BIOLOGY Volume 2 - A Guide to General Biology - 2004

12. MICROBIOLOGY AND BIOTECHNOLOGY

What is microbiology?

Microbiology is the science of microorganisms—organisms so small that they can only be seen with a Microscope. These include Bacteria, Viruses, Fungi, and protists, such as Protozoa and microscopic Algae. The Classification and some of the Main characteristics of these organisms are discussed in Chapter 2.

Microorganisms are extremely diverse and hold enormous potential for human use. Under suitable conditions, they grow and reproduce rapidly while consuming and producing a wide range of chemical substances. It is this versatility that makes them so useful. Through Introduction/32.html">Genetic Engineering, they can even be made to produce beneficial products that are not naturally their own, such as Insulin. Although human utilization of microorganisms is seemingly just beginning, considerable successes have already been achieved in this field. The application of microorganisms and other biological entities for human benefit can be summed up in a single word: biotechnology.

What is biotechnology?

Biotechnology is The Use of organisms, biological systems, or biological processes in industrial production. Microorganisms are not the only entities applied in biotechnology. In fact, any production process based on a biological Procedure can be considered biotechnology. This also encompasses Genetic Engineering and the cloning of agricultural plants and animals. Examples of biotechnologies are shown in Fig. 12.1.

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Fig. 12.1. Potential Applications of biotechnology. The classification presented is conventional, and various fields may overlap. Genetic engineering is a key method in biotechnology. It is employed whenever microorganisms, plants, or animals need to be "improved." The Role of genetic engineering will increase significantly in the 21st century.

Biotechnology allows not only the Production of Human-essential products such as ethanol, beer, or the hormone insulin, but also encompasses processes like wastewater Treatment, solid waste recycling, or biosensor-based pollution detection. Here, the process is more important than the final product.

More broadly, biotechnology can be defined as the use of living organisms for human needs. Thus, in principle, biotechnology can include the breeding and improvement of farm animals, such as cattle and pigs, as well as crops like wheat or potatoes. New Genetic engineering Methods are especially vital for these purposes because they allow living organisms to be endowed with new desired traits much more precisely and rapidly than traditional breeding methods.

In this chapter, we will examine the Basic principles of large-scale microbiological production and look at a few examples. New technologies will transform our society just as older ones did in their time. As they emerge, controversial social and ethical issues will arise; some of these are discussed at the end of Chapter 25 in the section dealing with problems in applied genetics.

12.1. Growth Requirements

Scientists first attempted to culture bacteria and fungi under controlled conditions in the mid-nineteenth century. The pioneers of bacteriological work were Louis Pasteur in Paris and Robert Koch in Berlin. Researchers fully understood Structure/19.html">The Importance of being able to grow pure cultures of the organisms under study. This required developing methods to separate various microorganisms from one another. Culturing certain microorganisms, particularly those that are pathogenic and parasitic, requires complex nutrient media, whereas the requirements of other microorganisms are relatively simple.

12.1.1. Essential Nutrients

Growth, maintenance of vital activity, and reproduction require A wide variety of substances, In addition to an energy source. Microorganisms are cultivated using so-called nutrient media enriched with nutrients. Any culture medium must contain:

1. A carbon source. Most bacteria, all fungi, and all protozoa are heterotrophs, meaning they require an organic carbon source (see Section 2.5.4 and Table 2.3). Typically, this source is glucose or an organic acid salt, such as sodium acetate. In general, however, bacteria can utilize a wide range of organic substances as carbon sources, including Fatty acids, alcohols, Proteins, CARBOHYDRATES, and methane. Certain soil bacteria and fungi, as well as A number of bacteria inhabiting the gut of herbivores (such as ruminants), can digest Cellulose and use it as a carbon source. All pathogenic bacteria are heterotrophs.

Algae and some bacteria, such as cyanobacteria (blue-green algae), are autotrophs, meaning carbon dioxide serves as their carbon source. Algae are photosynthetic organisms, whereas bacteria include both photosynthetic and chemosynthetic forms (Table 2.3).

2. A nitrogen source can be of organic origin, such as Amino Acids, Peptides, and proteins, or inorganic origin, such as ammonium salts or nitrates. Amino acids are typically added as solutions of partially digested proteins known as peptones.

3. Growth factors, or Vitamins, are sometimes necessary for the CULTIVATION OF MICROORGANISMS. Growth factors are equivalent to the vitamins required by animals, and many of them are indeed vitamins. These are organic substances essential for growth and required in very small quantities. They include certain B vitamins (thiamine, or B₁; riboflavin, or B₂; niacin, or B₃ and B₆), as well as Folic acid and p-aminobenzoic acid. Only trace amounts of vitamins are needed for normal growth. Additionally, other organic substances such as Purines and Pyrimidines may be required.

Microorganisms vary in their ability to synthesize their own growth factors from simpler substrates. If microorganisms are particularly demanding regarding their growth conditions, media for laboratory cultivation are prepared using natural substrates on which these microorganisms normally grow (such substrates include Blood, soil, meat extract, or Yeast extract).

4. Mineral salts. Most commonly, growth requires positively charged calcium, potassium, sodium, iron, and magnesium ions, as well as negatively charged chloride, phosphate (a phosphorus source), and sulfate ions (a sulfur source). As noted above, nitrogen is supplied as ammonium or nitrate. The growth requirements of algae are roughly similar to those of plants (see Tables 7.7 and 7.8).

12.1. Give one example of the role of each of the following elements:

1) iron and phosphorus for heterotrophic bacteria;

2) nitrogen and magnesium for autotrophic bacteria.

(If necessary, use Table 7.7).

5. Energy source. The Energy Requirements of living Cells were discussed at the beginning of Chapters 7 and 9. Energy may be supplied in the form of chemical energy or light energy. An Organism that consumes chemical energy is called a chemotroph, while an organism that utilizes light energy is called a phototroph, or photosynthetic organism (Table 2.3). Photosynthetic microorganisms include algae and certain bacteria, such as cyanobacteria. When chemical Energy is required, it is usually provided in the form of a sugar, such as glucose.

6. Water. Although not strictly a nutrient, water is essential for all living cells. Generally, bacteria require more moisture than Yeasts, and yeasts require more than Molds.

An example of a relatively simple culture medium is given in Table 12.1.

12.2. What is the function of each component in the medium listed in Table 12.1?

Table 12.1. A relatively simple medium used for the growth of the bacterium Escherichia coli, which normally inhabits the human intestine