microbe mission 2 Flashcards
What are the parts of a bright-field microscope?
- Eyepiece/ocular lens
- Objective lenses
- Condenser lens
- Illuminator
- Diaphragm
- Stage
- Focus knob
These components work together to magnify and illuminate the specimen.
What is the function of a bright-field microscope?
To transmit light through a specimen to create contrast against the background
This allows for the visualization of the specimen’s structure.
What type of image does a bright-field microscope provide?
High resolution images of the specimen’s structure with dark images against a light background.
How are specimens prepared for a bright-field microscope?
Specimens are stained to improve contrast and then mounted on a slide.
What are the parts of a phase contrast microscope?
- Phase plate
- Condenser annulus
- Objective lenses
- Eyepiece
These components enhance contrast in transparent specimens.
What is the function of a phase contrast microscope?
To enhance contrast in transparent specimens without staining.
What type of image does a phase contrast microscope provide?
High contrast images of transparent unstained specimens, allowing visibility of organelles.
How are specimens prepared for a phase contrast microscope?
No staining is required; specimens are simply placed on a slide.
What are the parts of a fluorescence microscope?
- Excitation light source
- Excitation filter
- Emission filter
- Objective lens
- Fluorescent detectors
- Beam splitter/dichroic mirror
These components work together to produce images based on fluorescence.
What is the function of a fluorescence microscope?
To study specific molecules using the fluorescence properties of certain molecules.
What type of image does a fluorescence microscope provide?
Images with bright fluorescence against a dark background.
How are specimens prepared for a fluorescence microscope?
By treating samples with fluorescent dyes that emit light upon excitation.
What are the parts of a transmission electron microscope (TEM)?
- Emission gun
- Condenser lens
- Objective lens
- Projector lens
- Viewing screen/photographic film
- Vacuum system
These components allow for high-resolution imaging of internal structures.
What is the function of a transmission electron microscope?
To transmit an electron beam through a thin sample to form a high-resolution image.
What type of image does a TEM provide?
High-resolution images showing detailed structures at cellular and subcellular levels.
How are specimens prepared for a transmission electron microscope?
- Fixed with chemical agents
- Embedded in resin or plastic
- Sectioned into ultra-thin slices
- Stained with heavy metals
This preparation is crucial for preserving structures and enhancing contrast.
What are the parts of a scanning electron microscope (SEM)?
- Electron gun
- Condenser lens
- Scanning coils
- Detector
- Vacuum system
- Monitor/computer system
These components allow for detailed 3D imaging of specimen surfaces.
What is the function of a scanning electron microscope?
To scan the surface of a specimen with a focused electron beam to create 3D images.
What type of image does an SEM provide?
High-resolution 3D images of the specimen’s surface.
How are specimens prepared for a scanning electron microscope?
- Fixed to preserve structure
- Coated with a thin layer of metal
- Placed on a metal stub
This preparation enhances conductivity and image quality.
What are the uses of a bright-field microscope?
- Structural observations of stained cells or tissues
- Quantitative cell/colony counting
- Examination of fixed and stained specimens
What are the uses of a phase contrast microscope?
- Study live, unstained samples
- Behavioral study of live organisms
What are the uses of a fluorescence microscope?
- Localize and quantify specific molecules
- Tracking molecular interactions or dynamics
- Gene expression and protein localization
What are the uses of a transmission electron microscope?
- Detailed ultrastructure of cells and organelles
- Subcellular features
- Identify viral particles or nanostructures
What are the uses of a scanning electron microscope?
- Surface morphology and topography studies
- Analyze surface interactions or adhesion
- Material science and nanotechnology
What is the purpose of a scale bar in microscopy?
To estimate the size of a specimen corresponding to real-life size.
How do you calculate magnification?
Eyepiece magnification * Objective lens magnification.
How do you calculate resolution?
(0.61 * light wavelength in nanometers) / numerical aperture.
What is a Neubauer counting chamber used for?
To directly count cells in a liquid sample.
How do you determine cell count with a Neubauer counting chamber?
Concentration of cells = (number of cells counted * dilution factor * 10^4) / volume of counted area in mL.
What is the structure of bacteria?
Unicellular organisms with a simple structure.
What is the bacterial membrane composed of?
- Phospholipid bilayer
- Proteins
- Lipopolysaccharides (in gram-negative bacteria)
What is the function of the bacterial cell wall?
Provides structural support and protection, maintains cell shape, and prevents osmotic lysis.
What are bacterial flagella used for?
Enable bacterial motility through rotation.
What are bacterial pili (plus) used for?
- Genetic material transfer (conjugation)
- Attachment to surfaces or each other
What are bacterial fimbriae?
Short hair-like structures used to attach to surfaces or host tissues.
What is the bacterial nucleoid?
Region within cytoplasm containing DNA.
What is the bacterial cytoplasm composed of?
- Water
- Enzymes
- Ions
- Small molecules
- Ribosomes
What are bacterial gas vesicles used for?
Provide buoyancy to allow aquatic bacteria to float at specific depths.
What are endospores?
Highly resistant, dormant forms of bacteria encased in a tough coat.
What are archaea?
Microorganisms similar to bacteria but capable of surviving in extreme environments.
What is unique about the archaeal cell membrane?
Contains ether linkages and can be lipid monolayers or bilayers.
What is the archaeal cell wall composed of?
- Pseudopeptidoglycan
- Polysaccharides
- Proteins
What are eukaryotic cells characterized by?
More complex structure with membrane-bound organelles.
What is the eukaryotic cell membrane composed of?
- Lipid bilayer
- Embedded proteins
- Cholesterol
What are the organelles of the eukaryotic cell?
- Mitochondria
- Endoplasmic reticulum
- Golgi apparatus
- Lysosomes
What is the function of contractile vacuoles?
Maintain osmotic balance in some protists.
What are eyespots used for in some protists?
Detect light to help the organism orient itself.
What are carboxysomes?
Protein shells containing enzymes for carbon fixation.
What is the structure of gram-positive bacteria?
Thick peptidoglycan layer with teichoic acids, no outer membrane.
How do gram-negative bacteria differ from gram-positive bacteria?
Thin peptidoglycan layer with an outer membrane made of lipopolysaccharides.
What characterizes acid-fast bacteria?
Cell wall made of mycolic acids, appears red/pink after staining.
What is the gram stain procedure?
Distinguishes between gram-positive and gram-negative bacteria.
What is a virus?
Unique microorganisms capable of infecting host organisms.
What does a viral genome consist of?
Either DNA or RNA, can be single or double stranded.
What is a capsid?
Protein shell that surrounds and protects the viral genome.
What is an envelope in the context of viruses?
A lipid bilayer from the host cell that surrounds some viruses.
What are spike proteins/glycoproteins?
Glycoproteins that recognize and bind to host cell receptors.
What role do enzymes play in some viruses?
Contribute to replication in the host cell.
What is a lipid culture/broth culture?
Bacterial culture method using nutrient-rich liquid medium.
What is an agar culture/solid culture?
Bacterial culture method using gelatinous agar to isolate colonies.
What are selective media?
Media that allow growth of specific bacteria while inhibiting others.
What are differential media?
Media that allow many types of bacteria to grow with appearance changes.
What are enriched media?
Media supplemented with extra nutrients for fastidious bacteria.
What is selective media?
Media that allows certain types of bacteria to grow while inhibiting others.
Examples include MacConkey agar which differentiates based on lactose fermentation.
What are enriched media?
Media supplemented with extra nutrients to support fastidious bacteria growth.
Examples include chocolate agar and blood agar.
What are the phases of the bacterial growth curve?
Lag phase, log phase, stationary phase, death phase.
What occurs during the lag phase of bacterial growth?
Bacteria adapt to the environment and prepare for growth without dividing.
What characterizes the log phase of bacterial growth?
Bacteria divide at a constant rate, exhibiting exponential growth.
What happens during the stationary phase of bacterial growth?
The rate of cell division slows and becomes equal to the rate of cell death.
What is the death phase of bacterial growth?
The number of dying bacteria exceeds the number of new cells being formed.
What is the plate count method?
A method for counting living bacterial cells by diluting and counting colonies on agar plates.
How is optical density measured in bacterial cultures?
By measuring the cloudiness or turbidity of the culture using a spectrophotometer.
What is the formula for bacterial population size?
Initial population size * e^(growth rate*time).
Define bacterial growth rate.
r = (ln(population size) - ln(initial population))/t.
List major classes of antibiotics.
- Penicillin
- Tetracyclines
- Beta-lactams
- Cephalosporins
- Fluoroquinolones.
What is the role of penicillins?
They target bacterial cell wall synthesis and are bactericidal.
How do tetracyclines function?
They inhibit bacterial protein synthesis by binding to the 30S ribosomal subunit and are bacteriostatic.
What do beta-lactams do?
They inhibit transpeptidase enzymes to prevent cell wall synthesis and are bactericidal.
What are cephalosporins?
A subclass of beta-lactams that have a broader spectrum of activity against bacteria.
What is the mechanism of fluoroquinolones?
They inhibit bacterial topoisomerases to interfere with DNA synthesis.
What is heat sterilization?
A bactericidal method that disrupts microbial structure and function using heat.
What does UV radiation do to microorganisms?
It damages microbial DNA, preventing replication and transcription.
Describe the process of filtration in microbial control.
A mechanical process that removes microorganisms by passing liquids through filters.
What are the types of chemical sterilization?
- Alcohols
- Aldehydes
- Halogens
- Hydrogen peroxide
- Phenolics.
What are limitations of culture-based approaches to study microbes?
Microbes may require specific conditions to culture, behave differently in isolation, and may not reflect natural communities.
What is binary fission?
Asexual bacterial cell division.
What are the steps of binary fission?
- Initiation
- DNA unwinding
- Pre-replication complex formation
- Priming and polymerase binding
- DNA strand elongation
- Primer removal and ligation
- Termination of replication
- Cell division.
What is the role of RNA polymerase in transcription?
It binds to the promoter and catalyzes RNA synthesis.
What happens during the initiation phase of transcription?
RNA polymerase binds to the promoter, forming a transcription bubble.
What occurs during the elongation phase of transcription?
RNA polymerase adds ribonucleotides complementary to the DNA template.
Describe termination in transcription.
RNA polymerase encounters a terminator sequence, releasing the RNA.
What is the lac operon?
An inducible system for lactose metabolism with genes for breakdown and uptake.
How is the lac operon regulated?
By the lac repressor protein and the presence of allolactose.
What is the trp operon?
A repressible system involved in tryptophan synthesis.
How does the trp operon regulation work?
Tryptophan binds to the trp repressor, blocking RNA polymerase when levels are high.
What is the endosymbiotic theory?
Proposes that mitochondria and chloroplasts evolved from prokaryotic ancestors.
What are some adaptations of microbes to extreme environments?
- Accumulation of sugars and amino acids
- Changing lipid bilayer composition
- Resistant spores or extremozymes.
Describe the morphology of Escherichia coli.
Rod-shaped, 1-3 µm in length, gram-negative.
What diseases are caused by Escherichia coli?
- Diarrheal diseases
- UTIs
- Neonatal meningitis
- Sepsis.
What is Rickettsia rickettsii responsible for?
Causes Rocky Mountain spotted fever (RMSF).
What are the characteristics of Mycobacterium tuberculosis?
Gram-positive, rod-shaped, and causes tuberculosis.
What disease is caused by Rickettsia rickettsii?
Rocky Mountain spotted fever (RMSF)
RMSF involves widespread endothelial damage due to the invasion of endothelial cells.
What type of bacteria is characterized as small, pleomorphic, gram-negative rods or coccobacilli?
Rickettsia rickettsii
It stains poorly and is 0.3–0.5 µm in width and 0.8–2.0 µm in length.
What components are found in the outer membrane of Rickettsia rickettsii?
- Lipopolysaccharides (LPS)
- Surface proteins (OmpA and OmpB)
These components aid in adhesion and immune evasion.
What is the primary method of transmission for Mycobacterium tuberculosis?
Droplets
It blocks phagosome-lysosome functions, replicating within macrophages.
What are the key processes involved in the pathogenicity of Mycobacterium tuberculosis?
- Invasion
- Phagosomal arrest
- Dormancy
- Reactivation
These processes contribute to the development of tuberculosis.
What type of bacteria is Microcystis aeruginosa?
Cyanobacteria
It forms harmful algal blooms that produce toxins (microcystins).
What is the primary reproduction method for Microcystis aeruginosa?
Binary fission
Cells aggregate into colonies for protection and buoyancy.
What is a characteristic feature of Staphylococcus aureus?
Arranged in characteristic grape-like clusters
It is golden-yellow due to carotenoid pigments.
What virulence factor is associated with Staphylococcus aureus that provides antibiotic resistance?
mecA gene
This gene encodes an alternative penicillin-binding protein (PBP2a).
What type of infections can Staphylococcus aureus cause?
- Skin and Soft Tissue Infections
- Sepsis
- Endocarditis
- Pneumonia
- Toxic shock
These infections are a result of its virulence factors.
What is the shape and gram classification of Helicobacter pylori?
Gram negative, spiral-shaped
It adheres to gastric epithelial cells and survives in the stomach by producing urease.
What diseases are associated with Helicobacter pylori?
- Gastritis
- Peptic ulcer diseases
- Gastric cancer
- MALT lymphoma
These conditions arise from its colonization in the gastric epithelium.
What is a unique feature of Pyrococcus furiosus?
Survives in geothermal environments at high temperatures (80–110°C)
It relies on fermentation and produces hydrogen gas.
What type of organism is Methanococcus sp.?
Archaea
It reduces CO2 or converts acetate to generate methane.
What type of life cycle does Plasmodium falciparum undergo?
Complex life cycle involving mosquitoes and humans
It causes malaria through various developmental stages.
What is the reproductive method of Saccharomyces cerevisiae?
Asexual reproduction as budding
Yeast mating can also form ascospores.
What type of reproduction does Nannochloropsis sp. exhibit?
Binary fission or sexual reproduction
It is a microalgae known for its high lipid content.
What is the structure of Escherichia virus T4?
Icosahedral head with contractile tail
It has a lytic life cycle and infects E. coli.
What type of virus is the Human Immunodeficiency Virus (HIV)?
Positive sense ssRNA retrovirus
It causes AIDS by infecting and destroying immune cells.
What is the main characteristic of prions?
Misfolded proteins that induce misfolding of normal proteins
Prions do not have a nucleic acid genome.
