Compare and contrast the different uses of heat to reduce microbial contamination, including their relative efficacy
What will be an ideal response?
Autoclaving, the use of super-heated steam, is a rapid, effective means of sterilization, both because the temperature achieved (121°C) inactivates every infectious agent except prions, and the steam is penetrating. Dry heat sterilization is equally effective but requires higher temperatures for longer periods of time (up to 170°C and/or 2 hours). Boiling is effective in killing vegetative cells of all microbes but is not effective on bacterial endospores and some cysts. Ultra-high-temperature sterilization is a highly effective process for sterilizing liquids. Standard Pasteurization procedures effectively kill the mesophilic microbes responsible for disease and most spoilage, but does not remove endospores, nor thermoduric and hyperthermophilic microbes. This lower level of microbial reduction is sufficient in the short term since it is the mesophiles that are most troublesome in terms of disease and spoilage. The primary effect of these methods is denaturation proteins, thus inhibiting metabolism. Higher temperature methods cause additional damage, including to cell membranes, cell walls, and DNA.
Low temperature heating that produces desiccation is effective in inhibiting the metabolism of most microbes by reducing the water content of the materials. It is not effective against some fungi, and does not destroy endospores.
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Maximum Likelihood and Bayesian Methods
A. involve the use of an evolutionary model. B. are a set of assumptions about how evolution is likely to happen. C. can be applied along with the principle of parsimony. D. ask the questions "what is the probability that an evolutionary model and proposed phylogenetic tree would give rise to the observed data and what is the probability that a particular phylogenetic tree is correct given the observed data and particular evolutionary model" respectively. E. involve the use of an evolutionary model; are a set of assumptions about how evolution is likely to happen; can be applied along with the principle of parsimony and ask the questions "what is the probability that an evolutionary model and proposed phylogenetic tree would give rise to the observed data and what is the probability that a particular phylogenetic tree is correct given the observed data and particular evolutionary model" respectively.
After a meal,
a. ATP production slows. b. blood glucose levels remain constant. c. insulin levels rise. d. glycogen is used. e. glucagon levels rise
Character displacement makes competing species less similar, which facilitates __________. Fill in the blank(s) with the appropriate word(s)
Restriction enzymes cut double-stranded DNA
a. between genes. b. at specific base sequences c. between bacterial and viral DNAs. d. between purines and pyrimidines. e. between promoter and operator DNA sequences.