Bacterial DNA and Features Quiz

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Questions and Answers

What is the primary function of plasmids in bacteria?

To produce extracellular enzymes

To store genetic information

To transfer genes between cells (correct)

To form cellular membranes

What is a characteristic feature of inclusion bodies in bacteria?

They are involved in cell division

They function as food and energy storage (correct)

They act as sites for protein synthesis

They are components of bacterial flagella

Which type of plasmid is capable of being transferred between bacterial cells?

Circular plasmids

Transmissible plasmids (correct)

Non transmissible plasmids

Stable plasmids

What role do flagella play in bacteria?

Motility Signup and view all the answers

What structure in prokaryotic cells is functionally equivalent to the eukaryotic nucleus?

Nucleoid Signup and view all the answers

Which is TRUE about the structure of bacterial flagella?

They consist of the protein flagellin Signup and view all the answers

Which characteristic is associated with plasmids in bacteria?

They replicate independently of the bacterial chromosome Signup and view all the answers

What type of granules are a characteristic feature of Corynebacterium diphtheriae?

Metachromatic granules Signup and view all the answers

What color do gram-positive bacteria stain after the crystal violet application?

Purple Signup and view all the answers

What component is unique to gram-negative bacteria's outer membrane?

Lipopolysaccharide Signup and view all the answers

Which feature is characteristic of the gram-positive bacterial cell wall?

Presence of teichoic acid Signup and view all the answers

What is the primary function of beta-lactamases produced by bacteria?

Providing resistance to beta-lactam antibiotics Signup and view all the answers

Which statement about lipopolysaccharide (LPS) is correct?

It is an integral part of the cell wall of gram-negative bacteria. Signup and view all the answers

What is NOT a function of the cytoplasmic (plasma) membrane?

Storage of genetic material Signup and view all the answers

What binds to the plasma membrane in gram-positive bacteria?

Teichoic acid Signup and view all the answers

Which feature distinguishes gram-negative bacteria from gram-positive bacteria?

Presence of an outer membrane Signup and view all the answers

What is the primary function of teichoic acids in Gram-positive bacteria?

To induce inflammation and septic shock Signup and view all the answers

Where is the periplasmic space located in Gram-negative bacteria?

Between the inner and outer membranes Signup and view all the answers

What charge do teichoic acids impart to the outer surface of Gram-positive bacteria?

A negative charge Signup and view all the answers

What type of ribosomes do bacteria possess?

70S composed of 50S and 30S subunits Signup and view all the answers

Which of the following enzymes is located in the periplasmic space of Gram-negative bacteria?

β-lactamases Signup and view all the answers

What is the role of bacterial ribosomes?

To synthesize proteins Signup and view all the answers

What component of teichoic acids can covalently link to the lipid in the cytoplasmic membrane?

Lipoteichoic acid Signup and view all the answers

What is contained within the nucleoid region of bacterial cytoplasm?

Bacterial DNA Signup and view all the answers

What is medical microbiology primarily concerned with?

Control of infectious diseases Signup and view all the answers

Which of the following is a characteristic feature of bacteria?

Lack a nuclear membrane Signup and view all the answers

Which classification refers to organisms like protozoa and fungi?

Eukaryotic Signup and view all the answers

What is the typical size range of bacteria?

0.3 µm to 5 µm Signup and view all the answers

Which structure is commonly found in bacterial cells?

Cell membrane Signup and view all the answers

Which of the following statements about eukaryotic cells is accurate?

They have complex cell structures. Signup and view all the answers

Which of the following best describes the function of peptidoglycan in bacteria?

Cell structure and protection Signup and view all the answers

What differentiates viruses from bacteria?

Viruses have DNA or RNA surrounded by a protein coat. Signup and view all the answers

What is the primary role of the glycocalyx in relation to Streptococcus mutans?

To mediate adherence to teeth Signup and view all the answers

Under what conditions do some gram-positive bacteria produce spores?

Under environmental stress or nutrient depletion Signup and view all the answers

Which of the following bacteria is NOT known for forming spores?

Escherichia coli Signup and view all the answers

What is contained within the central core of an endospore?

A single strand of DNA Signup and view all the answers

Which layer of the endospore contains a double layer of peptidoglycan?

Cortex layer Signup and view all the answers

What contributes to the resistance of spores?

High content of calcium and dipicolinic acid Signup and view all the answers

How do mature spores vary among different species?

By shape and position Signup and view all the answers

Which of the following statements about the spore coat is true?

It contains special hard resistant proteins Signup and view all the answers

Study Notes

DNA Features in Bacteria

Prokaryotic nucleoid contains a long, circular, double-stranded DNA molecule, localized within the cytoplasm and not membrane-bound.
Plasmids are extra chromosomal circular DNA present in some bacteria, crucial for gene transfer and often carry genes for antibiotic resistance and bacteriocin production.
Plasmids can replicate independently of the bacterial chromosome and can be categorized into transmissible (transferable between cells) and non-transmissible (smaller, without transfer genes).

Inclusion Bodies

Inclusion bodies are cytoplasmic or nuclear aggregates of proteins, functioning as storage for nutrients and energy.
Glycogen, starch, and metachromatic granules serve as food reserves; metachromatic granules are notably present in Corynebacterium diphtheriae.

Surface Appendages

Flagella are long, whip-like structures made of flagellin that provide motility to bacteria.
Flagella can be arranged differently (monotrichous, lophotrichous, peritrichous) among various bacterial species.
Many rod-shaped bacteria possess flagella, while most cocci are non-motile.

Medical Microbiology

Medical microbiology focuses on infectious disease causative agents, their pathogenesis, diagnosis, treatment, and immunization.
Major branches include:
- Bacteriology: Study of bacteria.
- Virology: Study of viruses.
- Immunology: Study of body defenses against pathogens.
- Mycology: Study of fungi.
- Parasitology: Study of protozoa and parasitic worms.

Classification of Microorganisms

Microorganisms are classified by structure:
- Viruses: Subcellular, containing either DNA or RNA surrounded by protein.
- Prokaryotic: Simple cells lacking a nucleus or organelles (bacteria).
- Eukaryotic: Complex cells with nucleus and organelles (protozoa, fungi, worms).

Bacterial Characteristics

Bacteria are unicellular prokaryotes that reproduce by binary fission, lacking a nucleus and organelles.
They possess a peptidoglycan-rich cell wall, differing from eukaryotic cells which have 80S ribosomes (bacterial ribosomes are 70S).
Size ranges from 0.3 μm to 5 μm, visible under light microscopy.

Gram Staining

Gram-positive bacteria retain crystal violet dye, appearing purple due to thick peptidoglycan layers (50-90% cell wall).
Gram-negative bacteria do not retain the crystal violet and are stained pink/red with safranin due to thinner peptidoglycan layers (10% cell wall).

Cell Wall Differences

Gram-positive cell wall: Thick peptidoglycan and significant teichoic acid content.
Gram-negative cell wall: Outer membrane made of lipopolysaccharides (endotoxin), a thin peptidoglycan layer, and periplasmic space containing enzymes like β-lactamases.

Cytoplasmic Membrane

Plasma membrane is a semipermeable lipid bilayer with integrated proteins.
Functions include active transport, cell wall precursor synthesis, energy generation, and toxin secretion.

Teichoic Acids

Composed of glycerol or ribitol phosphate, providing a negative charge and antigenic properties.
Found in gram-positive bacteria, they play roles in inflammation and bacterial adherence to host tissues.

Cytoplasm and Nucleoid

Cytoplasm is an aqueous solution containing ribosomes, nutrient granules, and the nucleoid where bacterial DNA resides.
Ribosomes in bacteria consist of 70S size with 50S and 30S subunits, differing from eukaryotic ribosomes.

Bacterial Spores

Some gram-positive bacteria can produce spores under stressful conditions; these spores are resistant to extreme conditions and are dormant.
Key genera include Bacillus (e.g., anthrax agent) and Clostridium (e.g., tetanus, botulism agents).
Spore structure includes a central core with DNA, a cortex of peptidoglycan, a protective spore coat, and an outer keratinized exosporium.

Spore Resistance Factors

Resistance attributed to impermeability of the cortex, high calcium and dipicolinic acid content, and low water concentration.
Spores can remain viable for years in dry conditions, stained for identification, and vary in appearance (spherical, ovoid, or elongated).

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Description

Test your knowledge on the unique DNA characteristics of bacteria, including plasmids, inclusion bodies, and surface appendages. This quiz covers crucial aspects such as gene transfer, nutrient storage, and bacterial motility mechanisms.