Test 3 Intro to Microbiology

What is microbiology?

The study of very small living organisms called microorganisms or microbes.

Name three acellular infectious agents mentioned in the files.

Viroids, prions, and viruses.

Into which two broad cellular groups are microorganisms divided?

Prokaryotes and eukaryotes.

What kingdom are typical bacteria placed in (as per these slides)?

Kingdom Monera.

List two general functions/roles of nonpathogenic bacteria given in the slides.

Soil decomposition and sewage treatment (fermentative & putrefactive).

What is binary fission?

Asexual reproduction in bacteria where a cell copies its circular DNA, grows, and divides into two identical cells.

Give one example of an opportunistic or pathogenic bacterium from the material.

E. coli O157:H7 (example of a pathogenic strain).

What are the primary lab steps for bacterial culture diagnosis mentioned?

Collect swab in transport media, culture on agar plate, and incubate (about 18 hours for growth).

Name two forms unicellular fungi (yeasts) reproduce by.

Budding and occasional spore formation.

Give one pathogenic and one non-pathogenic example of unicellular fungi from the slides.

Pathogenic: Candida albicans. Non-pathogenic: Saccharomyces sp.

How long can fungal cultures take to yield results according to the slides?

Approximately 6–8 weeks for culture results.

What polysaccharide composes fungal cell walls instead of plant cellulose?

Chitin.

What are two examples of diseases caused by multicellular fungi (molds)?

Ringworm and athlete’s foot.

What is a trophozoite?

The active, feeding form of a protozoan.

What is a cyst in protozoa?

A dormant, egg-like form that is commonly the infective stage.

Name one flagellate and one ameba example from the slides.

Flagellate: Giardia lamblia. Ameba example: Dientamoeba fragilis.

Which kingdom includes multicellular parasitic worms like tapeworms?

Kingdom Animalia (Metazoa).

What is the scolex?

The head of a tapeworm, often with hooks or suckers.

How are parasite (metazoa) clinical samples preserved for lab diagnosis?

Placed into a preservative/fixative such as formalin or alcohol.

List three criteria used to classify viruses in the slides.

Genetic material (DNA or RNA), capsid shape, and host infected.

What size range for viruses is given in the files?

About 10–300 nm.

What is a bacteriophage?

A virus that infects bacteria.

Define a viroid as given in the slides.

A short, naked single-strand RNA loop (~300–400 nucleotides) that causes plant disease.

What is a prion?

A proteinaceous infectious particle that deposits in brain tissue and causes neurodegenerative disease.

Name two laboratory methods used for viral diagnosis listed in the files.

PCR (polymerase chain reaction) and serological detection of antigens or antibodies.

What does PCR do in molecular terms?

Amplifies selected sections of DNA or RNA so minute quantities can be analyzed or detected.

What are the five steps of the lytic bacteriophage cycle (names only)?

Attachment (adsorption), penetration, biosynthesis, assembly, release.

Which lytic step involves injection of phage DNA into the bacterial cell?

Penetration.

During which lytic step are phage components produced inside the host?

Biosynthesis.

How does release occur in the bacterial lytic cycle?

Complete phages escape by lysis of the bacterial cell.

List the six steps in multiplication of animal viruses (names only).

Attachment (adsorption), penetration, uncoating, biosynthesis, assembly, release.

What is uncoating in animal virus infection?

The viral nucleic acid escapes from the capsid inside the host cell.

Give two examples of obligate intracellular bacterial-like organisms mentioned.

Rickettsia and Chlamydia.

Why are Chlamydiae called “energy parasites” in the slides?

Because they lack essential enzymes for ATP production and rely on host energy.

What is Mycoplasma notable for regarding cell structure?

It lacks a cell wall.

Give the Mycoplasma species example listed and the disease it causes.

Mycoplasma pneumoniae — causes "walking pneumonia."

Who is considered the “father of microbiology” according to the slides?

Antonie van Leeuwenhoek.

State Koch’s first postulate as given in the slides.

Microorganisms must always be found in similarly diseased animals and not in healthy ones.

State Koch’s postulate that involves re-isolation.

The same microorganism must be re-isolated from the newly diseased host.

What is binomial nomenclature?

A two-part scientific naming: genus (capitalized) and species (lowercase), italicized or underlined (e.g., Escherichia coli).

What taxonomic rank follows Order in the classification list provided?

Family (Order → Family → Tribe → Genus → Species as listed).

Define “strain” in bacterial classification as used in the files.

A population within a species that differs by one or more traits (biochemical, genetic, or antigenic).

Name the major chemical difference between prokaryotic and eukaryotic cells emphasized in the files.

Prokaryotes lack membrane-enclosed nucleus and organelles; eukaryotes have a nucleus and membrane-bound organelles.

What component of the bacterial cell wall is targeted by beta-lactam antibiotics?

Peptidoglycan synthesis (cell wall).

Describe the gross structural difference between Gram-positive and Gram-negative cell walls.

Gram-positive: thick peptidoglycan, contains teichoic acids. Gram-negative: thin peptidoglycan plus an outer membrane with lipopolysaccharide (LPS).

What toxin type is associated with Gram-negative bacteria’s outer membrane?

Endotoxin (LPS is an endotoxin).

Why might old bacterial cultures give misleading Gram stain results?

Old cells can break down and lose crystal violet retention, appearing Gram-negative. Fresh cultures (18–24 h) are required.

List the four reagents (in order) used in the Gram stain.

Crystal violet (primary), iodine (mordant), decolorizer (ethanol/acetone), safranin (counterstain).

What color do Gram-positive bacteria appear after Gram staining?

Blue-purple.

What color do Gram-negative bacteria appear after Gram staining?

Pink-red.

Give two precautions for performing a Gram stain from the slides.

Rinse gently between steps and use fresh cultures (18–24 h).

Name three functions of the bacterial plasma membrane listed in the files.

Site of respiration/energy production, active transport, and contains receptors/attachment sites (e.g., for flagella).

What is the capsule and one of its virulence functions?

A mucilaginous polysaccharide envelope external to the cell wall that resists phagocytosis.

What antigen types are associated with capsule and somatic (O) structure?

Capsular antigen: K or Vi antigen (heat labile). Somatic antigen: O antigen (heat stable, part of LPS).

What is the H antigen?

The antigenic protein component of flagella (heat labile).

Differentiate pili and fimbriae in function terms per the slides.

Pili (longer) are involved in conjugation (DNA transfer); fimbriae (shorter) are for attachment to host cells.

State the ribosome size in bacteria and its subunit composition as listed.

70S ribosomes composed of 50S + 30S subunits.

Define a plasmid according to the material.

A circular, double-stranded DNA that replicates independently from the chromosome and may carry beneficial genes like antibiotic resistance.

What genera are noted as producers of endospores?

Bacillus and Clostridium.

Why must autoclaving be used for sterilization in relation to spores?

Endospores are highly resistant to heat and chemicals; autoclaving (121°C steam under pressure) is required to reliably destroy them.

Name the three basic bacterial shapes given in the slides.

Spherical (cocci), rod (bacilli), and spiral (spirillum/spirochete/vibrio).

What is generation time?

The interval between one bacterial division and the start of the next; time for the population to double.

What are the four phases of the bacterial growth curve in order?

Lag phase, log (exponential) phase, stationary phase, death (decline) phase.

During which growth phase are bacteria most uniform and best for identification/testing?

Log (exponential) phase.

Give one reason bacteria enter stationary phase.

Nutrient depletion leading to balance between new cell production and cell death.

What oxygen classification describes organisms that must have oxygen?

Obligate aerobe.

What oxygen classification describes organisms that can live with or without oxygen?

Facultative anaerobe.

What is a capnophile?

An organism that requires reduced oxygen with increased CO₂ (typically 3–10%).

What percentage of a bacterial cell is water roughly, and why is moisture important?

About 80% water; moisture is required for growth and replication.

Define mesophile, thermophile, and psychrophile with their optimum temperatures.

Mesophile ≈ 37°C; thermophile ≈ 55°C; psychrophile ≈ 10–15°C.

What pH range do most bacteria prefer?

Approximately pH 6–8, with optimum around neutral pH 7.

Name two bacterial enzymes or factors listed that contribute to pathogenicity.

Coagulase (clots plasma) and streptolysin (causes hemolysis).

What is the difference between endotoxins and exotoxins in basic terms?

Endotoxins (e.g., LPS) are part of Gram-negative cell structures; exotoxins are proteins secreted by bacteria—both increase pathogenicity.

Name three mechanisms by which bacteria can acquire new genetic material.

Transformation, transduction, and conjugation.

What is bacterial transformation?

Uptake of naked DNA fragments from the environment by a competent cell, integrating into the chromosome.

What is transduction?

Transfer of bacterial genes from one cell to another via bacteriophage (viral) vectors.

Differentiate generalized and specialized transduction briefly.

Generalized: random DNA fragments packaged into phage heads (many genes possible). Specialized: only certain genes near prophage insertion sites are transferred.

What is conjugation and what structure mediates it?

Direct transfer of DNA from donor to recipient via an F pilus (conjugation bridge) often transferring plasmids.

What does F+, F-, Hfr, and F' signify in conjugation terminology?

F+: cell carries fertility (F) plasmid; F-: lacks F plasmid; Hfr: F factor integrated into chromosome (high frequency recombination); F': plasmid that carries some chromosomal genes after excision.

Give two clinical implications of bacterial gene transfer listed in the slides.

Spread of antibiotic resistance (e.g., MRSA, VRE) and transfer of virulence factors (toxins, capsules).