(BIO 120) Chp 4 Slides Prokaryotic Cells

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Prokaryotes are mainly divided into 2 domains:

1. Bacteria

2. Archaea

Bacteria v.s. Archaea

Similarities

They both have…

• Unicellular

• Circular DNA in a nucleoid (DNA is not enclosed in a nucelus)

• 70S ribosomes

• Reproduce by binary fission

• May have flagella, plasmids, and cell walls

Differences

Feature	Bacteria	Archaea
Cell Wall	Most have peptidoglycan (murein).	No peptidoglycan; may have pseudopeptidoglycan, proteins, or polysaccharides.
Membrane Lipids	Fatty acids linked to glycerol by ester bonds.	Ether bonds link branched isoprenoid chains to glycerol → more stable in extremes.
Ribosomes	70S, sensitive to antibiotics like streptomycin and chloramphenicol.	70S, but proteins and rRNA more similar to eukaryotes. Not affected by many bacterial antibiotics.
RNA Polymerase	One simple type.	Multiple complex types (similar to eukaryotic RNA polymerases).
Genetic Organization	No introns (mostly).	Some genes have introns (like eukaryotes).
Environment	Found almost everywhere (soil, water, inside hosts).	Often extremophiles: halophiles (salt), thermophiles (heat), acidophiles (acid), methanogens (anaerobic).
Pathogenicity	Many pathogenic species (e.g., E. coli, Salmonella, S. aureus).	No known human pathogens.
Examples	Escherichia coli, Staphylococcus aureus, Mycobacterium tuberculosis.	Halobacterium (salt-loving), Methanobrevibacter (methane-producing), Sulfolobus (acid-thermophile).

T or F: Prokaryotic cells ALWAYS have a cell wall.

T or F: Eukaryotic cells have 70S ribosomes, while prokaryotic cells have more at 80S ribosomes.

False

Prokaryotic cells have more —> 70S ribosomes

Eukaryotic cells —> 80S ribosomes

Genetically, which prokaryote — archaea or bacteria — is close to eukaryotes than the other prokaryote.

Genetically, archaea are closer to eukaryotes than to bacteria, even though both are prokaryotic in structure.

________ are highly diverse and medically important because many are pathogens.

Bacteria are highly diverse and medically important because many are pathogens.

________ are unique biochemically, adapted to extreme environments, and provide clues about early life on Earth.

Archaea are unique biochemically, adapted to extreme environments, and provide clues about early life on Earth.

Define “Prokaryote”

Unicellular organisms that lack a nucleus and any other membrane-bound organelle.

2 domains: archaea & bacteria

Name and briefly describe the 2 domains of prokaryotes.

1) Bacteria -

• most medically relevant (bc they make up majority of pathogens)

• cell wall —> contains peptidoglycan

2) Archaea

• often extremophiles (organisms able to live in extreme environments)

• not usually pathogenic

• cell wall —> no peptidoglycan

Prokaryotes reproduced by ______________.

Prokaryotes reproduced by binary fission.

Another term for “binary fission” is “__________________” or “__________________”.

Another term for “binary fission” is “asexual reproduction” or “cell division”.

Name & describe the 3 general shapes of abcteria.

• Coccus: spheres, oval

• Bacillus: cylindrical, rod

• Vibrio: Curved

Pleomorphism

Variations in size & shape among cells of a single species.

Name & describe the various arrangements on coccus-shaped prokaryotes.

Name & describe the arrangements on bacillus-shaped prokaryotes.

Bacilli (rods) divide in one plane and then can separate.

Sinle bacci

Diplobacci — two bacilli

Streptobacci — chain of bacilli

Palisades (less common) — rods lined up parallel or at sharp angles due to snapping division of the bacilli

Coccobacillus — A very short, oval rod that looks like a “fat bacillus” or an elongated coccus.

• Appears intermediate between cocci and bacilli under the microscope.

• Shape: plump, oval rods.

• Arrangement: Usually occur singly, sometimes in pairs.

• Size: Shorter than typical bacilli, but not perfectly round like cocci.

“coccobacillus” literally means coccus-like bacillus.

🔹 Examples of Coccobacilli

• Haemophilus influenzae → causes meningitis, pneumonia.

• Bordetella pertussis → causes whooping cough.

• Brucella species → cause brucellosis (zoonotic infection).

• Chlamydia trachomatis → obligate intracellular coccobacillus.

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🔹 Clinical Relevance

• Many pathogenic bacteria are coccobacilli.

• Because they are hard to classify at first glance (not purely cocci or bacilli), lab tests like Gram stain, culture, and molecular methods are important for identification.

Name & describe the irregular prokaryotic shapes.

What type of shape & arrangement is this?

Streptococci

What type of shape & arrangement is this?

Streptococci

Streptococcus pyogenes is also called “____________”.

Streptococcus pyogenes is also called “Step Group A”.

Streptococcus pyogenes

• also called “Step Group A”

• gram-positive bacteria

• appears as cocci arranged in chains

• causes —> pharyngitis (strep throat)

• major symptom: “strawberry throat” — sore throat w/ red & swollen tonsils

• can progress into scarlet fever if bacteria produces erythrogenic toxin

  • these toxins produce immune reaction that presents as red cheeks & rash

Streptococcus pyogenes

Pathogen

• also called “Step Group A”

• gram-positive bacteria

• appears as cocci arranged in chains

Conditions it causes:

• pharyngitis (strep throat)

• can progress into —> scarlet fever if bacteria produces erythrogenic toxin

  • these toxins produce immune reaction that presents as red cheeks, red tongue, rash

• if untreated —> rheumatic heart fever (RHF) which is leading cause of heart disease in children worldwide

Staphylococcus aureus Folliculitis

• aka S. aureus Folliculitis

• bacterial infection of hair follicles caused by Staph aureus

• presents as:

  • small red bumps

  • pustules/bumps

  • shaving bumps

• treatment:

  • mild cases —> warm compresses

  • severe cases —> topical & oral antibiotics/ointments

• prevention

  • good hygiene

  • handwashing

Stye

• cause: Staphylococcus aureus on eyelid

• what: infected/inflamed skin gland or hair follicle

• presents as:

  • small painful bump on eye

  • redenss

  • swelling

  • tenderness

• treatment:

  • most cases —> condition resolves on its own w/ warm compression

  • severe cases —> antibiotics

_______ divide in one plane, then can separate.

Bacilli divide in one plane, then can separate.

Cocci can divide in different planes (meaning _________) and how they divide determines their _________.

Cocci can divide in different planes (meaning directions) and how they divide determines their arrangement.

_____ is spherical bacteria.

Cocci is spherical bacteria.

If cocci divide in one plane —> they line up in a ______, called __________.

If cocci divide in one plane —> they line up in a chain, called streptococcus.

If cocci divide in two planes —> they form groups of 4, called tetrads.

If cocci divide in two planes —> they form groups of 4, called tetrads.

If cocci divide in three planes —> they form cube-like packets of 8, called sarcinae.

If cocci divide in three planes —> they form cube-like packets of 8, called sarcinae.

If cocci divide in many random planes —> they form grape-like clusters, called staphylococcus.

If cocci divide in many random planes —> they form grape-like clusters, called staphylococcus.

(“staphylo” = cluster).

T or F: Streptococcus pyogenes are cocci in chains (one plane division)

True.

Staphylococcus aureus → cocci in clusters (many plane division).

Staphylococcus aureus → cocci in clusters (many plane division).

T or F: Unlike cocci, bacilli usually divide in one plane.

True. Results in arrangements of singles, pairs, or chains.