Diet-related factors strongly shaped the gut microbiota of Japanese macaques.

Although knowledge of the functions of the gut microbiome has increased greatly over the past few decades, our understanding of the mechanisms governing its ecology and evolution remains obscure. While host genetic distance is a strong predictor of the gut microbiome in large-scale studies and captive settings, its influence has not always been evident at finer taxonomic scales, especially when considering among the recently diverged animals in natural settings. Comparing the gut microbiome of 19 populations of Japanese macaques Macaca fuscata across the Japanese archipelago, we assessed the relative roles of host genetic distance, geographic distance and dietary factors in influencing the macaque gut microbiome. Our results suggested that the macaques may maintain a core gut microbiome, while each population may have acquired some microbes from its specific habitat/diet. Diet-related factors such as season, forest, and reliance on anthropogenic foods played a stronger role in shaping the macaque gut microbiome. Among closely related mammalian hosts, host genetics may have limited effects on the gut microbiome since the hosts generally have smaller physiological differences. This study contributes to our understanding of the relative roles of host phylogeography and dietary factors in shaping the gut microbiome of closely related mammalian hosts.

In vitro digestion and fermentation of Japanese macaque (Macaca fuscata) food: The influence of food type and particle size.

Chewing is critical for herbivores to obtain nutrients. Measuring digesta particle size as the outcome of chewing can improve our understanding of the relationship between food and digestion. Previous studies of feeds of domestic animals have shown that smaller digesta particle size leads to more efficient digestion. Increased digesta particle size-either due to animal factors (e.g., a senile dentition) or to feed factors (e.g., fracture resistance) could be a sign of an animal experiencing compromised nutritional intake. However, for some primates that are dietary generalists, digesta particle size has been shown to increase when consuming preferred foods, which raises doubts about the role of chewing in digesting such foods. This uncertainty makes it difficult to understand the connection between diet, chewing, and digestion through digesta particle size in dietary generalists. In this study, using five typical food items from the Japanese macaque (Macaca fuscata) diet, we conducted in vitro digestibility and fermentation assays to explore the effects of particle size on enzymatic and microbial digestion. For the fermentation assays, we used feces from captive Japanese macaques as inoculum. Among the five food items, we found that particle size has a stronger influence on the digestibility of seeds and mature leaves compared to young leaves and pulp. The influence of particle size on the fermentation rate was stronger in pulp and seeds compared to that in leaves. The differences in physical structure, texture, digestion barriers, and soluble components may play important roles in such differences. These results support the hypothesis that reducing food particle size is less important for consuming fruits than for consuming leaves. The limited effects of particle size on digesting fruits suggest that the two fruits examined in this study are cost-effective concerning food processing and chewing.

Seasonal responses and host uniqueness of gut microbiome of Japanese macaques in lowland Yakushima.

BACKGROUND: Changes in the gut microbial composition is an important response to cope with the seasonal fluctuations in the environment such as food availability. We examined the bacterial gut microbiome of the wild nonhuman primate, Japanese macaque (Macaca fuscata) in Yakushima over 13 months by noninvasive continuous sampling from three identified adult females. RESULTS: Dietary composition varied considerably over the study period and displayed marked shifts with the seasons. Feeding of leaves, fruits, and invertebrates were their main foods for at least one month. Diet had a significant influence on the gut microbiome. We also confirmed significant effect of host uniqueness in the gut microbiome among the three macaques. Leaf-dominated diet shaped unique gut microbiome structures where the macaques had the highest alpha diversity and their gut microbiome was enriched with Spirochaetes and Tenericutes. Diet-related differences in the putative function were detected, such as a differentially abundant urea cycle during the leaf-feeding season. CONCLUSION: Both diet and host individuality exerted similar amounts of effect on gut microbe community composition. Major bacterial taxa showed a similar response to monthly fluctuations of fruit and invertebrate feeding, which was largely opposite to that of leaf feeding. The main constituents of fruits and invertebrates are both digestible with the enzyme of the host animals, but that of leaves is not available as an energy source without the aid of the fermentation of the gut microbiome.

Effects of diet and age-sex class on the fecal particle size of wild Japanese macaques (Macaca fuscata yakui).

Fecal particle size provides important information on the feeding and digestion of herbivores. Understanding the effects of the potential proximate determinants on fecal particle size helps us interpret this widely used measurement. In folivores, previous studies found that diet composition, dietary toughness, and age-sex-related factors, such as body size and tooth wear, influenced fecal particle size. However, the role of these factors remains unknown in frugivorous and omnivorous primates. This study aims to clarify how age-sex class and diet influence fecal particle size in omnivorous Japanese macaques in Yakushima. We expected that their variable diet and differences among age-sex classes would cause variations in fecal particle size. We simultaneously documented Japanese macaques' diet, dietary toughness, and fecal particle size in the lowland area of Yakushima in the period from March 2018 to April 2019. Unexpectedly, fecal particle size showed limited differences across months and no difference among age-sex classes. Dietary toughness showed no effects on fecal particle size, while the consumption of fruits showed only a marginally significant negative effect. Our data indicate that the results of chewing were not affected by dietary toughness in our study subjects, while age-sex classes showed no difference in food comminution. This lack of variation might derive from a diet with low dietary toughness. We also found that the physical structure of preferred foods played an important role in fecal particle size variations. These results suggest that food comminution is less variable in frugivorous and omnivorous primates compared to highly specialized species (e.g., geladas). Factors other than what we examined in this study, such as food physical structure and chewing behavior, should also be taken into consideration.

Stomach and colonic microbiome of wild Japanese macaques.

Within the gastrointestinal tract, the physiochemical microenvironments are highly diversified among the different stages of food digestion. Accordingly, gut microbiome composition and function vary at different gut sites. In this study, we examine and compare the compositional and functional potential between the stomach and colonic microbiome of wild Japanese macaques (Macaca fuscata yakui) living in the evergreen forest of Yakushima Island. We find a significantly lower microbial diversity in the stomach than in the colon, possibly due to the stomach's acidic and aerobic environment, which is suboptimal for microbial survival. According to past studies, the microbial taxa enriched in the stomach are aero- and acid-tolerant. By functional prediction through PICRUSt2, we reveal that the stomach microbiome is more enriched in pathways relating to the metabolism of simple sugars. On the contrary, the colonic microbiota is more enriched with fiber-degrading microbes, such as those from Lachnospiracea, Ruminococcaceae, and Prevotella. Our study shows a clear difference in the microbiome between the stomach and colon of Japanese macaques in both composition and function. This study provides a preliminary look at the alpha diversity and taxonomic composition within the stomach microbiome of Japanese macaques, a hindgut-fermenting nonhuman primate.

Fermentation Ability of Gut Microbiota of Wild Japanese Macaques in the Highland and Lowland Yakushima: In Vitro Fermentation Assay and Genetic Analyses.

Wild Japanese macaques (Macaca fuscata Blyth) living in the highland and lowland areas of Yakushima are known to have different diets, with highland individuals consuming more leaves. We aim to clarify whether and how these differences in diet are also reflected by gut microbial composition and fermentation ability. Therefore, we conduct an in vitro fermentation assay using fresh feces from macaques as inoculum and dry leaf powder of Eurya japonica Thunb. as a substrate. Fermentation activity was higher for feces collected in the highland, as evidenced by higher gas and butyric acid production and lower pH. Genetic analysis indicated separation of highland and lowland in terms of both community structure and function of the gut microbiota. Comparison of feces and suspension after fermentation indicated that the community structure changed during fermentation, and the change was larger for lowland samples. Analysis of the 16S rRNA V3-V4 barcoding region of the gut microbiota showed that community structure was clearly clustered between the two areas. Furthermore, metagenomic analysis indicated separation by gene and pathway abundance patterns. Two pathways (glycogen biosynthesis I and D-galacturonate degradation I) were enriched in lowland samples, possibly related to the fruit-eating lifestyle in the lowland. Overall, we demonstrated that the more leaf-eating highland Japanese macaques harbor gut microbiota with higher leaf fermentation ability compared with the more fruit-eating lowland ones. Broad, non-specific taxonomic and functional gut microbiome differences suggest that this pattern may be driven by a complex interplay between many taxa and pathways rather than single functional traits.

Gut microbiota composition of Japanese macaques associates with extent of human encroachment.

In recent decades, human-wildlife interaction and associated anthropogenic food provisioning has been increasing and becoming more severe due to fast population growth and urban development. Noting the role of the gut microbiome in host physiology like nutrition and health, it is thus essential to understand how human-wildlife interactions and availability of anthropogenic food in habitats can affect an animal's gut microbiome. This study, therefore, set out to examine the gut microbiota of Japanese macaques (Macaca fuscata) with varying accessibility to anthropogenic food and the possibility of using gut microbiota as indicator for macaques' reliance on anthropogenic food. Using 16S ribosomal RNA gene sequencing, we described the microbial composition of Japanese macaques experiencing different types of human disturbance and anthropogenic food availability-captive, provisioned, crop-raiding, and wild. In terms of alpha diversity, our results showed that observed richness of gut microbiota did not differ significantly between disturbance types but among collection sites, whereas Shannon diversity index differed by both disturbance types and sites. In terms of beta diversity, captive populations harbored the most distinctive gut microbial composition, and had the greatest difference compared with wild populations. Whereas for provisioned and crop-raiding groups, the macaques exhibited intermediate microbiota between wild and captive. We identified several potential bacterial taxa at different taxonomic ranks whose abundance potentially could help in assessing macaques' accessibility to anthropogenic food. This study revealed the flexibility of the gut microbiome of Japanese macaques and provided possible indices based on the gut microbiome profile in assessing macaques' accessibility to/reliance on anthropogenic foods.

Visible light-induced electronic structure modulation of Nb- and Ta-doped α-Fe2O3 nanorods for effective photoelectrochemical water splitting.

The photoelectrochemical (PEC) water splitting activity of Nb and Ta-doped hematite (α-Fe2O3) nanorods was investigated with reference to electronic structures by in situ synchrotron x-ray absorption spectroscopy (XAS). Current density-potential measurements demonstrate that the PEC activity of α-Fe2O3 nanorods depends strongly on the species and concentrations of dopants. The doping of α-Fe2O3 nanorods with a low level of Nb or Ta can improve their electrical conductivity and thereby facilitate charge transport and reduced electron-hole recombination therein. The photoconversion effects of Nb and Ta-doped α-Fe2O3 by in situ XAS in the dark and under illumination revealed opposite evolutions of the spectral intensities of the Fe L-edge and Nb/Ta L-edge, indicating that charge transfer and a conduction pathway are involved in the photoconversion. Analytic in situ XAS results reveal that the α-Fe2O3 that is doped with a low level of Nb has a greater photoconversion efficiency than that doped with Ta because Nb sites are more active than Ta sites in α-Fe2O3. The correlation between PEC activity and the electronic structure of Nb/Ta-doped α-Fe2O3 is examined in detail using in situ XAS and helps to elucidate the mechanism of PEC water splitting in terms of the electronic structure.

Solution growth of Ta-doped hematite nanorods for efficient photoelectrochemical water splitting: a tradeoff between electronic structure and nanostructure evolution.

Ta-doped hematite (α-Fe2O3) nanorod array films were successfully prepared on fluorine-doped tin dioxide (FTO) coated glass substrates via a facile solution growth process with TaCl5 as a Ta doping precursor. Under 1 sun illumination and at an applied potential of 1.0 V vs. Ag/AgCl, the Ta-doped α-Fe2O3 photoanode with optimized dopant concentration showed a photocurrent density as high as 0.53 mA cm(-2), which was about 3.5 times higher than that of the undoped sample. As demonstrated by Mott-Schottky and X-ray absorption spectroscopy measurements, considerable increase in photoelectrochemical (PEC) performance achieved for Ta-doped α-Fe2O3 nanorod films should be mainly attributed to the increased electron donor density induced by Ta doping. However, with superfluous Ta doping, the [110]-oriented nanorod structure was destroyed, which caused greatly restrained photoinduced holes transferring to the surface and retarded surface water oxidation reaction, leading to decreased PEC water splitting activity. This study clearly demonstrated that doping could be effective to enhance the PEC activity of α-Fe2O3 nanorods as photoanodes, while it is of great necessity to balance the trade-off between the electronic structure and nanostructure evolution by optimizing the dopant concentration, for increased donor density and meanwhile with the nanorod nanostructure well preserved for directed charge transfer.