Bacterial Cultures

(Harley, 2011, pp. 102-103) Sucrose and lactose serve as a fermentable carbohydrate sources which promote its growth of fecal forms and provide color change differentiation. (Harley, 2011, p. 104) Therefore, if E. coli is being platted on the EMB, after plate’s incubation period, it should produce a green metallic sheen on the agar due to the bacteria being a strong fermenter. My unknown bacteria tested positive for growth, and agar was fermented reddish burgundy in color. Subsequently, the unknown bacteria was later inoculated with a sterilized loop into the liquid tryptic soy broth and incubated at an appropriate temperature. Its results were used for proper identification of turbidity, spots and flocculation. (BD™ Tryptic Soy Broth (TSB), 2008) The results of the unknown were cloudiness and some settlement on the bottom of the tryptic soy liquid. The next step was conducted to find out if all the bacteria, as well as the unknown culture, required oxygen for growth, varying from an aerobic environment, where bacteria needs oxygen to grow, to facultative anaerobic environment, where bacteria will grow either with or without oxygen but better in its presence. All the bacteria, along with the unknown, were separately inoculated and tested. My unknown culture results tested positive for growth in facultative anaerobic environment. In the next sequence of lab experiments, the results of unknown bacteria were determined by glucose fermentation,

UNKNOW BACTERIA LAB REPORT UNKNOWN 36 Introduction The purpose of this lab was to identify two unknown bacteria from a mixed culture. The reason for identification of unknown bacteria was to help students recognize different bacteria through different biochemical tests and characteristics. This is important in the medical field because identification of unknown

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

| |Gram-negative bacteria |lactose and or sucrose and those that|green metallic sheen or|aeruginosa | | | |do not. |pink. | | |MSA Agar |For organisms that are |Isolates for mannitol fermentation |Yellow color change in |Staphylococcus aureus |

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

Unknown Experiment Introduction: 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.

Our world has changed dramatically since the day Antoine van Leeuwenhoek discovered microorganisms in 1676 using a simple microscope. In early days, scientists first thought life arose from inanimate materials. This theory, known as abiogenesis or spontaneous generation, was disproved later on by scientists including Lazarro Spallanzani and Louis Pasteur.

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

After gaining some knowledge about bacteria, we were giving an investigating bacteria growth lab to do. Our objective was to observe the conditions required for bacteria to grow and to test the effectiveness of substances that may be antibacterial, disinfecting, and or sanitizing. My group and I began our procedure by gathering all the bacteria by swabbing our necks and mouths. After this, we inoculated the culture by rubbing the bacteria on the agar, a nutrient rich gel made from sea kelp, on the bottom side of the container where we grow bacteria, the Petridish. We hoped for the results to come back with little or even no colonies and an immense zone of inhibition around the tiny circle cut out of filter paper covered in toothpaste, Neosporin, and Chlorhexidine Gluconate 4% Solution.

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.

In this experiment, pH indicators, colour indicators, metallic ions, and Kovac’s reagent all aide in the differentiation of different bacteria under different conditions. Proteus vulgaris for example is a rapid production of urease and this is shown through the phenol red indicator, turning from yellow to pink. This experiment is usually done to distinguish from Proteus and other bacteria, which helps to isolate these bacteria since they are infectious (O'hara, et al., 2000).

For the most part, the two culture methods do agree with each other. However, with some of the bacteria there were conflicts with the data. For example. M.

A positive bacterial growth on nutrient agar plate used as control as well as bacteria colony morphology. The EMB was used to select for coliform gram negative bacteria and determine if the bacteria is able to ferment lactose. The Purple color colonies indicated a positive result for strong fermentation of sugars by fecal coliforms. The last plate is the PEA plate, white showed inhibited growth of the bacteria indicating that the unknown bacteria is gram negative.

: In the field of microbiology, there are times when a sample will contain more than one species of bacteria. The goal is to separate each bacterium and culture them independently from one another to identify them. This was the objective of this lab. Each stock contained two unknown bacterium, and the possible unknowns were Eserichia coli, Enterobacter aerogenes, Enterobacter cloacae, Serratia marcescens, Proteus vulgaris, Klebsiella pneumoniae, Shigella flexneri, Shigella sonnei, and Salmonella enterica. The tests available were MacConkey agar, Endo agar, Hektoen Enteric agar, Tryptone Soya Agar (TSA), carbohydrate sugar broths, Triple Sugar Iron (TSI) agar, decarboxylase broths (arginine, lysine, and ornithine), Simmon’s Citrate Agar, urease

Bacteria are identified systematically by using various different techniques and narrow down their species present in an unknown bacterial culture. This is highly usefully in identifying infections correctly and in research regarding microorganism. Laboratories use identification techniques based on primary characteristics and gram stains to carefully identify unknown organism in samples collected (faeces, blood, sputum, mucosal swabs), to determine the cause of infection and define a disease.