Fundamentals of Microbiology and Acellular Agents Review

Comprehensive practice flashcards covering bacterial cell wall structures, archaeal envelopes, cytoskeletal elements, acellular agents, bacteriophage genetics, and historical microbiology milestones.

What are the primary structural components of Gram-positive cell walls?

Gram-positive cell walls are composed primarily of peptidoglycan and may also contain large amounts of negatively charged teichoic acids.

What is the function of exoenzymes secreted into the periplasmic space of Gram-positive bacteria?

Exoenzymes aid in the degradation of large nutrients so they can be transported into the cell.

What three structural parts compose a lipopolysaccharide (LPS) molecule found in Gram-negative cell walls?

Lipid A, core polysaccharide, and O side chain (also known as the O antigen).

Which component of lipopolysaccharide (LPS) is embedded in the outer membrane and acts as an endotoxin?

Lipid A.

What endotoxin detection assay, first reported by Fred Bang in 1956, uses blood cell lysates containing the clotting factor coagulogen?

The Limulus Amoebocyte Lysate (LAL) assay.

What size limit determines which small molecules can pass through porin protein channels in the Gram-negative outer membrane?

Molecules ranging from $600\text{--}700\text{ daltons}$ can pass through porin channels.

How does the Gram stain mechanism prevent the loss of crystal violet in Gram-positive bacteria during decolorization?

Decolorization causes shrinkage of the thick peptidoglycan pores in Gram-positive cells, constricting the wall and preventing the crystal violet-iodine complex from washing out.

Which specific chemical bond in peptidoglycan is cleaved by the enzyme lysozyme?

Lysozyme breaks the glycosidic bond between N-acetylglucosamine and N-acetylmuramic acid.

What term refers to a Gram-positive bacterial cell that has completely lost its cell wall?

A protoplast.

How does pseudomurein in Archaeal cell walls chemically differ from bacterial peptidoglycan?

Pseudomurein possesses $1\rightarrow 3$ glycosidic bonds (instead of $1\rightarrow 4$), contains L-amino acids (instead of D-amino acids), and uses N-acetyltalosaminuronic acid (instead of N-acetylmuramic acid).

What unique lipid linkages and carbon chains distinguish archaeal plasma membranes from bacterial and eukaryotic membranes?

Archaeal membranes contain five-carbon branched isoprene units attached to glycerol via ether linkages rather than ester linkages.

Which bacterial cytoskeletal protein is a tubulin homolog that forms a ring during septum formation in cell division?

FtsZ.

Which actin homolog helps determine cell shape in rod-shaped bacteria by positioning peptidoglycan synthesis machinery?

MreB.

What organelle in Planctomycetes serves as the site for anaerobic ammonium oxidation, converting $\text{NH}_4^+ + \text{NO}_2^-$ into $\text{N}_2 + 2\text{H}_2\text{O}$?

The anammoxosome.

Which cytoskeletal protein is responsible for forming and organizing magnetosome chains in magnetotactic aquatic bacteria?

MamK.

What additional ribosomal RNA component is found in the large subunit of Archaeal ribosomes that is absent in Bacteria?

The 5.8S rRNA subunit.

What synthetic organism was created by J. Craig Venter, and how many total genes make up its minimal genome?

Mycoplasma mycoides JCVI-syn1.0, which contains 473 total genes in its minimal genome.

What are the four main groups of acellular biological agents and their minimal compositions?

Viruses (protein and nucleic acid), viroids (RNA only), virusoids (RNA only), and prions (protein only).

What genetic alteration in the PRNP gene on chromosome 20 is characteristically associated with Gerstmann-Sträussler-Scheinker syndrome?

A codon change from proline to leucine at position 102 (codon 102).

Which human prion protein variant conferred strong protection against kuru in the Fore population of Papua New Guinea?

The G127V variant of the human prion protein.

What roles do hemagglutinin and neuraminidase spikes play in the life cycle of the influenza virus?

Hemagglutinin functions in attachment to host cell receptors, while neuraminidase functions in enzymatic activity and virion release.

What three primary methods do animal viruses use to enter host cells?

Fusion of the viral envelope with the host cell membrane, receptor-mediated endocytosis into vesicles, and direct injection of nucleic acid.

What is an integrated bacteriophage genome within a lysogenic host chromosome called?

A prophage.

By what strategies do bacteriophages solve the lagging-strand primer problem at the ends of linear DNA molecules?

They synthesize single-stranded circular DNA, utilize protein primers, rely on terminal redundancies, or form hairpin ends resolved by protelomerases.

In the T7 pET expression system, what molecule acts as a mimic of allolactose to induce host T7 RNA polymerase expression?

Isopropyl \beta-D-1-thiogalactopyranoside (IPTG).

What three phage proteins cooperate to control and execute bacterial host cell lysis?

Lysozyme (degrades the peptidoglycan cell wall), holins (form membrane pores), and antiholins (regulate the timing of lysis).

Who constructed the first compound microscope and introduced the term 'cell' in the 1665 book Micrographia?

Robert Hooke.

Who was the first person to observe microscopic single-celled organisms, which he termed 'animalcules'?

Antonie van Leeuwenhoek.

What molecular sequence did Carl Woese use to divide cellular life into the three domains Bacteria, Archaea, and Eukarya?

The 16S rRNA gene sequence.

Which bacterial species undergoes multicellular differentiation to form fruiting bodies upon sensing food scarcity?

Myxococcus.

According to the endosymbiotic theory, which ancestral bacterial lineages were internalized to give rise to mitochondria and chloroplasts?

Mitochondria descended from ancestral Rickettsiae, and chloroplasts descended from ancestral Prochlorococcus (cyanobacteria).

How did Louis Pasteur's swan-necked flask experiment disprove the theory of spontaneous generation?

The swan-necked flasks allowed air access to boiled broth while trapping micro-organisms in the neck bend; broth remained sterile until the neck was broken, demonstrating micro-organisms originate from airborne microbes.

What are Koch's four postulates used to establish the cause of an infectious disease?

1. The microbe must be present in every case of disease and absent in healthy individuals. 2. The microbe must be isolated and grown in pure culture. 3. Inoculation of the isolated microbe into a healthy host must cause the same disease. 4. The same microbe must be re-isolated from the newly diseased host.

What discovery did Barry Marshall make in 1984 by fulfilling Koch's postulates?

He proved that Helicobacter pylori is the causative agent of stomach ulcers (gastritis).

What is the global estimate for the total number of microbial cells on Earth?

Approximately $5 \times 10^{30}$ cells.