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Sep 30, 2021 · Researchers divide soil bacteria into four different groups based on their function in soil. Most examples of microorganisms in soil are decomposers . The decomposer bacteria in soil feed on dead organic matter such as decaying plants and animals. Fungi, such as mushrooms, are another example of a decomposer.
- Microorganisms Found in Soil
- Bacteria in Soil
- Fungi in Soil
- Actinomycetes in Soil
- Protozoa in Soil
- Blue-Green Algae (Cyanobacteria) in Soil
- Viruses in Soil
- Nematodes in Soil
- References
Due to the diversity in nutrients and essential factors, soil harbors a diverse group of microorganisms.Soil microorganisms are classified into seven different categories; bacteria, fungi, virus, blue-green algae, actinomycetes, protozoa, and nematodes.Each of these groups has different characteristic features and their role in the soil they inhabit.Such microorganisms are found not only in surface soil but also in subsurface soil at depths ranging from hundreds to thousands of meters below the ground.What are Bacteria?
1. Bacteria are the smallest and most numerous cellular organisms in soils. They are prokaryotic organisms that are usually 0.5 to 1 mm wide and 1 to 2 mm long. 2. The tiny bacteria, termed ultramicrobacteria, can be as small as 0.3 mm in diameter with cell volumes less than 0.1 mm3. 3. Although a variety of cell shapes exists for bacteria, including rod, spherical, spiral, and filamentous, the most common cell shape found in soil is a short rod (coccoid rod). 4. Bacteria are one of the most...
Examples of Bacteria found in Soils
1. Bacterial biomass found in soil ranges from 300 to 3000 kg/ ha. There are approximately 108 to 109bacteria in a gram of soil, most of them (>99%) have not been or cannot be cultured in the laboratory. 2. Common bacterial genera isolated from soil include Bacillus, Arthrobacter, Pseudomonas, Agrobacterium, Alcaligenes, Clostridium, Flavobacterium, Corynebacterium, Micrococcus, Xanthomonas, and Mycobacterium. 3. In contrast to simple morphology, bacteria have the greatest metabolic diversity...
Positive effects of Bacteria in Soil
1. Bacteria are an important part of the biotic component of soil as they are responsible for numerous physiological activities occurring in the soil. 2. Soil bacterial communities provide a multitude of ecosystem services that directly, and indirectly, affect the overall functioning of the soil environment. 3. Many bacteria in the soil produce polysaccharides or glycoproteins that form a layer on the surface of the soil particle. These substances thus, act as cementing agents and improve the...
What are Fungi?
1. Soil fungi are eukaryotic organisms, which can be unicellular, but often are multicellular. 2. Compared to bacteria, fungi have more complex morphologies and life cycles. Yeasts are single-celled fungi that reproduce asexually through budding. 3. Most other fungi have highly branched filaments with strands 2 to 30 mm in diameter and several centimeters long. 4. Most fungi are aerobic except for yeasts, which can survive in anaerobic environments by fermenting sugars into alcohol.
Examples of Fungi found in Soils
1. In many ecosystems, fungi constitute the largest biomass of all the soil organisms, ranging from 500 to 5000 kg/ha. 2. An individual fungus can include many fruiting bodies scattered across a large area with extensive underground hyphae. 3. Among the soil fungi, one can find oomycetes, hyphochytriomycetes, trichomycetes, chytridiomycetes, zygomycetes, ascomycetes, basidiomycetes, and imperfect fungi. 4. Fungi found in soil fall mostly within three groups; decomposers, mutualists (mycorrhiz...
Positive effects of fungi in Soil
1. Fungi play essential roles in the soil where they help in nutrient cycling, water dynamics, and disease suppression, all of which maintain the health of the soil and increases crop yield. 2. Fungal hyphae bind soil particles together and stabilize soil aggregates. 3. Fungi also form beneficial mycorrhizal symbioses with almost all terrestrial plants. Mycorrhizal fungi enhance the uptake of mineral nutrients (e.g., phosphorus and zinc) to the plant in exchange for carbon compounds fixed by...
What are Actinomycetes?
1. Actinomycetes are filamentous bacteria, most of which are Gram-positive bacteria and are more abundant in neutral to alkaline soils. 2. Actinomycetes are mostly anaerobic that form either colonies or extensive mycelia. However, in some cases, the mycelia might break off, resulting in rod- or coccoid-shaped forms. 3. Even though they are bacteria, their biomass and distinct characteristic resulted in a distinct classification. 4. Depending on the species, the size of actinomycetes ranges be...
Examples of Actinomycetes found in Soils
1. Actinomycete population is largest in the surface layer of soils and gradually decreases with the depth; individual actinomycete strains are present in all soil layers. 2. They are widely distributed in the soil with estimated values ranging from 104 to 108per gram of soil. 3. They grow as hyphae like fungi, resulting in the characteristically “earth” smell of freshly turned healthy soil. 4. Streptomyces is the most abundant species of actinomycetes in soil, followed by other species like...
Positive effects of Actinomycetes in Soil
1. Actinomycetes decompose the more resistant and indecomposable organic substances and produce several dark black to brown pigments which contribute to the dark color of the soil humus. 2. These organisms are also responsible for the subsequent decomposition of humus (resistant material) in soil. 3. Actinomycetes are important in agricultural soils because they contribute to the carbon cycle by fixation (photosynthesis) and decomposition. 4. Actinomycetes form associations with some non-legu...
What are Protozoa?
1. Protozoa are unicellular eukaryotic microorganisms that lack cell walls. 2. They are motile heterotrophs that obtain food by ingesting bacteria, yeasts, algae, small protozoa, and organic matter. 3. Free-living soil protozoa fall into three categories: flagellates, amoebae, and ciliates. 4. These single-celled animals differ in shape, size, and distribution with some protozoan species found in land habitats like soil.
Examples of Protozoa found in Soils
1. Amoeba, ciliates, and flagellates are the three groups of protozoans found in soil. 2. Numerous heterotrophic flagellates and naked amoebae are available in agricultural soils, grassland, forest soil, bottom sediment of freshwater, coastal and marine waters. 3. The presence of protozoa in the soil is influenced by the presence of living and dead plant roots and the organic content of the soil. 4. The inhabitation of soil by protozoa depends on the structure and texture of the soil. Mastigo...
Positive effects of Protozoa in Soil
1. Protozoans are crucial in terrestrial ecosystems where they act as bacterial consumers, leading to mineralization of organic soil nitrogen to form ammonium. 2. Protozoans community in the soil can also be used to assess and monitor the changes in the biotic and abiotic component of soil, thus acting as bioindicators of the soil. 3. Protozoa have been found to increase plant biomass independently of nutrient contents in plant tissue. 4. Many protozoan species feed on bacteria and other micr...
What are Blue-green algae?
1. Cyanobacteria are phototrophic bacteria that are important in soils where light and water are available. 2. Cyanobacteria are autotrophic eukaryotes that consist of both free-living photosynthetic bacteria and endosymbiotic organisms. 3. Blue-green algae exist in the form of motile filaments of cells that travel away to form new colonies. 4. Blue-green algae are found in colonial or filamentous form, and the filamentous forms show heterocystous or non-heterocystous filament. 5. The heteroc...
Examples of Blue-green algae found in Soil
1. Blue-green algae in the soil are present in a wide variety of moist soils, primarily present around the plant root in the form of the symbiotic association. 2. These organisms might either occur freely in the soil or in the form of symbiotic relationships with plants of lichen-forming fungi. 3. Cyanobacteria species have certain structures like heterocysts that are involved in nitrogen fixation and thus, are present in the anaerobic area of soil. 4. Some of the common cyanobacteria include...
Positive effects of Blue-green algae in Soil
1. Cyanobacteria are among the first microbial communities to colonize terrestrial ecosystems. 2. These microorganisms play essential roles in soil by fixing nitrogen and carbon by the synthesis of exopolysaccharides that increase soil fertility and water retention capacity. 3. The application of cyanobacteria as inoculants to induce biocrust formation on the soil is a novel technology that restores barren degraded areas and prevents desertification processes. 4. They play important roles in...
What are Viruses?
1. Viruses are genetic elements that can replicate independently of a cell’s chromosomes but not independently of cells themselves. 2. Viruses are smaller than bacteria and range in size from 20 to 30 nm in diameter. Viruses are obligate parasites of bacteria, fungi, insects, plants, and animals that inhabit the soil. 3. Viruses can act as dormant structures or particles that can survive for a long period in different habitats. 4. As viruses are obligate parasites, they can be found anywhere...
Examples of Viruses found in Soil
1. Viruses are the most abundant biological entities on our planet and exceed the number of cellular organisms in marine and soil habitats. 2. The concentration of viruses in soil has been estimated to be 109virus particles per gram dry weight. 3. The majority of the soil viruses are tailed bacteriophages that prefer wetland forest soil over drier agricultural soils. 4. Some of the common viruses inhabiting soil include small spherical virus particles similar in size to single-stranded (ss) R...
Positive effects of Viruses in Soil
1. The main way in which viruses in soils act beneficially is by transferring genes between microbial hosts by horizontal gene transfer. The gene transfer enables the transfer of beneficial characteristics between different communities. 2. Another way that viruses in soils have potential benefits for plants is by infecting organisms that are pathogenic for plants. 3. Viruses of different microbes in the soil as pathogens have an essential role in regulating the population structure of their m...
What are Nematodes?
1. Nematodes are small invertebrates with smooth, unsegmented bodies that are typically 50 µm in diameter and 1 mm in length. 2. Most nematode species are highly specialized parasites of vertebrates, including humans, insects, and other invertebrates. 3. Nematodes are different from other worms in that they are mostly parasitic with non-segmented bodies. These also generally reside in soil surfaces and water bodies.
Examples of Nematodes found in Soil
1. Nematodes found in soil reside in the top layer of the soil with organic matter even if they do not feed on the dead and decaying matter. 2. These feed on living microorganisms that are present on the soil surfaces. Nematodes in the soil can be either free-living or parasitic. 3. Most of the nematodes present in the soil include roundworms that move through the soil if they are free-living. 4. Soil nematodes can be classified into four different groups; bacterial feeders, fungal feeders, p...
Positive effects of Nematodes in Soil
1. Soil nematodes, especially those feeding on bacteria and fungi, help maintain the microbial community of the soil and also ensure that enough nitrogen is available in the soil for the plants. 2. Some free-living nematodes are capable of mineralization where they convert organic compounds into their inorganic forms, aiding in the biogeochemical cycles. 3. Nematodes might even enhance soil fertility by decomposing complex organic compounds into simpler forms. 4. Some of these animals feed on...
Schinner, F., Öhlinger, R., Kandeler, E., and Margesin, R. (2012). Methods in Soil Biology.Berlin: SpringerGupta R.K. et al. (2008) Soil Microbiology. In: Chesworth W. (eds) Encyclopedia of Soil Science. Encyclopedia of Earth Sciences Series. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-3995-...Hermans SM, Buckley HL, Case BS, Curran-Cournane F, Taylor M, Lear G. Bacteria as Emerging Indicators of Soil Condition. Appl Environ Microbiol. 2016;83(1):e02826-16. Published 2016 Dec 15. doi:10....Anupama Sapkota, Aishwarya Thapa, Anupa Budhathoki, Muskan Sainju, Prativa Shrestha, Sagar Aryal, “Isolation, Characterization, and Screening of Antimicrobial-Producing Actinomycetes from Soil Samp...Soil microorganisms can be classified as bacteria, actinomycetes, fungi, algae and protozoa. Each of these groups has characteristics that define them and their functions in soil. [6][7] Up to 10 billion bacterial cells inhabit each gram of soil in and around plant roots, a region known as the rhizosphere.
Bacteroidetes is a phylum of Gram-negative bacteria found in all ecosystems. They are particularly dominant in soils and the gut of animals and human beings where they exist as degraders of carbohydrates, carbohydrate-based substances, and proteins.
Soil microbes play both beneficial (decomposition and nutrient cycling) and detrimental roles as pathogens and contributors to soil environmental problems such as global warming and groundwater contamination.
Morphologically, soil bacteria are divided into three groups, viz., Cocci (round/spherical), rod-shaped (Bacilli), and Spirillum (cells with long wavy chains). Bacillus species dominate the bacterial population in soil and are numerous. They are followed by Cocci and Spirillum species.
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bacillus, (genus Bacillus), any of a genus of rod-shaped, gram-positive, aerobic or (under some conditions) anaerobic bacteria widely found in soil and water. The term bacillus has been applied in a general sense to all cylindrical or rodlike bacteria.
