Facultative anaerobes grow best in the presence of oxygen but still grow in its absence, obligate aerobes cannot grow in the presence of oxygen while obligate anaerobes only grow in the absence of oxygen. While working with microorganisms, it is important to sterilize the working bench and the working area and close all windows and doors to avoid drafts of air. It is also important to put on protective gloves or to sterilize one’s hands after work. A low number of colonies indicates a dilute microorganism concentration while a large number of colonies indicates a higher concentration of microbes. Salt s and sugar inhibit the growth of microorganisms, therefore, work as food preservatives. Bacteria reproduce by binary fission that is the splitting of a single bacterial cell to produce two daughter cells. After inoculation, the bacteria population increases slowly because of the few number of cells that are reproducing (Lag phase). The rate of growth then increases with increased population leading to a steep slope in the graph (Log phase). The growth rate then stabilizes when the population reaches and equilibrium where the number of bacteria dying is equal to those dying (stationary phase). The food resource gets depleted, and the population begins to decrease (death phase).Bacteria are classified into the following categories according to growth temperatures
• Hyperthermophile (above 600C)
• Thermophile (between 450C and 600C)
• Mesophile (between 200C and 450C)
• Psychrotrophs (survive at 00C but prefer mesophilic temperature conditions)
• psychrophiles (-150C and 100C or lower)
Generation time refers to the period it takes for a microorganism’s population to double. Halophiles refer to a microorganism that grows under saline conditions. Obligate aerobes grow on top of the solid media, facultative anaerobes are evenly distributed within the media while obligate anaerobes grow at the bottom of the media. Aerotolerant anaerobes grow all through the media, but the population is thinnest near the surface. Microaerophiles grow all through the media but with the highest population near the surface. Biofilms are any group of microorganisms in which cells stick together forming a film. They cause infection by spreading over the bruised region and releasing spores into the wounds. Autoclaving exposes microorganisms to super-heated steam at temperatures of 1170C therefore causing the death of all microorganisms and sterilizing the media. The disinfectant is placed at one side of the media, and then the media is inoculated with microorganisms. If the disinfectant is effective, the population of microorganisms should increase away from the disinfectant.
A gene is a location on a chromosome that controls a single trait. DNA replication is the process whereby a double-stranded DNA molecule is copied to produce two identical DNA molecules (Kornberg and Tania 45). DNA is a polymer molecule consisting of two strands of polynucleotides coiled together to form a double helix. The polymers that make up the DNA molecule are Adenine, Thymine, Guanine, and Cytosine. During replication, the DNA bases pair. Guanine pairs with Cytosine while Thymine pairs with Adenine. Genetic change in bacteria can be brought about by the processes of deletion, insertion or replication. A DNA vector is a portion of DNA taken from a bacteria or another organism and is used to transfer genetic information during cloning. cDNA is more appropriate for use as a vector because it is mobile, unlike genomic DNA that is localized. In biotechnology, library refers to a collection of all genotypes and genetic information.
An operon consists of three regions. These are the promoter region that induces the enzyme to start catalyzing, an operator region that promotes enzyme activity and a terminator region which instructs the enzyme on when to terminate the enzyme catalyzed reaction. Allosteric enzyme regulation refers to the process by which enzyme activity is regulated through binding of inhibitors on other sites except the active site of the enzyme known as allosteric sites. Inducible enzymes are those enzymes whose production can be stimulated by the introduction of their substrate. Repressible enzymes, on the other hand, are enzymes whose production can be eliminated by eliminating the introduction of their substrates.

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  • Kornberg, Arthur, and Tania A. Baker. Dna Replication: Arthur Kornberg, Tania A. Baker. Sausalito, Calif: University Science Books, 2005. Print.