Lectures 1-3 Linda Stewart

Question 1

Differentiate the biological entities studied by microorganisms from those studied by other biologists

Answer 1

• Microbiology is the study of microorganisms.
• Microorganisms are organisms which are too small to be clearly seen by the unaided eye.
• Microbiology includes the study of bacteria, viruses, fungi, protozoa, and algae.
• Microbiology revolves around understanding basic life processes and applying that knowledge to the benefit of humans.
• Biologists study larger organisms which is much less specific than the study of a microbiologist.

Question 2

Explain Carl Woese’s contribution in establishing the three domain system for classifying cellular life

Answer 2

• By comparing ribosomal RNA, Carl Woese demonstrated that there are two very different groups of organisms called Bacteria and Archaea.
• A universal phylogenetic tree was created based on comparisons of small subunit RNA by aligning rRNA sequences from diverse organisms and counting the differences in the sequences to derive a value of evolutionary distance.
• Later studies based on RNA comparisons showed that Protista is not a cohesive taxon and that it should be divided into three more kingdoms.
• These studies led many taxonomists to reject the five-kingdom system in favour of one that divides cellular organisms intro three domains known as Bacteria, Archaea and Eukarya.

Question 3

Provide an example of the importance to humans of each of the major types of microbes

Answer 3

• Bacteria - Present in the gastrointestinal tract where they synthesise vitamins, compete with pathogens for space and resources, and prime the immune system.
• Fungi - Involved in the fermentation of food which preserves the food and renders in its characteristic flavour. Yields products such as cheese and beer.
• Algae - Form the basis of the marine food chain and photosynthesise to produce large amounts of oxygen.
• Archaea - Potential for bioremediation or help in cleaning contaminated sites.
• Protozoa - Help control the population of bacteria and other protozoan a by feeding on them. This helps maintain ecological balance and diversity.
  Viruses - Can be used in cancer treatment by causing the lysis of cancer cells.

Question 4

How did Robert Hooke contribute to microbiology

Answer 4

• Published the first drawings of microorganisms.
• In 1665 he published a highly detailed drawing of the fungus Mucor in his book Micrographia.
• Micrographia also provides information on building microscopes.

Question 5

How did Antony van Leeuwenhoek contribute to microbiology

Answer 5

• First person to observe and describe microorganisms accurately.
• Spent his spare time building simple microscopes.
• He saw both bacteria and protests.

Question 6

How did Louis Pasteur contribute to microbiology

Answer 6

• Carried out ‘Swan-neck’ flask experiments. He placed nutrient solution in flasks. Created flasks with long, curved necks. Boiled the solutions. Left the flasks exposed to air. The result was no growth of microorganisms. This proved that germs were carried on dust particles. This helped disprove spontaneous generation.
• Demonstrated that microorganisms carried out fermentation so, helping French wine industry.
• Developed pasteurisation to avoid wine spoilage by microbes.
• Developed vaccines for anthrax, fowl cholera and rabies.

Question 7

How did Robert Koch contribute to microbiology

Answer 7

• Demonstrated the link between microbes and infectious disease.
• Established the link between Bacillus anthracis and anthrax.
• Used criteria developed by his teacher Jacob Henle which are now known as Koch’s postulates. These are used today to establish the link between a particular microorganism and a particular disease.

Question 8

How did Ferdinand Cohn contribute to microbiology

Answer 8

• Discovered that heat-resistant bacteria recognised by John Tyndall were capable of producing endoscopes.
• Played an important role in establishing a classification system for bacteria based on their morphology and physiology.

Question 9

How did Martinus Beijerinck contribute to microbiology

Answer 9

• Developed enrichment culture techniques. Microbes can be isolated from natural samples in a highly selective fashion by manipulating nutrient and incubation conditions.
• Isolated nitrogen-fixing bacteria and surface-reducing bacteria.
• Discovered that soil microorganisms can obtain energy from inorganic chemicals.

Question 10

How did Sergei Winogradsky contribute to microbiology

Answer 10

• Demonstrated that specific bacteria are linked to specific biogeochemical transformations such as in the soulful and nitrogen cycles.
• Proposed concept of chemolithotrophy as he discovered that soil bacteria could oxidise iron, sulfur, and ammonia to obtain energy and that many of these bacteria could incorporate CO2 into organic matter the same way photosynthetic organisms do.

Question 11

Outline Koch’s postulates

Answer 11

• The microorganism must be present in every case of the disease but absent from healthy organisms.
• The suspected microorganisms must be isolated and grown in a pure culture.
• The same disease must result when the isolated microorganism is inoculated into a healthy host.
• The same microorganisms must be isolated again from the diseased host.

Question 12

Outline Koch’s experiment

Answer 12

• Koch developed a staining technique to examine human tissue. Mycobacterium tuberculosis could be identified in diseased tissue.
• Koch grew M. tuberculosis in pure culture on coagulated blood serum.
• Koch injected cells from the pure culture of M. tuberculosis into guinea pigs. The Guinea pigs subsequently died of tuberculosis.
• Koch isolated M. tuberculosis in pure culture on coagulated blood serum from the dead guinea pigs.

Question 13

Predict the difficulties that might arise when using Koch’s postulates to determine if a microbe causes a disease unique to humans

Answer 13

• Some organisms cannot be grown in pure culture (only 1% can be grown in pure culture).
• Using humans in completing the postulates is unethical.

Question 14

Support the belief held by many microbiologists that microbiology is experiencing its second golden age

Answer 14

• Recently there has been a wide expansion of knowledge in the area of molecular and genomic methods.
• The restriction endonuclease enzymes used to cut double-stranded DNA into smaller pieces were discovered by Werner Arber and Hamilton Smith in the 1960s.
• In 1972 David Jackson, Robert Symons, and Paul Berg had successfully generated recombinant DNA molecules. This was done by cutting DNA from two different organisms with the same restriction enzyme, mixing the two DNA molecules together, and annealing them with an enzyme called DNA ligand.
  In the late 1970s, Frederick Sanger introduced a method which has been adapted to determine the sequence of nucleotides in DNA. Today, entire genomes of organisms can be sequenced in a matter of days
• Bioinformaticists manage the ever-increasing amount of genetic information available for analysis. They also determine the function of genes and generate hypotheses that can be tested either in silico (in the computer) or in the laboratory.