Chapter 1 - Brock Biology of Microorganisms

Which of the following statements is FALSE?

Microbial cells include both bacteria and viruses.

Which of the following statements is correct?

Microorganisms are significant contributors to the total biomass on Earth.

Differential selection and reproduction of phenotypes occurs during a process called

evolution

In what/which domain(s) of life is/are microorganisms represented?

Archaea, Bacteria, and Eukarya

Biological catalysts involved in the acceleration of the rate of chemical reactions are called

enzymes

Regarding early life on Earth

microbial life existed for billions of years before plant and animal life.

The person who described the "wee animalcules" was

Antoni van Leeuwenhoek

Walther Hesse and _____________ pioneered the use of agar as a solidifying agent

Robert Koch

Which of the following is/are characteristic of all cellular organisms?

evolution

Deduce why viruses are excluded from the ribosomal RNA- based tree of life

they lack ribosomal RNA (rRNA)

Louise Pasteur developed the vaccine(s) for

anthrax, fowl cholera, and rabies

The discovery of antibiotics and other important chemicals led to the field of

industrial microbiology

Microbial sterilization is used to

kill all microbes in or on objects

Transparent double-sided dishes used for growing microbes are most commonly called

petri dishes

Microbes playing a role in nitrogen fixation in plants live in ________, while those playing a role in the digestive tract of certain herbivores live in ________.

nodules / rumens

Which of the following is NOT an accomplishment of Louis Pasteur?

developed enrichment culture techniques

The theory of spontaneous generation was refuted by the work of

Louis Pasteur

A Pasteur flask has a(n)

swan neck to prevent particulate matter from getting into the main body of the flask.

Predict how Pasteur's conclusions on spontaneous generation with swan flasks would have changed if he worked with and maintained the flasks in a sterile laminar flow hood.

Pasteur's flasks never would have putrefied (decayed/rotted), and the experiment would not have refuted spontaneous generation.

A pure culture

is a population of identical cells

Martinus Beijerinck was the first to isolate

green algae, certain nitrogen-fixing root nodule bacteria, and certain sulfate-reducing bacteria.

Chemolithotrophy involves

oxidation of inorganic compounds

Developments in the fields of immunology and medical microbiology were practical extensions of the work of

Robert Koch

Microbial control in wastewaters would most logically be a part of

aquatic microbiology

Robert Koch contributed to the field of microbiology by being the first person to

develop the tuberculin test, formulate four postulates for definitively linking a specific microorganism to a specific disease, and use agar as a solidifying agent in growth media

Mycobacterium tuberculosis is very difficult to stain because of the

large amounts of a waxlike lipids present in its cell wall

Louis Pasteur's most famous success was his work on

the rabies vaccine

Microorganisms play key roles in the cycling of important nutrients in plant nutrition, particularly those of

carbon, nitrogen, and sulfur

Microbial ecology is the study of

microorganisms in their natural environments

The structure that confers structural strength on the cell is known as the

cell wall

A microbial cell's membrane is considered ________, because its internal constituents are maintained within the cell. However, it also imports and exports other molecules in response to its environment.

semipermeable

Some microorganisms can undergo ________ in which various cell types can become specialized and arise from one parent cell type.

differentiation

Cyanobacteria and purple sulfur bacteria both obtain energy from light. However, only the ________ are capable of releasing ________.

cyanobacteria / oxygen

The process whereby microorganisms are used to help clean up pollution created by human activities is known as

bioremediation

Robert Koch received the 1905 Nobel Prize in Physiology or Medicine for

identifying Mycobacterium tuberculosis as the causative agent of tuberculosis

Bacillus anthracis deficient in its ability to differentiate would not be able to

form endospores

Microbial biochemistry most specifically involves the discovery of microbial ________ and the ________ they perform.

biomolecules / functions

Microbial cells first evolved on Earth approximately ________ billion years ago.

3.8 to 4.3

The disease anthrax is caused by the pathogenic bacterium ________, which produces heat- resistant structures known as ________.

Bacillus anthracis / endospores

The first documented description of a microorganism was of a ________ by ________.

mold / Robert Hooke

________ produced by microbial fermentation of glucose from cellulose or cornstarch is becoming a more important component of biofuels in the United States, and specialized ________ are needed to make this a commercially available product.

Ethanol / industrial microbiologists

________ was the first to describe microorganisms, while ________ was the first person to see bacteria.

Robert Hooke / Antoni van Leeuwenhoek

The production of human proteins (e.g., insulin) by genetically engineered microorganisms is an example of ________, a subdiscipline of microbiology.

biotechnology

Approximately two billion years ago, ________ were primarily responsible for initially oxygenating Earth.

cyanobacteria

Archaea and Bacteria are unified as prokaryotes in lacking ________ which Eukarya contain, such as mitochondria.

nuclei and membrane-enclosed organelles

Bioremediation ________ by introducing pollutant-consuming microorganisms or specific nutrients that help microorganisms degrade pollutants.

accelerates the natural cleanup process

________ was the first to identify a new form of autotrophy in which energy is obtained from oxidizing inorganic compounds called ________.

Sergei Winogradsky / chemolithotrophy

Electron microscopy has greater ________ than light microscopy, because the wavelength of visible light is much larger than the wavelength of electrons.

resolution

Which of the following types of microscopy is especially effective for viewing details of internal structures within live cells?

phase-contrast microscopy

Which of the following types of microscopy could be used to visualize the layers of the cell membrane and the cell wall?

transmission electron microscopy

Who was the first researcher to provide direct experimental data that supported the germ theory to explain infectious disease?

Koch

When medical devices are left in the body, bacteria may grow on them as ________, which makes them especially resistant to treatment.

communities

Microbes that live at high temperatures in hot springs are ________.

called extremophiles.

What field focuses specifically on the use of microbes to make products, such as antibiotics, on a large scale?

industrial microbiology

Which statement about the relationship between microbes and humans is FALSE?

Most microbes are pathogenic.

Why is ribosomal RNA especially useful for the study of phylogenetic relationships?

It is highly conserved.

Why is it important to use cultivation-independent methods to help understand microbial diversity?

It allows researchers to identify species that cannot be grown in culture.

T/F Most microorganisms are pathogenic.

false

T/F All microorganisms require molecular oxygen to carry on life functions.

false

T/F Metabolism is a unifying characteristic of all cellular organisms.

true

T/F According to our present understanding, each of the three major domains has what is known as its own universal ancestor.

False

T/F Both environmental conditions and nutrient resources strongly influence the composition of a microbial community.

True

T/F The environment in which a microbial population lives is called its habitat.

True

T/F Differentiation occurs only in multicellular organisms.

false

T/F The discipline of microbiology is intimately associated with biochemistry and genetics, because cells are both biochemical catalysts and genetic coding devices.

True

T/F Today, the enrichment culture technique developed over a century ago by Martinus Beijerinck remains a feasible approach to discovering bacteria capable of degrading pollutants.

True

T/F Sergei Winogradsky worked with bacteria involved in cycling nitrogen and sulfur.

True

T/F Treponema pallidum, a bacterium associated with syphilis, is not considered a pathogen because to date it remains unculturable in the lab, and, therefore, Koch's postulates are unable to be fulfilled.

False

T/F Not only do some microorganisms tolerate extremely hot temperatures, some actually require high temperatures for optimal growth.

True

T/F Electron microscopes have less resolving power (resolution) than light microscopes.

False

Explain the nature and function of an enrichment culture.

Answers will vary, but an enrichment culture uses media, chemicals, or culture conditions to select for or encourage the growth of organisms with specific characteristics. An answer could describe providing only carbon dioxide as a source of carbon to select for autotrophs, for example.

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

Sterile means the absence of all living organisms. Something is either sterile or it is not.
Other terms are used to describe objects that have been cleaned but are not sterile, such as disinfected.

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.

Answers will vary, but a theme should be the lack of powerful microscopy tools. Without sufficient microscopes individual cells could not be seen, but the activities of microorganisms could be observed, such as the production of ethanol in Louis Pasteur's experiments on fermentation.

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

Answers could possibly include: founding bacteriology as a separate science, studying Beggiatoa, discovering the genus Bacillus (along with its endospore formation and its life cycle), and devising methods to prevent contamination.

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

Answers will vary, but should highlight the differences between basic scientific research in which fundamental ideas are discovered opposed to the usage of microbiological principles to solve larger questions. Examples of Pasteur's basic science contributions are his work showing that fermentation was mediated by microorganisms and the preferential metabolism of particular optical isomers by microbes. Pasteur also applied his ideas to develop sterilization techniques. Robert Koch focused more on the application of microbiology to identify the cause of tuberculosis by developing pure culturing techniques and the four postulates to link microbes to a disease.

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

Answers will vary but should include commonality of function, biochemical and genetic similarities, and ease and speed with which they can be grown in large quantities.

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?

Answers will vary, but a focus should be that pathogens that killed people in the early 1900s are now treatable due to knowledge learned from microbiologists.

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

Answers will vary but will need to detail how S. pyogenes will be subjected to all four postulates.

The text states that antibiotics are derived from microorganisms. What is the benefit to an antibiotic-producing microorganism of producing an antibiotic in its natural habitat?

Answers will vary, but it must first be stated the antibiotic-producing microbe would need to be resistant to the antibiotic. This should then follow into a discussion on how antibiotic production could be viewed as a way to persist in the environment, such as maintaining dominance in a community over others.

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

Certain microbes are beneficial to crops when they produce nutrients (e.g., NH 4+, SO42-) usable by a crop from a substrate that was unusable. Other microbes can cause diseases in plants, much like pathogens cause disease in humans.

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

Answers will vary, but one example could be oxygen depletion, where a loss of oxygen would then favor anaerobic microorganisms.

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

The key idea is an anoxic environment will not allow aerobic organisms to survive.

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

Answers will vary, but ultimately this could have confounded Pasteur if the endospores sometimes went into a vegetative growth phase and other times no growth was observed.

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. Another issue is the inability to cultivate some microorganisms outside of the host.

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

Answers will vary but should emphasize ways in which increased knowledge about microbial pathogenesis has influenced preventative care (e.g., sanitation) and treatment (e.g., antimicrobial drugs).

Describe two capabilities of microbes that exemplify their dynamic nature in interacting with their environment.

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

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

Answers will vary but should focus on humans having a high cell localized density in the colon (large intestine), whereas rumens have higher microbial populations in the rumen. Microbes in both systems aid in digestion and improve nutrition/health of the host.

The explosive chemical trinitrotoluene (TNT) can remain in soils after use and is hazardous to humans. Propose an experiment in which TNT-degrading microorganisms could be isolated for purposes of bioremediation. Also indicate what experimental evidence would be useful to isolate TNT-degrading microorganisms.

Experimental designs will vary, but one example would be to use the enrichment culture technique with soil from an ammunition site. While adding TNT to the enrichment culture, a key piece of experimental evidence could be the loss of TNT in the culture to initiate isolation attempts.

What type of microscope would you use to visualize the internal structures of a chloroplast? Support your answer with evidence based on the size of the structures you want to see and the resolution and magnification power of different types of microscopes.

Transmission electron microscopy would be necessary to visualize the internal structures of a chloroplast. Chloroplasts are less than 5 μm in diameter and the internal membranes are only 10 nm thick. Light microscopes only have a resolution of 200 nm, thus any structure less than 200 nm will not be visible. Individual chloroplasts could be seen with a light microscope, but not the structures inside. Scanning electron microscopy can only see external features because electrons cannot penetrate the cell, thus the cell must be sectioned and prepared for transmission electron microscopy to see the inside of the chloroplasts.