Seasonal shifts in the gut microbiome indicate plastic responses to diet in wild geladas.

BACKGROUND: Adaptive shifts in gut microbiome composition are one route by which animals adapt to seasonal changes in food availability and diet. However, outside of dietary shifts, other potential environmental drivers of gut microbial composition have rarely been investigated, particularly in organisms living in their natural environments. RESULTS: Here, we generated the largest wild nonhuman primate gut microbiome dataset to date to identify the environmental drivers of gut microbial diversity and function in 758 samples collected from wild Ethiopian geladas (Theropithecus gelada). Because geladas live in a cold, high-altitude environment and have a low-quality grass-based diet, they face extreme thermoregulatory and energetic constraints. We tested how proxies of food availability (rainfall) and thermoregulatory stress (temperature) predicted gut microbiome composition of geladas. The gelada gut microbiome composition covaried with rainfall and temperature in a pattern that suggests distinct responses to dietary and thermoregulatory challenges. Microbial changes were driven by differences in the main components of the diet across seasons: in rainier periods, the gut was dominated by cellulolytic/fermentative bacteria that specialized in digesting grass, while during dry periods the gut was dominated by bacteria that break down starches found in underground plant parts. Temperature had a comparatively smaller, but detectable, effect on the gut microbiome. During cold and dry periods, bacterial genes involved in energy, amino acid, and lipid metabolism increased, suggesting a stimulation of fermentation activity in the gut when thermoregulatory and nutritional stress co-occurred, and potentially helping geladas to maintain energy balance during challenging periods. CONCLUSION: Together, these results shed light on the extent to which gut microbiota plasticity provides dietary and metabolic flexibility to the host, and might be a key factor to thriving in changing environments. On a longer evolutionary timescale, such metabolic flexibility provided by the gut microbiome may have also allowed members of Theropithecus to adopt a specialized diet, and colonize new high-altitude grassland habitats in East Africa. Video abstract.

Alloscardovia theropitheci sp. nov., isolated from the faeces of gelada baboon, the 'bleeding heart' monkey (Theropithecus gelada).

A novel irregularly shaped and slightly curved rod bacterial strain, GLDI4/2T, showing activity of fructose 6-phosphate phosphoketolase was isolated from a faecal sample of an adult gelada baboon (Theropithecus gelada). Phylogenetic analyses based on 16S rRNA genes as well as multilocus sequences (representing fusA, gyrB and xfp genes) and the core genome revealed that GLDI4/2T exhibited phylogenetic relatedness to Alloscardovia omnicolens DSM 21503T and to Alloscardovia macacae DSM 24762T. Comparative analysis of 16S rRNA gene sequences confirmed the phylogenetic results showing the highest gene sequence identity with strain A. omnicolens DSM 21503T (96.0 %). Activities of α- and ß-gluco(galacto)sidases were detected in strain GLDI4/2T, which is characteristic for almost all members of the family Bifidobacteriaceae. Compared to other Alloscardovia species its DNA G+C content (43.8 mol%) was very low. Phylogenetic studies and the evaluation of phenotypic characteristics, including the results of biochemical, physiological and chemotaxonomic analyses, confirmed the novel species status for strain GLDI4/2T, for which the name Alloscardoviatheropitheci sp. nov. is proposed. The type strain is GLDI4/2T (=DSM 106019T=JCM 32430T).

Multilevel social structure and diet shape the gut microbiota of the gelada monkey, the only grazing primate.

BACKGROUND: The gelada monkey (Theropithecus gelada), endemic to the Ethiopian highlands, is the only graminivorous primate, i.e., it feeds mainly on grasses and sedges. In spite of known dental, manual, and locomotor adaptations, the intestinal anatomy of geladas is similar to that of other primates. We currently lack a clear understanding of the adaptations in digestive physiology necessary for this species to subsist on a graminoid-based diet, but digestion in other graminivores, such as ruminants, relies heavily on the microbial community residing in the gastrointestinal (GI) system. Furthermore, geladas form complex, multilevel societies, making them a suitable system for investigating links between sociality and the GI microbiota. RESULTS: Here, we explore the gastrointestinal microbiota of gelada monkeys inhabiting an intact ecosystem and document how factors like multilevel social structure and seasonal changes in diet shape the GI microbiota. We compare the gelada GI microbiota to those of other primate species, reporting a gradient from geladas to herbivorous specialist monkeys to dietary generalist monkeys and lastly humans, the ultimate ecological generalists. We also compare the microbiotas of the gelada GI tract and the sheep rumen, finding that geladas are highly enriched for cellulolytic bacteria associated with ruminant digestion, relative to other primates. CONCLUSIONS: This study represents the first analysis of the gelada GI microbiota, providing insights into the adaptations underlying graminivory in a primate. Our results also highlight the role of social organization in structuring the GI microbiota within a society of wild animals.

A field study of infection with human T-cell leukemia virus among African primates.

African non-human primates were surveyed seroepidemiologically for natural infection of human T-cell leukemia virus type I (ATLV/HTLV-I) or its closely related virus(es). Materials from three genera (Cercopithecus, Papio, and Theropithecus), four species (grivet monkey, Anubis baboon, Hamadryas baboon, and gelada), totalling 983 animals under natural conditions, were obtained in a field study in Ethiopia. Virus infection was determined by the indirect immunofluorescence test using HTLV-I specific antigens. Animals seropositive for HTLV-I were found among grivet monkeys and Anubis baboons including the hybrid offspring between Anubis and Hamadryas baboons but not pure-Hamadryas baboons and geladas. From these results, the HTLV-I family was proved to be widespread on the African continent and was regarded as a common retrovirus among catarrhines.