Category Archives: Microbiome

Research – Don’t freak out: These are the microbes living on your tongue

Science Mag

STEVEN WILBERT AND GARY BORISY/FORSYTH INSTITUTE

Microbes are everywhere in our guts—and in our mouths. Now, a new study reveals our tongue-dwelling companions aren’t all mixed together randomly; instead, they seem to prefer living close to their own kind, separating out into distinct groups based on their species.

Researchers started by scraping the tongues of 21 healthy human volunteers. Then, they used fluorescent tags to identify specific groups of bacteria, some of which produce nutrients for us, so they could see exactly where each one lived on the tongue’s surface. Without exception, the bacteria formed tight-knit, well-defined clusters of the same species, the researchers report today in Cell Reports.

The clusters (above) resemble a microbial rainbow under the microscope. For instance, Actinomyces bacteria, in red, grow close to the epithelial tissue of the tongue, shown in gray, while Rothia bacteria, in cyan, form long patches between other communities. Streptococcus, in green, form a thin crust on the edge of the tongue and slender veins in the interior. By looking at the images, the researchers could guess at how these colonies establish themselves and grow over time.

Research – Some E. coli Strains May Be Linked to Development of Bowel Cancer

Food Poisoning Bulletin

CDC E.coli

Image CDC

According to a new study in the journal Nature, E. coli infections may be linked to bowel cancer. Some species of the intestinal microbiota, which is the collection of bacteria and viruses that live in the human gut, have been associated with colorectal cancer, but a direct role hasn’t been proven.

As it turns out, E. coli bacteria carry what is called a pathogenicity island pks, that creates enzymes that synthesize a compound called colibactin. Colibactin causes double-strand breaks in cultured cells. This damage can lead to cancer over time. Colibactin is found more often in fecal samples of people who do have bowel cancer than healthy people.

Research – Analyzing the differences in antibiotic resistance between the gut and mouth microbiome

Science Daily

The threat of antimicrobial resistance to medication is a global health issue. Recent years have seen a surge in our awareness of resistance genes; and as a result of the prevalence of these genes, antibiotics are becoming less effective at treating microbial infections, such as TB and gonorrhoea.

Although much work has been done analysing the human gut microbiome and its associated genes, little is currently known about these genes in the mouth.

In a paper published today in Nature Communications, academics from King’s College London have taken the first step to examine the antimicrobial resistance potential of the mouth — the oral resistome. As the mouth is the first point of entry for food and many medications, it has the potential to influence the spread of antimicrobial resistance in the human microbiome. Antimicrobial resistance arises when the microbe acquires genes that attempt to avoid or destroy the drugs.

Research -Tiny droplets allow bacteria to survive daytime dryness on leaves

Science Daily

Microscopic droplets on the surface of leaves give refuge to bacteria that otherwise may not survive during the dry daytime, according to a new study published today in eLife.

Understanding this bacterial survival strategy for dry conditions may enable scientists to develop practices that support healthy plant microbiomes in agricultural and natural settings.

The surface of an average plant leaf is teeming with about 10 million microbes — a population comparable to that of large cities — that contribute to the health and day-to-day functioning of the plant. Scientists have long wondered how bacteria are able to survive as daytime temperatures and sunlight dry off leaf surfaces.

“While leaves may appear to be completely dry during the day, there is evidence that they are frequently covered by thin liquid films or micrometre-sized droplets that are invisible to the naked eye,” says co-lead author Maor Grinberg, a PhD student at Hebrew University’s Robert H. Smith Faculty of Agriculture, Food, and Environment in Rehovot, Israel. “It wasn’t clear until now whether this microscopic wetness was enough to protect bacteria from drying out.”

To answer this question, Grinberg, together with co-lead author and Research Scientist Tomer Orevi and their team, recreated leaf surface-like conditions in the laboratory using glass plates that were exposed to various levels of humidity. They then conducted experiments with more than a dozen different bacteria species in these conditions.

They observed that while these surfaces appeared dry to the naked eye, under a microscope bacteria cells and aggregates were safely shielded in miniscule droplets. Interestingly, larger droplets formed around aggregates of more than one cell, while only tiny droplets formed around solitary cells. This microscopic wetness is caused by a process called deliquescence — where hygroscopic substances, such as aerosols, that are prevalent on leaves absorb moisture from the atmosphere and dissolve within the moisture to form the droplets.

“We found that bacteria cells can survive inside these droplets for more than 24 hours and that survival rates were much higher in larger droplets,” Orevi explains. “Our results suggest that through methods of self-organisation, for example by aggregation, these cells can improve their survival chances in environments frequently exposed to drying.”

These findings could have important implications for agriculture as human practices may inadvertently interfere with this bacterial survival mechanism, endangering the health of crops and natural vegetation, according to senior author Nadav Kashtan, PhD, Assistant Professor at Hebrew University’s Robert H. Smith Faculty of Agriculture, Food, and Environment. “A greater understanding of how microscopic leaf wetness may protect the healthy plant microbiome and how it might be disrupted by agricultural practices and human aerosol emissions is of great importance,” he says.

Kashtan also notes that similar microscopic surface wetness likely occurs in soil, in the built environment, on human and animal skin, and potentially even in extra-terrestrial systems where conditions might allow, suggesting such bacterial survival strategies are not limited to leaf surfaces.


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Materials provided by eLife.