Microbiology Lec: Quiz 3~ Viruses & Prions, Urinirary Tract, Microbial Metabolism

Q's 1-24=ch. 6; Q's 25 - 56=7; Q's _ - _ =8 Q's _-_= 19

What is a virus?

a noncellular parasite with a definite size, shape, and chemical composition that can infect any type of cell of any class or organism that replicates inside other organisms only

What are the only components of viruses? (2)

nucleic acid (DNA or RNA) and a protein capsid

What is the viral capsid?

The protective protein coating around viruses

What is the nucleocapsid? What is the physical relation to the viral capsid?

A nucleic acid covering for the RNA/DNA inside the viral capsid, this is inside the viral capsid

What is the difference between an enveloped virus and a naked virus?

enveloped viruses have a lipid bilayer covering the protein capsid and naked viruses usually are more virulent

What are the 5 shapes viruses come in?

icosahedral, helical, polyhedral, spherical, and
complex

What is a bacteriophage virus? What is the most common example?

A virus that can infect bacteria and a common example is e.coli

Describe an icosahedral viral shape

a virus with a capsule that is a 20 sided polygon

Describe a complex viral shape and what is a common example?

A viral shape that differs from the common ones and are usually a combination of 2 or more of the forms, a common example is a bacteriophage

What are the major steps of bacteriophage replication? (5)

adsorption, penetration where the viral nucleic acid enters the cell, replication, assembly, maturation, lysis and release of the virus where lysosomes from the virus digest the cell wall 

What is lytic replication cycle reproduction in bacteriophages?

A viral reproduction cycle that ends in the lysis/ death of the host cells and release of a new virus. 

What is the Lysogenic cycle of reproduction in bacteriophages? What is a prophage?

A viral reproduction cycle that results in the phage DNA integrating with the bacterial DNA and generating a prophage that replicates when the bacterial DNA replicates. A prophage is the viral DNA after it integrates into the chromosomes of the host bacteria.

What is phage therapy? What is the importance of phage therapy?

Using bacteriophages to target certain bacteria in the body. It can treat antibiotic-resistant infections with no major side effects

Name two viruses that are associated with cancer? 

Hepatitis B and C are involved in liver cancer.

What are 3 methods used for viral cultivation?

In vitro cell culture, in vivo where you inoculate lab grown animals, and embryonic bird tissue

What is the major difference between animal viral replication and bacteriophage viral replication?

The main difference is in the penetration step. Bacteriophages attach to the cell wall and inject their nucleic acids into the bacteria while animal viruses are fully engulfed by the host cell and then have their envelopes dissolved or fuse their cell membranes with the host’s and inject their nucleic acids that way.

What are the steps in animal viral replication?

absorption, penetration (which could be cell membrane fusion or endocytosis), uncoating, synthesis, assembly, release

How do assembled animal viruses leave the cell?

They leave either by host cell lysis or budding/exocytosis but only if they have an envelope.

What is the cytopathic effect? What are the specific damages to host cells after a viral infection? (4)

Cytopathic effects are virus-induced damage to cells. The damages could be changes in cell size and shape, Cells fusing to form multinucleated cells (known as syncytia), Cell lysis, and having alter DNA that can transform cells into cancerous ones. 

What is the host range?

Viruses can only invade a host cell by making itself an exact fit with the host cell receptor or host cell molecules thereby limited the number of host cells it can infect which is called it’s host range.

What is a retrovirus? Which enzyme is responsible for the conversion of RNA to DNA
in HIV?

single-stranded, enveloped RNA viruses, many of which infect humans. retroviruses convert their RNA to DNA. The enzyme responsible for this is called reverse transcriptase

What is a prion? What is 1 example of a prion caused disease?

an abnormal, pathogenic agents that can induce abnormal folding of specific normal cellular proteins. An example is CJD which comes from eating contaminated meat.

What is virion? What are the components it must have? (4)

Basically a virus when it is outside of a cell , so it is a complete functional virus that has the capacity to infect living tissue. It includes the genetic material, either RNA or DNA, capsid, envelope and membrane proteins

What is a viroid? What do they mainly infect

infectious agents that consist only of naked RNA without any protective layer such as a protein coat. It mainly infects plants

Define Heterotroph

must obtain carbon in an organic form made by other living organisms (proteins, carbohydrates, lipids and nucleic acids)

Define autotroph

an organism that uses CO2, an inorganic gas, as its carbon Source, they are not nutritionally dependent on other living things

Define Chemotroph

A chemotroph is an organism that obtains its energy by oxidizing organic or inorganic chemical compounds

Define phototroph

A chemotroph is an organism that obtains its energy by oxidizing chemical compounds, either organic or inorganic

What are the energy source and the carbon source of a photoautotroph?

Energy= sunlight Carbon= CO2

What are the energy source and the carbon source of a photoheterotroph?

Energy= sunlight Carbon= Organic compounds

What are the energy source and the carbon source of a chemoautotroph?

Energy= inorganic chemicals Carbon= CO2

What are the energy source and the carbon source of a chemoheterotroph?

Energy= organic compounds, Carbon= Organic compounds

Microbial growth occurs at what two levels?

Growth at a cellular level with increase in size and an increase in population

Division of bacterial cells occurs mainly through? Describe the process.

binary fission where parent cell enlarges, duplicates its chromosome, and forms a central transverse septum dividing the cell into two daughter cells

What are the 4 phases of the bacterial colony growth curve?

the lag phase, the log/ exponential phase, the stationary phase, and the death phase

What happens during the lag phase of bacterial colony growth?

bacterial cells make the necessary molecules required for multiplication (examples: enzymes, ribosomes, nucleic acid)

What happens during the log phase of bacterial colony growth?

bacterial cells are dividing at a constant rate

What happens during the stationary phase of bacterial colony growth?

Rate of cell growth equals rate of cell death caused by depleted nutrients and O2

What happens during the death phase of bacterial colony growth?

The period when the total number of live cells in the population decreases as cells die off at a constant rate due to lack of nutrients

Define turbidity as a measure of bacterial population?

Degree of cloudiness in a broth culture that reflects the relative population size

What are two ways to enumerate bacterial colonies on a growth medium? Briefly explain both. 

Viable colony count : count all cells present Direct cell count total cell count-dead and alive, automated or manual

Define generation time and why is it important?

the time it takes for a population of bacteria to double its number through binary fission. It is an important measure for understanding growth rates, which are influenced by factors like temperature, nutrient availability, and waste products.

What are the 3 groups of bacteria based on the pH they can grow in?

Alkalophiles, Neutrophiles, and Acidophiles

Define alkalophile bacteria

bacteria that grows best in a pH above 8.5

Define neutrophile bacteria

bacteria that can grow in a pH of 5-8 but prefers 7

Define acidophile bacteria

bacteria that grow best in a pH below 5.5

Define Psychrophile bacteria

bacteria whose optimum temperature is below 15 degrees C, but is capable of growth at or below 0 degrees C

Define Mesophile bacteria and what is a fact about them

bacteria whose optimum temperature is 20 - 40 degrees C which is most most human pathogens

Define thermophile bacteria

bacteria whose optimum temperature is greater than 45 degrees C

Define obligate aerobes & Where would this group of bacteria be found in a liquid culture?

cannot grow without oxygen; bacteria gather at top of test tube to absorb maximal amount of oxygen

Define obligate anaerobes & Where would this group of bacteria be found in a liquid culture?

lack the enzymes to detoxify oxygen so cannot survive in an oxygen environment; gather at bottom to avoid oxygen

Define facultative anaerobes; Where would this group of bacteria be found in a liquid culture?

utilize oxygen if present but can also grow in its absence; gather mostly at the top, but as lack of oxygen does not hurt them, they can be found all along the test tube

Define Microaerophiles and Where would this group of bacteria be found in a liquid culture?

microbes that require only a small amount of oxygen; gather at upper part of test tube, not at top. Require O2, but at low concentration

Define aerotolerant anaerobes and where would this group of bacteria be found in a liquid culture?

do not utilize oxygen but can survive and grow in its presence; bacteria are not affected by oxygen, and they are evenly spread along the test tube

Define Anabolism

chemical reactions that build larger structural and functional components from smaller molecules. Uses energy

Define catabolism

chemical reactions that break down larger molecules into smaller ones. Releases energy.

What is an enzyme and what role does it play in chemical reactions? What are active sites of enzymes?

Enzymes are biological catalysts, mainly proteins, that speed up chemical reactions by lowering the energy of activation (the resistance to a reaction) The enzyme is not permanently altered in the reaction Enzymes promote a reaction by serving as a physical site for specific substrate molecules to position

What is considered the most accurate model for how enzymes work?

The lock and key model

What are simple enzymes?

enzymes that consist of protein only

What are holoenzymes?

enzymes that consist of a protein portion called an apoenzyme and a non-protein molecule called a cofactor that can be a metallic atom or coenzymes like vitamins

What are exoenzymes? What can they also be refereed to as?

enzymes that are transported extracellularly “out”, where they break down large food molecules or harmful chemicals, Many pathogens secrete exoenzymes that help them evade host Defenses which contributes to the pathogenicity so they are referred to as virulence factors

What are endoenzymes?

retained intracellularly “in” and function there which is the majority of enzymes

What are constitutive enzymes?

an action of enzyme that is always present, always produced in equal amounts, regardless of the amount of substrate

What are regulated enzymes?

an action of enzyme not constantly present; production is turned on (induced) or turned off (repressed) in response to changes in the substrate concentration

Define oxidation in terms of metabolism 

the removal of electrons from a molecule, decreases potential energy

Define reduction in terms of metabolism

the addition of electrons to a molecule, increase potential energy

What is glycolysis and what are the products in exact amounts?

Metabolic pathway that converts glucose to pyruvate that releases 2 ATP, 2 NADH, 2 pyruvate

Where do you expect the electron transport chain will be in bacteria?

In the cell membrane 

What are the two major virulence factors of mycobacterium tuberculosis?

1) contain complex cell wall lipids that prevent destruction by immune cells for example: Mycolic acid gives it defense against the complement system, free radicals and phagocytosis. 2) Cord factor prevents destruction by lysosomes in Macrophages and increases inflammation by forming granulomas

How can we detect Streptococcus pneumoniae in the laboratory?

Strep latex agglutination test

How do you distinguish between Streptococcus groups?

Checking for hemolysis reaction type on a blood agar plate

Which (2) complications would you expect if Group A Streptococcal pharyngitis is untreated?

rheumatic fever and glomerulonephritis (inflammation of the glomeruluses in the kidneys)

What is RSV and what is the major characteristic of the virulence factor?

Respiratory Syncytial Virus and it is a common upper respiratory infection and usually presents like a normal cold in healthy adults. the virulence factor produces giant multinucleated cells or syncytia

What is the final electron acceptor in fermentation?

organic compounds

What is the final electron acceptor in anaerobic respiration?

Oxygen bound to an organic molcule

What is the final electron acceptor in aerobic respiration?

oxygen