Lab Exam #1 Flashcards
Diplococci
Sarcina
Staphylococci
Cocci
Tetrads
Streptococci
Eukaryote bacteria
Mouth
- Irreguar shape
- Streptococci
Skin
-Folde over
Mouth
- Iregular shape
- Scattered
Environmental Characterisitics of Skin
- Moisture
- Salt conc.
- Nutrients
- Competition
- Turnover
- Moisture- Poor
- Salt conc.- Great
- Nutrients- Poor
- Competition- Poor
- Turn over- Moderate
Environmental factors Oral Cavity (mouth)
- Moisture
- Salt conc.
- Nutrients
- Competition
- Turnover
- Moisture- Great
- Salt conc.- About 0.9%
- Nutrients- Great
- Competition- Great
- Turnover- Great
Calculation used to determine the # of cells/ml in saliva with scientific notation
colonies/plate x positive value of the dilution factor (10^3)
Ex: 223 colonies x 10^3 = 223,000 cells/ml = 2.23 x 10^5 cells/ml saliva
What is “M”?
Condenser- focuses light from light source to solid cone of light on specimen
What is “N”?
Course focusing knob- moves objectives in greater increments
- used for initial focusing
- lens 4X and 10X
What is “E”?
Fine focusing knob- moves objective in small increments
-Used once specimen is in view on high power lens
What would “X” be on our microscopes?
Light intensity knob- Adjusts amount of light projected by light source
What is “K”?
Light source- projects light upward toward the condenser
What is “J”?
Main power switch- Turns light source on and off
What controls “L”?
Mechanical stage control (X-Y axis controls)- allows positioning of the slide
What is “H”?
Ocular lens (eyepiece)- The lens nearest your eye magnifies sample to 10X
What is “Y”?
Objective lenses- Lens nearest to specimen, collects ight and magnifies specimen image 4X, 10X, 40X, or 100X
What is”V”?
Objective turret- houses the objective lenses
-Rotates to move objective lenses into light path
Wat is “P”?
Observation tube- Holds our lens and allows for adjustment for both eyes to see image
What holds specimen on the stage?
Stage clip
What is “L”?
Stage- Platform to hold specimen on slide
What is the importance of magnification?
- Magnification is used to tell the actual size of object being viewed
- Magnification without resolution is ineffective.
What is the importance of resolution?
- Magnification without resolution is ineffective
- Maximum resolution is a combination of highest magnification with maximum resolution 100X lens and a layer of immersion oil atop the sample
- oil allows for light to bend
How does the immersion oil improve the magnification and resolution?
- Light will bend when passing between two objects with different refractive indices
- Increases the resolving power of the microscope as it has a similar refractive index as glass
What is the size comparison of prokaryotic cells and eukaryotic cells?
- At 0.1–5.0 µm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10–100 µm.
- The small size of prokaryotes allows ions and organic molecules that enter them to quickly spread to other parts of the cell.
Bacilli
Spirilli
What is the purpose of air drying?
If you heat fix before the slide is done drying the cells will lysis
What is the purpose of heat fixing?
- Kills bacteria
- Firmly attaché smear to the slide
- Allows specimen to more readily take up the stain
What is a bacterial colony?
A colony is a clone of bacteria
What are some human habitats for bacteria?
- Oral cavity (mouth)
- Skin
What is the diversity in bacterial species number found on the human body?
Humans may have >150 different species of bacteria making up 100,000,000 bacterial cells inhabiting the mouth.
What is the purpose of performing a serial dilution when enumerating bacteria?
-Using specific volumes of dilute the so it will be possible to back calculate to determine the number of cell/ml of salivaThe countable.
—
What is purpose of gram staining?
- Gram stianing differentiates between Gram (+) and. Gram (
- Based on peptidoglycan percent conte of cell wall
- Gram (+)- purple.
- Gram (—
What are the functions of each of the regiments for Gram staining?
- Crystal violet - primary stain
- Grams iodine - mordant
- Alcohol - decolorizer
- Safranin - counterstain
Compare and contrast a simple stain and a gram stain?
Simple stain-
- involves only one stain.
- Used to determine the cell shape, size, and arrangement on microorganisms
Gram stain-
- Will differentiate between Gram (+) and Gram (-)
- Used for identification of a bacterial organism
What is the Purpose of a acid fast stain?
- It is important stain to distinguish bacteria of the genus
- Day is steamed into the cell and bind to the mycolic acids
What is the purpose of a capsule stain?
- Distinguish the presence of a capsule
- Capsule is a thick plysaccharide structure that surouds the cell wall
- Allows bacteria to avoid phagocytosis, increases virulence
- Known as negative stain as it repels the stain, look like a clear bubble around cell
Define bacterial growth in a closed system?
- Growth is limited over time because new nutrients are not added and waste is not removed
- Bacteria exhibit four distinct phases of growth:
1. Lag phase
2. Log (exponential) phase
3. Stationary phase
4. Decline (death) phase
Lag phase
- adjustment period
- no cell division
- organisms use time to repair damaged cell components and synthesize enzymes to begin using resources of new environment
- duration is variable
Log (exponential) phase
- cell uses resources of new environment and starts reproducing
- max growth that is limited exclusively by organisms reproductive potential
- medium and other physical factors influence growth slightly, but mostly its growth conditions
- cell division and doubling of population at regular time intervals
- smooth, upward sweep
Stationary phase
- as nutrients in medium decrease and toxic waste increases
- growth rate declines to where death = more than reproduction
- last until nutrients are depelted or medium becomes toxic
Decline (death) phase
- decline of organism
- exponential
- fixed propriton die in given time regardless of population size
What effects do changes in physiological condones have on bacterial growth?
- Low Oxygen
- Low pH
- High glucose
- High temperature
- Low oxygen- decrease
- Low pH- decrease
- High glucose- Increase
- High temperature- decrease
What are the growth patterns for obligate aerobe?
- these bacteria must grow in oxygen because their metabolism requires oxygen.
- they carry out respiration in which oxygen is utilized as the terminal electron acceptor in the electron transport chain.
What are the growth patterns of facultative anaerobe?
- these bacteria grow very well aerobically but also have the capacity to grow anaerobically if oxygen is not present.
- Their metabolism is flexible because under aerobic conditions they can carry out respiration to produce energy but if oxygen is absent they can switch to fermentation that does not require oxygen for energy
What are the growth patterns of aerotolerant?
-these anaerobes can tolerate oxygen and even grow in its presence, but they do not require oxygen for energy production.
What are the growth patterns of obligate anaerobe?
- cannot tolerate oxygen and must be cultured under conditions in which oxygen is completely eliminated
- otherwise they are harmed or killed by its presence.
- these organisms carry out fermentation or anaerobic respiration in which inorganic compounds such as nitrate and sulfate replace oxygen in electron transport as the terminal electron acceptor.
- they are found only among the prokaryotes and in some protozoa
Define the function of superoxide dismutase?
- will act on the superoxide anion and convert it to oxygen and hydrogen peroxide
- the latter can be degraded by a catalase
Define the function of catalyst?
-will degrade hydrogen peroxide into oxygen and water
Define the function of perioxidase?
-degrades hydrogen peroxide
What are 3 enzymes among the oxygen classification of bacteria?
- superoxide dismutase
- peroxidase
- catalase.
What is the purpose of using mannitol salt agar (MSA)?
- Used selectivly and differential growth medium
- (Staphylococcus) S. Aureus- bright yellow; it ferments mannitol
- S. Epidemic- pink; due to cellular respiration of mannitol
-
What is the purpose of EBM?
- To distinguish E. Coli from other enterics by the amount of acid endproducts that are released from lactose fermentation.
- Metallic green color- large amounts of acid endproducts
- Dull pink or purple color- moderate or no acid end products
What is the purpose of using blood agars?
What do the alpha, beta, or gamma hemolysis look like?
-determining the hemolytic capabilities of an organism
What is the selective agent in MSA
7.5 NaCl (salt)
Define hemolysis?
Damage or destruction of RBC
Define bacteriostatic?
Prevent growth of bacteria on tissues or on objects in the environment.
Define bacteriocidal antibiotics?
A chemical that destroys bacteria except for those in the endosperm stage.
Define narrow spectrum antibiotics?
Antimicrobials effective against a limited array of microbial types
Define broad spectrum antibiotics?
Antimicrrobials effects against a wide variety of microbial types
Why is it important to test for antibiotic sensitivity or resistance in a clinical setting?
To determine if a patient is susceptible or resistant against an antibiotic and how much to prescribe them based on the results
Explain the disk diffusion method for testing antibiotic sensitivity?
small discs containing different antibiotics, or impregnated paper discs, are dropped in different zones of the culture on an agar plate, which is a nutrient-rich environment in which bacteria can grow.
What is the zone of inhibition?
The clear region around disk is an indication of the absence, or the effective inhibition, of microbial growth by the antimicrobial agent.
How do you measure the zone of inhibition?
use a ruler to measure the diameter of the disk plus the surrounding clear area in millimeters (mm)
Identify the factors that infuence the size of the zone of inhibition?
Diffusion of the antibiotic, the size of the inoculum, the type of medium, and resistance mechanism of organism.
Does the size of the zone of inhibition directly determine the effectiveness of the antibiotic on the patient?
zone of inhibition” can be observed and measured to determine the susceptibility to an antibiotic for that particular organism
What it the importance f the standardized chart?
You compare the results to thee cart to determine if the species is susceptible or resistant to the antibiotic
What is resolution?
Resolution is the minimum distance between to objects that allows them to be distinguished as a separate entities
