Final Exam - Study Guide and Practice Questions

What is the difference/similarity between a bacteriophage and a virus?

Virus is the general class of an organism

Phage is a subclass of virus that infects bacteria

How big is a typical bacteriophage or virus?

MUCH smaller than the cell it infects; most are 30 to 300 nm (bacteria average 1000 nm in diameter)

What is the basic structure of a bacteriophage or virus?

Nucleic acid surrounded by protein capsid

What types of nucleic acids are present in their genomes?

All varieties - ssDNA, dsDNA, ssRNA, and dsRNA

What steps are involved in the reproductive cycle of a T4 lytic phage?

Early - takeover of host cell machinery

Middle - replication of phage genome

Late - capsomer production, capsid assembly, genome packaging, and host cell lysis

What is happening during the latent period of a phage lytic infection?

No increase in the number of phage-forming units = early and middle functions; PFU only increase during packaging

What is involved in the reproductive cycle of a lambda lysogenic phage?

Most phage go into lytic cycle, some go into lysogenic cycle where phage gene expression is silenced and the phage DNA is inserted into the host chromosome

The phage DNA is replicated along with the host DNA during all ‘LYSOGEN’ cell growth and division; eventually, the ‘PROPHAGE’ can be induced, it exits the host chromosome and starts the lytic cycle anew

How can you measure the abundance of bacteriophages?

Plaque assay: spread phage sample on plate along with many host cells, and incubate to get bacterial lawn; count the number of clear spots where cells were lysed = plaques (each plaque derived from one phage particle)

What is involved in the reproductive cycle of a retrovirus?

ssRNA is used as template to produce dsDNA by REVERSE TRANSCRIPTASE

• DNA inserts into host cell chromosome by INTEGRASE

• HIV genes are expressed from that PROVIRUS to produce mRNA, which is also the positive (+) strand RNA assembled into viral particles

• Translation produces polyprotein, which is cleaved into individual viral protein components by HIV protease

What is an enveloped virus and what types of molecules make up the envelope?

A virus that has a membrane surrounding the nucleocapsid, generally infecting animal cells

The envelope contains lipids from the host cell cytoplasmic membrane plus viral ‘spike’ proteins that were inserted into that membrane during viral growth

What is the difference between ‘RNA replicase’ and ‘reverse transcriptase’?

RNA-directed RNA synthesis vs. RNA-directed DNA synthesis

How do influenza viruses undergo antigenic shift?

They acquire as significantly different gene encoding one of the two major antigens (H or N) when a single cell is infected by two different influenza virus strains—this can happen only because of the Influenza genome is made up of 8 separate RNA molecules, each encoding a different protein

What is a viroid?

An infectious RNA molecule, infecting plants, that does not encode any protein

What is a prion?

An infectious protein molecule that is not produced from any infectious nucleic acid; the gene is in the hos chromosome, and the protein is only infectious when it is improperly folded and able to catalyze the further misfolding of host-produce proteins

What is positive (+) strand RNA?

mRNA

What is negative (-) strand RNA?

The complement of mRNA, which can be used as a template by RNA replicase to produce positive strand RNA

What is the structure of the human airways?

What size particles can enter the alveoli of the lungs and how does this help prevent airborne infections?

What is the appearance of a strep throat infection and which tissues in the throat are involved?

Where does a diphtheria infection occur in the body?

Why is diphtheria toxin so deadly (what does it do to host cells)?

Where does a pertussis infection (whooping cough) occur in the body?

What aspect of whooping cough is so deadly to infected infants?

How common are TB infections in people around the world?

What cells in the body are infected by TB bacteria?

In what organ is the level of infection highest and in what part of that organ are the most bacteria found?

What does measles look like in humans? What are some of the long term and sometimes life-threatening consequences that can occur from these infections? What vaccines are used to prevent these infections?

What does rubella look like in humans? What are some of the long term and sometimes life-threatening consequences that can occur from these infections? What vaccines are used to prevent these infections?

What does mumps look like in humans? What are some of the long term and sometimes life-threatening consequences that can occur from these infections? What vaccines are used to prevent these infections?

What does chicken pox look like in humans? What are some of the long term and sometimes life-threatening consequences that can occur from these infections? What vaccines are used to prevent these infections?

What are the symptoms of colds and flu and how are these infections spread from person to person? Which one occurs at higher frequency?

How do flu viruses use infections in pigs and birds to change their antigens on a yearly basis?

What does a flu pandemic look like if you draw it on a map showing the spread of the disease?

What are perishable foods?

Fresh foods (highest water content)

What are semi-perishable foods?

Potatoes and nuts

What are stable or non-perishable foods?

Flour and sugar (least water content)

What are common ways that foods can be prepared to improve their shelf-life?

Acidity (pickling)

Drying, or add sugar or water to reduce water activity

Chemical preservatives

Canning

Irradiation

Pasteurization

What is food poisoning?

Intoxication means microbe grew in the food and produced a toxin; the microbe may or may not survive ingestion, but the toxin still acts (generally ‘self-limiting’)

What is food infection?

Microbe is in the food but then grows inside body (once consumed)

How is an enterotoxin the same or different in comparison to endotoxins and exotoxins?

What are main characteristics of food poisoning caused by Staphylococcus aureus?

Heat stable enterotoxins

Nausea, vomiting, diarrhea (1-6 hours)

• Egg/meat salads, salad dressing, desserts, meat, improper heating/chilling

What are main characteristics of food poisoning caused by Clostridium perfringens?

Spore former (can survive cooking)

>10^8 cells ingested, sporulation occurs in small intestine

Produces CPE (C. perfringens enterotoxin)

Diarrhea and cramps (7-15 hours)

• Chili, salads containing meat, improper heating/chilling

What are main characteristics of food poisoning caused by Clostridium botulinum?

Spore former (can survive cooking)

Botulinum toxin (heat labile), cosmetic applications

Few cases, but high mortality

Paralysis (18-24 hours)

Treatment with ventilation and antitoxin

Where can organisms—such as Staphylococcus aureus, Clostridium perfringens, and Clostridium botulinum—be found naturally and how do they end up in food products?

Staph is on your hands

Clostridia spores are everywhere

How does botulism toxin work?

What are main characteristics of food infection caused by Listeria monocytogenes?

What are main characteristics of food infection caused by Norovirus?

Where can infant botulism be found naturally and how do they end up in food products?

Often from honey, can be environmental

Due to immature immune system and immature intestinal flora

Hypotonia

Treatment with ventilation and tube feeding

Generally self-limiting (3-6 weeks)

Where can Listeria monocytogenes be found naturally and how do they end up in food products?

Found in many water and soil samples, contamination during food processing

Meat, dairy products, and fresh produce

Acid and salt tolerant; psychrotolerant

Most infections are minor and not even recognized

Acute disease rare, but deadly (bacteremia and meningitis)

Intracellular pathogen

Polymerizes host cell actin to drive motility, breaks from one cell into another

Where can Norovirus be found naturally and how do they end up in food products?

RNA virus; stomach flu or viral gastroenteritis

Fever, chills, headache, muscle aches

Self-limiting (1-2 days)

Highly contagious and passed via contact with infected people or contaminated surfaces or food

How are bacteria used to help leach copper metal from crude ores? What chemicals are added to the ore and at what stage do the bacteria play an important role?

What is the toxic chemical produced in most acid mine drainage from coal mine? How is the chemical made and what metal plays an important role?

How are bacteria used to remove uranium from contaminated environments? What property of uranium ions is important in the process?

Why was the Valdez oil spill in Alaska so difficult to clean up? What metabolic property of bacteria is used in the clean-up process?

How is the organic pollutant 2,4,5-T broken down by bacteria? What products are made from the breakdown?

Give an example of a difficult plastic to break down and one that is easy to break down using bacterial action.

In wastewater treatment, how many stages are there? What takes place at each stage?

What are the two types of secondary treatment in wastewater treatment, and how do they differ from one another?

What process (its name) is used to remove NH4+ from wastewater? What is the NH4+ converted to that is not toxic to the environment?

What chemical is added to water to kill most bacteria remaining after treatment?

How is water distributed to a town and how is water pressure maintained even if the electricity is shut down?