Bacterial Cultures

The purpose of this experiment is to distinguish and indentify an unknown bacterium. There are several tests that can help one eliminate and narrow down the options. The most useful test, and the very first one done, is a gram stain. This test will tell whether the bacterium is gram-positive or gram-negative. After the type of gram stain is identified, the tester has a wide array of differentiating tests at their disposal. Based on the results from these tests, and the numerous others that are available, one can accurately establish the identity of an unknown bacterium.

You can grow microorganisms in liquid media or on solid media. Most bacteria can be grown in labs as long as the media contain a source of the major nutrients; carbon, nitrogen, sulphur, and phosphorous. They may also need to have other nutrients. These nutrients are made into a broth and the pH and salinity can be adjusted. The nutrient broth is placed in test tubes, which are plugged with cotton wool, capped with foil and then sterilised in an autoclave, at 121c for 20minutes. These tubes are then cooled before they are inoculated. To prepare the streak plates we dipped an inoculating loop into ethanol then placed it in the flame until the loop glowed red. Still holding the inoculating loop by its handle we removed the lid from

MSA agar is selective and differential medium which was used to see if the bacteria fermented mannitol or not. Selective because it selects for gram positive bacteria specifically Staph. species and it has 7.59% NaCl which means the bacteria must tolerate high concentrations of salt to grow and differential because it has a mannitol phenol red pH indicator. After running most of the test, I was able to conclude that my gram positive unknown is either Staphylococcus aureus or Staphylococcus epidermis. To differentiate between the two MSA agar was used because Staphylococcus aureus ferments mannitol and should have growth because it is a gram positive bacteria but Staphylococcus epidermis does not ferment mannitol but can have growth on the agar. So, using aseptic technique, I split the plate in half and inoculated my 2 unknowns onto MSA plate, then incubated at 37 for 24 hours. I knew my unknown A would not grow because it is a gram negative bacteria but it was inoculated as a control to make sure the test is running properly. When I came the next day, the gram-positive bacteria of my plate had growth and the color changed from red to yellow indicating that the bacteria fermented mannitol, which produced acid lowering the pH of the medium. Gram-positive bacteria had yellow color growth and it was surrounded by a yellow halo and gram-negative bacteria did not have any growth and the agar was still red in

Just like eukaryote species, not all bacteria species are identical in the way they behave, grow or interact with their environment (Mujtaba & DeJarnette, 2012). Microbes can be unique in the way they grow on nutrient agar (NA) plates. How their colonies form on the agar plates can also be an exclusive property of specific bacteria species. Microbes can grow in the presence of different nutrients, environments and can also be inhibited by or thrive in the presence of specific agents in the medium. For example inoculating a blood agar plate with the organism, can indicate its hemolysis activity, which it will fall in one of the three groups alpha (α), beta (β), or gamma (γ).

When reflecting back to experiment 3, Aseptic Technique and Culturing Microbes, I realized the large amount of microorganisms that can be found in everyday life. Many different types are found with in the human body. Theses experiments focused on two types of bacteria. First was Staphylococcus epidermidis, found on the skin, and second was Lactobacillus acidophilus, found in the gastrointestinal tract. Both have similar needs for growth when it comes to temperature, however, different growth environments are used.

The medias used in the experiment were the EMB agar and LT broth. LT broths are a selective/differential medium which contains sodium lauryl sulfate which is a detergent that stomach and intestinal bacteria have the ability to withstand. LT broths also contain lactose that supoorts coliform growth by fermentation. EMB agars are differential mediums that contain dyes that are inhibitors of Gram-positive organisms. They also produce dark colored colonies around

Bacteriology Lab Eric Li Kieran Dulmage Ms. Hillier SBI 3U February 17, 2016 March 8, 2016 Purpose One: To attempt to culture bacteria from swabs taken from different areas of a school environment and to observe the growth of bacteria.

Introduction The main purpose for completing the experiment is to understand bacterial growth. In order for bacteria to grow effectively, two important factors are required, physical and nutritional. Physical factors include temperature, pH, osmotic pressure and gaseous requirements1. Bacterial growth is temperature sensitive.

When determining which bacteria I wanted to use for this experiment I had to decide on E.coli bacteria which is gram negative and staphylococcus a gram positive bacterium. These were chosen because they are safe enough to grow in a college laboratory and were supplied by the technician. Gram negative bacteria has an outer membrane making it more resistant to antiseptics and antibiotics, it also makes it more fatal to the human host it is inhabiting. Whereas gram

Title Selective and Differential Media, Replica Plating, Rapid Microbiological Systems Andrisha Smith Microbiology 275 Dr.McCann October 20, 2017 Introduction Microbiological media is used to grow microorganisms, select or identify a particular type of microorganism based on aspects of their biochemistry. The two types of medias used in tis lab were selective and differential media. Selective medias are designed to grow some microorganisms and inhibit the growth of others.

Nutrient Broth and Nutrient Agar were used to inoculate bacteria taken from different surfaces. Nutrient agar plate was inoculated with a sample taken from skin surface. A sterile cotton swab was first immersed on sterile water, then, rubbed against the skin with swirling motion and transferred to an agar plate by rubbing

|EMB Agar | |Distinguishes bacteria that ferment |Dark blue colonies with|E. coli and P. |

The Unknown Bacteria 36/Bacteria # 2 on a TSA plate was examined by the naked eye and under a dissecting microscope. Bacteria # 2 was approximately 3 - 4 mm in diameter. They were circular in form with an entire margin and a flat elevation. The colonies were rough (granular), translucent, and white brownish color with black granules. The Gram stain resulted in a Gram negative rod. After the Gram stain was completed, the bacteria were streaked on an Eosin -Methylene Blue Agar plate and an Enterotube II was inoculated.

A few different factors that affect bacterial growth are the availability of resources and nutrients, temperature and pH. (Act For Libraries) stated in the above paragraph, once the resources and nutrients are

Ans: Every individual colony in a mixed growth might present different bacteria. We isolate them to help us effectively to determine on their differences.