Actinobacteria

Actinobacteria are a diverse phylum of Gram-positive bacteria with high guanine and cytosine DNA content, commonly found in both aquatic and terrestrial environments. These bacteria exhibit a mycelial lifestyle and undergo complex morphological differentiation. 

Renowned for their prolific secondary metabolism, Actinobacteria are the source of about two-thirds of clinically used antibiotics and many anticancer, anthelmintic, and antifungal compounds. 

They inhabit various ecological niches, including pathogenic species like Corynebacterium and Mycobacterium, soil-dwelling Streptomyces, plant-associated Frankia, and gastrointestinal commensals such as Bifidobacterium and Actinomycetales, which may be commensal or pathogenic. 

In the human body, Actinobacteria are integral to the microbiota of the gut, oral cavity, lungs, and skin, contributing to health by aiding in digestion, nutrient production, immune modulation, and protection against pathogens. 

However, some Actinobacteria can also cause diseases, including tuberculosis, leprosy, and actinomycosis. 

Understanding the roles of Actinobacteria in health and disease highlights their importance in both medical and environmental contexts.

What is Actinobacteria?

Actinobacteria are a diverse phylum of Gram-positive bacteria with high guanine and cytosine DNA content, prevalent in aquatic and terrestrial environments. These bacteria are characterized by their mycelial lifestyle and complex morphological differentiation. 

Known for their extensive secondary metabolism, Actinobacteria produce about two-thirds of clinically used antibiotics, as well as numerous anticancer, anthelmintic, and antifungal compounds. [3.]

Their diverse lifestyles include pathogenic (e.g., Corynebacterium, Mycobacterium), soil-dwelling (e.g., Streptomyces), plant commensals (e.g., Frankia), and gastrointestinal commensals (e.g., Bifidobacterium). [3.] 

Gut Actinobacteria reside in the digestive systems of animals, aiding in nutrition and pathogen resistance. [1.] Specifically, some strains of Actinobacteria provide essential nutrients, like B vitamins, to their hosts, as seen in mammalian gut bacteria like Bifidobacterium. [6.] 

As probiotics, Actinobacteria enhance host health by modulating the gut microbiota. [1.] 

While beneficial, some Actinobacteria cause diseases in plants and animals. In humans and animals, Actinobacteria can cause diseases such as tuberculosis, leprosy, and actinomycosis. [1.] 

Actinobacteria in The Human Body [4.] 

Actinobacteria are part of the human microbiota, residing in various body regions, including the gut, oral cavity, lungs, and skin. These bacteria are integral to maintaining health and are involved in numerous physiological functions.

Gut Microbiota

In the gut, Actinobacteria contribute to the fermentation of food, protection against pathogens, immune response stimulation, and vitamin production. They are part of the six major phyla present in the gut, playing a crucial role in maintaining a balanced microbial community.

Oral Microbiota

Actinobacteria are also significant in the oral microbiota, the second largest microbial community in the human body. They inhabit various oral niches such as saliva, gums, and tooth surfaces. These bacteria are involved in maintaining oral health and preventing diseases through their interactions within the microbial community.

Lung Microbiota

Once considered sterile, the lungs also host Actinobacteria among other core microbiota. These bacteria help maintain lung health by contributing to immune tolerance and preventing unnecessary inflammatory responses.

Skin Microbiota

The skin harbors diverse microbial communities, including Actinobacteria. These bacteria are crucial for maintaining skin health by preventing pathogenic infections and contributing to the skin's immune defense mechanisms.

Actinobacteria in Human Health

In the healthy adult gut, Actinobacteria make up a smaller portion of the microbiota, which is predominantly composed of Firmicutes and Bacteroidetes. Dysbiosis, an imbalance of the gut microbiota, has been linked to chronic diseases and altered by factors such as diet, antibiotics, and stress. [5.] 

The gut microbiota, including Actinobacteria, plays a critical role in immune system regulation and gut-brain signaling. 

Microbiota produce neuroactive metabolites, including GABA by Bifidobacteria (famous members of the Actinobacteria phylum). These metabolites influence brain function and behavior, as shown in animal models where probiotics increased exploratory behavior and stress responses. [5.] 

Dysbiosis can impair intestinal and blood-brain barrier integrity, facilitating the translocation of bacterial metabolites and immune mediators into circulation.

Actinobacteria, particularly the Bifidobacterium genus, are crucial for maintaining gut health; they are also known for their anti-pathogenic and anti-inflammatory effects. 

High fiber diets, typical of vegetarian and vegan regimes, increase Bifidobacterium levels, which are associated with enhanced gut barrier function and protection against pathogens. [11.] 

These bacteria also help produce SCFAs, which contribute to gut and overall health.

Plant-based diets foster a gut microbiota rich in beneficial bacteria and metabolites. High fiber intake boosts Bifidobacterium, enhancing cardiovascular and anti-inflammatory benefits. [11.] 

In contrast, diets high in animal protein and fat increase pro-inflammatory bacteria like Bacteroides and Clostridia, which may elevate the risk of colorectal cancer and inflammatory diseases.

Actinobacteria Associations with Disease

Inflammatory Bowel Disease (IBD)

IBD, including Crohn’s disease (CD) and ulcerative colitis (UC), is a chronic inflammatory condition of the gastrointestinal (GI) tract. 

The gut microbiota plays a crucial role in IBD, with dysbiosis (an imbalance in the microbial community) contributing to disease progression. 

In healthy individuals, the predominant gut bacteria are Firmicutes and Bacteroidetes, followed by Proteobacteria and Actinobacteria. 

Studies show that IBD patients have altered gut microbiota, including reduced Bacteroidetes to Firmicutes ratio and increased gammaproteobacterial abundance. 

Protective bacteria like Bacteroides, Eubacterium, and Lactobacillus are significantly reduced in IBD patients. And Actinobacteria levels are also often altered in IBD, indicating their potential role in maintaining gut health and implicating their imbalance in IBD development. [7.] 

Actinobacteria levels were notably higher in both UC and CD patients compared to healthy controls, with the increase being more pronounced in UC patients. [7.] Actinobacteria, including genera such as Actinomyces, have been implicated in exacerbating intestinal inflammation and contributing to disease progression.

IBS and Depression

IBS patients often have co-morbid psychological distress such as depression or anxiety.

Dysbiosis, which can be seen in IBS, is also associated with depressed symptoms.  Specifically, increased levels of Actinomycetales have been correlated with depression. [2.] 

In contrast, psychobiotics, like those containing Bifidobacterium longum, have been shown to improve depression in IBS patients. [8.] 

A randomized controlled trial found that a “psychobiotic”, or probiotic with possible psychological benefit, containing Bifidobacterium longum for 6 weeks improved depression in IBS patients.

Improvements in depression were associated with changes in brain activation patterns as seen in functional magnetic resonance imaging (fMRI) in the group receiving psychobiotic therapy.

Probiotics can impact psychological symptoms, including depression, in healthy individuals.

The connection between gut dysbiosis, altered intestinal permeability, gut immune activation, and psychological symptoms like depression suggests a shared pathophysiology between IBS and depression. [8.] 

Brain Disorders 

Research indicates that gut microbiota, including Actinobacteria, influences brain disorders through the gut-brain axis. [4.] 

The gut microbiota affects brain function by modulating stress responses, neurotransmitter systems, and immune responses. Changes in gut microbiota composition have been linked to neuropsychiatric and neurodegenerative disorders. For instance, patients with major depressive disorder exhibit increased levels of Actinobacteria compared to healthy controls. 

[2.] 

A higher number of Actinomycineae was also noted in depressed individuals. [2.] This change suggests a possible role for these bacterial families in the gut-brain axis related to depression.

However, other research has shown an amelioration in depression symptoms when Bifido-containing probiotics were given to patients with IBS. [8.] 

In Alzheimer’s disease (AD), a decrease in Actinobacteria (specifically Bifidobacterium) is observed, along with reduced Firmicutes and increased Bacteroidetes and Proteobacteria. 

This dysbiosis is associated with increased inflammatory cytokines and amyloidosis, highlighting the significant impact of gut microbiota on brain health.

Lung Cancer [12.] 

The composition of respiratory microbiota, including a higher abundance of Actinobacteria, significantly differs between lung cancer patients and healthy individuals. These findings suggest that respiratory microbiota, including Actinobacteria, could serve as potential biomarkers for lung cancer.

Infectious Diseases [6.] 

Mycobacterium tuberculosis is the causative agent of tuberculosis (TB), one of the most devastating diseases in human history. Another significant pathogen within the Actinobacteria phylum is Mycobacterium leprae, which is responsible for leprosy. [6.] 

Corynebacterium diphtheria is known for causing diphtheria, while Tropheryma whipplei is the pathogen behind Whipple’s disease. [6.] 

Additionally, Gardnerella is associated with bacterial vaginosis, further illustrating the impact of Actinobacteria on human health. [6.] 

Actinomyces, another member of the Actinobacteria phylum, are often found in cervicofacial and dental infections, particularly in a condition known as cervicofacial actinomycosis. [9.] 

Actinomyces are normal inhabitants of the oral cavity but can become opportunistic pathogens when the mucosal barrier is disrupted, often due to dental procedures, trauma, or poor oral hygiene. [9.] 

The infection is characterized by the formation of painful abscesses, typically in the mandibular region, which can spread to surrounding tissues without regard for fascial planes. [9.] 

Cervicofacial actinomycosis often presents with nonspecific symptoms that can mimic other conditions, including malignancies, making early diagnosis challenging. Treatment usually involves a prolonged course of high-dose penicillin, sometimes in combination with surgical intervention for extensive lesions.

Laboratory Testing for Actinobacteria

Test Type, Sample Collection and Preparation

Actinobacteria levels are commonly assessed in stool samples.  Stool samples may be collected from the comfort of home.  

With concern for infections, tissue or other sample cultures may be performed.

Testing may require avoidance of certain medications and/or supplements including probiotics prior to sample collection.  It is important to consult with the ordering provider for full test preparation instructions.  

Interpretation of Test Results

Optimal Levels of Actinobacteria

It is important to consult with the laboratory company used for test interpretation.  Actinobacteria levels may be assessed as one phylum, or according to genera, such as Actinomycetales or Bifidobacteria. 

One lab company provides the following reference range for Actinobacteria levels and reports this on a scale from -3 (low prevalence of these organisms) to +3 (high prevalence of these organisms). [10.] It also reports levels of Actinomycetales and Bifidobacterium spp. According to the same scale.

Elevated Levels of Actinobacteria

Elevated levels of Actinobacteria should be interpreted in the context of an individual’s symptoms.  Elevated levels of Actinobacteria are commonly seen with: 

Gut Microbiome Imbalance

Actinobacteria, particularly Bifidobacterium species, are important components of the normal human gut microbiome. Elevated levels could potentially indicate a disruption in the normal balance of gut bacteria.

Possible Link to Depression in IBS Patients

High levels of some Actinobacteria such as Acinetomycetales have been linked to depression and IBS. [2.] 

Dietary Influence

A strict vegetarian diet may increase the total count of Actinomyces spp. compared to a Western diet. This indicates that diet can influence Actinobacteria levels, though the clinical significance of this is not clear.

Potential for Infections 

Some Actinobacteria species can cause infections. For example, Actinomyces species can cause actinomycosis, a rare but serious infection characterized by abscess formation, often occurring as a cervicofacial or dental infection.  

However, it's important to note that the presence of these bacteria doesn't necessarily indicate an infection, as many are part of the normal flora.

Decreased Levels of Actinobacteria

Low levels of Actinobacteria should be interpreted within the context of an individual’s symptoms.  Low levels may indicate:

Gut Microbiome Imbalance

Actinobacteria, particularly Bifidobacterium species, are important components of the normal human gut microbiome. 

Low levels could potentially indicate a disruption in the normal balance of gut bacteria, especially if an individual presents with symptoms including gas, bloating, digestive discomfort, and/or systemic symptoms such as fatigue, brain fog, and body pains.

Potential Impact on Immune Function

Actinobacteria play a role in maintaining gut health and immune function. Low levels might potentially affect these processes, though more research would be needed to confirm this.

Dietary Influence

Since a strict vegetarian diet may increase the total count of Actinomyces spp. compared to a Western diet, low levels might potentially be associated with certain dietary patterns such as the standard American diet.

Natural Ways to Optimize Microbiome Health [4.] 

A healthy diet and lifestyle are foundational for microbiome health.  

Diet and Nutrition

• Consume Diverse Foods: increase the variety of fruits, vegetables, whole grains, nuts, seeds, and legumes to promote microbial diversity.

• High-Fiber Diet: focus on fiber-rich foods to support the growth of beneficial bacteria.

• Fermented Foods: include yogurt, kefir, sauerkraut, kimchi, and other fermented foods to introduce probiotics.

• Polyphenol-Rich Foods: consume foods high in polyphenols such as berries, green tea, dark chocolate, and red wine to stimulate beneficial bacteria growth.

• Prebiotics: incorporate prebiotic-rich foods like garlic, onions, asparagus, and bananas to nourish beneficial bacteria.

Lifestyle

• Regular Exercise: engage in consistent physical activity to enhance gut microbiota diversity and composition.

• Stress Management: practice stress-reducing activities such as yoga, meditation, and mindfulness to prevent microbiota dysbiosis.

Medications and Supplements

• Probiotics: consider probiotic supplements to increase beneficial bacteria in the gut.

• Avoid Unnecessary Antibiotics: use antibiotics only when necessary to avoid disrupting the gut microbiome.

Environmental Factors

• Limit Artificial Sweeteners: avoid artificial sweeteners that can negatively affect gut microbiota.

• Healthy Sleep Patterns: maintain regular sleep patterns to support a balanced gut microbiome.

Hygiene Practices

• Avoid Over-Sanitization: limit the use of antibacterial soaps and sanitizers to maintain a healthy microbiota balance.

FAQ: Understanding Actinobacteria 

Actinobacteria are a diverse group of Gram-positive bacteria known for their significant roles in health, disease, and biotechnology. 

This FAQ section aims to answer common questions about Actinobacteria, their functions, and their importance as biomarkers in various fields.

What is Actinobacteria?

Actinobacteria are a group of Gram-positive bacteria with high guanine and cytosine content in their DNA. They are known for their complex and diverse morphologies, including filamentous forms similar to fungi. 

Actinobacteria are abundant in soil and water and play vital roles in decomposing organic materials.

What Are the Functions of Actinobacteria in the Environment?

In the environment, Actinobacteria are crucial for decomposing complex organic substances such as cellulose and chitin, contributing to nutrient cycling and soil fertility. 

They also produce a wide range of secondary metabolites, including antibiotics, enzymes, and pigments, which have various ecological functions.

Why Are Actinobacteria Significant in Medical Research?

Actinobacteria are significant in medical research due to their ability to produce antibiotics and other bioactive compounds. Streptomyces, a genus of Actinobacteria, is the source of many clinically important antibiotics such as streptomycin and tetracycline. 

How Are Actinobacteria Related to Human Health?

Actinobacteria are part of the normal microbiota in humans, particularly in the skin, oral cavity, and gastrointestinal tract. 

They play a role in maintaining health by preventing pathogenic infections, contributing to immune system function, and participating in the digestion of complex carbohydrates.

How is Actinobacteria Measured as a Biomarker?

Actinobacteria can be measured as biomarkers using molecular techniques such as quantitative PCR (qPCR), 16S rRNA gene sequencing, and metagenomics. 

These methods allow for the detection and quantification of Actinobacteria in various samples, including soil, water, stool and human tissues.

What Are the Clinical Implications of Actinobacteria as Biomarkers?

Actinobacteria can serve as biomarkers for various clinical conditions. For example, changes in the abundance of Actinobacteria in the gut microbiome have been linked to diseases such as inflammatory bowel disease, obesity, and colorectal cancer. 

Monitoring Actinobacteria levels can provide insights into disease states and therapeutic responses.

What Is the Role of Actinobacteria in Biotechnology?

In biotechnology, Actinobacteria are known for their ability to produce a wide range of bioactive compounds, including antibiotics and enzymes. They are used in industrial applications for the production of pharmaceuticals, biopesticides, and bioremediation agents.

When Should I Consult a Healthcare Provider About Actinobacteria-Related Concerns?

If you experience symptoms that may be related to an imbalance in your microbiota, such as digestive issues or skin infections, consult a healthcare provider. They can evaluate your condition and determine if Actinobacteria or other microbiota components are contributing to your symptoms.

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