Bacterial Characteristics and Classification

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Questions and Answers

What is the primary function of the cell wall in bacterial cells?

To regulate gene expression

To synthesize proteins

To facilitate cell movement

To provide structural support and maintain cell shape (correct)

Which of the following is NOT a characteristic of peptidoglycan?

It is a polymer composed of hexose sugars and amino acids

It is found in the cell walls of both Gram-positive and Gram-negative bacteria

It provides structural support to the bacterial cell

It is a component of the bacterial plasma membrane (correct)

What is the main difference between Gram-positive and Gram-negative bacteria?

The ability to form spores

The type of flagella present

The presence or absence of a cell wall

The composition of the cell wall peptidoglycan layer (correct)

Which of the following is an example of an opportunistic fungal infection?

Candidiasis Signup and view all the answers

What is the function of the capsule in bacterial cells?

To protect the cell from the host's immune system Signup and view all the answers

What is the primary function of the flagella in bacterial cells?

To facilitate cell movement Signup and view all the answers

Which of the following is NOT a component of a bacterial cell?

Mitochondria Signup and view all the answers

What is the function of the plasmid in bacterial cells?

To facilitate horizontal gene transfer Signup and view all the answers

What is the minimum number of subunits in an icosahedral capsid?

60 Signup and view all the answers

Which type of viral symmetry is characterized by capsomeres bound in a periodic fashion to the viral genome, winding the genome into a helix?

Helical Signup and view all the answers

What is the function of the viral matrix protein in the viral envelope?

Mediates the interaction between the capsid and envelope Signup and view all the answers

Which of the following viruses has a complex capsid?

Smallpox virus Signup and view all the answers

What is the function of viral surface proteins?

To attach to membrane proteins (receptors) in host cell Signup and view all the answers

Which type of virus is stable in the environment and may be transmitted by food or water?

Non-enveloped virus Signup and view all the answers

What is the viral genome enclosed by?

Nucleocapsid Signup and view all the answers

What is the term for the continuous cylinder surrounded by a lipid layer and complex proteinaceous core wall in poxviruses?

Pallisade layer Signup and view all the answers

Which of the following types of genomes typically encodes its own RNA-dependent RNA polymerase?

RNA genomes Signup and view all the answers

What is the primary function of reverse transcriptase in retroviruses?

To copy a +ve ssRNA genome into dsDNA Signup and view all the answers

What is the characteristic of the infectious agent responsible for prion diseases?

A misfolded protein that alters the folding of the normal host version of the protein Signup and view all the answers

Which of the following diseases is NOT a parasitic infection?

Prion disease Signup and view all the answers

What is a characteristic of Schistosomiasis?

It is a parasitic infection caused by a helminth Signup and view all the answers

Which of the following statements about Toxoplasmosis is TRUE?

It is a parasitic infection that can cause severe symptoms in immunocompromised individuals Signup and view all the answers

What is the primary function of the thick keratin-like coat of a bacterial spore?

To confer resistance to heat, chemicals, and drying Signup and view all the answers

Which of the following is a characteristic of viral genomes?

They can be either DNA or RNA, but never both Signup and view all the answers

What is the primary function of the capsid protein in a virus?

To construct the protein coat of the virus Signup and view all the answers

Which of the following is a characteristic of bacterial spores?

They are highly resistant to both heat and chemicals Signup and view all the answers

What is the term for the process of killing bacterial spores using high pressure and heat?

Autoclaving Signup and view all the answers

What is the primary function of the viral polymerase protein?

To replicate the viral genome Signup and view all the answers

What is the term for the protein subunits that make up the capsid of a virus?

Capsomeres Signup and view all the answers

What is the primary function of the host cell machinery during viral replication?

To provide the necessary components for viral assembly Signup and view all the answers

Which of the following characteristics is NOT used for bacterial classification?

Motility Signup and view all the answers

What is the primary way in which bacterial growth is affected?

Oxygen availability Signup and view all the answers

Which of the following bacteria is classified as Gram Positive?

Staphylococcus aureus Signup and view all the answers

What is the primary difference between obligate aerobes and facultative anaerobes?

Their energy-generating system Signup and view all the answers

Which of the following is an example of a biochemical property used for bacterial classification?

Production of coagulase Signup and view all the answers

What is a more recent method used for bacterial classification?

DNA sequencing of their genome Signup and view all the answers

Which of the following bacteria is an example of an acid-fast stain?

Mycobacteria Signup and view all the answers

Which of the following is NOT a type of bacteria that infects humans?

Archaea Signup and view all the answers

Study Notes

Characteristics of Bacteria

Morphological characteristics used for classification:
- Nature of the cell wall
- Staining (e.g., Gram stain)
- Shape (e.g., cocci, bacilli/rods, spirilla/spirochetes)
- Spore-forming abilities
Biochemical properties:
- Metabolism (e.g., obligate aerobes, facultative anaerobes, obligate anaerobes)
- Production of specific enzymes (e.g., coagulase) or toxins (e.g., hemolysins)
DNA sequencing of their genome

Examples of Bacteria Infecting Humans

Gram-positive bacteria:
- Cocci (e.g., Staphylococcus aureus)
- Rods (Bacilli) (e.g., Bacillus subtilis)
Gram-negative bacteria:
- Cocci (e.g., Neisseria gonorrhoeae)
- Rods (Bacilli) (e.g., Pseudomonas aeruginosa)
Miscellaneous/poorly staining bacteria:
- Intracellular bacteria (e.g., Chlamydia)
- Acid-fast stain bacteria (e.g., Mycobacterium tuberculosis)
- Mycoplasma
- Opportunistic bacteria (e.g., Pseudomonas aeruginosa)
Examples of bacterial infections:
- Cryptococcosis (Cryptococcus spp.)
- Candidiasis (Candida spp.)
- Aspergillosis (Aspergillus spp.)
- Pneumocystis pneumonia (Pneumocystis spp.)
- Ringworm (e.g., Microsporum spp.)
- Athlete’s foot (Trichophyton spp.)

General Properties of Bacteria

Components of a bacterial cell:
- Essential components:
  - Cell wall
  - Plasma membrane
  - Ribosome
  - Nucleoid
- Non-essential components:
  - Capsule
  - Flagella
  - Pili (Fimbriae)
  - Plasmid
  - Spore
Structure of bacteria:
- Cell wall: multilayered structure mainly composed of peptidoglycan
- Peptidoglycan: polymer composed of hexose sugars (N-acetylglucosamine and N-acetylmuramic acid) and amino acids
- Gram stain: classification based on cell wall characteristics
- Spores: highly resistant structures formed in response to adverse conditions

General Properties of Viruses

Distinguishing characteristics:
- Intracellular parasites
- Contain either DNA or RNA genomes (never both)
- Novel genetic material encoding structural and functional proteins
Basic virus structure:
- Essential components:
  - Genome (DNA or RNA)
  - Capsid
  - Polymerase protein
- Non-essential components:
  - Envelope
  - Envelope protein
Structure of viruses:
- Capsid: constructed from virally-encoded protein subunits (capsomeres)
- Viral genome: enclosed by the capsid protein coat
- Symmetry: icosahedral, helical, or complex

Importance of Viral Surface Proteins

Attach to membrane proteins (Receptors) in host cell: determinants of tropism
RNA genomes:
- Most examples encode their own RNA-dependent RNA polymerase
- Retroviruses (and hepadna-): use reverse transcriptase to copy a +ve ssRNA genome into dsDNA

Additional Information

Prion (PRoteinaceous Infectious particle) Diseases:
- Group of fatal and infectious neurodegenerative diseases
- Infectious agent propagates in the absence of nucleic acid
- Infectious agent is a misfolded protein that alters folding of the normal host version of the protein
Examples of parasitic diseases:
- Taenia solium (pork tapeworm)
- Schistosomiasis
- Malaria
- Toxoplasmosis
- Leishmaniasis

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Description

This quiz covers the characteristics of bacteria used for classification, including morphological and biochemical properties. Learn about the importance of cell walls, staining, shape, spore-forming abilities, and metabolic processes in identifying bacteria.