Agricultural microbiology

Agricultural microbiology is a field of study concerned with plant-associated microbes. It aims to address problems in agricultural practices usually caused by a lack of biodiversity in microbial communities. An understanding of microbial strains relevant to agricultural applications is useful in the enhancement of factors such as soil nutrients, plant-pathogen resistance, crop robustness, fertilization uptake efficiency, and more. The many symbiotic relationships between plants and microbes can ultimately be exploited for greater food production necessary to feed the expanding human populace, in addition to safer farming techniques for the sake of minimizing ecological disruption.

Plant-microbe symbiosis

Strains of free-living bacteria, actinomycetes, fungi, and protozoa have coevolved with a variety of plants to produce symbiotic relationships that often benefit one or more of the organisms involved. A majority of these plant growth promoting organisms colonize the surface of plant roots, known as the rhizosphere. (Ahmad 2008) Among these, there are three major groups of microbial inoculants used on agricultural crops:

Arbuscular mycorrhizal fungi (AMF)

AMF species produce structures like arbuscules and vesicles (sites of nutrient transfer and storage, respectively). They also build scaffoldings of hyphal networks surrounding the plant roots they colonize. (Kloepper 1989) AMF species are highly abundant and play a vital role in their ecosystems by promoting plant growth through numerous mechanisms. (Smith & Read, 2010. Mycorrhizal Symbiosis (book)) AMF symbiosis promotes host plant uptake of nitrogen and phosphorous. They are most commonly found in well-aerated and cultivated top soils. Common genera include Aspergillus, Mucor, Penicillium Trichoderma, Alternaria, and Rhizopus. (Adesemoye 2009)

Plant growth-promoting Rhizobacteria (PGPR)

This broad group of soil bacteria colonizes developing plant roots. Plant growth is promoted in a variety of fashions; some bacteria synthesize plant growth hormones like indoleacetic acid and other auxins (Zhao, Yunde 2010 Auxin biosynthesis), while others supply the plant with nutrients from the soil. Phytohormone expression by PGPR have also been proposed to promote the growth of roots through improved water and mineral uptake. (Dobbelaere 2001, Bashan 2004)

Nitrogen-fixing rhizobia

Triple-bonded diatomic nitrogen, constituting about 78% of our atmosphere, is highly stable and unable to be used by plants. (Kale 1992) Symbiotic rhizobia form anaerobic nodules on the roots of legumes and express genes for enzymes like nitrogenase to fix nitrogen into bioavailable compounds for their host plants. Nitrogen is an element ubiquitously found in amino acids, proteins, and many other cellular components; its bioavailability is crucial to the growth of a plant. (Tengerdy 1998)

2. Description and significance

Describe the appearance, habitat, etc. of the organism, and why you think it is important.

• Include as many headings as are relevant to your microbe. Consider using the headings below, as they will allow readers to quickly locate specific information of major interest*

3. Genome structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?

4. Cell structure

Interesting features of cell structure. Can be combined with “metabolic processes”

5. Metabolic processes

Describe important sources of energy, electrons, and carbon (i.e. trophy) for the organism/organisms you are focusing on, as well as important molecules it/they synthesize(s).

6. Ecology

Habitat; symbiosis; contributions to the environment.

7. Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

7. Key microorganisms

Include this section if your Wiki page focuses on a microbial process, rather than a specific taxon/group of organisms

8. Current Research

Include information about how this microbe (or related microbes) are currently being studied and for what purpose

9. References

It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.