[생물공정실험] 4주차 Bacterial Identification(Durham bubble test & Gram staining) 결과보고서

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• 1. Bacterial Identification

  이번 실험에서는 Durham bubble test, EMB plate, Gram staining을 통해 그람양성균과 그람음성균을 분류해보았다. Durham bubble test를 통해 lactose를 분해하는 균을 확인하였고, EMB agar test를 통해 균의 증식 및 색상 변화를 관찰하여 균의 종류를 추정하였다. Gram staining을 통해 세포벽 구조의 차이를 이용하여 최종적으로 균의 종류를 확인하였다.

• 2. Durham Bubble Test

  Durham bubble test는 lactose를 대사 과정에서 이용하는 균의 존재를 알기 위해 진행되었다. Lactose broth가 든 tube에 bacteria colony 1개를 풀어주고 durham 관을 넣어 기포 발생 여부를 관찰하였다. Lactose를 분해하는 균은 가스를 생성하여 durham 관 내부에 기포가 발생하지만, Salmonella Typhimuirium은 기체를 생성하지 않았다.

• 3. EMB Agar Test

  EMB agar test는 그람양성균의 성장을 억제하고 대장균 등 그람음성균의 선택적 생존 및 증식을 가능하게 하는 배지이다. E.coli가 lactose를 분해하면 산성 부산물을 생성하여 주위 pH가 낮아지고, 이로 인해 염료 흡수가 잘 일어나 보라색 colony를 형성한다. 반면 lactose 분해가 잘 안되는 균은 무색 colony를 형성한다.

• 4. Gram Staining

  Gram staining은 세포벽 구조의 차이를 이용한 세균 분류법이다. 그람양성균은 세포벽이 두꺼워 ethanol로 탈색되지 않고 보라색을 유지하지만, 그람음성균은 세포벽이 얇아 탈색되어 붉은색으로 염색된다. 실험 결과 Lactobacillus paracasei는 보라색으로 잘 염색되어 그람양성균임을 확인할 수 있었다.

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• 1. Bacterial Identification

  Bacterial identification is a crucial process in microbiology and clinical diagnostics. It involves the accurate classification and characterization of bacterial species based on their morphological, biochemical, and genetic properties. This process is essential for understanding the role of bacteria in various environments, diagnosing and treating infectious diseases, and developing effective antimicrobial strategies. The accurate identification of bacteria can provide valuable insights into their ecology, pathogenicity, and potential applications in biotechnology and medicine. However, the identification of bacteria can be a complex and challenging task, as there are thousands of known bacterial species, and new species are constantly being discovered. Advances in molecular techniques, such as DNA sequencing and mass spectrometry, have significantly improved the accuracy and speed of bacterial identification, but traditional phenotypic methods, such as microscopy and biochemical tests, remain important tools in the field. Overall, the accurate identification of bacteria is a fundamental aspect of microbiology and plays a crucial role in various scientific and clinical applications.

• 2. Durham Bubble Test

  The Durham Bubble Test is a simple and widely used microbiological technique for the detection of gas production by bacteria. This test is particularly useful for the identification of certain bacterial species, as the ability to produce gas, such as carbon dioxide or hydrogen, is a characteristic feature of some bacteria. The Durham Bubble Test involves the use of a Durham tube, which is a small inverted test tube placed within a larger test tube containing the bacterial culture and growth medium. If the bacteria are capable of producing gas, the gas will be trapped in the Durham tube, forming a bubble. The presence or absence of a bubble in the Durham tube can then be used to infer the gas-producing capabilities of the bacteria under investigation. This test is commonly used in the identification of members of the Enterobacteriaceae family, such as Escherichia coli and Klebsiella species, which are known to produce gas during fermentation. The Durham Bubble Test is a simple, cost-effective, and reliable method for the initial screening and identification of gas-producing bacteria, and it remains an important tool in the field of microbiology and clinical diagnostics.

• 3. EMB Agar Test

  The EMB (Eosin-Methylene Blue) Agar Test is a widely used microbiological technique for the selective isolation and identification of Gram-negative bacteria, particularly members of the Enterobacteriaceae family. EMB agar is a selective and differential medium that contains eosin and methylene blue dyes, which inhibit the growth of Gram-positive bacteria while allowing the growth of Gram-negative bacteria. The unique feature of EMB agar is its ability to differentiate between different types of Gram-negative bacteria based on their lactose fermentation abilities. Bacteria that are able to ferment lactose, such as Escherichia coli, will produce a characteristic metallic green sheen on the EMB agar surface, while non-lactose fermenters, such as Salmonella and Shigella, will appear as colorless or pink colonies. The EMB Agar Test is a valuable tool in the identification and differentiation of Gram-negative bacteria, particularly in clinical settings where the rapid and accurate detection of pathogenic bacteria is crucial for effective treatment and disease management. Additionally, the EMB Agar Test is widely used in food microbiology, environmental microbiology, and other areas where the identification of Gram-negative bacteria is of importance.

• 4. Gram Staining

  Gram staining is a fundamental microbiological technique that is widely used for the rapid and reliable identification of bacteria based on their cell wall structure. The Gram staining method involves the use of a series of dyes and decolorizing agents to differentiate bacteria into two main groups: Gram-positive and Gram-negative. Gram-positive bacteria, such as Staphylococcus and Streptococcus, retain the primary dye (crystal violet) and appear purple under a microscope, while Gram-negative bacteria, such as Escherichia coli and Pseudomonas, lose the primary dye and appear pink or red. This distinction is based on the differences in the composition and structure of the bacterial cell wall, with Gram-positive bacteria having a thicker peptidoglycan layer and Gram-negative bacteria having a thinner peptidoglycan layer and an additional outer membrane. The Gram staining technique is a simple, rapid, and cost-effective method for the initial characterization of bacteria, and it provides valuable information about the cell wall structure, which is often correlated with other important bacterial properties, such as antibiotic susceptibility, pathogenicity, and ecological niche. Gram staining remains an essential tool in microbiology, clinical diagnostics, and various other fields where the rapid and accurate identification of bacteria is crucial.