A better understanding of homing or finding a distinct niche by specific symbiotic gut bacteria

Amazing stuff!

"... However, the microbiome isn’t uniform throughout the gut. Just as various organs within the gastrointestinal system have different specialties when it comes to digesting food and absorbing nutrients, different microbial communities are localized within each zone and play unique roles there.

Successful colonization of each region of the G.I. tract by different microbial populations is dependent on a variety of factors such as nutrient requirements of the bacteria; the local pH and dissolved oxygen content; competition with other bacterial strains; and survivability in harsh conditions—including stomach acid, bile salts, and immune-response cells. ...

incredibly complex system of interconnected microbial communities, and each species needs to get to the right place where it can thrive and contribute to host health ...

Successful colonization hinges on proteins in bacterial cell walls called adhesins. As you might guess from their name, they can stick to a variety of different surfaces within the body. But they typically bind non-specifically, meaning they could just as soon attach to one tissue as another.

So how do symbiotic microbiome species get to the place they need to go? ...

developed technology that enabled them to watch a single cell of the bacterial species Lactiplantibacillus plantarum colonize its niche within the fruit fly gut in real time. ...

Watching the events unfold in such high-resolution detail enabled the scientists to see the difference between short-lived colonization and long-term success. ...

They found that L. plantarum isolated from the guts of wild fruit flies was able to stably attach to host tissue whereas L. plantarum from humans and other sources formed only transient attachments.

With this information in hand, the researchers set out to determine the genetic basis for this super-affinity. Through diligent and painstaking work, they were able to identify a set of genes for symbiotic gut colonization within a niche. ..."

From the perspective abstract:

"Lactiplantibacillus plantarum is a bacterium found in diverse environments, from fermented foods to plant and animal hosts. Many lactobacilli have been found to promote metabolic, immune, and musculoskeletal health in various animal hosts, including flies, fish, mice, and humans. 

This combination of habitat versatility and health-promoting properties has sparked interest in understanding how lactobacilli evolve to colonize new hosts and how these adaptations influence their health-promoting activities . ... report a plasmid-encoded sugar-binding adhesin used by an L. plantarum strain isolated from a wild fruit fly (LpWF) to colonize the foregut of its host. They show that related sugar-binding adhesins are widely conserved across host-associated bacteria, demonstrating how sugar structures can serve as footholds for both mutualists and pathogens when making a host a home."

From the editor' summary and abstract:

"Editor’s summary

The benign organisms constituting a microbiota have mechanisms for recognizing an appropriate host. Although homing into niches is better understood for pathogens than for quotidian commensals, Gutiérrez-García et al. looked for signs of “symbiosis” islands in the microbiome of the fruit fly gut  ... 

The authors used live imaging to track the specificity of niche localization of the commensal bacterium Lactiplantibacillus plantarum to the fly foregut during passage in vitro. They identified a linear plasmid with a gene cluster that they refer to as a colonization island that contained many open reading frames for serine-rich repeat protein adhesins and auxiliary genes. Colonization islands seem to be broadly conserved among gut Firmicute bacteria and indicate a common mechanism for niche recognition. ...

Abstract

Animals selectively acquire specific symbiotic gut bacteria from their environments that aid host fitness. To colonize, a symbiont must locate its niche and sustain growth within the gut. Adhesins are bacterial cell surface proteins that facilitate attachment to host tissues and are often virulence factors for opportunistic pathogens. However, the attachments are often transient and nonspecific, and additional mechanisms are required to sustain infection. In this work, we use live imaging of individual symbiotic bacterial cells colonizing the gut of living Drosophila melanogaster to show that Lactiplantibacillus plantarum specifically recognizes the fruit fly foregut as a distinct physical niche. L. plantarum establishes stably within its niche through host-specific adhesins encoded by genes carried on a colonization island. The adhesin binding domains are conserved throughout the Lactobacillales, and the island also encodes a secretion system widely conserved among commensal and pathogenic bacteria."

Engineering the gut microbiome just became a reality

Could we engineer stability in the microbiome? New research opens the door (original news release) "New research from Carnegie Science biologists opens could lead to the creation of probiotics that are optimized for specific niches in the human gut."

Home sweet home "Sugar-binding adhesins enable bacteria to persist in specific host niches"

A conserved bacterial genetic basis for commensal-host specificity

Lactobacillus, a beneficial bacterial species (magenta), attaches to specific regions (green) of the fruit fly gastrointestinal tract (white).

Lactobacillus, a beneficial bacterial species (red), has genes that enable it to attach to a specific region of the fruit fly gastrointestinal tract (blue/cyan).