Regarding Louis Pasteur's experiments with the S-neck flask, which of the following statements is TRUE? O A food source was provided. O The possibility of contamination was removed. O Air exchange was involved. Air exchange occurred, a food source was provided, preexisting microorganisms were killed and contamination was prevented O All preexisting microorganisms were killed.

Which of these structures is most resistant to chemical disinfection? (Which is hardest to kill?)     fungal spores   chlamydia bacteria   protozoa cells   bacterial spores

All of the following are beneficial for a pathogenic bacterium, but O adhesins O fructose O endotoxin Olipid A is/are the most crucial in order for a bacterium to establish an infection.

Based upon your knowledge of the 5 I's of microbiology, which type(s) of tests were used in this study to identify the group A streptococci in the specimens collected? How were the other four I's also used in this study? Give specific examples.

You are given a mixed culture of 3 bacteria with following characteristics- 1) Bacteria 1 - Methicillin- resistant Staphylococcus aureus (MRSA) (does not ferment any of these 4 sugars but forms endospores and is sensitive to penicillin) 2) Bacteria 2 - Escherichia coli (can ferment glucose, maltose, sucrose and lactose) and also produce carbon dioxide gas on fermenting these 3) Bacteria 3 - Enterobacter aerogenes. (can ferment only sucrose and cannot ferment glucose, maltose and lactose. Also on fermenting sucrose it produces hydrogen sulphide gas.) Also they all give similar looking white-colored colonies on an agar plate. Question: Generate separate pure cultures of these 3 bacteria from the mixed culture using the following tools that you learned in the lab. Use any (some or all) of these tools to generate pure cultures as well as confirm them. Any other technique that you use should be one you learned in lab. No need to give detailed info about how to perform the technique but it…

You are given a culture medium on which only Gram negative bacteria will grow. Organisms that are capable of fermenting lactose will produce dark red colonies, while those that do not will remain colorless. This medium is best described as: O differential medium, O selective and differential medium. O selective medium. O enrichment culture. A Moving to the next question prevents changes to this answer. Question 4 of

48)Researchers are designing several experiments to test the ability of Salmonella bacteria to develop antibiotic resistance. A culture of Salmonella bacteria is exposed to the same concentrations (200 mg/L) of an antibiotic for four days. The table shows the number of isolated resistant bacteria over a four-day period. Which of the following statements best explains these results? Day Number of Resistant Bacteria in the Culture 1 5 59 3 677 4 32,456 The bacteria were not affected by the antibiotic. After being exposed to the antibiotic, the bacteria altered their DNA. A new species of bacteria emerged after the antibiotics were introduced. Random mutations led some bacteria to be resistant and, over time, they increased in the population.