Quizzes and Worksheet Answers

WORKSHEET 1 eukaryotic, multi-cellular and non-photosynthetic. - The organism is most likely a fungus – eukaryotic eliminates archaea and bacteria, protists are typically unicellular and often photosynthetic. eukaryotic, multi-cellular, photosynthetic and macroscopic - Organisms is most likely member of the group protist – eukaryotic eliminates archaea and bacteria, protists are often photosynthetic but fungi are not. Some protists can be multicellular, e.g. algae/seaweed Does the experiment depicted below support or refute the hypothesis of spontaneous generation? Explain. Refute – if spontaneous generation was correct, maggots should appear on the meat in both the cork-sealed container and gauze-covered container instead of only in the open container Explain how you would use Robert Koch's postulates to determine that Streptococcus pyogenes is the causative agent of streptococcal pharyngitis ("strep throat"). 1. Postulate 1 - Collect a sample from a diseased individual (i.e., someone with strep throat) and a healthy individual. Confirm that the suspected microorganism is present in the sick person but not in the healthy person. 2. Postulate 2 – Grow the suspected organism in pure culture. 3. Postulate 3 – Use pure culture to inoculate a healthy individual. Confirm that they become sick and develop strep throat. 4. Postulate 4 – Re-collect a sample and confirm presence of same microorganism as identified in Postulate 1.

WORKSHEET 2 Lysozyme is an enzyme that cleaves glycosidic bonds between N-acteylglucosamine and N-acetylmuramic acid. Lysozyme is present in human secretions including tears and saliva. What is the function of Lysozyme in human secretions? - Lysozyme acts as an anti-microbial substance. The lysozyme in secretions protects e.g. our eyes, from microorganisms such as pathogens by attacking the bonds present in peptidoglycan found in the cell wall. This causes the cells to lyse (die). You have a microbial specimen you want to identify. You follow these steps: a) Fix and stain the specimen with nucleic acid stain, you observe that the specimen has a DNA arranged in a single circular chromosome, and no nucleus. Is the specimen prokaryotic or eukaryotic? Explain. Prokaryotic because nuclear material is not membrane-bound and single circular chromosome commonly found in microorganisms (as compared to multiple linear) b) Analyze the cell wall composition of the specimen and determine that the cell wall is made of peptidoglycan. Is the specimen Bacteria or Archaea? Explain. Bacteria – only bacteria contain peptidoglycan, archaea do not c) Gram stain the specimen and it stains purple. Is the specimen gram positive or gram negative? Explain. Gram-positive – Gram-negative cells do not retain the crystal violet after rinsing with alcohol and instead stain pink with the safranin counter stain Compare & contrast: List one advantage and one disadvantage of complex media and defined media. Media Type Advantage Disadvantage Complex Able to culture diverse microbial populations as most nutritional requirements are met. media is not standardized and recreating experimental results are difficult as many inconsistencies arise. Defined The culture is grown under well-defined conditions allowing for control over the environment. Not able to culture many microorganisms as not all nutritional requirements are met.

QUIZZES What structures are commonly referred to as the cell envelope? (all correct) - plasma membrane - peptidoglycan layer - outer membrane Which of the following is the CORRECT function of a spectrophotometer in regards to bacterial cultures? - The greater the transmittance of a bacterial culture, the lower the bacterial concentration - The greater the absorbace of a bacterial culture, the greater its optical density - The greater the absorbance of a bacterial culture, the higher the bacterial concentration On a streak plate preparation of a pure culture, colonies were found along the streak line as well as below the surface of the agar. What is a reasonable conclusion for this observation? - The agar plate was contaminated before inoculation by the streaker. Which of the following may be a function of proteins within a cell? - To catalyze chemical reactions Select the CORRECT statement describing the domains of living organisms - the eukarya which are organisms containing cells that have a membrane-bound nucleus. - the bacteria which are simple single celled organisms that synthesize mRNA and proteins. How do hyperthermophiles keep their proteins from denaturing at high temperatures? (all correct) - large percentage of α helical domains - more salt bridge and side chain interactions between the amino acids - differences in amino acid composition How are archaeons similar and different from bacteria? - Archaeons are similar to bacteria in morphology, size and in the size of their genomes. Like bacteria, the archaeons lack a membrane-bounded nucleus to contain their genomes. Which of the following properties of archaea are more like bacteria than eukarya? - cell size - cell shape - chromosomal structure Select the CORRECT statement regarding the reason why microbes do not generally grow in salty environments - they reduce water availability for microbe use - they increase osmotic stress for the microbe - they decrease water activity (aw) in the environment Which of the following microbial control methods is a complete sterilization method? - Autoclaving