[6][7] Up to 10 billion bacterial cells inhabit each gram of soil in and around plant roots, a region known as the rhizosphere.
The genus Clostridium is an example of bacterial versatility because it, unlike most species, can grow in the absence of oxygen, respiring anaerobically.
Autotrophic bacteria derive their energy by making their own food through oxidation, like the Nitrobacter species, rather than feeding on plants or other organisms.
They are a type of bacteria, but they share some characteristics with fungi that are most likely a result of convergent evolution due to a common habitat and lifestyle.
[12] Although they are members of the Bacteria kingdom, many actinomycetes share characteristics with fungi, including shape and branching properties, spore formation and secondary metabolite production.
Fungi can be split into species based primarily on the size, shape and color of their reproductive spores, which are used to reproduce.
Algae do not have to be directly exposed to the Sun, but can live below the soil surface given uniform temperature and moisture conditions.
These factors include intensity of sunlight, concentration of inorganic and organic nitrogen sources and ambient temperature and stability.
[12] Ciliates are the largest of the protozoa group, and move by means of short, numerous cilia that produce beating movements.
Mutants impaired in salicylic acid synthesis and signaling are hypersusceptible to microbes that colonize the host plant to obtain nutrients, whereas mutants impaired in jasmonic acid and ethylene synthesis and signaling are hypersusceptible to herbivorous insects and microbes that kill host cells to extract nutrients.
Changes in salicylic acid signaling stimulated a reproducible shift in the relative abundance of bacterial phyla in the endophytic compartment.
These changes were consistent across many families within the affected phyla, indicating that salicylic acid may be a key regulator of microbiome community structure.
In general a more diverse soil microbiome results in fewer plant diseases and higher yield.
By contrast, healthy soil can increase fertility in multiple ways, including supplying nutrients such as nitrogen and protecting against pests and disease, while reducing the need for water and other inputs.
[8] The group of bacteria called rhizobia live inside the roots of legumes and fix nitrogen from the air into a biologically useful form.
Serenade is a biopesticide containing a Bacillus subtilis strain that has antifungal and antibacterial properties and promotes plant growth.
Its €10 million annual research budget funds field-tests of dozens of new fungi and bacteria to replace chemical pesticides or to serve as biostimulants to promote crop health and growth.
[8] A 2007 study showed that a complex symbiosis with fungi and viruses makes it possible for a grass called Dichanthelium lanuginosum to thrive in geothermal soils in Yellowstone National Park, where temperatures reach 60 °C (140 °F).
Stevens et al 1998 find bacterial denitrification and dissimilatory nitrate reduction to ammonium to especially occur at high pH.
[16] A funguslike unicellular organism named Phytophthora infestans, responsible for potato blight and other crop diseases, has caused famines throughout history.
Serenade stimulates a high initial B. subtilis density, but levels decrease because the bacteria lacks a defensible niche.
[8] Fertilizers deplete soil of organic matter and trace elements, cause salination and suppress mycorrhizae; they can also turn symbiotic bacteria into competitors.
They split an unirrigated 100-hectare field into three zones, one treated with chemical fertilizer and pesticides; and the other two with different amounts of an organic biofertilizer, consisting of fermented grape leftovers and a variety of bacteria and fungi, along with four types of mycorrhiza spores.