Microbial generalists form planet-wide networks across ecosystems

A groundbreaking new study published in Cell reveals a surprising interconnectedness within the world’s microbiomes. Scientists at the Bork Group at EMBL Heidelberg discovered that microbes inhabiting similar environments share more similarities than those found in the same geographic region. Their analysis of tens of thousands of microbial genomes identified a subset of microbes, termed ‘generalists,’ capable of thriving across vastly different habitats.

A New Perspective on Microbial Life

Historically, large-scale microbiome studies have focused on specific ecosystems due to logistical challenges. However, the development of databases like SPIRE (Searchable, Planetary-scale mIcrobiome REsource) by EMBL scientists and their partners has enabled planet-wide investigations. SPIRE integrates and analyzes microbial data from around the globe, allowing researchers to pinpoint 40 distinct microbial habitat types using 85,604 metagenomic samples.

“Rather than presuming which environmental drivers shape the microbiome structure, we let the microbes tell us themselves,” explained Daniel Podlesny, a Research Scientist at EMBL and co-first author of the study. Researchers quantified microbiome similarity and identified compositional clusters, then used contextual metadata to determine common factors like host age or ocean temperature.

Did You Know? Rudolf Virchow, a German physician and physiologist, coined the term ‘zoonosis’ in the nineteenth century to describe the transmission of infectious diseases between animals and humans.

Generalists: The Microscopic Network Builders

Microbes are broadly categorized as either specialists, adapted to specific conditions, or generalists, capable of surviving in diverse environments. These generalists aren’t simply adaptable; they actively transfer genes to other microbes through horizontal gene transfer, creating genetic ‘bridges’ between distant habitats. According to Jonas Schiller, Predoctoral Fellow in the Bork Group and co-first author, “Even disparate habitats, with fundamentally different physiochemical conditions, are connected by generalist species.”

Human activities are accelerating the spread of these generalists. Sewage disposal and climate change create new pathways for microbial movement, while the overuse of antibiotics drives the evolution of antimicrobial resistance genes within these adaptable species. The World Health Organisation identifies antimicrobial resistance as one of the top ten global public health threats, surpassing the annual death toll of malaria and HIV/AIDS combined, as historically treatable infections become increasingly difficult to cure.

Expert Insight: This research underscores the complex interplay between environmental factors, microbial evolution and public health. The ability of microbes to share genetic information across vast distances highlights the need for a more comprehensive understanding of how human actions impact the global microbiome and, our own well-being.

The One Health Connection

The study’s findings emphasize the interconnectedness of human, animal, and environmental health – a concept known as One Health. Chan Yeong Kim, Postdoctoral Fellow in the Bork Group and co-first author, stated, “Our findings show that such microbes play an important role in linking human, animal, and environmental health – also known as One Health – emphasising the need to view planetary health beyond a purely human-centred perspective.” This perspective is embraced by the Quadripartite organisations: the World Health Organisation (WHO), Food and Agriculture Organisation (FAO), World Organisation for Animal Health (WOAH), and United Nations Environment Programme (UNEP).

By demonstrating the gene transfer capabilities of generalists between environments like wastewater and the human gut, the research highlights the critical dependence of human health on the health of both animals and the planet.

Frequently Asked Questions

What are ‘generalist’ microbes?

Generalist microbes are a rarer subset of microbes capable of thriving in a wide range of habitats, unlike ‘specialist’ microbes which are limited to specific environmental conditions.

How do generalists connect different microbiomes?

Generalists transfer their genes to other microbes through horizontal gene transfer as they move between ecosystems, creating genetic ‘bridges’ between geographically distant habitats.

What is the One Health approach?

One Health is an approach that recognizes the interconnectedness of human, animal, and environmental health, emphasizing the need to view planetary health beyond a purely human-centred perspective.

As research continues, could a deeper understanding of these microbial networks lead to new strategies for combating antimicrobial resistance and promoting global health?