Chapter 1 Lecture 2

Question 1

Microbial genetics:

Answer 1

Ribozymes- RNA molecules with ability to catalyze reactions

RNA could serve the dual purpose of genetic information storage AND catalyzing reactions!

Lipid membrane formed around RNA

Question 2

Earliest Molecules—RNA

Answer 2

Original molecule must have fulfilled protein and hereditary function.

Ribozymes.
RNA molecules that form peptide bonds.
Perform cellular work and replication.

Earliest cells may have been RNA surrounded by liposomes.

Question 3

Today’s Versions of RNA vs. Ancient Versions

Answer 3

Cellular pool of RNA in modern day cells exists in and is associated with the ribosome (rRNA, tRNA, mRNA).

RNA catalytic in protein synthesis.
RNA may be precursor to double stranded DNA.

Adenosine triphosphate (ATP) is the energy currency and is a ribonucleotide.

RNA can regulate gene expression.

Question 4

Evolution of Cellular Microbes

Answer 4

Mutation of genetic material led to selected traits.

New genes and genotypes evolved—producing mosaic of genetic information.

Question 5

Bacteria and Archaea increase genetic pool by

Answer 5

horizontal gene transfer within the same generation

Question 6

Endosymbiotic Hypothesis

Answer 6

When/how did eukaryotes appear?

Question 7

Endosymbiotic theory:

Answer 7

Primitive prokaryotic microbes ingested other microbes, starting a symbiotic relationship, forming the first basic eukaryotes.

• Ingested microbes that could use oxygen for a respiratory process to produce chemical energy became mitochondria.
• Ingested microbes that could fix carbon dioxide into organic molecules using light energy became chloroplasts.

Question 8

Endosymbiotic theory: Evidences

Answer 8

• SSU rRNA genes show bacterial lineage.
• Genome sequences closely related to proteobacteria and Prochloron, respectively.

Hydrogenosomes.
- Anaerobic endosymbiont.

Question 9

Microbial Species

Answer 9

Eukaryotic microbes fit definition of reproducing isolated populations.

Question 10

Bacteria and Archaea are referred to as strains which are….

Answer 10

• A strain consists of descendants of a single, pure microbial culture.
• May be biovars, morphovars, serovars, and pathovars.

Question 11

Bacteria and Archaea reproduce _____

Answer 11

Asexually

Question 12

Binomial nomenclature.

Answer 12

Genus and species epithet.

Question 13

Assigning Specific Names

Answer 13

Binomial (scientific) nomenclature

Gives each microbe 2 names:
- Genus - capitalized
- species - lowercase

Both italicized or underlined
Staphylococcus aureus (S. aureus)

Inspiration for names is extremely varied and often imaginative!

Question 14

The Origin and Evolution of Microorganisms

Answer 14

Phylogeny: natural relatedness between groups of organisms

Evolution
All new species originate from preexisting species
Closely related organism have similar features because they evolved from common ancestral forms

Evolution usually progresses toward greater complexity

Question 15

Phylogeny

Answer 15

natural relatedness between hroups of organisms

Question 16

Earliest Metabolism

Answer 16

Early energy sources under harsh conditions.
- Inorganics, for example, FeS.

Photosynthesis.
- Cyanobacteria evolved 2.7 billion years ago.
- Stromatolites—mineralized layers of microorganisms.

Question 17

Stromatolites

Answer 17

mineralized layers of microorganisms

Question 18

Energy Sources

Answer 18

Chemicals –>
Chemotrophy –>
Organic–> Chemoorganotrophs–> ATP
or
Inorganic–> Chemolithotrophs–> ATP

Light –>
Phototrophy–>
Phototrophs–> ATP

Question 19

Chemoorganotrophs

Answer 19

Regardless of how they get organic molecules, they are then broken down by microbes to harness chemical energy (A T P).

• Fermentation doesn’t need oxygen but doesn’t yield much energy for microbes.
• Aerobic respiration does require oxygen but yields much more energy!

Question 20

Microbial Ecology

Answer 20

How do microbes interact with the world around them?

Microbes can also help in biogeochemical cycling as they interact with the environment.

• This is a process by which inorganic molecules are cycled to organic molecules and back again.

Question 21

Microbes live in diverse groups in nature, with many different members forming a microbial community and ecosystem.

Name some

Answer 21

• Microbes in the intestines
• Plaque on teeth
• Slime on rocks on beaches
• Mold growths on bathroom surfaces

Question 22

Great Plate anomaly

Answer 22

Microbes will not behave normally in an isolated laboratory environment (replicate, reproduce, feed, etc.), even if food source is present, they work as a community, so when they are isolated from community, they sense something is off.

Question 23

Microbial Biotechnology

Answer 23

Can studying the genetics of microbes help us to use them to benefit humans? YES!

• By altering the genomes of microbes, we can mass-produce molecules that humans want.
• A classic example of this is the production of human insulin by inserting the gene into E. coli cells (done in 19 78 by Genentech in San Francisco).

Question 24

Major Fields in Microbiology

Answer 24

Medical microbiology—diseases of humans and animals.

Public health microbiology—control and spread of communicable diseases.

Immunology—how the immune system protects a host from pathogens.

Microbial ecology is concerned with the relationship of organisms with their environment.

Agricultural microbiology is concerned with the impact of microorganisms on food production.

Food microbiology—microbes used to make food and beverages as well as spoilage microbes.

Question 25

More Microbiology Fields

Answer 25

-Industrial microbiology.
Penicillin and other antibiotics.
Vaccines, steroids, alcohols and other solvents, vitamins, amino acids, enzymes, and biofuels.

-Microbial physiology studies metabolic pathways of microorganisms.

-Microbial genetics, molecular biology, and bioinformatics study the nature of genetic information and how it regulates the development and function of cells and organisms.

–Synthetic Microbiology
Microbes are a model system of genomics.

Question 26

Microbes and Disease

Answer 26

How are microbes associated with disease?

-We didn’t always believe that microbes caused disease or existed around us unseen.

-People used to believe that disease was associated with angry gods or bad air.

-Even when microbes were known to exist, people thought they could spontaneously form as life from nonliving matter (the spontaneous generation theory).

-It took the work of many people to debunk these ideas, but two were very important: Louis Pasteur and Robert Koch.

Question 27

Louis Pasteur

Answer 27

Louis Pasteur performed a simple yet elegant experiment to disprove spontaneous generation theory in the late 1800s.

Question 28

Robert Koch

Answer 28

Robert Koch determined Bacillus anthracis and Mycobacterium tuberculosis were the causes of anthrax and tuberculosis (respectively).

His work with anthrax helped sheepherders and cattle ranchers avoid costly animal losses.

Question 29

Koch’s Postulates

Answer 29

1) the microorganism must be present in every case of the disease but absent from healthy individuals
2) the suspected microorganism must be isolated and grown in a pure culture
3) the same disease must result when the isolated microorganism is inoculated into a healthy host
4) the same microorganism must be isolated again from the diseased host

The basic rules Koch established made it possible for others to determine which microbes caused which diseases. They are still in use to this day

Question 30

Limitations of Koch’s Postulates

Answer 30

some organisms cannot be grown in pure culture (e.g. Mycobacterium leprae)

using humans in completing the postulates is unethical (e.g. Ebola hemorrhagic fever)

molecular and genetic evidence may be used instead

Question 31

20th century disease

Answer 31

In the twentieth century, we have seen a dramatic drop in U.S. deaths from infectious diseases

Question 32

Microbes & Infectious Diseases

Answer 32

Pathogens: Microbes that do harm

Nearly 2,000 different microbes cause diseases

10 B new infections/year worldwide

12 M deaths from infections/year worldwide

Question 33

Where has this reduction in deaths come from?

Answer 33

Prevention of infection through

-Use of antiseptics (Joseph Lister)
-Sanitation improvements (sewage treatment)
-Food/water safety (pasteurization)
-Personal hygiene improvements
-Vaccination

Treatment of infections (antibiotics!)