Originally posy by DLtoker over @ Mp

This was written for a one-hundred level college course. Check it out and take or leave what you would like.


The science of microbiology is vast and diverse. Scholars and biologists who have devoted their careers to the various subtopics of the science are constantly making new discoveries that may very well change the world forever. Most people don’t realize just how much the microscopic world that they have never seen truly affects their everyday lives. Over the years, science has taught us that some bacteria can make us sick, so we should take precautionary measures to avoid these. We are told to sanitize our hands regularly as a means to kill such dangerous bacteria, and to be sure to thoroughly cleanse and cook our food to be sure that it is safe for consumption. Antibiotics have been developed as a means to kill off these dangerous bacteria should something actually make an individual sick. However, even though there are some very dangerous illnesses out there that can be caused by bacteria, over 90 % of the microbes out there are non-pathogenic. On the contrary, they can be and are beneficial for most living organisms. One might go so far as to say that microbes are integral for all living creatures because they assist in the building of immunities against infection and they also help with growth in agriculture and in defense of many predatory species. For mankind, microbes in agriculture are of the utmost importance, as they quite literally fill the soil that plants grown in. As time progresses, the methods for vegetative farming are being modified in order to keep up with demand and to maximize profits. Different farmers use different fertilizers and entirely different methods for maintaining their soil. Through personal research, I have been able to attain some information about how fertilizers affect the levels of microbes in different types of soil.
All organic matter is made up of long chains of many molecules and always contains some carbon. Bacteria need to break the bonds holding the chains of these organic molecules into smaller simple sugars and amino acids. The bacteria break these bonds and digest these by secreting enzymes in a disorderly fashion. The ingestion of this organic matter is quite a task in itself due to bacteria’s diminutive size. (Calvaruso p.3023) Most of these microbes need to produce adenosine triphosphate or ATP. Simply put, this is created via active transport through the cells membrane powered by charged electrons on each side of the membrane. Only aerobic bacteria produce ATP and ATP is the most ubiquitous form of energy in the prokaryotic world. Anaerobic bacteria not only have a foul odor most times, but many times are pathogenic or can produce alcohol and are not beneficial for the soil in any way. Even worse, these bacteria kill the beneficial, aerobic bacteria.
Microbes are the real farmers when it comes down to the basic elements. A farmer can say he makes his own compost, but who does the real composting? The means of using bacteria to farm with is much more beneficial and practical than trying to fight nature by using synthetic fertilizers.
Bacteria play a major role in the recycling of a few major elements in nature which are carbon, sulfur and nitrogen in the soil. The soil carbon cycle is just the same as the carbon cycle on a global level and is a part of it. CO2 is a by-product of aerobic bacterial metabolism. Then the bacterium dies and it’s gas is cycled into CO2 during decay. Through photosynthesis, the plant then converts the CO2 into organic compounds which are consumed by bacteria and recycled back into CO2. (Janzen 400-409) Sulfur is recycled in a similar way except anaerobic bacteria oxidize sulfur. Both nitrogen and sulfur are key elements for any type of farming. Instead of adding a synthetic version of these elements, the bacteria produce them themselves.
The nitrogen cycle is one of the most specialized and important in the maintenance of terrestrial life. Nitrogen is the most abundant and inert for any practical purpose and is useless for plants in this state. Nitrogen must be combined with oxygen or hydrogen (nitrogen fixation) to become useful for vegetation thus becoming ammonium, nitrate or nitrite. There are only a few genuses of bacteria that can accomplish nitrogen fixation which are Azotobacter, Azosperillum, Clostridium, and Rhizobium. Nitrifying bacteria generally do not like acidic soil, therefore, their numbers decrease when the pH drops below 7. (Grayston 1691-93) A soil that has a basic pH is not ideal for annual plants like tomatoes. However, if the colony is large enough, they can create a biofilm and keep the pH above 7 in the colonies local. These biofilms are most common in the rhizosphere where pH is most crucial component for proper nutrient uptake. This can be beneficial by keeping the pH relatively stable with no extra human effort. Not only do biofilms help with the pH, they help protect these bacteria from antibiotics and other predators.
Natural soil is chalked full of bacteria. A culture of bacteria the size of a period on this page can contain anywhere from 250,000 to 500,000 prokaryotic cells. One teaspoon of healthy soil can potentially contain up to one billion bacteria, and an acre can contain a metric ton. (USDA) With that said, one might say that the microbes are far more in control of how well a plant grows than the farmer is. If the person in charge does not have a firm grasp on how bacteria affect pH levels and Nitrogen, Phosphorous and Potassium availability levels in their soil, they could very well lose their crop for lack of knowledge.
Each bacterium plays its own essential role in the soil food web as you can see with the carbon and nitrogen cycles. Most important, is the bacterium’s ability to retain nutrients will help the plants have a constant food supply. Bacteria are Earth’s primary decomposers with fungi coming in at a close second. Bacteria can decompose all plant and animal material and waste and ingest mainly nitrogen and carbon compounds along with other nutrients. These broken down nutrients are then retained and immobilized within the bacteria’s membranes and the cells are attached to the soil particles, thus preventing mobilization and leaching of the nutrients from the rhizosphere during a heavy rain for example. (USDA)
The highest concentration and most active area for binary fission of bacteria is in the rhizosphere. In this area, the soil is directly affected by the secretions and exudates of sugars and proteins by the plants roots. In addition to the secretions, the bacteria obtain sustenance from the cells shed off from the growing root-tip. Life in this area for microbes is like a walk in the park when it comes to finding food therefore, bacteria don’t have to travel far from the root zone. When the nutrients are released from the bacteria due to death, or more likely consumption, the wastes will be deposited in the rhizosphere for easy absorption by the roots. (Appuhn 1044-46)
Soil fungi are also very beneficial to a plants overall health. They help control nutrient uptake, decompose and recycle, just like bacteria. Their physical appearance, however, can be much different. Unlike most bacteria, fungi have long strands called hyphae that grow between soil particles, holding them together and forming a stable place for the roots as well as help with water retention. Mycorrhizal fungi are the most beneficial of all. They colonize the roots and help with the uptake of phosphorous specifically. Phosphorous promotes explosive growth in the flowering or budding stages of plants. Fungi enjoy a basic soil on the pH scale. So, an organic gardener can water the plants with water that has a slightly higher pH during the flowering stage to encourage a prolific presence of fungi, therefore providing more phosphorous for root uptake. (Harris 1522)
Farmers that grow annual plants such as tomatoes prefer acidic soils therefore, support a bacterial dominant soil through all stages of growth. Through my research, I can assume organic soils will host many more microbes than soil which is bombarded with synthetic fertilizers at an interval. I obtained samples from three different soil beds. These samples were taken from the surface and subsurface to get a broad view of the entire soil system. I took 5 gram samples from the three and placed them in 10ml of sterile water in a sterile test tube. These were then let to sit for a period of one hour. The tubes were then shaken and then a loop was used to make a culture on a tryptic soy agar plate. The plates were then placed in a dark area at room temperature for 48 hours before my observations were made.
The first soil sample was from a tomato patch in a green house. The soil mix consisted of cow, rabbit and chicken manures. Every year, before the seedlings were planted, the soil was tilled to aerate the soil. In addition, a synthetic chemical fertilizer was applied weekly. This culture showed no colonies after the 48 hour period. The plate was even allowed to sit for an additional 48 hours with no signs of growth. The use of the chemical fertilizers and tilling of the soil causes a large amount of stress and is not conducive for a strong bacterial of fungal population.
The second soil sample was also from a tomato patch that is located outside. The farmer tilled the field before planting and also added cow, rabbit and chicken manure. However, he fertilized this field with only custom organic teas with his manures. The results were drastically different than the first sample. The bacterial content of the soil was diverse and abundant. The colonies were white, yellow and brown, and they were all opaque.
The final culture was of a three year no-till organic field. Every season the field had cow, rabbit and chicken manure placed as a top dressing. The fertilizer was also of a custom manure tea. This culture was exploding with colonies. Large fuzzy colonies of fungi were also visible. The uninterrupted, all natural process of farming also proved to be very beneficial as his yields are increasing yearly as well as maintenance decreasing.
As time and science progress, many people have come to think that they can outwit Mother Nature. The data that I collected and the research that I conducted have bolstered my feelings that one must not tamper with the organic, natural methods for farming that have stood the test of time. Organic fields yield heartier, healthier crops than the fields that have been fed with unnatural fertilizers placed there by the farmer. I feel that if one were to conduct further research on this subject, they would only find data that would collaborate with the information I collected. In the meantime, I will do my best to eat more organics and learn more about the conditions in which my produce has been grown.


Work Cited

http://soils.usda.gov/sqi/concepts/soil_biology/biology.html. 6/1/07
Appuhn, Astrid; Joergensen, Rainer Georg. Microbial colonisation of roots as a function of plant specie.
Soil Biology and Biochemistry. 38:5, pp. 1040-1051. 6/1/07
Calvaruso, C ; Uroz, S. Effect of the Mycorrhizosphere on the Genotypic and Metabolic Diversity of the
Bacterial Communities Involved in Mineral Weathering in a Forest Soil. Journal of Applied and
Environmental Microbiology. 73: 9, pp. 3019-3027. 6/1/07.
Grayston, Susan J; Ross, DesJ. Changes in soil carbon and nitrogen properties and microbial communities
in relation to growth of Pinus radiata and Nothofagus fusca trees after 6 years at ambient and
elevated atmospheric CO sub(2). Global Change Biology . 12:9, pp. 1690-1706. 6/1/07.
Harris, Jodie N; New, Peter B. Laboratory tests can predict beneficial effects of phosphate-solubilising
bacteria on plant. Soil Biology and Biochemistry. 38:7, pp. 1521-1526. 6/1/07.
Janzen, H. H. (2004). Carbon cycling in earth systems — a soil science perspective. In Agriculture,
ecosystems and environment, 104, 399 – 417. 6/1/07

too much reading my frnd