Chapter 4.3 Bacterial Cytoplasmic Structures

What is the cytoplasm and what is its consistency like?

an aqueous environment inside the cell that supports cellular processes. Its consistency is gel-like, closer to a gel than a typical aqueous solution.

What is the primary function of cytoplasm in bacterial cells?

the site for ALL metabolic reactions in bacteria because they lack the membrane-bound organelles found in eukaryotes.

What is the chemical composition of bacterial cytoplasm?

Mostly water (70-80%) with a mixture of monosaccharides, small polysaccharides, amino acids, small peptides, ions, salts, and various nutrients.

What structures are suspended within the bacterial cytoplasm?

• DNA (chromosome)

• ribosomes

• granules

• cytoskeletal elements

How many chromosomes do bacteria typically have, and what is their structure?

Bacteria typically have ONE large, circular, double-stranded chromosome (unlike eukaryotes which have multiple linear chromosomes).

What is the nucleoid?

a specific area of the cytoplasm where the bacterial chromosome is typically located. It is not membrane-bound like a eukaryotic nucleus.

How does the bacterial cell package its large chromosome?

by wrapping around specialized proteins, making the packaging more efficient (chromosome is ~1000x larger than the cell).

What are plasmids?

small, circular, double-stranded DNA molecules that are separate from the main chromosome and contain non-essential genes.

What are three advantages of plasmids for bacteria?

• Can be gained or lost without affecting normal cellular processes

• Can be replicated and passed to offspring

• Can provide genes for virulence factors.

What types of virulence factors can plasmids carry?

Genes for making capsules, fimbriae for attachment, and antibiotic resistance genes.

Give an example of how plasmids are used in biotechnology.

Most insulin for type 1 diabetics is produced by bacteria genetically engineered with plasmids containing human insulin genes.

What is the primary function of ribosomes?

they translate messenger RNA (mRNA) into proteins by assembling amino acids into polypeptide sequences.

What are ribosomes made of?

ribosomal RNA (rRNA) and specialized proteins

Are ribosomes the most or least numerous organelles in cells?

Ribosomes are the MOST numerous organelles in any cell.

What are Svedberg units (S) and what do they measure?

measure the density of an object and where it settles during centrifugation, rather than weight or mass.

Size of bacterial ribosomes

70S

Size of eukaryotic ribosomes

80S

What are the two subunits of bacterial ribosomes?

• Small subunit (30S)

• large subunit (50S)

Can ribosomal subunits function individually?

No, individual subunits have no function at all. Only the complete ribosome can translate mRNA into proteins.

Why can't you simply add the Svedberg units of subunits to get the total?

Because Svedberg units measure density, not mass, so the sizes cannot be simply added together.

What proteins make up the bacterial cytoskeleton?

Proteins that behave very much like eukaryotic actin, arranged in helical ribbons around the cell.

What are the two main functions of the bacterial cytoskeleton?

• Move materials within the cytoplasm

• Contribute to the shape of the bacteria

How is the bacterial cytoskeleton arranged within the cell?

The proteins are arranged in helical ribbons around the cell, just under the cell membrane.

What are endospores?

Highly specialized, extremely resistant structures made by select bacteria to protect their DNA from environmental conditions that would kill the living cell.

Which two bacterial genera are known to produce endospores?

Bacillus and Clostridium.

What are the two stages in the life cycle of endospore-forming bacteria?

• Vegetative cell

• Endospore (protective, dormant structure).

Vegetative cell stage

living, metabolically active

Endospore stage

protective, dormant structure

Define sporulation.

the process by which a vegetative cell creates an endospore when environmental conditions become hostile.

Define germination in the context of endospores.

the process by which an endospore develops into a new active vegetative cell when favorable conditions return.

What environmental conditions can trigger sporulation?

Extremely hot or cold temperatures, lack of water, increased UV radiation, and exposure to harmful chemicals.

What initiates endospore germination?

The absorption of water by the endospore, which activates a germination agent inside the spore.

What is the cortex and why is it important?

the tough coating that makes endospores resistant to harsh environmental factors.

Enzymes must digest it during germination.

Name five diseases caused by endospore-forming bacteria.

• Anthrax (Bacillus anthracis)

• Tetanus (Clostridium tetani)

• Pseudomembranous colitis (Clostridium difficile)

• Gas gangrene (Clostridium perfringens)

• Botulism (Clostridium botulinum)

What environmental factors can endospores resist?

Heating, drying, freezing, radiation, and chemicals.

Why are endospores problematic in laboratory settings?

Many normal sanitization techniques are ineffective against endospores, and they can contaminate laboratory media and cultures.

Why are endospores a concern in hospitals?

Hospitals must protect wounds (pre-existing or surgical) from endospore exposure, and endospores resist ordinary cleaning methods.

Why are endospores important in the food canning industry?

they can survive normal food processing and cause spoilage or foodborne illness, so their destruction is critical for food safety.

Why don't bacteria need membrane-bound organelles like eukaryotes?

all bacterial metabolic reactions occur in the cytoplasm, eliminating the need for compartmentalization.

How does the bacterial ribosome size difference from eukaryotes relate to antibiotic targeting?

The structural differences between 70S (bacterial) and 80S (eukaryotic) ribosomes allow antibiotics to target bacterial protein synthesis without affecting human cells.

Why are plasmids considered "non-essential" but still important?

They're non-essential because bacteria can survive without them, but they're important because they can provide survival advantages like antibiotic resistance or virulence factors.

What makes endospores so much more resistant than vegetative cells?

The thick cortex layer and the dehydrated state of the endospore core make them extremely resistant to environmental stresses that would kill vegetative cells.

How do endospores contribute to the persistence of certain bacterial diseases?

they can survive harsh conditions and remain dormant for long periods, then germinate when conditions improve, allowing the bacteria to cause disease even after apparent elimination.