What is Bacteria?
Bacteria are small, single-celled microbes that grow and live in thin water films around soil particles near roots. They perform many key ecosystem services in soil including improving soil structure and aggregation, recycling of soil nutrients such as carbon, nitrogen, phosphorus, and sulfur, fixing atmospheric nitrogen and carbon, and water recycling. They serve as the building blocks for improving soil structure, which leads to increased water infiltration and holding capacity. In fact, some researchers think that it may be possible to control the plant species within an area by managing the soil bacteria community!
Most bacteria are classified into one of the four following categories:
1) Bacteria Shape
First, when classifying bacteria, scientists evaluate their shape. Generally, the three major shapes are rod, sphere, or spiral; however, this may become complex as many bacteria have different shapes and arrangements.
Microbiology of Bacterial Morphology & Shape. Source: Microbiology Videos
2) Aerobic vs Anaerobic Bacteria
Soil oxygen levels often determine soil bacteria activity. Most aerobic soil bacteria prefer well-oxygenated soil and use this oxygen to decompose most carbon compounds. Anaerobic bacteria on the other hand prefer environments with no oxygen and are mainly found in the intestines of animals. They are often associated with manure and are known to kill off aerobic bacteria in the soil.
3) Gram-Negative vs Gram-Positive Bacteria
When a staining agent is used in the lab, bacteria can be classified as gram-positive or gram-negative; this staining agent works by attaching to a bacteria’s cell walls. Gram-positive bacteria are much larger in size, tend to resist water stress, have thicker cell walls, and negative charges on the outside cell wall surface. Gram-negative bacteria are generally smaller in size and sensitive to drought and water stress.
Cell wall structure in gram-positive vs. gram-negative bacteria. Source: Biology Dictionary
4) Other
Growth and reproduction are other ways to classify bacteria. As advancements in DNA sequencing continue, scientists are classifying bacteria based on the type of environment they inhabit since some bacteria can live in extreme heat like hot springs or extreme cold like the Arctic waters. They may also be classified based on the acidity of the environment (i.e. acidic versus alkaline).
The Benefits of Bacteria for Soil
Bacteria provide large amounts of nitrogen to plants, which is often lacking in soil. Many bacteria secrete enzymes that make phosphorus more soluble and available to plants. Along with bacteria, fungi are important decomposers in the food web. They convert indigestible organic material into forms that other organisms may use.
For example, fungal hyphae physically bind soil particles together which creates stable aggregates, increasing water infiltration and soil water holding capacity. Generally, bacteria tend to outnumber fungi in tilled or disrupted soils because fungi prefer more acidic environments without soil disturbance. Most fungi need oxygen to survive; meanwhile, bacteria are capable of surviving in dry or flooded conditions due to their small size, high numbers, and ability to live in small microsites within the soil.
In order for bacteria to survive, they must adapt to a variety of microenvironments. In soil, oxygen concentrations vary from one microsite to another, but once environmental conditions are favorable, bacteria quickly multiply. For example, large pore spaces filled with air provide high oxygen levels, favoring aerobic conditions and attracting aerobic bacteria. Just a few inches away, smaller micropores may be anaerobic or lack oxygen, completely altering the composition of bacteria in that space. This diversity in soil microenvironments is what allows bacteria to thrive under various soil moisture and oxygen levels.
Natural succession happens in a number of plant environments, including soil. Bacteria improve soil which is known to encourage plant growth; without it, new plant populations and communities struggle to survive or even exist. In fact, bacteria have a large impact on the soil environment allowing certain plant species to exist and proliferate! As soil is disturbed less and plant diversity increases, the soil food web becomes more balanced and diverse, making soil nutrients more available in any given environment and soil bacteria essential for all living organisms.
Benefits Bacteria Hold for Humans
Human health is inextricably linked to microbe health. Unfortunately, over the years we have destroyed vital human gut microbes through the overuse of antibiotics and highly processed foods. We have also severely harmed soil microbiota, which is essential to plant health, through the overuse of certain chemical fertilizers, fungicides, herbicides, and pesticides.
Some of these bacteria serve as the “stomachs” of plants, as they form symbiotic relationships and provide nitrogen, phosphorus, and many other nutrients in a form which plants cells can assimilate to. Luckily, thanks to advancements in technology, we are able to map genetic sequences of soil microorganisms and ultimately reintroduce them back to the soil to ensure we as humans are gaining the proper nutrients we should be getting from plants.
Similar to the human biome, the microbial community in the soil provides “invasion resistance” services. Consequently, researchers believe that the increase in autoimmune diseases in western U.S may be attributed to the lack of nutrients we are gaining through our soil. If we do not act soon to improve soil health, we are on a downward path towards poor environmental and human health.
How to Protect Soil Bacteria
With the rate of current greenhouse gas emissions and increasing climate change, there is one leverage point with hopes of a healthy and sustainable future: the living soil that grows our food. Reintroducing microorganisms and organic matter into soil has the potential to be a key part of the next revolution in human health regarding the development of sustainable agriculture. We must do everything in our power to ensure bacteria stay alive and populous as they serve an essential role in both environmental and human health!
Below there are some other articles that you might be interested in:
Leave A Comment