Latest Update 22nd March 2017.

  • Bacteria can be found everywhere. Their habitat includes the air, soil, water, plants and animals.
  • Plants and animals form symbiotic relationships with bacteria.
  • A single teaspoon of healthy soil contains about a billion bacteria.
  • In humans more than 500 species of bacteria live in the mouth, and every square centimetre of skin carries about 100,000 bacteria. 
Interactions with Other Organisms  
  • Despite their size, bacteria form complex associations with other organisms. These associations can be divided into parasitism, mutualism and commensalism. 
  • Bacteria which form a parasitic association with other organisms are classed as pathogens.  
  • Bacterial diseases cause serious problems in agriculture as leaf spot, fire blight and wilts infect plants, and paratuberculosis, mastitis, salmonella and anthrax infect farm animals. 
  • In soil, microorganisms that live in the rhizosphere (soil close to the roots of the plant) fix atmospheric nitrogen as nitrogenous compounds including ammonia and nitrates.
  • Through a complex process involving a web of microorganisms an easily assimilated form of nitrogen is made available to plants which can't fix nitrogen for themselves.
  • Commensal bacteria are very small and grow on animals, plants and any other external surfaces.
  • In the warm environment of the human body, fed by sweat and dead skin, they lead a comfortable life doing no more harm to their host than causing body odour. 
  • Some species of bacteria kill and then consume other microorganisms, these species are called predatory bacteria.
  • Bacterial predators either attach to their prey to digest them and absorb nutrients, or invade them and multiply inside them.  
  • These predatory bacteria are thought to have evolved from saprophages that consume dead microorganisms.  They perform an important function in the provision of easily assimilated nutrients to plants.
In my Garden
  • Macro organisms in the soil including small beetles and earthworms, break down organic waste from larger pieces into smaller more manageable sizes for the microbes to devour efficiently.
  • Bacteria, fungi and actinomycetes are always present in good soil and do the heavy lifting by breaking down organic waste and parent rock particles such as clay and sand.  
  • They incorporate the widest possible range of minerals from a given soil into their body structures.
  • Predatory microbes prey on them and excrete waste which is high in plant available nutrients.
  • Most of these bugs are beneficial to the organic gardener, but there are many microbes in the soil relying on plant tissue for their food.  These microbes are plant pathogens and attack the plant's roots and green tissue.  They can either kill or severely damaging plants.
  • Most aerobic microbes are regarded as beneficial because they attack and kill these plant pathogens.
  • Many organic gardeners use hot composting to provide conditions favouring beneficial microbes at the expense of plant pathogens.  
  • Beneficial bacteria form mutualistic relationships with plants and are attracted to their root zones where exudates manufactured by the plant are released into the soil.  These exudates comprise sugars, proteins and complex carbohydrate and provide the bacteria with energy.
  • Similarly, conditions which prevail in the aerobic compost tea making process favour rapid growth of aerobic microbes.  When a plant's foliage is sprayed with this preparation the microbes anchor themselves to the plant and keep pathogenic microbes at bay.  At the same time they form nutrition sharing, mutualistic relationships with the plants in their phyllosphere.
  • As an organic gardener it is my prime objective to maintain high concentrations of beneficial microbes including bacteria on all plant surfaces to maximize good health and growth.
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