The small, often-forgotten depression in the center of the abdomen, the navel, is far from an empty space. This remnant of the umbilical cord is a highly specialized habitat for an entire community of microscopic life. Scientists have increasingly found that this overlooked area harbors an astonishing diversity of organisms. The human belly button functions as a miniature world, confirming its biological complexity.
Defining the Navel as a Micro-Ecosystem
An ecosystem is a community of interacting organisms and their non-living environment, functioning as a single ecological unit. This requires both biotic components (living things) and abiotic components (non-living physical elements). The navel meets these criteria, containing a multitude of microorganisms (biotic) existing within a specific physical space influenced by factors like temperature and moisture (abiotic).
These factors interact constantly, with microbes utilizing the physical environment and its resources. For example, bacteria consume the oils and dead skin cells produced by the surrounding tissue. This continuous exchange of energy and matter confirms the navel’s status as a functioning micro-ecosystem.
The Specific Inhabitants
The life within the navel is dominated by bacteria, exhibiting a high level of diversity. A large-scale citizen science project found over 2,300 different types of bacteria, called phylotypes, across a group of volunteers. While the average person hosts around 67 distinct types, the majority of these species were unique to only one or a few individuals.
The microbial community is anchored by common skin bacteria like Staphylococcus and Corynebacterium species, which are adapted to moist environments. The navel also hosts transient species picked up from the environment, including organisms previously known only from soil. Researchers have identified species of Archaea, a group of single-celled organisms, in individuals with unique hygiene practices. Fungi and even microscopic mites are occasionally found, adding to the complexity of this habitat.
Factors Creating the Unique Habitat
The physical characteristics of the navel create an environment highly favorable for microbial colonization and growth. Anatomically, the folds and depth of an “innie” navel provide a sheltered niche rarely disturbed by daily life. This protected space offers a stable refuge from external factors like sunlight and abrasive scrubbing.
Several abiotic factors combine within this shelter to support the microbial community. The area is naturally warm, as it is close to the core body temperature and often covered by clothing. Moisture is retained from eccrine sweat glands. Apocrine glands release a milky secretion, and sebaceous glands produce an oily substance called sebum. These secretions provide lipids and nutrients that feed the organisms living there.
Practical Implications for Health and Hygiene
The continuous microbial activity within this warm, moist environment can lead to the most common issue: odor. This smell is caused by bacteria breaking down organic compounds, such as oils and dead skin cells, into volatile compounds. For most people, the diverse community of microbes is not harmful; it may contribute to skin health by occupying space that could otherwise be colonized by pathogens.
Maintaining a healthy balance requires gentle, consistent hygiene. Simple, regular cleaning with mild soap and water is sufficient to manage the population without disrupting beneficial microbial diversity. It is important to thoroughly dry the navel after washing, as excessive moisture can encourage the overgrowth of certain organisms, potentially leading to irritation or infection. The navel microbiome is benign, and its biodiversity is a normal feature of the human body.