Midterm Prep Flashcards
What is the first step in the Gram staining procedure?
The bacteria are stained with the basic dye crystal violet (primary stain)
Both gram-positive and gram-negative bacteria appear purple after this step.
What role does Gram’s iodine play in the Gram staining procedure?
It is the mordant that enhances the retention of the stain by forming an insoluble crystal violet-iodine complex
Both gram-positive and gram-negative bacteria remain purple after this step.
What happens during the decolorization step in Gram staining?
Gram-positive bacteria retain the crystal violet-iodine complex while gram-negative bacteria are decolorized
This step is critical for differentiating between the two types of bacteria.
What is the final step in the Gram staining procedure?
The counter stain safranin is applied
Gram-positive bacteria remain purple, while gram-negative bacteria become pink.
What are the main components of the Gram-positive bacterial cell wall?
Thick peptidoglycan layer and wall teichoic acids
The peptidoglycan consists of alternating N-acetylmuramic acid and N-acetylglucosamine monomers.
What characterizes Gram-negative bacteria?
An outer membrane of phospholipids and lipopolysaccharides, and a thin peptidoglycan layer
They also have a periplasmic space that protects against certain antibiotics.
What is the Baltimore classification system?
A system that classifies viruses according to their genomes, including DNA or RNA, single versus double stranded, and mode of replication
It creates seven groups of viruses with common genetics and biology.
What is the significance of the International Committee on Taxonomy of Viruses (ICTV)?
It develops and maintains a universal virus taxonomy
Since 1971, it has classified viruses into seven orders, 96 families, and 350 genera.
What is a characteristic feature of viral family names?
They end in -viridae
For example, Parvoviridae.
What are the key characteristics of viruses?
Infectious, acellular pathogens, obligate intracellular parasites, DNA or RNA genome, lack genes for reproduction
They require host cells to replicate.
Define host range in the context of viruses.
The specific species of organism that a virus can infect
Most viruses typically infect only specific hosts and cell types.
What are bacteriophages?
Viruses that infect bacteria
They are also known as phages.
What are the two types of viral transmission?
Mechanical transmission and biological transmission
Mechanical transmission occurs via physical contact, while biological transmission occurs through biting.
What is a virion?
A viral particle that is typically too small to be seen with a light microscope
Sizes can range from 20 nm to 900 nm.
What is a capsid?
A protein coat that surrounds the nucleic acid of a virus
It is composed of protein subunits called capsomeres.
What distinguishes naked viruses from enveloped viruses?
Naked viruses consist only of nucleic acid and capsid, while enveloped viruses have a lipid layer surrounding the capsid
The viral envelope is obtained from the host cell’s membrane.
What are the four major shapes of bacteria?
Bacillus, coccus, spirilla, and vibrio
Additional forms include spirochetes.
What is the difference between zygomycetes and ascomycetes in fungi?
Zygomycetes form zygospores and sporangiospores, while ascomycetes form ascospores and conidiospores
Ascomycetes are also known as sac fungi.
What characterizes monotrichous flagella distribution?
A single flagellum at one end of the bacterium
Example: Vibrio cholerae.
Fill in the blank: Gram-positive bacteria appear ______ after the Gram staining procedure.
purple
Fill in the blank: Gram-negative bacteria appear ______ after decolorization and counter staining.
pink
True or False: Viruses contain both DNA and RNA.
False
What are the sexual spores of zygomycetes called?
Zygospores
What are the asexual spores of zygomycetes called?
Sporangiospores
What is the characteristic of hyphae in zygomycetes?
Without septa
What are ascomycetes commonly known as?
Sac fungi
What type of spores do ascomycetes produce sexually?
Ascospores
What is the method of asexual reproduction in ascomycetes?
Conidiospores
What is an example of ascomycetes?
Saccharomyces
What are the most commonly found basidiomycetes?
Mushrooms
What type of spores do basidiomycetes produce sexually?
Basidiospores
What is an example of basidiomycetes?
Agaricus
What are deuteromycetes also known as?
Imperfect fungi
What is the mode of reproduction in deuteromycetes?
Asexual reproduction by conidia
What is an example of deuteromycetes?
Trichoderma
How are fungi classified based on mode of nutrition?
Saprophytic, Parasitic, Symbiotic
What do saprophytic fungi feed on?
Dead organic substances
What do parasitic fungi obtain their nutrition from?
Living organisms
What characterizes symbiotic fungi?
Mutually beneficial relationships
What is an example of a symbiotic association involving fungi?
Lichens
What are the general characteristics of fungi?
- Eukaryotic
- Non-vascular
- Non-motile
- Heterotrophic
What do fungi store their food in?
Glycogen
What is the primary structural component of the fungal cell wall?
Chitin
What is the phenomenon of alternation of generation in fungi?
Reproductive cycle involving both sexual and asexual phases
What is the term for the sexual mode of reproduction in fungi?
Teleomorph
What is the term for the asexual mode of reproduction in fungi?
Anamorph
What is the process of vegetative reproduction in fungi?
Budding, fission, fragmentation
What is the intermediate stage in some fungi between haploid and diploid cells called?
Dikaryophase
What does a purple or violet color in Gram staining indicate?
Gram positive bacterium
What does a pink or red color in Gram staining indicate?
Gram negative bacterium
What is colony morphology?
Description of characteristics of a fungal colony
What are the key characteristics used to describe colony morphology?
- Form
- Size
- Elevation
- Margin
- Surface
- Opacity
- Colour
What type of cells are bacteria classified as?
Prokaryotic
What structure is commonly found in bacteria’s cell wall?
Peptidoglycan
How do bacteria typically reproduce?
Binary fission
What is the primary structure of fungi?
Filamentous structure
What are the long thread-like structures in fungi called?
Hyphae
What do hyphae form together in fungi?
Mycelium
What is the role of the fungal cell wall?
Provides structure and protection
What is the function of the nucleus in fungi?
Contains genetic material
