Microbiology

Course CodeBSC209
Fee CodeS3
Duration (approx)100 hours
QualificationStatement of Attainment

Microbiology Course

Microbiology is an increasingly important area of science; not only because of its obvious significance to human health, but also its significance to environmental management, veterinary care, farming and horticulture.

Anyone who has an interest in horticulture can benefit from a deeper understanding of microbiology.

Microorganisms are critical to so much of what happens in our gardens and on our farms. Microbes help plants absorb nutrients, they enrich our soils, they enable us to make compost and they help us clean up toxins that would otherwise build up in the environment.

This course will help you to better manage soils, plant growth, pests and diseases and much more. After studying microbiology, your perspective of what is going on in your garden or farm will change forever -and for the better.

     

    Lesson Structure

    There are 9 lessons in this course:

    1. Scope and Nature of Microbiology
    2. Microscopes
    3. Cultures
    4. Microbial Taxonomy
    5. Bacteria
    6. Viruses
    7. Other Microbes - Protists, Fungi, Helminths
    8. Immunology
    9. Applied Microbiology

    Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.


    Microbes are Very Significant to Plants

    Here are just some of the ways microbes impact on plants:

    Mycorrhizae

    Some beneficial fungi grow in a symbiotic relationship with the root cells of higher green plants.  This is termed a mycorrhizal association.  Roots of many cultivated plants including corn, soybeans, cotton, tobacco, peas, red clover, apples, citrus, pines, eucalypts and others have mycorrhizal relationships with higher fungi.  The mycorrhiza appears to be highly beneficial for optimal growth of many plants.  Establishing proper mycorrhizal fungi with cultivated plants offers a great potential for improved plant growth.  

    Some mycorrhiza form a kind of sheath around the roots sometimes giving a hairy or cottony appearance. The plant roots transmit substances to the fungi and the fungi aid in securing and transmitting nutrients and water for the plant roots.  Because they provide a protective cover, mycorrhizae increase the plant's tolerance to drought, high temperatures, infection from disease causing fungi and even to extreme soil acidity.
    Because mycorrhizae are able to improve the efficiency of nutrient absorption, their use in horticulture is likely to become more widespread as the cost of fertiliser increases. Relatively cheap mycorrhizal inoculations are likely to become more available.

    Mycorrhizae are killed by steam sterilization or fumigation.  Thus when nursery soils are sterilized, or artificial mixes are used, it is usually beneficial to inoculate them with the appropriate mycorrhiza.

    Mycorrhizae grow and develop best in a well aerated soil, in a sunny position.  High applications of nutrients tend to inhibit their development.  The greatest growth responses to mycorrhiza are likely to occur in highly weathered soils which are low in basic cations and are low in phosphorus.

    Types of Mycorrhiza

      Mycorrhiza work by effectively increasing the amount of soil or growing medium from which nutrients may be extracted in return for the additional supply of nutrients the plant supplies carbohydrates to the fungus.

      Inoculating seed with ectomycorrhial fungi is a process that is widely carried out. The seed must initially be washed free of undesirable fungi.  A suspension of spores is then made by shaking fruiting bodies of the required fungus in distilled water and mixing this with the seeds.  The seeds can be sown immediately or dried and stored for a short while before sowing.  Producing inoculum of endomycorrhizal fungi is more difficult and involves growing large amounts of infected root tissue to be incorporated into the soil.  

      Soil Biological Management

      Most soil organisms are found in the topsoil and it is the action of microbes (microscopic organisms) which results in humus production. Organic matter only becomes humus when it has passed through a microbe's body. Of these microbes, certain bacteria are most important. Specifically, antinomycetes, which are thread-like in appearance, decompose organic matter into humus releasing nutrients as they do so. They also produce antibiotics which combat root diseases.

      When dead plant material, or animal material, is added to the soil the decomposition begins. Initially, only those compounds which are easy to break down are decomposed through the action of soil organisms e.g. proteins, sugars. Over the next few years more complex compounds are decomposed e.g. lignins, cellulose. During the next ten years ever more complex compounds such as waxes, phenols and relatively stable compounds within the soil peds are decomposed. Finally, over hundreds and up to thousands of years, the remaining compounds are broken down into humus. The compounds within humus are extremely complex and are not recognisable as plant material. When humus has reached a point whereby it can no longer be broken down, it is said to be stable.

      Plant Diseases

      Many plant diseases are caused by microbes.
      There are three main methods by which diseases can infect a plant. Whether they are fungi, bacteria, or nematodes - these methods are direct penetration, penetration through natural openings, or penetration through wounds.

      Direct Penetration
      In the case of fungi, the spore ('seed' of a fungus) may germinate to produce a mycelium (fruiting body of a fungus) that grows directly:
      1.    Into cells via haustoria (i.e. a slim projection from the root of the parasitic plant or the hyphae of a parasitic fungus, which when penetrated into the host plant, allows the parasite to absorb nutrients from it).
      2.    Beneath the external cuticle.
      3.    Throughout cells via intracellular mycelium (mycelium the growing within cells).
      4.    Between cells via intercellular mycelium (mycelium growing between cells).
      5.    Combinations of the above.

      Nematodes enter plants by direct methods in addition to using natural openings. Ectoparasitic and endoparasitic nematodes enter via direct penetration of the cells; Ectoparasites feed on plant tissues from outside the plant’s roots and endoparasites feed inside the plant tissues.