Microbiology and Cell Biology: Key Concepts and Organisms

Salmonella

A type of bacteria that can cause food poisoning and illness.

Streptococcus

A type of bacteria that grows in chains or groups; some types cause strep throat.

Saccharomyces

A type of yeast (fungus) used to make bread and alcoholic drinks.

Penicillin

An antibiotic originally discovered from a mold; it kills or stops the growth of certain bacteria.

Trypanosoma

A single-celled parasite that can cause diseases such as African sleeping sickness.

What is the most likely pathogen if a throat swab reveals spherical bacteria growing in chains?

Streptococcus pyogenes.

Which organism is used to ferment malt sugars into beer?

Saccharomyces cerevisiae.

What is the total magnification achieved with a 10X ocular lens and a 40X objective lens?

400X.

How can an unstained bacterial smear be made visible under brightfield illumination?

By applying contrast dyes such as crystal violet or safranin.

Which staining reagents provide electron density for transmission electron microscopy?

Osmium tetroxide (OsO4) and lead citrate.

What happens if the electron beam is fired while ambient air remains in the column?

Air molecules scatter the electrons, distorting or destroying the image.

Which instrument is required to resolve the tail fibers of a 60 nm T-even bacteriophage?

Transmission electron microscope (TEM).

What instrument is standard for performing a manual erythrocyte count on red blood cells?

Light microscope (LM).

What does the Svedberg (S) unit measure?

Sedimentation rate in a centrifugal field.

After centrifuging a bacterial culture, which portion must be kept to harvest an extracellular enzyme?

The liquid supernatant at the top.

Which layer from a centrifuged blood specimen should be harvested to measure circulating antibodies?

Liquid plasma layer on top.

What method should be used to sterilize heat-sensitive peptide antibiotics?

Membrane filtration collecting the sterile permeate (filtrate).

Which filter pore size is appropriate to retain fungi while allowing bacteria to pass through?

3.0 μm.

Which molecular target must be sequenced to classify an unculturable single-celled organism?

Ribosomal RNA (rRNA).

Which cells will have their protein synthesis blocked by an antibiotic that inhibits the 16S rRNA?

Bacteria and Archaea.

Which organism will be inhibited by a compound disrupting formylmethionine during translation initiation?

Escherichia coli.

What structures contain circular DNA unassociated with histone proteins and divide by binary fission?

Mitochondria and chloroplasts.

By which process did ancestral nucleated host cells internalize primitive bacteria?

Endocytosis.

Which cycle must a therapeutic phage follow to clear an antibiotic-resistant infection?

Strictly lytic cycle.

What agent is responsible for potato crops showing severe stunting and cracking?

Potato spindle tuber viroid (PSTVd).

What is the cellular outcome of human germ cells completing meiosis?

Four genetically distinct haploid daughter cells.

Which two domains encompass all unicellular prokaryotic organisms?

Bacteria and Archaea.

What term describes the lighter liquid or material that remains on top after centrifugation?

Supernatant.

Amoeba proteus is which type of microorganism?

Unicellular eukaryotic protozoan.

E. Coli is?

Unicellular prokaryote.

What happens immediately after the viral DNA is injected into the host cell during the lytic cycle of bacteriophage?

Viral DNA circularizes.

During which phase of Meiosis does crossing over occur?

Prophase I.

Eukaryotic mitochondria and chloroplasts share which specific genetic characteristics with prokaryotic cells?

Circular DNA structures.

What visual characteristics give Penicillium its genus name?

Tuftlike or paintbrush appearance.

Where did the genus Streptococcus get its name from?

Appearance of its cells growing in chains.

Which cellular process is responsible for the continuous renewal of skin and hair roots?

Mitosis.

In the cell membrane of Archaea, branched carbon chains are attached to the glycerol by which specific chemical bond?

Ether linkage.

In the lysogenic cycle, what is the term for viral DNA once it has integrated into the bacterial host's chromosome?

Prophage.

Instead of glass lenses, what does an electron microscope focus on?

Electromagnets.

Prions are unique infectious agents because they are composed of what?

Misfolded proteins.

Eukaryotic organelles like mitochondria and chloroplasts replicate through which process?

Binary fission.

The endosymbiotic theory primarily explains the evolutionary origins of which two cellular structures?

Mitochondria and chloroplasts.

Amoeba is classified biologically as a unicellular eukaryotic member of which group?

Protozoan.

What does the specific epithet chrysogenum in Penicillium chrysogenum refer to?

Ability to produce penicillin.

What is the Svedberg unit (S) utilized to measure?

How fast a particle sediments in a centrifugal field.

Transduction is a form of horizontal gene transfer that requires which biological agent?

Bacteriophage.

Viroids are non-cellular infectious agents composed exclusively of what type of molecule?

RNA.

What are the respective sizes of the large and small subunits that make up a prokaryotic 70S ribosome?

50S and 30S.

What biological characteristics does the genus name Saccharomyces describe?

Fungus that uses sugar.

What does the specific epithet enterica indicate about the bacterium Salmonella enterica?

Typically found in intestines.

What does the specific epithet pyogenes in Streptococcus signify?

Forms pus.

What is the approximate limit of resolution for an unaided human eye?

200 micrometers.

What is the final cellular outcome of a complete meiotic division from a single starting cell?

Four genetically unique haploid cells.

What is the meaning of the specific epithet cerevisiae in Saccharomyces?

Makes beer.

What is the primary biological function of histone proteins in eukaryotic cells?

Pack DNA tightly inside the nucleus.

What is the primary biological purpose of meiosis in humans and higher plants?

To produce gametes for sexual reproduction.

What is the process of reducing the chromosome number in half to create sperm and egg cells?

Meiosis

What is the primary function of centrifuge sedimentation?

Accelerate normal gravitational setting

What is total magnification achieved with a 10X ocular lens and 100X immersion oil objective lens?

1,000X

What is the ultimate outcome for the host cell at the completion of the bacteriophage lytic cycle?

Bursts (lyses) and releases new active viruses

What structural feature is described by the roots of the genus Trypanosoma?

corkscrew ; borer or auger

What type of lenses does a standard light microscope utilize to magnify specimens?

Convex glass lenses

What will happen if a water sample containing a dangerous 100 nm bacterium is filtered using a membrane filter with a 450 nm pore size?

Bacterium will easily pass through the filter

When a sample of human blood is properly centrifuged, which distinct layer forms directly between plasma and the RBC?

Buffy coat

Which small subunit rRNA molecule is utilized as a genetic marker for eukaryotes?

18S rRNA

Which amino acid serves as the first amino acid during protein synthesis in the domain Archaea?

Methionine

Which conserved genetic marker is located within the small subunit of prokaryotic ribosomes?

16S rRNA

Which distinct amino acid is uniquely utilized as the starting amino acid during protein synthesis in Bacteria?

Formylmethionine

Which domain of life consists of unicellular organisms commonly recognized as extremophiles?

Archaea

Which epidemiologist is honored by the specific epithet of the protozoan Trypanosoma cruzi?

Oswaldo Cruz

What event occurs during binary fission immediately following DNA replication and cell elongation?

Cross-wall forms to completely separate the two DNA copies

Which heavy metal compounds are frequently applied as stains in electron microscopy?

Osmium tetroxide and lead citrate

Which horizontal gene transfer process relies on direct, cell-to-cell transfer of DNA using pili?

Conjugation

Which mechanism of horizontal gene transfer occurs when a bacterium takes up naked, free-floating DNA?

Transformation

Which microbiologist is honored by the genus Salmonella enterica?

Daniel Salmon

What is the typical resolution range of a standard light microscope?

200 nm to 10 mm

Which cells would be successfully trapped by a membrane filter equipped with a 450 nm pore size?

1000 nm cell

Which dyes are commonly used to provide contrast for colorless specimens viewed under a light microscope?

Crystal violet and safranin

Which entities completely lack histone proteins for packing genetic material?

Bacteria

Which neurological disease is caused by prion infection in humans?

Creutzfeldt-Jakob disease

What physical cellular process enabled large ancestral cells to engulf smaller prokaryotes?

Endocytosis

Which specific agricultural disease is directly caused by a viroid?

Potato Spindle Tuber

Which two subunits combine to form the larger 80S ribosome in eukaryotic cells?

60S and 40S

What type of chemical linkage attaches straight carbon chains to glycerol in cell membranes?

Ester linkage

Which universal cellular structure performs protein synthesis across all three domains of life?

Ribosomes

Why must an electron microscope operate under a strict vacuum?

Prevent air molecules from scattering the electrons

fanny hesse

founder of agar ; a jelly-like polysaccharide extracted from red algae that serves as a solidifying agent