Discover the fundamentals of general microbiology through hands-on experiments and observations. This comprehensive introduction covers essential techniques, including sterile environment protocols, antiseptic testing, Gram staining, and bacterial colony analysis. Explore how temperature affects bacterial growth, comparing the effects on different strains and observing the presence of enzymes like oxidase and catalase. Investigate the microbiology of everyday items, such as yogurt, and environmental samples, including ambient air and skin germs. Learn how to characterize bacteria using various staining methods and understand the importance of controlled environments in microbiological studies. Uncover the optimal conditions for bacterial development and the impact of antiseptics on microbial growth.
Extract
[...] Alcohol and bleach therefore have a bactericidal action. This experiment reminds us of the importance of washing our hands before our experiments and also in our daily life. 4. Observation of germs of a yaourt perished and of a yogurt still consumable We have performed two smears: one with the expired yogurt and one with the consumable yogurt. We have colored the two smears with methylene blue in order to highlight the bacteria present in the two yogurts. Expired Yogurt Consumable Yogurt It is noticeable that there are more bacteria in the expired yogurt even though we can distinguish a few in the consumable yogurt. [...]
[...] The colonies are flat and the edges are regular." In addition, we can notice that the ambient air is not as contaminated as one might have imagined, since the number of colonies observed is low compared to other experiments performed during this TP. The colonies formed show the interest of working in a sterile environment to study a certain bacterial strain. - Surface Control We studied here a bracelet, so a surface in contact with the skin at all times. For this, we moistened the bracelet so that the bacteria adhere better to the swab. [...]
[...] By studying the germs of a spoiled yogurt and a still consumable yogurt, we realize that the bacteria inside these two yogurts are the same, but we note that the spoiled yogurt seems to have much more, which seems quite logical given its expiration date exceeded by one year. During the study of heat on two bacterial strains, we realized that bacteria cannot develop under any conditions: the studied bacteria seem to be poorly resistant to very low and very high temperatures. We then colored two bacterial strains with Gram staining and studied the presence of two interesting enzymes to characterize the bacteria: oxidase and catalase. [...]
[...] We have obtained these results : strain A strain B 4 degrees We can observe that no colony has developed, thus we can conclude that the A strain bacterium is not resistant to cold. We can observe that no colony has developed, thus we can conclude that the bacterium of strain B is not resistant to cold. ambient temperature We can observe the development of several colonies at ambient temperature. Thus, we can conclude that this temperature is optimal for the A strain bacterium. We have well isolated the A strain, the colonies are punctiform in shape, they are convex with borders that seem wavy. [...]
[...] The colonies are very numerous and very close to each other. We notice that the surface was very contaminated probably due to its contact with the skin. 2. Skin Germs In the sterile environment of the electric beak, we washed our hands with sterile physiological water above the petri dish. The environment being sterile, all the bacteria that will develop will come from the skin. We observe : Here we observe circular colonies with regular edges of small sizes and circular colonies that are lighter in color than the small ones with wavy edges, which are also much larger than the others. [...]
