Plan the perfect garden with our interactive tool →

Harmful Bacteria in Soil

Dirt Road image by Antonio Oquias from <a href=''></a>

In a well-balanced soil, millions of bacteria are working at a time. A single gram of soil typically contains around 40 million bacterial cells. Soil bacteria are necessary to produce healthy plants. However, there is a thin line separating the good bacteria from the bad bacteria.


Bacteria consist of a single cell without membrane-surrounded nucleus or organelles, according to Medical News Today . Microscopic organisms, such as bacteria, function in the soil to break down, build up and enhance. Bacteria certainly outnumber all other microbes in the soil. Without bacteria, the soil cannot use organic materials to provide nutrients for plant growth. However, many different types of bacteria are harmful to both plants and humans.

How Damage Occurs

Bacteria that attack plants enter through cuts or damage in the leaves, stems or roots of the plant. According to Types of Bacteria, while there are thousands of bacteria that cause disease in mammals, only about 100 types of bacteria infect and damage plants. The most common areas where bacterial infection occurs have tropical climates.

Types of Harmful Bacteria

Gardeners refer to beneficial soil bacteria as probiotics. Harmful bacteria are called proteobacteria. A very large group, proteobacteria includes many bacteria that also affect humans, such as Vibro cholarae, the root cause of cholera.

Xanthomonas campestris, one example of proteobacteria, works in the soil to fix nitrogen and forms useful compounds for platn growth; however, it also causes black rot in Arabidopsis and Brassicas. Bacteria that cause rot in plants do so by blocking the vessels that carry water to the various parts of the plant.

Effects on Humans

According to Types of Bacteria, there are no recorded cases of bacteria being passed from a plant to a person that results in an infection. The bacteria affecting plants are highly specific. People working with soils should understand that while most bacteria are beneficial, the potential exists for contact with harmful bacteria. The potential for catching tetanus exists, despite the reduced risk resulting from frequent immunizations. Soil contaminated with fecal matter can harbor E. coli 0157, according to Soil-Net. Although rare, anthrax can also exist in the soil. It is recommended that gardeners wear gloves and wash hands thoroughly after working in garden soil.

Fixing Good Bacteria

Beneficial bacteria can be fixed into the soil to help reduce harmful bacteria. In most instances of bacterium-based disease, the recommended action is to avoid planting the specific species of plant affected for several seasons in the affected area. The nurturing of beneficial bacteria in the soil may help to eliminate the risk from harmful bacteria. Anecdotal evidence points to the removal of damaging bacteria through the heating of the soil by use of black plastic mulching. Frequent turning and aeration of the soil may help to reduce tetanus, which thrives in oxygen-free environments. However, methods that reduce harmful bacteria often remove beneficial bacteria as well. Starter bacterial inocula are available to help diversify the bacterial species in the soil. Fish emulsion, green plant material and sugars help increase the full range of beneficial bacteria.

Garden Guides