BIOL 112: Exam 2

How does horizontal transmissions in plant viruses occur?

A virus (may come from pollen, another plant, vectors) enters through a damaged part of a plant’s cell wall

How does vertical transmission in plant viruses occur?

The parent plant transmits the virus to its offspring

What are some symptoms of plant viruses?

Hyperplasia, hypoplasia, or necrosis

What is hyperplasia?

Abnormal, uncontrolled cell growth

What is hypoplasia?

Decreased cell growth

What is necrosis?

Premature cell death

What kind of viruses are most plant viruses?

Single-stranded RNA viruses

Do animal viruses have to penetrate a cell wall to gain access to a host cell?

No

What is an acute disease?

When symptoms get increasingly worse for a short period of time, but then the immune system eliminates the virus and the body recovers

Give an example of an acute disease.

The common cold and flu

What is a chronic infection?

A long-term viral infection

Give an example of a chronic infection.

Hepatitis C

What is an oncogenic virus?

A virus that can cause cancer

Give an example of an oncogenic virus.

HPV

What are intermittent symptoms?

Symptoms that alternate between periods of severity and complete relief

Give an example of a virus that causes intermittent symptoms.

Herpes simplex virus

What is an asymptomatic infection?

A virus that causes productive infections without causing any symptoms in the host

Give an example of an asymptomatic infection.

Human herpesviruses 6 and 7

What is the primary method of controlling viral disease?

Vaccination

What components of a virus are used to make live and killed vaccines?

The entire virus

What components of a virus are used to make molecular subunit vaccines?

Only the antigenic parts of a virus

How are live vaccines usually made?

By attenuating the wild-type virus

What does attenuating mean?

To weaken

Who developed the mRNA vaccines and when?

Katalin Kariko and Drew Weissman during COVID

What drugs do not kill viruses and why?

Antibiotics, because they are designed to kill bacteria

What is the main criteria for antiviral drugs?

The targeted viral proteins must be encoded by viral genes and cannot be present in a healthy host cell

How does Tamiflu work?

It inhibits an enzyme called neuraminidase (NA), which stops the flu virus from detaching from the host cell and infecting new cells

What are prions (proteinaceous infectious particles)?

Particles that are smaller than viruses, contain no DNA and RNA, and cause fatal neurodegenerative diseases

Are prions destroyed by cooking?

No

How do abnormal prions affect normal prions?

Abnormal prions (misfolded versions of normal proteins) induce abnormal folding in normal prion proteins

What are viroids?

Small circles of RNA that infect plants and can cause crop failure

Rank bacteria, viruses, prions, and viroids from smallest to largest.

Viroids, prions, viruses, bacteria

Who is credited with discovering the techniques for pure culture, staining, and growth media?

Robert Koch

What is a culture medium?

A solution that contains all of the nutrients needed by the target microorganism, can be liquid or solid

What is a pure culture?

A laboratory culture containing a single species of microogranism

What is inoculation?

The process of introducing a microorganism into media

What are Robert Koch’s 4 postulates to prove a causal relationship between a microorganism and an individual?

1. The microorganism must be found in abundance in all organisms suffering from the disease, but not in healthy organisms

2. The microorganisms must be isolated from a diseased organism and grown in pure culture

3. The cultured microorganism should cause disease when introduced in a healthy organism

4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as identical to the original, contagious microorganism

What cells can only be seen under an electron microscope?

Prokaryotes (bacteria and archaea)

What cells can be seen under a light microscope?

Eukaryotes

What are the 3 main categories of prokaryotic shape?

Cocci, bacilli, and spirilli

What are the characteristics of cocci?

Spherical or round

What are the characteristics of bacilli?

Rod-shaped

What are the characteristics of spirilli?

Spiral-shaped

Do prokaryotes usually appear alone or in aggregates?

Aggregates

What are the 4 common structures found in all cells?

Plasma membrane, cytoplasm, DNA, and ribosomes

Who developed gram-staining and when?

Hans Christian Gram in 1882

What is gram-staining based on?

Differences in cell wall composition in bacteria

What is gram-positive bacteria?

Bacteria with a thick peptidoglycan layer

What color does gram-positive bacteria appear when stained?

Purple

What is gram-negative bacteria?

Bacteria with a thin peptidoglycan layer and an outer lipopolysaccharide layer

What color does gram-negative bacteria appear when stained?

Pink

What is a capsule/slime layer in a prokaryote made out of?

Sticky carbs and proteins that are secreted outside the cell wall

What is the function of capsule/slime layer’s in a prokaryote?

Sticks cells together or to a surface, resists attacks from the immune system, and holds in moisture

What is the function of fimbriae (short pili) in a prokaryote?

Help cells stick to surfaces and to each other

What does a sex pilus do?

It pulls two bacteria cells together and forms a mating bridge for DNA transfer (conjugation)

What is taxis in the context of prokaryotes?

Movement directed toward (positive) or away (negative) from stimulus

What is chemotaxis?

Movement away from or toward a chemical

What is phototaxis?

Movement away from or toward a light source

What is geotaxis (magnetotaxis)?

Movement away from or toward a magnetic field

What are plasmids in prokaryotes?

Extra tiny DNA rings with a few genes that replicate independently

What are the 5 fundamental differences between bacteria and archaea?

Plasma membranes, cell walls, DNA replication, gene expression, and 16S rRNA sequences

How are bacteria and archaea plasma membranes different?

Bacteria plasma membranes are formed by unbranched lipids that use ester bonds. Archaea membranes are formed by branched lipids on the glycerol skeletons with ether linkages.

What compound in an archaea’s cell membrane allows it to withstand high temperatures?

Tetraether polymer

What are photoautotrophs?

Prokaryotes that get their energy from sunlight and their carbon from CO2

What are photoheterotrophs?

Prokaryotes that get their energy from sunlight and their carbon from organic compounds

What are chemoheterotrophs?

Prokaryotes that get both their energy and carbon from chemical sourcesW

What are chemolithoautotrophs?

Prokaryotes that get their energy from inorganic compounds and build their complex molecules from CO2

What is symbiosis?

When two species live in a close relationship

What does it mean when two species are free-living?

They are not in symbiosis

What is parasitism?

When a small parasite benefits at the expense of the host species

What is commensalism?

When one species benefits without any good/bad impact on the other species

What is mutualism?

When both species benefit from each other

What are the 4 roles of prokaryotes in the ecosystem?

They are decomposers, produce O2, and play roles in both the carbon and nitrogen cycle

What bacteria are the most important decomposers on Earth?

Chemoheterotrophic bacteria

What was the ancient atmosphere like?

Anoxic, it had no molecular oxygen

What organism began oxygenation in the ancient atmosphere?

Cyanobacteria

What does conjugation require?

The presence of F plasmid in the donor

What is the F plasmid in a bacteria?

It contains all of the materials required to make a pilus for conjugation

What are endospores?

Structures that are formed inside bacteria under high-stress conditions that can lay dormant and survive heat/drought for years

What are the 5 groups under the domain bacteria?

Proteobacteria, chlamydias, spirochetes, cyanobacteria, and gram-positive bacteria

What are the 5 taxa in proteobacteria?

Alpha, beta, gamma, delta, and epsilon

What are some important characteristics of proteobacteria?

Gram-negative, diverse metabolism, most are nitrogen-fixing, includes common gastrointestinal pathogens

What are some examples of proteobacteria?

Salmonella, E. coli, vibrio cholerae

What are some important characteristics of chlamydias?

Gram-negative and all are endoparasites (they live inside animal cells)

List an example of chlamydias.

Chlamydia trachomatis (causes pelvic inflammatory disease)

What are some important characteristics of spirochetes?

Gram-negative, are spiral shaped, many are free-living but can also be pathogens

What are some examples of spirochetes?

Syphilis and Lyme disease

What are some important characteristics of cyanobacteria?

Gram-negative, generate oxygen with photosynthesis, some are nitrogen-fixers, blooms can create toxins

What are some examples of cyanobacteria?

Blue-green algae

What are some important characteristics of gram-positive bacteria?

They are decomposers in the soil

What are some examples of gram-positive bacteria?

Staphylococcus aureus (staph infection) and streptococcus (strep throat)

What do pathogenic bacteria secrete?

Exotoxins

What are endotoxins?

Toxic outer membranes of some gram-negative bacteria

What are endotoxins made of?

Lipopolysaccharide

What are saprobes?

Subtypes of heterotrophs that absorb nutrients from dead organisms or their wastes

What are mixotrophs?

Organisms that combine photosynthesis and heterotrophy to get energy