Bacterial Growth Rates Essay

The following tests according to the lab manual were performed: gram stain, fermentation tubes, methyl red, vogues proskauer, sulfur, indole, motility and growing it up on MacConkey agar. The gram stain was performed incorrectly the first time. This is because the decolorizer was not on the bacterium slide for long enough, giving a false outcome.

The colonies were smooth, translucent, and had a white brownish color. The Gram stain resulted in Gram positive cocci. After the Gram stain was completed, the bacteria were streaked on a Mannitol-Salt Agar plate and a Catalase test was performed. After these test were completed a Phenol Red Dextrose Fermentation tube was inoculated, and a SIM Tube inoculated.

In the beginning of lab, we were advised to obtain a nutrient agar petri plate, which is used for the cultivation of microbes supporting growth of non-fastidious organisms. Since it contains many nutrients, a wide variety of bacteria and fungi can grow. Taking the plate,

The next step of the project included preparing a Gram stain to discover the cell shape, arrangement, and if the bacteria is gram positive or

Read in your lab manual about the following agar mediums: Blood Agar (pg 168), EMB Agar (pg 170), Mannitol Salt Agar (MSA)(pg 172) ), MacConkey Agar (pg 174), and PEA Agar (pg 176) to answer the following:

Shigella infection is characterized by cramping and diarrhea, with bloody or mucus containing stools. Duration of illness lasts between 4-7 days, and

Escherichia is a genus of aerobic gram-negative rod-shaped bacteria of the family Enterobacteriaceae that form acid and gas on many carbohydrates, such as dextrose and lactose, but not acetone, which include occasional pathogenic forms, including some strains of E. coli which are normally present in the human intestine as well as other forms which typically occur in soil and water (Webster). Escherichia coli is a gram-negative bacilli that rarely varies in shape and size and when stained often resemble safety pins because the ends of some bacilli stain more densely than does the middle; which is a characteristic called bipolar staining which is common in enteric gram-negative bacilli (ASM). Gram negative cells have a thin cell wall layer and will stain red to pink. The staining process is the same as Gram positive, requiring four steps: applying a primary stain, adding a mordant, then rapid decolorization and completing with a counter stain. Applying the alcohol for decolorization dissolves the outer membrane and leaves small holes in the thin peptidoglycan layer through which the crystal violet-iodine diffuse. The gram-negative bacteria is colorless after the decolorization; therefore adding safranin

The lag phase is when the organisms are first place into a new medium and will take time to get used the their new environment. During this phase, organisms will grow in size but cannot replicate. The next phase is the log phase. In this phase cells are dividing and growing at a very fast rate. DNA replication begins in this phase as well as their metabolic rate starts to increase rapidly. (Bacterial Growth Curve) Cells divide by binary fission. The organisms will eventually reach maximum growth and start to level off beginning the next phase, the stationary phase. In this phase, the bacterial population will start to slow down and stop dividing because the nutrients needed for them to grow are being used up. The pH and temperatures start to shift making the environment and unfavorable one and the accumulation of waste and toxic metabolites the growth starts to die off, transitioning into the last and final stage. (Bacterial Growth Curve) The death phase is when there is longer any nutrients to grow and to much waste has built up along with toxic materials, killing the cells. However, some organisms can withstand this environment and begin to produce endospores. (Bacterial Growth Curve)

Shigella is a genus of Gram-negative, facultative anaerobic, nonspore-forming, nonmotile, rod-shaped bacteria. The genus is named after Kiyoshi Shiga, who first discovered it in 1897. The causative agent of human shigellosis, Shigella causes disease in primates, and is the only naturally found in humans and apes. Shigella is one of the leading bacterial causes of diarrhea worldwide and it is suggested that Shigella causes about 90 million cases of severe dysentery, with at least 100,000 of these resulting in death each year. Shigella originates from a human-adapted E. coli that has

faecalis is belonged to Alcaligenes genus in Alcaligenaceae family, according to Foundations in Microbiology: “It is a group of non-fermentative, oxidase-positive, motile bacteria … Members of Alcaligenes live primarily in soil and water habitats, and they may also become established as normal microbiota. The most common clinical species. A. faecalis, is isolated from feces, sputum, and urine. It is occasionally associated with opportunistic infections such as pneumonia, septicemia, and meningitis” (pg. 612). A. faecalis bacterium has those characteristics such as tiny size, thin/ rod/ coccobacillus shaped, a light cream color that is growth at room temperature (37 Celsius degree) as least from 24 to 48 hours to be seen. The bacteria also preferably to growth on nutrient agar slant broth and medium; the elevation is flat. Base on my observation, it is a gram-negative aerobe bacteria have motile and flagellated because when I looked under the microscope for gram-stain with oil immersion lens, and the color of the bacterium is pink. Moreover, Microbacteria: A Laboratory Manual does provide a chart on page 216 giving all of the important of cultural and biochemical characteristics about A. faecalis bacterium; litmus milk reaction test results as alkaline, fermentation including lactose, dextrose, and sucrose are having negative results, majority tests are negative except citrate test (can be positive or negative), catalase activity, and oxidase activity is giving positive

Being able to control bacterial growth is something that is important in our everyday lives. As shown in the previous labs, bacteria can grow and create colonies extremely quickly especially in the right environments. By acknowledging this, it is then important to get an understanding of how bacterial growth can be controlled by humans. To control microorganisms it means to inhibit their growth (static) and or kill them (cidal) (Kenneth Todar, 2015); therefore since focusing on bacteria the terms bactericidal and bacteriostatic are both extremely important for this lab. One broad method we will use to control bacterial growth is heat. The amount of heat needed to control bacterial growth is different for different species of bacteria (Kenneth Todar, 2015). Bacteria can also respond differently depending if moist heating method such as an autoclave with steam is used, or a dry heating method such as inoculating a loop over a fire is used (Kenneth Todar, 2015). UV works by damaging the cells DNA, without proper DNA, the cells will die and the object

1.Shigella germs are present in the stools of infected people. It can occur for up to a week or two even after the diarrhea has stopped. Shigella is very contagious; exposure to even a tiniest amount of contaminated fecal matter can cause an infection. Transmission of Shigella occurs when the infected bacteria is contacted with someone´s mouth or the bacteria from stool is swallowed. This can happen when contaminated hands touch your food and your mouth. Hands get contaminated when we touch surfaces, for example toys and bathrooms that have been contaminated by a person with this infection. Hands can also become contaminated with Shigella while even shaking hands with someone who didn´t wash their hands after going to the bathroom.

Thirty two strains which showed high and medium growth ability at 55oC were retested at the same conditions, i.e. streptomycin supplementation and at 55oC, results are present in Table 12.

Introduction: Through the conduction of numerous experiments, the identity of two bacterial isolates was determined. The tested specimen was an unknown sample of a mixed culture of two different species of bacteria. The first step that was taken was obtaining a pure culture of each species of bacteria by isolating one species from the other. Once isolation was complete, the isolated cultures were tested using procedures that had been performed during previous lab sessions. A gram stain was performed on the two isolates. The isolate which had tested gram negative was then tested for the presence of cytochrome C and lactose fermentation. For the gram positive isolate, cell shape was determined and a catalase test was performed.

Abu-Elyazeed et.al.(2004) conducted a prospective cohort study between 1995 to 1998. They found out that the incidence of Shigella-associated diarrhea was 0.2 episodes/child-year. Shigella flexneri was the most common serotype isolated (55%). Younger age and the warm months increased the risk of developing Shigella-associated diarrhea, while breastfeeding was protective. Common signs and symptoms included fever (35%), vomiting (19%), and dehydration