Colliding and interacting microbiomes and microbial communities - consequences for human health

Living ‘things’ coexist with microorganisms, known as the microbiota/microbiome that provides essential physiological functions to its host. Despite this reliance, the microbiome is malleable and can be altered by several factors including birth-mode, age, antibiotics, nutrition, and disease. In this minireview, we consider how other microbiomes and microbial communities impact the host microbiome and the host through the concept of microbiome collisions (initial exposures) and interactions. Interactions include changes in host microbiome composition and functionality and/or host responses. Understanding the impact of other microbiomes and microbial communities on the microbiome and host are important considering the decline in human microbiota diversity in the developed world – paralleled by the surge of non-communicable, inflammatory-based diseases. Thus, surrounding ourselves with rich and diverse beneficial microbiomes and microbial communities to collide and interact with should help to diminish the loss in microbial diversity and protect from certain diseases. In the same vein, our microbiomes not only influence our health but potentially the health of those close to us. We also consider strategies for enhanced host microbiome collisions and interactions through the surrounding environment that ensure increased microbiome diversity and functionality contributing to enhanced symbiotic return to the host in terms of health benefit.     

An overview of major metagenomic studies on human microbiomes in health and disease

Many microbes are important symbiotes of human. They form specific microbiota communities, participate in various kinds of biological processes of their host and thus deeply affect human health status. Metagenomic sequencing has been widely used in human microbiota study due to its capacity of studying all genetic materials in an environment as a whole without any extra need of isolation or cultivation of microorganisms. Many efforts have been made by researchers in this area trying to dig out interesting knowledge from various metagenome data. In this review, we go through some prominent studies in the metagenomic area. We summarize them into three categories, constructing taxonomy and gene reference, characterization of microbiome distribution patterns, and detection of microbiome alternations associated with specific human phenotypes or diseases. Some available data resources are also provided. This review can serve as an entrance to this exciting and rapidly developing field for researchers interested in human microbiomes.     

The human microbiome in evolution

The trillions of microbes living in the gut—the gut microbiota—play an important role in human biology and disease. While much has been done to explore its diversity, a full understanding of our microbiomes demands an evolutionary perspective. In this review, we compare microbiomes from human populations, placing them in the context of microbes from humanity’s near and distant animal relatives. We discuss potential mechanisms to generate host-specific microbiome configurations and the consequences of disrupting those configurations. Finally, we propose that this broader phylogenetic perspective is useful for understanding the mechanisms underlying human–microbiome interactions.     

Microbiome engineering: Current applications and its future

Microbiomes exist in all ecosystems and are composed of diverse microbial communities. Perturbation to microbiomes brings about undesirable phenotypes in the hosts, resulting in diseases and disorders, and disturbs the balance of the associated ecosystems. Engineering of microbiomes can be used to modify structures of the microbiota and restore ecological balance. Consequently, microbiome engineering has been employed for improving human health and agricultural productivity. The importance and current applications of microbiome engineering, particularly in humans, animals, plants and soil is reviewed. Furthermore, we explore the challenges in engineering microbiome and the future of this field, thus providing perspectives and outlook of microbiome engineering.     

The potential for probiotic manipulation of the gastrointestinal microbiome

Multiple internal and external sites of the healthy human body are colonized by a diversity of symbiotic microbes. The microbial assemblages found in the intestine represent some of the most dense and diverse of these human-associated ecosystems. Unsurprisingly, the enteric microbiome, that is the totality of microbes, their combined genomes, and their interactions with the human body, has a profound impact on physiological aspects of mammalian function, not least, host immune response. Lack of early-life exposure to certain microbes, or shifts in the composition of the gastrointestinal microbiome have been linked to the development and progression of several intestinal and extra-intestinal diseases, including childhood asthma development and inflammatory bowel disease. Modulating microbial exposure through probiotic supplementation represents a long-held strategy towards ameliorating disease via intestinal microbial community restructuring. This field has experienced somewhat of a resurgence over the past few years, primarily due to the exponential increase in human microbiome studies and a growing appreciation of our dependence on resident microbiota to modulate human health. This review aims to review recent regulatory aspects related to probiotics in food. It also summarizes what is known to date with respect to human gastrointestinal microbiota - the niche which has been most extensively studied in the human system - and the evidence for probiotic supplementation as a viable therapeutic strategy for modulating this consortium.     

The role of gut microbiota in pathogenesis of Alzheimer's disease

This paper describes the effects of the gut microbiota on the pathogenesis of Alzheimer's pathology by evaluating the current original key findings and identifying gaps in the knowledge required for validation. The diversity of the gut microbiota declines in the elderly and in patients with Alzheimer's disease (AD). Restoring the diversity with probiotic treatment alleviates the psychiatric and histopathological findings. This presents a problem: How does gut microbiota interact with the pathogenesis of AD? The starting point of this comprehensive review is addressing the role of bacterial metabolites and neurotransmitters in the brain under various conditions, ranging from a healthy state to ageing and disease. In the light of current literature, we describe three different linkages between the present gut microbiome hypothesis and the other major theories for the pathogenesis of AD as follows: bacterial metabolites and amyloids can trigger central nervous system inflammation and cerebrovascular degeneration; impaired gut microbiome flora inhibits the autophagy-mediated protein clearance process; and gut microbiomes can change the neurotransmitter levels in the brain through the vagal afferent fibres.     

Nasonia–microbiome associations: a model for evolutionary hologenomics research

In recent years, with the development of microbial research technologies, microbiota research has received widespread attention. The parasitoid wasp genus Nasonia is a good model organism for studying insect behavior, development, evolutionary genetics, speciation, and symbiosis. This review describes key advances and progress in the field of the Nasonia–microbiome interactions. We provide an overview of the advantages of Nasonia as a model organism for microbiome studies, list research methods to study the Nasonia microbiome, and discuss recent discoveries in Nasonia microbiome research. This summary of the complexities of Nasonia–microbiome relationships will help to contribute to a better understanding of the interactions between animals and their microbiomes and establish a clear research direction for Nasonia–microbiome interactions in the future.     

A comparison of nonlethal sampling methods for amphibian gut microbiome analyses

Noninvasive sampling methods for studying intestinal microbiomes are widely applied in studies of endangered species and in those conducting temporal monitoring during manipulative experiments. Although existing studies show that noninvasive sampling methods among different taxa vary in their accuracy, no studies have yet been published comparing nonlethal sampling methods in adult amphibians. In this study, we compare microbiomes from two noninvasive sample types (faeces and cloacal swabs) to that of the large intestine in adult cane toads, Rhinella marina. We use 16S rRNA gene sequencing to investigate how microbial communities change along the digestive tract and which nonlethal sampling method better represents large intestinal microbiota. We found that cane toads' intestinal microbiota was dominated by Bacteroidetes, Proteobacteria and Firmicutes and, interestingly, we also saw a high proportion of Fusobacteria, which has previously been associated with marine species and changes in frog immunity. The large and small intestine of cane toads had a similar microbial composition, but the large intestine showed higher diversity. Our results indicate that cloacal swabs were more similar to large intestine samples than were faecal samples, and small intestine samples were significantly different from both nonlethal sample types. Our study provides valuable information for future investigations of the cane toad gut microbiome and validates the use of cloacal swabs as a nonlethal method to study changes in the large intestine microbiome. These data provide insights for future studies requiring nonlethal sampling of amphibian gut microbiota.     

Primate microbiomes over time: Longitudinal answers to standing questions in microbiome research

To date, most insights into the processes shaping vertebrate gut microbiomes have emerged from studies with cross‐sectional designs. While this approach has been valuable, emerging time series analyses on vertebrate gut microbiomes show that gut microbial composition can change rapidly from 1 day to the next, with consequences for host physical functioning, health, and fitness. Hence, the next frontier of microbiome research will require longitudinal perspectives. Here we argue that primatologists, with their traditional focus on tracking the lives of individual animals and familiarity with longitudinal fecal sampling, are well positioned to conduct research at the forefront of gut microbiome dynamics. We begin by reviewing some of the most important ecological processes governing microbiome change over time, and briefly summarizing statistical challenges and approaches to microbiome time series analysis. We then introduce five questions of general interest to microbiome science where we think field‐based primate studies are especially well positioned to fill major gaps: (a) Do early life events shape gut microbiome composition in adulthood? (b) Do shifting social landscapes cause gut microbial change? (c) Are gut microbiome phenotypes heritable across variable environments? (d) Does the gut microbiome show signs of host aging? And (e) do gut microbiome composition and dynamics predict host health and fitness? For all of these questions, we highlight areas where primatologists are uniquely positioned to make substantial contributions. We review preliminary evidence, discuss possible study designs, and suggest future directions.     

On the origin of species: Factors shaping the establishment of infant's gut microbiota

The human gut microbiota is a complex and dynamic ecosystem, which naturally lives in a symbiotic relationship with the host. Perturbations of the microbial composition (dysbiosis) and reduced diversity may promote disease susceptibility and recurrence. In contrast to the mature intestinal microbiota of healthy adults, which appears relatively stable over time, the infant's microbiome only establishes and matures during the first years of life. In this respect, early childhood seems to represent a crucial age‐window in disease prevention, since microbial diversification and maturation of the microbiome primarily occurs during this period of life. A better understanding of ecological processes and pioneer consortia in microbial development is crucial, in order to support the development of a beneficial microbiota. Various deterministic and stochastic aspects seem to shape the microbiome in early life, including maternal, environmental, and host factors. Here, we review the current understanding of the origin of pioneer bacteria and the evolutionary factors that influence the development of the gut microbiota in infants. In addition, future perspectives, including manipulating and promoting the succession of initial bacteria during infancy, will be highlighted. Birth Defects Research (Part C) 105:240–251, 2015. © 2015 Wiley Periodicals, Inc.