Saturday, 17 August 2019

Is anxiety linked to our gut microbiome?

Microbiome research has advanced considerably since the first results from the U.S. National Institutes of Health led Human Microbiome Project were released. One area of interest is the connection between our microorganisms and anxiety symptoms. At first glance, the connection between the array of different microorganisms that are found within the human gut and feelings such as anxiety is not an obvious one. However, there is a growing level of evidence that variations within microbial communities are influential upon metabolic processes.
Human microbiome
The human microbiome refers to the totality of microorganisms and their genetic interactions within a given niche. Our understanding of the microbiome has advanced following a study of 300 men and women, who volunteered to take part in an international study. The advancement in understanding relating to developments with the methods used to characterize the microorganisms (including metagenomics) and the in-depth nature of the study, relating to the sampling of many body parts over a prolonged period of time, and drawing upon of the subjects from different geographical locales.
FDA microbiologist prepares DNA samples for gel electrophoresis analysis
FDA microbiologist prepares DNA samples for gel electrophoresis analysis
FDA / File
With the specific effects in relation to the human gut, then the understanding by scientists of the gut-brain axis has increased during the past ten years, suggesting a bidirectional nature between the gut and brain microbiome interactions. This includes a connection relating to the pathophysiology and pathogenesis of irritable bowel syndrome (IBS), as an example.
In another research field, there is growing evidence of psychiatric and neurologic disorders like autism spectrum disorders, affective disorders, Parkinson's disease, and multiple sclerosis, being connected to the human gut microbiome.
The reason for this is that, with most people, the gut microbiota assist with the healthy functioning of the immune system. Furthermore, organisms assist with the metabolism by contributing inflammatory mediators, vitamins, and nutrients. Moreover, microbiologists have demonstrated that the intestinal microbiota can modulate communication between the intestinal tract and human brain via the nervous, immune, and endocrine systems.
It may be possible to treat superbugs with a predatory bacteria.
It may be possible to treat superbugs with a predatory bacteria.
University of Nottingham
However, when the intestinal microbial balance is altered, then changes occur and these can be manifest in terms of physical, and potentially mental, symptoms. One area being investigated in relation to a mental system is anxiety.
Anxiety is an emotion characterized by an inner turmoil. It is often accompanied by nervous behaviour, somatic complaints, and rumination. The condition includes subjectively unpleasant feelings of dread over anticipated events. When experienced regularly the individual may suffer from an anxiety disorder. The global incidence of anxiety disorder is estimated to be between 3-25 percent. Typical treatment for anxiety is usually psychopharmacological therapies and psychotherapy.
New research
With the new research, scientists have attempted to see if anxiety symptoms can be improved by regulation of intestinal microorganisms. By assessing some 3,334 published articles the researchers focus on 21 major studies. Across these studies,1,503 participants included "patients with IBS (10 studies), healthy controls (six studies) and other patients with chronic diseases such as chronic fatigue syndrome (CFS), rheumatoid arthritis (RA), obesity, fibromyalgia, and type 2 diabetes mellitus."
Of the 21 studies, 14 had chosen probiotics as interventions to regulate intestinal microbiota (IRIFs), and seven chose non-probiotic ways, such as adjusting daily diets. Those studies that utilized "interventions regulating intestinal flora" consisting of probiotics with Lactobacillus alone or a mixture of LactobacillusStreptococcus, and Bifidobacterium, showed some positive results. Overall, 11 of the 21 studies suggested a positive effect on anxiety symptoms by regulating intestinal microbiota, meaning that more than half (52 percent) of the studies showed this approach to be effective.
Some of the bacteria found by scientists in 3.5-billion-year-oldĀ fossils are now extinct  while oth...
Some of the bacteria found by scientists in 3.5-billion-year-old fossils are now extinct, while others are similar to contemporary microbes
To draw these conclusions the review was subjected to meta-analysis, considering the research design, subjects, interventions, and anxiety assessment scales. This drew out the connected between anxiety and disturbances to the gut microbiome and indicated that it may be possible to regulate the intestinal microbiota through the use of probiotics, although further research will be required.
The researchers conclude: "We find that more than half of the studies included showed it was positive to treat anxiety symptoms by regulation of intestinal microbiota.
"There are two kinds of interventions (probiotic and non-probiotic interventions) to regulate intestinal microbiota, and it should be highlighted that the non-probiotic interventions were more effective than the probiotic interventions. More studies are needed to clarify this conclusion since we still cannot run meta-analysis so far."
Research paper
The new research has been published in the British Medical Journal, with the research paper titled “Effects of regulating intestinal microbiota on anxiety symptoms: A systematic review.”

Written by Dr. Tim Sandle, Pharmaceutical Microbiology

Thursday, 1 August 2019

Microbes can grow on nitric oxide

Nitric oxide (NO) is a central molecule of the global nitrogen cycle. A study reveals that microorganisms can grow on NO. Their results change our view of the earth's nitrogen cycle and how microorganisms regulate the release of greenhouse gases from natural and human-made environments.

Intriguingly, long before there was oxygen on Earth, nitric oxide was available as a high-energy oxidant, and might have played a fundamental role in the emergence and evolution of life on Earth. A study by Max-Planck-scientist Boran Kartal and colleagues now published in Nature Communications sheds a new light on microbial transformations of this molecule. Yes they can -- with implications for our climate.

One major question about nitric oxide remained unanswered up to now: Can organisms use it to grow? "One would think so," Kartal explains, "as nitric oxide has been around since the emergence of life on earth." However, no microbe growing on NO has been found -- until now. Kartal and his colleagues from Radboud University in the Netherlands have now discovered that the anaerobic ammonium-oxidizing (anammox*) bacteria directly use NO to grow. In detail, these microorganisms couple ammonium oxidation to NO reduction, producing nothing but dinitrogen gas (N2) in the process.

The latter -- the sole production of N2 -- is particularly intriguing: Some microbes convert NO to nitrous oxide (N2O), which is a potent greenhouse gas. N2, in contrast, is harmless. Thus, each molecule of NO that is transformed into N2 instead of N2O is one less molecule adding to climate change. "In this way, anammox bacteria reduce the amount of NO available for N2O production, and reduce the amount of released greenhouse gas," Kartal explains. "Our work is interesting in understanding how anammox bacteria can regulate N2O and NO emissions from natural and human-made ecosystems, such as wastewater treatment plants, where these microorganisms contribute significantly to N2-release to the atmosphere."

Nitric oxide is a central molecule in the global cycling of nitrogen. "These findings change our understanding of the earth's nitrogen cycle. Nitric oxide has been primarily thought of as a toxin, but now we show that anammox bacteria can make a living from converting NO to N2," says Kartal. The present study raises new questions. "Anammox, a globally important microbial process of the nitrogen cycle relevant for the earth's climate, does not work the way we assumed it did." Moreover, other microbes than the ones investigated here could be using NO directly as well. Anammox bacteria are found all over the planet. "In this sense, the anammox microbes growing on nitric oxide could also be basically everywhere," Kartal continues.

Now, Kartal and his group at Max Planck Institute in Bremen are exploring different ecosystems from all around the world, hunting for specialized nitric oxide converting microorganisms. They want to understand better how microbes use NO in environments both with and without oxygen. This will probably pave the way to the discovery of new enzymes involved in nitric oxide transformation. "Basically, we want to understand how organisms can make a living on NO."

See: Ziye Hu, Hans JCT Wessels, Theo van Alen, Mike SM Jetten and Boran Kartal. Nitric oxide-dependent anaerobic ammonium oxidation. Nature Communications, 2019 DOI: 10.1038/s41467-019-09268-w

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology

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