There were several factors that affect the rate of bacterial growth. The results after the six day observation period showed that the four types of milk which are kept in the fridge underwent little to no changes in appearance, odour, pH level or colour, whereas the milk that were left in the cupboards presented drastic changes in all aspects. In unfavourable conditions, a few bacteria were able to reproduce sexually by a process called conjugation with the intention of increasing the survival probability. The colour of milk was due to the ability of these protein molecules to refract light. The ability to ferment foods enables communities to safely consume both dairy and vegetables regardless of season and to lengthen shelf life without refrigeration (Steinkr… Do you have a 2:1 degree or higher? There were several factors that affect the rate of bacterial growth. You can view samples of our professional work here. The OD was checked at every 30 minutes interval and recorded. Therefore, after a few days the pH values of buttermilk sample in the cupboards increased as more bacteria died and stopped producing lactic acid. The nutrients in the four different types of milk were also a big factor that influenced the rate of bacterial growth. Bacteria were the only living organisms that existed on Earth for approximately 3.5 billion years implying that these prokaryotic organisms were able to survive through all the harsh climate changes in Earth’s history. Hyperthermophilic bacteria will grow extreme heat, 70 to 110 degrees C (158 to 230 degrees F). All work is written to order. Warm temperature provided bacteria a favourable environment for reproduction which caused them to multiply quickly as opposed to cooler temperatures. If it takes less than 20 minutes, then there are over 20 million organisms/ml. The chocolate milk in both the fridge and the cupboard seemed to have undergone the greatest amount of change after the six days compared to the other three types of milk left in the corresponding conditions. Fission occurs rapidly in as little as 20 minu… Place the methylene blue in one of the test tubes. Procedure: The other 4 glass cups filled with different types of milk samples were placed in a cupboard/cabinet. Experiments were conducted using a simplified human milk spoilage model based on goat's milk as a human milk surrogate, spiked with a single bacterial strain (Staphylococcus epidermidis), in which pH and carbon dioxide (CO 2) concentration were measured along with bacteria count over 160 hr. Our academic experts are ready and waiting to assist with any writing project you may have. 74 0 obj <>/Filter/FlateDecode/ID[<51743C8C586D7346A2AE8CB8467C70D2>]/Index[57 44]/Info 56 0 R/Length 91/Prev 1615106/Root 58 0 R/Size 101/Type/XRef/W[1 2 1]>>stream The Kingdom Bacteria consisted of anaerobic unicellular microorganisms with exceptional abilities of adapting to wide ranges of environment conditions. Based on the sugar content of the milks, it was shown that the rate of bacterial reproduction in the chocolate milk was faster than the other types of milk because of its high sugar content which was about double the sugar content of the other types of milk. The chocolate milk with the most amount of sugar content, which provided the bacteria more food supply, spoiled the quickest compared to the other types of milk. All science fair projects This experiment was testing how effective natural plant extracts are as antibiotics by placing a mixture of the bacteria and natural plant extract combined together with milk and measured the diameter of the bacterial colony in the agar plate and compared it a mixture of only milk and the bacteria without the plant extract to see if the plant extract was effective in killing the bacteria. That much amount (V1) of the inoculums was pipetted out before adding an equivalent amount of the broth to it, so that the net volume remains constant. To export a reference to this article please select a referencing stye below: If you are the original writer of this essay and no longer wish to have your work published on UKEssays.com then please: Our academic writing and marking services can help you! Take the lid off of the Petri dish (the lid is larger than the dish) and carefully cover the bottom-half of … This is not an example of the work produced by our Essay Writing Service. These errors would’ve altered the observations that were made significantly. Moreover, bacteria commonly grew in distinguishing arrangements. Lastly, the sharp sour odour of the cupboard samples after a few days were produced by the lactic acid present in the milk. Company Registration No: 4964706. The purpose of this experiment was to understand the conditions which encouraged and inhibited bacterial growth by observing the rate of bacterial reproduction in milk samples stored at different temperatures. 2 . The effect of water dilution on bac- terial growth as measured by logarithms of bacterial counts made after 6 hr. This was what happened at the molecular level when milk developed curd. Subsequently, the model was extended with the average competition coefficients (E-BR–GD model) that represented quantitative relations among the populations. Additionally, these organisms came in several different shapes; the most common being cocci (round), bacilli (rod-shaped), and spirilli (spiral shaped) (“Classification of bacteria,” 2012).Each shape offered distinctive advantages. RESULTS Experiments with raw milk as inoculum. Biology Hence, the clumps of a cheese-like substance that was formed at the end of the experiment in the cupboard samples were protein (casein) molecules. Historically, communities produced fermented foods within the home, a practice that continues to this day in many settings. Classification of the Bacteria Kingdom was based on the shape, structure/thickness of cell walls, sources of food and energy, and the analysis of RNA sequences. 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