Introduction

The Bacillales bacterium, primarily represented by the genus Bacillus, is a diverse group of Gram-positive, spore-forming bacteria. While frequently associated with soil environments, specific strains are key commensals within the human body. Through metagenomics and shotgun sequencing, we now understand that these bacteria play a multifaceted role in maintaining the gut ecosystem and skin health. Depending on the strain and its location, the Bacillales bacterium can act as a protective probiotic or, in rare cases, an opportunistic pathogen, highlighting the importance of microbial balance and niche context in overall health.

Location of Microbe

Gut Ecosystem

In the human gastrointestinal tract, Bacillales are found as commensals. They are particularly adapted to survive the harsh conditions of the digestive system through the formation of endospores, which remain dormant until they reach the small intestine.

Skin Ecosystem

Bacillales are also present on the skin, where they contribute to the surface microbiome. They interact with the host's innate immune system and other resident microbes to maintain the integrity of the skin barrier.

Behavior During Dysbiosis

Gut Ecosystem

During intestinal dysbiosis, such as following antibiotic therapy for H. pylori, the introduction of Bacillus subtilis is associated with a faster restoration of gut α-diversity and an enrichment of beneficial butyrate-producing taxa.

Skin Ecosystem

In the skin ecosystem, a loss of microbial diversity or an imbalance in commensal populations can lead to a state of dysbiosis, potentially allowing opportunistic strains to interfere with the skin's natural protective signaling.

Disease Associations

Gut Ecosystem

In the gut, certain strains of Bacillales are associated with various health outcomes. Probiotic strains like B. subtilis DE111 have been associated with the attenuation of endothelial dysfunction induced by a Western diet in animal models, potentially reducing cardiovascular risk. Furthermore, the presence of specific Bacillus strains is associated with the reduction of gastrointestinal symptoms such as diarrhea and acid reflux during eradication therapy. However, specific pathogenic strains retrieved from surgical sites have been associated with a high degree of collagenolytic activity, which may contribute to the pathogenesis of anastomotic leaks, particularly in hosts with obesity.

Skin and Oral Ecosystems

In the oral and skin-adjacent ecosystems, Bacillus subtilis is significantly associated with healthy controls. Conversely, a reduction in its abundance is associated with the salivary profiles of children with Juvenile Idiopathic Arthritis (JIA), suggesting a potential link between the loss of these commensals and systemic chronic inflammation.

Foods Supporting Healthy Balance

Maintaining a healthy abundance of beneficial Bacillales and supporting the broader gut ecosystem can be achieved through targeted dietary choices. Fermented foods are a primary source of these bacteria; products such as natto, soybean pastes, and various fermented soybean products naturally contain Bacillus subtilis. Beyond the microbes themselves, providing the necessary substrates for their functional potential is crucial. Synbiotic approaches, combining B. subtilis with L-alanyl-L-glutamine, have been shown to increase the production of butyrate, a short-chain fatty acid essential for gut barrier integrity. Additionally, a diet rich in diverse fibers and nutrients supports the growth of butyrate-producing taxa, which work synergistically with Bacillales to modulate lipid and glucose homeostasis.

Actionable Insights

Microbiome Management Tips

• Incorporate Fermented Soy: Consider adding traditional fermented soy products like natto to your diet to introduce beneficial Bacillus species.
• Support Butyrate Production: Focus on a diet high in prebiotic fibers to encourage the production of short-chain fatty acids, which support the intestinal lining.
• Consider Synbiotics: Explore the use of synbiotics (probiotics combined with specific amino acids) if looking to modulate metabolic parameters like LDL cholesterol, under professional guidance.
• Maintain Skin Hygiene: Use gentle, pH-balanced cleansers to avoid disrupting the skin's microbial diversity, preserving the protective role of commensal Bacillales.
• Monitor Dietary Patterns: Reduce intake of highly processed 'Western-style' diets, as nutrient excess is associated with a decline in the beneficial effects of these microbes on vascular health.

Conclusion

The impact of the Bacillales bacterium on human health is highly dependent on the specific strain and its niche context. In the gut, beneficial strains act as powerful modulators of metabolic health and barrier function, promoting the production of butyrate and supporting the recovery of microbial diversity after antibiotic stress. In the skin and oral ecosystems, they serve as markers of health and contribute to the host's innate defense mechanisms. Understanding these host-microbe interactions allows for a more preventive approach to health, focusing on the balance of the ecosystem rather than the presence of a single species.