BIO 319- Ch.1 Short Answer Questions

Explain how you would use Robert Koch's postulates to determine that Streptococcus pyogenes is the causative agent of streptococcal pharyngitis (strep throat).

1. The suspected pathogen must be in all cases of the disease and absent from healthy animals 2. The suspected pathogen must be grown in pure culture 3. Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal 4. The suspected pathogen must be reisolated and shown to be the same as the original

Describe two capabilities of microbes that exemplify their dynamic nature.

Answers could possibly include cell-cell communication, ability to move (motility), and exchange of materials (any two).

Using specific examples, explain why it is sometimes impossible to satisfy Robert Koch's postulates.

Answers will vary, but one issue is the consideration for a model animal host that will react to the (human) pathogen in the same manner as in a human host. For example, a chicken would not show flu-like symptoms when infected with the influenza virus.

List three contributions of Ferdinand Cohn to the development of microbiology.

Cohn classified bacteria, discovered endospores (showed they were not killed by boiling), and devised methods for preventing contamination of a culture media (ex. use of cotton to close flasks and tubes)

Explain the nature and function of an enrichment culture.

Developed by Martinus Beijerinck; microbes can be isolated from natural samples in a highly selective fashion by manipulating nutrients and incubation conditions; used with nitrogen-fixing bacteria

Explain why infectious diseases are much less lethal in developed countries than in underdeveloped countries.

Developed countries have more resources in order to protect against these infectious diseases. They can improve sanitation and public health practices, have vaccine campaigns, and distribute antibiotics.

Describe beneficial and harmful ways in which microorganisms interact with agricultural crops.

Harmful: food spoilage; disease in plants and animals Beneficial: fermentation which preserves food/develops key acids (ex. milk, cheese, yogurt, sauerkraut, etc.); nitrogen-fixing bacteria (don't need to pay for nitrogen fertilizers); degrade cellulose; regenerate nutrients in soil & water

Microbes were first formally observed during the mid-1600s, but the cell theory was not enunciated until 1839. Write a brief essay explaining why microbiology did not become a formally recognized science until Louis Pasteur's and Robert Koch's time.

It was not until Pasteur's and Koch's times that somewhat powerful microscopy tools were available. Before this time, organisms' activities could be observed, but individual cells could not be seen.

Compare and contrast the functions microbes serve in the digestive systems of both humans and rumens (ex. cattle, sheep).

Microorganisms in the digestive system of rumen are important, as they help to digest and ferment cellulose. This is significant, as rumens ingest a lot of cellulose-rich food such as grass and hay and need these microorganisms to digest their food. The human colon lacks a large number of cellulose-degrading microorganisms but instead has a large number of microbial cells that assist in digestion by synthesizing vitamins/nutrients and compete with pathogenic microorganisms for space.

Provide evidence supporting the statement that an ecosystem is controlled by microbial activities.

Microorganisms that carry out metabolic processes remove nutrients from the ecosystem and use them to build new cells; microorganisms excrete waste products back into ecosystem; metabolic activity of microorganisms can physically & chemically alter an ecosystem

Compare and contrast the works of Louis Pasteur and Robert Koch in terms of both applied and basic science.

Note: Applied science is related to problem-solving and basic science is related to discovery. Louis Pasteur is credited with research in regards to alcohol fermentation (basic); he discredited the theory of spontaneous generation (basic); developed vaccines for anthrax, rabies, and cholera; developed aseptic techniques (applied). Robert Koch linked microbes with infectious diseases through Koch's postulates where he would isolate and grow pathogens (applied).

Explain why only anaerobic bacteria inhabited Earth for the first two billion years of its existence.

Only anaerobic bacteria initially inhabited Earth because the Earth's atmosphere was anoxic and only contained nitrogen and carbon dioxide. Therefore, only anaerobic bacteria could survive these conditions.

How would the presence of endospores in Louis Pasteur's nutrient solutions have affected his conclusions about spontaneous generation?

Pasteur used heat in his experiment to kill contaminating microorganisms that would cause the sample to putrefy. If Pasteur had used endospores, which are very heat resistant, he would not have killed the contaminating microorganisms and the sample was not made sterile, the sample would putrefy and spontaneous generation would not have been disproved.

Compare and contrast the leading causes of death in 1900 with the leading causes of death today. What roles have microbiologists played in the dramatic changes that are evident?

The leading cause of death in 1900 was influenza/pneumonia (infectious diseases). Today, the leading cause of death is heart disease and cancer (both nonmicrobial diseases). Microbiologists have increased our understanding of disease processes, improved sanitary and public health practices, introduced vaccines, and have developed antibiotics.

Why is it incorrect to say that an object is partially sterile?

The word "sterile" implies: free of all living organisms and viruses; kills ALL forms of life

Explain why microbial cells are excellent models for understanding cell function in higher organisms.

commonality of function, biochemical and genetic similarities, and ease and speed with which they can be grown in large quantities.