Soil Bacteria Species
Soil bacteria are a crucial part of soil health, responsible for transforming organic matter into chemicals and nutrients usable for plants. Bacteria in the soil play an especially important role in fixing nitrogen in the soil and decomposing matter. Conversely, bacteria in the soil is also responsible for loss of nitrogen in anaerobic environments and acidification. Healthy soil has a balance of many species of bacteria.
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Nitrogen Fixers
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Azobacter and Rhizobiaceae bacterial species are nitrogen fixers, meaning that they take nitrogen gas from the air and fix it into the soil in a way that is absorbable by plants. According to the University of Western Australia, Azobacter is a free-living bacteria that independently transforms atmospheric nitrogen into organic substances containing nitrogen. Bacteria from the Rhizobiaceae family, such as rhizobia. use a symbiotic relationship with legumes to fix nitrogen in the soil.
Disease Fighters
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Some species of bacteria in soil help fight diseases in plants. According to the NSW Department of Primary Industries, these include bacillus megaterium, which fights fungal diseases; Pseudomonas fluorescens, another fungal fighter; and Bacillus subtilis, which suppresses blight in certain seedlings.
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Disease Promoters
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Most disease promoting bacteria in soil are anaerobic, meaning that they thrive in conditions devoid of oxygen and they often find oxygen toxic. Anaerobes produce toxic compounds as a result of anaerobic respiration, and rather than processing organic matter, anaerobes putrefy it, which is why an unaerated compost heap will smell bad. According to the NSW Department of Primary Industries, anaerobes limit plant growth and make plants more susceptible to disease. Species of anaerobes in soil include the Clostridium family and the Paenibacillaceae family of bacteria.
Actinobacteria
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Actinobacteria are responsible for breaking down humates and humic acid in soils. Humates are directly related to the fertility of the soil. According to Tera Vita, they regulate soil structure, including water saturation, ion exchanges and thermal conditions. One species of Actinobacteria, knonwn as streptomyces, is used in medicine to create antibiotics. Other species, such as Rhodocuccus and Mycobacterium, are pathogens. Actinobacteria species are also responsible for the sweet smell that comes after a rain. According to DNA India, the streptococci bacteria in soils produces an enzyme called geosmin, which is responsible for the smell of rain. Because the bacteria produces geosmin in dry weather, the smell is particularly pungent after rain that follows a dry spell.
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References
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