease or impaired CSF reabsorption in the arachnoid villi as a result of cystine deposition might lead to the development of IIH in cystinosis.