what is the role of bacteria in the soil

Soil beneficial bacteria and their role in plant growth promotion: a review

• Abstract. Soil bacteria are very important in biogeochemical cycles and have been used for crop production for decades.
• Introduction. ...
• Symbiotic N 2 -fixing bacteria. ...
• Non-symbiotic N 2 -fixing bacteria. ...
• Phosphorus-solubilizing bacteria. ...
• Other mechanisms of plant growth promotion. ...
Conclusion. ...
Author information. ...
Rights and permissions
About this article. ...

Full Answer

What is the function of bacteria in soil?

Bacteria perform many important ecosystem services in the soil including improved soil structure and soil aggregation, recycling of soil nutrients, and water recycling. Soil bacteria form microaggregates in the soil by binding soil particles together with their secretions.

What is the most common bacteria in soil?

Types of Soil Bacteria

• Nitrification Bacteria. Nitrate is an essential nutrient required by the plants for their growth. ...
• Nitrogen Fixation Bacteria. Nitrogen, along with potassium and phosphorus, is one of the primary nutritive building blocks of plant life.
• Denitrification Bacteria. ...
• Actinobacteria. ...

Why is bacteria important to the soil?

Importance of Bacteria in the nitrogen cycle. 1. Fix nitrogen in soil: Bacteria like chlorella are used as green manures to increase soil fertility. There absorb nitrogen from the air and fix it in the soil. Thus the nitrogen content of the soil increase and provides fertility to crops. Ex: cyanobacteria.

Do microorganisms affect soil?

What bad effects do microorganisms have on soil? On the other hand, pathogenic microorganisms present in agricultural soils can have a harmful effect on the crop inducing: i) pathogenicity and disease, ii) resistance to crop control products, iii) poor soil health or reduced fertility, iv) poor crop health or poor yields, and lastly v) crop loss.

What is the role of bacteria in soil fertility?

Bacteria increase soil fertility through nutrient recycling such as carbon, nitrogen, sulphur and phosphorus. Bacteria decompose dead organic matter and release simple compounds in the soil, which can be taken up by plants.

Is there bacteria in soil?

Bacteria are the most abundant microbes in the soil. They are single celled organisms, and there can be billions of bacteria in a single gram of soil. Populations of bacteria can boom or bust in the space of a few days in response to changes in soil moisture, soil temperature or carbon substrate.

What is the role of fungi and bacteria in soil?

Along with bacteria, fungi are important as decomposers in the soil food web. They convert hard-to-digest organic material into forms that other organisms can use. Fungal hyphae physically bind soil particles together, creating stable aggregates that help increase water infiltration and soil water holding capacity.

What is the most common bacteria in soil?

Members of the phyla Proteobacteria and Acidobacteria are the most abundant soil bacteria, as judged by the occurrence of 16S rRNA and 16S rRNA genes that are assignable to these groups (Table 4).

How do bacteria help plants grow?

Friendly bacteria can help plants grow by helping the plants to obtain nutrients such as phosphorous and nitrogen, or by defending the plants from other microbes that can make them sick.

What are the roles of bacteria?

Most bacteria are good for us The bacteria in our bodies help degrade the food we eat, help make nutrients available to us and neutralize toxins, to name a few examples[7]; [8]. Also, they play an essential role in the defense against infections by protecting colonized surfaces from invading pathogens[8]; [9].

What types of bacteria are in soil?

Common bacterial genera isolated from soil include Bacillus, Arthrobacter, Pseudomonas, Agrobacterium, Alcaligenes, Clostridium, Flavobacterium, Corynebacterium, Micrococcus, Xanthomonas, and Mycobacterium. In contrast to simple morphology, bacteria have the greatest metabolic diversity.

What are the functions of bacteria?

Bacteria in the digestive system break down nutrients, such as complex sugars, into forms the body can use. Non-hazardous bacteria also help prevent diseases by occupying places that the pathogenic, or disease-causing, bacteria want to attach to. Some bacteria protect us from disease by attacking the pathogens.

What type of bacteria can be found in soil?

Examples of Bacteria found in Soils Common bacterial genera isolated from soil include Bacillus, Arthrobacter, Pseudomonas, Agrobacterium, Alcaligenes, Clostridium, Flavobacterium, Corynebacterium, Micrococcus, Xanthomonas, and Mycobacterium.

Is there harmful bacteria in soil?

In addition to tetanus, anthrax, and botulism, soil bacteria may cause gastrointestinal, wound, skin, and respiratory tract diseases.

How do you get bacteria in soil?

Bacteria were released and separated from soil by a simple blending-centrifugation procedure. The percent yield of bacterial cells (microscopic counts) in the supernatants varied over a wide range depending on the soil type.

Which is the natural place for bacteria?

Bacteria are found in every habitat on Earth: soil, rock, oceans and even arctic snow. Some live in or on other organisms including plants and animals including humans. There are approximately 10 times as many bacterial cells as human cells in the human body.

What are the functions of bacteria?

Bacteria fall into four functional groups. Most are decomposers that consume simple carbon compounds , such as root exudates and fresh plant litter. By this process, bacteria convert energy in soil organic matter into forms useful to the rest of the organisms in the soil food web. A number of decomposers can break down pesticides and pollutants in soil. Decomposers are especially important in immobilizing, or retaining, nutrients in their cells, thus preventing the loss of nutrients, such as nitrogen, from the rooting zone.

What Do Bacteria Do?

Bacteria from all four groups perform important services related to water dynamics, nutrient cycling, and disease suppression. Some bacteria affect water movement by producing substances that help bind soil particles into small aggregates (those with diameters of 1/10,000-1/100 of an inch or 2-200µm). Stable aggregates improve water infiltration and the soil’s water-holding ability. In a diverse bacterial community, many organisms will compete with disease-causing organisms in roots and on aboveground surfaces of plants.

What is the difference between denitrifiers and actinomycetes?

Denitrifiers are anaerobic, meaning they are active where oxygen is absent, such as in saturated soils or inside soil aggregates. Actinomycetes are a large group of bacteria that grow as hyphae like fungi. They are responsible for the characteristically “earthy” smell of freshly turned, healthy soil.

What happens to nitrogen in soil?

When leaves or roots from the host plant decompose, soil nitrogen increases in the surrounding area. Nitrifying bacteria change ammonium (NH4+) to nitrite (NO2-) then to nitrate (NO3-) – a preferred form of nitrogen for grasses and most row crops.

Why do farmers use nitrification inhibitors?

Nitrate is leached more easily from the soil, so some farmers use nitrification inhibitors to reduce the activity of one type of nitrifying bacteria. Nitrifying bacteria are suppressed in forest soils, so that most of the nitrogen remains as ammonium.

Which bacteria inhibits pathogens?

Certain strains of the soil bacteria Pseudomonas fluorescens have anti-fungal activity that inhibits some plant pathogens. P. fluorescens and other Pseudomonas and Xanthomonas species can increase plant growth in several ways. They may produce a compound that inhibits the growth of pathogens or reduces invasion of the plant by a pathogen. They may also produce compounds (growth factors) that directly increase plant growth.

Why are decomposers important?

Decomposers are especially important in immobilizing, or retaining, nutrients in their cells, thus preventing the loss of nutrients, such as nitrogen, from the rooting zone. A second group of bacteria are the mutualists that form partnerships with plants. The most well-known of these are the nitrogen-fixing bacteria.

How many bacteria are in a teaspoon of soil?

A teaspoon of productive soil generally contains between 100 million and 1 billion bacteria. That is as much mass as two cows per acre. A ton of microscopic bacteria may be active in each acre". While bacteria may be small, they make up both the largest number and biomass (weight) of any soil microorganism. Figure 1 shows ciliate protozoa consuming bacteria.

What are the smallest microbes in soil?

Bacteria are the smallest and most hardy microbe in the soil and can survive under harsh or changing soil conditions. Bacteria are only 20–30% efficient at recycling carbon, have a high N content (10 to 30% N, 3–10 C:N ratio), a lower C content, and a short life span. There are basically four functional soil bacteria groups including decomposers, mutalists, pathogens, and lithotrophs. Decomposer bacteria consume simple sugars and simple carbon compounds, while mutualistic bacteria form partnerships with plants including the nitrogen-fixing bacteria ( Rhizobia ). Bacteria can also become pathogens to plants and lithotrophic bacteria convert nitrogen, sulfur, or other nutrients for energy and are important in nitrogen cycling and pollution degradation. Actinomycetes are classified as bacteria but are very similar to fungus and decompose recalcitrant (hard to decompose) organic compounds. Bacteria have the ability to adapt to many different soil microenvironments (wet vs. dry, well oxygenated vs. low oxygen). They also have the ability to alter the soil environment to benefit certain plant communities as soil conditions change.

How do you classify bacteria?

Another way to classify bacteria is by their growth and reproduction. Autotrophic bacteria (also called autotrophs) process carbon dioxide to get their carbon. Some autotrophic bacteria directly use sunlight and carbon dioxide to produce sugars, while others depend on other chemical reactions to obtain energy. Algae and cyanobacteria are some examples of autotrophic bacteria. Heterotrophic bacteria obtain their carbohydrates and/or sugars from their environment or the living organism or cell they inhabit. Examples include Arthrobacter bacteria involved in nitrogen nitrification (Sylvia et al., 2005).

How are bacteria classified?

When scientist started first classifying bacteria, they started by looking at their basic shape. Bacteria generally have three major shapes: rod, sphere, or spiral. Actinomycetes are still classified as bacteria but are similar to fungi except they are smaller in size. Classifying bacteria by shape is complex because many bacteria have different shapes and different arrangements.

What are some examples of aerobic bacteria?

Most soil bacteria prefer well oxygenated soils and are called aerobic bacteria and use the oxygen to decompose most carbon compounds. Examples of aerobic bacteria include the Aerobacter genus which is widely distributed in the soil and actinomycetes bacteria genus Streptomyces which give soil its good "earthy" smell (Lowenfels & Lewis, 2006).

What is Gram negative?

When a staining agent is used in the lab , bacteria can be classified as "gram negative" or "gram positive". The staining agent attaches to the bacteria's cell walls. Gram negative bacteria are generally the smallest bacteria and are sensitive to drought and water stress. Gram positive bacteria are much larger in size, have thicker cell walls, negative charges on the outside cell wall surface and tend to resist water stress (Dick, R., 2009). Bacteroides are anaerobic gram negative bacteria that live in the gut of man and animals. Listeria is a gram positive aerobic rod shaped bacteria found in contaminated food.

How do bacteria help soil?

The fertility of the soil is always dependent on its nutrient and water content. Due to the continuous absorption of nutrients and water by the growing plants, soil loses its fertility. Bacteria decompose complex organic materials into their simple forms and also produce secondary products that lead to an increase in soil fertility. It also increases the moisture content of the soil. Thus, these bacteria help to increase the amount of nutrients in the soil that are needed by the plants.

What is soil microbiology?

The science of all these microorganisms present in air, soil, water is also called microbiology. Soil microbiology is one of the branches of microbiology. In soil microbiology, we study the interactions between the multiple factors responsible for various soil types in a particular place. Bacteria play a very important role in the agricultural field. Bacteria help in the decay or decomposition of organic matter in the soil. They can help in increasing soil fertility and also promote plant growth. The nitrogen-fixing bacteria are of two types: free-living (non-symbiotic) bacteria (e.g., cyanobacteria) and mutualistic (symbiotic) bacteria (e.g., Rhizobium associated with leguminous plants). Various bacterial products such as biofertilizers, biopesticides, and bioinsecticides are also used in agriculture instead of chemical products.

What are some examples of pathogenic bacteria that can kill weeds?

2. Biopesticides: The soil also has plant pathogenic bacteria present in the rhizospheric zone, and it can cause a lot of diseases in the plant. Using these pathogenic microbes, researchers have made a biological tool to control unwanted weeds and pests called biopesticides. These microbes possess genes that are invasive and can attack the weeds and kill them. For example, the bacterium Bacillus thuringiensis produces toxic proteins that kill certain insects but are harmless to humans. These are being made and marketed as biopesticides. Bacillus popillae (milky spore disease) can kill Japanese beetle larvae.

What is mutualistic bacteria?

b. Mutualistic (symbiotic) bacteria: Symbiotic bacteria are ones that live in symbiotic association with plants. For example, Rhizobium is associated with leguminous plants.

What is the purpose of green manure?

4. Green manure: Green manure is produced by leaving uprooted, sown crops and their parts to wither on a field so that they act as a mulch and soil amendment. Heterotrophic bacteria that consume organic matter are used to break down green manure into plant nutrient components. These are added for the purposes such as building soil organic matter and soil structure, supplying nitrogen and other essential nutrients to crops to prevent leaching of soluble nutrients from the soil, preventing damage to soil structure by providing ground cover, etc. Hence, green manures usually perform multiple functions such as soil improvement, soil protection, etc.

Why are microbes important in agriculture?

In modern agriculture, the utilisation of microbes as natural fertilisers is very common. The harmful impacts and high cost of chemical fertilisers are making them unfit to use. The agricultural productivity of the soil can also be improved by microbes found in the ground soil. Today, we are using naturally occurring microbes to produce biological products that can recycle nutrients and are eco-friendly. Following are some of the important biological products used in agriculture these days:

Which bacteria can fix nitrogen?

b. Azotobacter: Other than rhizobium bacteria, azotobacter can also fix nitrogen. Various species of azotobacter are present in the soil and can act as biofertilizers.

Bacteria Characteristics

Bacteria Functions/ Groups

• Bacteria perform many important ecosystem services in the soil including improved soil structure and soil aggregation, recycling of soil nutrients, and water recycling. Soil bacteria form microaggregates in the soil by binding soil particles together with their secretions. These microaggregates are like the building blocks for improving soil struct...

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