Why Bacterial Diversity Is Important for Health & Ecosystems

Bacterial diversity refers to the wide assortment of bacteria in any given environment. These microscopic organisms are found nearly everywhere on Earth, from deep oceans to backyard soil, encompassing millions of species with unique functions. Understanding this diversity is necessary to appreciate the influence bacteria have on planetary health and ecosystem stability.

Understanding Bacterial Variety

Scientists evaluate bacterial diversity in several ways, with the most direct measure being species richness—the total count of different bacterial species. For instance, a teaspoon of productive soil can contain thousands of distinct species, creating a complex community that contributes to ecosystem stability.

Species evenness describes the relative abundance of the different species present. In a balanced ecosystem, many species exist in roughly equal numbers. If one or two species dominate, evenness decreases, which can signal environmental stress and impact the range of functions performed by the community.

Functional diversity describes the different roles bacteria play, considering the variety of metabolic processes they use to acquire energy. Some bacteria are photosynthetic, using sunlight for energy, while others are chemosynthetic, deriving it from chemical reactions. This range of metabolic strategies allows bacteria to thrive in nearly every habitat.

Genetic diversity within a single bacterial species also contributes to the overall variety. This internal variation allows bacterial populations to adapt to changing conditions, like the introduction of an antibiotic or a shift in temperature. This adaptability makes bacteria a successful and persistent form of life.

Hotspots of Bacterial Life

The human gut is one of the most densely populated bacterial habitats, home to trillions of microorganisms called the gut microbiota. This internal ecosystem has co-evolved with humans, and its specific composition varies between people, influenced by diet, genetics, and environment.

Soil is another reservoir of bacterial diversity, containing numerous species that support terrestrial life. These bacteria perform functions like nutrient cycling and nitrogen fixation, which are foundational for agriculture and natural ecosystems.

The world’s oceans are also teeming with bacterial life, from sunlit surface waters to deep-sea vents. Photosynthetic bacteria like cyanobacteria are abundant in the upper ocean and produce a large portion of the planet’s oxygen. In the deep sea, chemosynthetic bacteria form the base of the food web around hydrothermal vents.

Why a World of Different Bacteria Matters

The variety of bacteria within an ecosystem is linked to its stability and ability to perform processes. Different bacteria carry out specialized roles in nutrient cycling, such as breaking down dead organic matter. Others convert elements like carbon, nitrogen, and phosphorus into forms that other organisms can use. A diverse community ensures these processes continue even if some species are lost.

For human health, a diverse microbiome provides numerous benefits. Gut bacteria help break down complex carbohydrates that the body cannot digest on its own. These microbes also produce vitamins, like B vitamins and vitamin K, and help regulate the immune system. A balanced gut microbiota can also prevent pathogenic bacteria from establishing themselves through colonization resistance.

Bacterial diversity is a resource for scientific and industrial innovation. Many antibiotics used in medicine were originally discovered in soil bacteria, which produce them to compete with other microbes. Industries also use bacterial enzymes for applications like manufacturing biofuels and producing detergents. Some bacteria are even used in bioremediation to clean up pollutants such as oil spills.

Ecosystem resilience often depends on the functional redundancy from a diverse microbial community. When an ecosystem faces a disturbance like pollution or a climate shift, a greater variety of bacteria increases the chance that some species will tolerate the new conditions. These survivors can continue their ecological roles, helping the ecosystem recover and maintain its functions.

Factors Shaping Microbial Communities

The composition of bacterial communities is influenced by several natural factors. Environmental conditions like temperature, pH, and nutrient availability create niches that favor certain bacteria. Geographical location also plays a part, as different regions have distinct microbial populations. Interactions within these communities, such as competition and cooperation, further shape their diversity.

In host-associated environments like the human gut, the host’s biology is also a factor. A person’s genetics, age, and immune system status can all affect the makeup of their resident microbiota. The relationship between a host and its microbes is dynamic, with changes in one affecting the other to maintain a balanced community.

Human activities can significantly alter bacterial diversity, sometimes with negative results. The use of antibiotics can reduce the diversity of the human gut microbiome, while pollution can be toxic to many bacterial species. Agricultural practices like using pesticides and fertilizers can also change the composition of soil microbes, affecting soil fertility.

Changes in diet and lifestyle are also drivers of shifts in the human microbiome. For example, a diet low in fiber can decrease the diversity of gut bacteria that ferment complex carbohydrates. Understanding how these factors shape microbial communities is an active area of research, aiming to find ways to preserve and restore healthy bacterial diversity.