High And Medium Growth Bacterial Code

A mixed culture of two unknown bacteria was provided by the instructor. The methods used for

The first result of importance was the result of the Gram stain. The observations of the unknown bacteria from the slant culture after Gram staining showed that the unknown bacteria were Gram negative bacilli (Image 1). After determining the unknown bacteria was Gram negative, an oxidase test was conducted on a sample from the slant culture. The cotton swap with the sample of bacteria did not change color when the oxidase reagent was applied, thus providing a negative result. With a negative oxidase test, further tests were conducted to determine various characteristics of the unknown bacteria. A MR-VP broth was inoculated with a sample from a slant culture of unknown bacteria. After incubation, the methyl red reagent was added to the broth, and the broth turned red, providing a positive result (Image 2). An EMB agar streak plate was inoculated with a sample from a slant culture of the unknown bacteria, and after incubation, growth was found on the plate, providing a positive result (Image 3). A Citrate agar slant was inoculated, and after incubation, growth was found on the media, providing a positive result (Image 4). A Urea agar slant was inoculated, and after incubation, the agar had changed from a peach color to a bright pink color, providing a positive result (Image 5). Using the flowchart (Figure 1) developed from the Table of Expected Results, the lab partners started at the oxidase test. Given the negative result of the oxidase test, the flowchart is

Many tests were completed on the unknown such as gram staining and inspection under microscopes to find whether the bacterium is gram positive or gram negative. Chemical resistance tests were also performed to see if certain chemicals affected the unknown growth or if it didn’t affect the bacteria at all. Each biochemical test

Although some agar plates were hard to see if the streptomycin had a definitive zone of inhibition. Ampicillin, erythro-mycin, penicillin, sulphafurazole was ineffective with no inhibition zone.

For the temperature test each bacteria was placed on a nutrient agar and incubated for either 10, 20, 30, 40, or 50 degrees Celsius for 48 hours. During the pH test, each organism was placed on four agars varying in pH level from pH 2, 4, 6 and 8 and incubated near 37 degrees Celsius for 48 hours. For the osmotic pressure test, each organism was placed on four agars one each containing 2%, 5%, 8%, and 11% NaCl concentration levels. These were incubated near 37 degrees Celsius for 48 hours. The results of the tests are recorded in Tables 1, 2, and 3. All tests were performed according to the instructions provided in Leboffe & Pierce(1). The biochemical tests used on both unknowns and the ubiquity are:

The purpose of this report is to analyse the growth of the bacteria known as Citrobacter Freundii as well as distinguishing what antibiotics effect its growth. This will be done so by answering the following question after completing its associated experiments. This question includes: what antibiotics are most effective in denaturing the bacteria? It has been predicted that chloramphenicol will be the most effective due to the fact that its medical uses are treating meningitis which is an infection caused by Citrobacter freundii. After conducting the experiments it was found that the chloramphenicol antibiotic was the most effective in denaturing the bacteria, although streptomycin was also affective. However, none of the other antibiotics were able to halt the growth of the bacteria.

The species ID from the Biolog was confirmed to be Staphylococcus epidermidis with a probability of 99.2%. The observed results of utilization of D-Mannitol, citric acid, D-fructose, and α -D-lactose matched the expected results. The bacteria sensitivity to NaCl differ from the expected results; the bacteria should be tolerant to NaCl up to 10-15%. The fermentation results of glucose and lactose from phenol red broth was different from the results observed in the Biolog. The Biolog results matched the expected results for S. epidermidis with a few exceptions. From the citrate slant test, it was observed that the bacteria was unable to utilize citrate; however, the observed results from the Biolog test was inconclusive indicting a positive and negative result. The bacteria was indicated to not be sensitive to Vancomycin, however, the bacteria is expected to be sensitive to the antimicrobial

The oxidation fermentation test was used to differentiate if the organism utilizes lactose, mannitol, glucose and citrate aerobically (oxidation) or anaerobically (fermentation). A methyl red test was performed to determine if the organism carried out mixed-acid fermentation when supplied glucose. A Voges-Proskauer test was performed to evaluate if the unknown was able to ferment glucose into butanediol. A citrate test was performed to determine if the unknown organism was able to break down citrate into ammonia. An oxidase test was then performed to determine if the unknown culture was oxidase positive or negate.

Over a two week period, eight prepared types of test media were provided to identify the assigned unknown mixed cultures. Not all of these tests were performed on every culture, as some were used only for gram positive or gram negative bacteria. The tests performed and what constituted a positive or negative test are as

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)

The purpose of this study and experiment was to analyze and compare the relative antibiotic resistance of the gram-negative bacterial species Serratia marcescens to the antimicrobial species streptomycin and ampicillin. Preceding researches have shown that streptomycin has a stronger effect on the bacteria species than the ampicillin. In this experiment, the disc-diffusion method has been introduced and the zone of inhibition was measure in millimeters around the disc saturated with the same molar concentration of the two antibiotics- streptomycin and ampicillin. The hypothesis is that if the colonies of S. marcescens were treated separately with streptomycin and ampicillin with all other factors remaining the same and controlled, the S. marcescens would display a stronger resistance toward the ampicillin than to streptomycin. The results from the experiment supports the hypothesis that S. marcescens is more resistant to ampicillin than to streptomycin.

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

L bulgaricus has shown the ability to cause homofermentation of lactic acid, meaning the lactic acid produced is the on byproduct. In a study conducted by (wheater ,1974) the strains of l bulgaricus grow optimally at temperatures between 45 and 50 degrees Celsius and they do not prefer environments high in salt concentrations

The main objective of this experiment is to investigate the effect of different types of antibiotics on bacteria Bacillus subtilis and Escherichia coli. Some of the main methods used in this experiment

Six experiments were carried in this report concerning the effect that different environmental factors have on microbial growth. The results were recorded into tables where (+) symbolises growth and (–) symbolises no growth.