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Decoding Microbiome Diversity: Is Increase Always Better? 

Our microbiome is uniquely composed of various bacterial and fungal species.

Diversity often serves as a fundamental indicator when discussing microbiome balance. Many believe that the rise in diversity signifies a healthier microbiome. Is this really true?

Well, it’s a bit more complex than that.

Generally, high diversity is believed to be associated with the health, stability, and resilience of the microbiome. Ecologically speaking, a microbial community made up of many diverse species is functionally redundant. This means that different species can perform the same functional role, and this redundancy reinforces stability and resilience, especially under times of stress or perturbation (think antibiotics). However, this principle of high diversity being “healthy” is not always true. Take the vaginal microbiome, for example, where increased diversity is associated with bacterial vaginosis and inflammation.

Particularly when it comes to the skin microbiome, the significance of shifted diversity is not yet fully understood. It’s important to note that many studies correlating a higher diversity with a healthy skin microbiome are based on studies of skin conditions like atopic dermatitis or psoriasis which often become overpopulated with a single pathogenic bacterium. These extreme cases highlight the significance of diversity as it relates to the overall health of the skin microbiome. However, the concept of diversity’s impact on skin health extends to various contexts and can vary depending on the specific skin condition, target area, and microbial dynamics.

Drawing conclusions solely based on changes in diversity, without considering taxonomy is akin to assessing health using just your Body Mass Index (BMI) without factoring in muscle mass, bone density, body fat percentage, diet, and lifestyle.

As shown in the graphs below, it is important to substantiate the shifts in diversity with taxonomic information before making any determinations about whether an increase or decrease in diversity is beneficial or detrimental.

Bacterial Microbiome Shift

An increase in diversity can indeed be advantageous when it results from the proliferation of beneficial bacteria rather than pathogenic ones. For example, when pathogenic bacteria like Staphylococcus aureus decrease and more commensal skin microbes increase.

Conversely, a decrease in diversity can also be beneficial if it occurs because beneficial microbes outcompete a diverse population to restore balance. An example of this is C. acnes, which serves as an indicator of an imbalanced microbiome when its presence falls below 60%. In such cases, replenishing C. acnes can lead to a decrease in the overall diversity but ultimately contributes to a more balanced microbiome.

Additionally, it’s imperative to acknowledge that alterations in microbial taxonomy and diversity must be approached through a holistic lens by gathering self-reported metadata and objective health measurements, especially as there is much more to uncover about the interplay between various species and their impact on health.

The intricate relationship between microbiome diversity and health is a multifaceted one, echoing the complexity of our own bodies. Diversity shifts likely have important consequences and significance when it comes to microbiome balance and health, therefore it is crucial to always contextualize these diversity differences and consider their many contributing factors. Overall, the dynamic interplay between the numerous microbial species colonizing our body and their effects on our health is a fascinating area of research, with much left to be discovered.

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