Week 4 Flashcards
Cultural and Cellular Morphology
Measuring Bacterial Growth: Number of bacteria cells in a sample can be measured by….
- Observation of sample using sight (turbidity)
- Spectrophotometer- the amount of light that passes through the sample and is measured using a detector
- Coulter Counter- electronically counts cells as they pass through device
- Petroff Hausser counting chamber- manual cell count with a microscope
- Membrane Filtration Method- sample is passed through a filter that traps cells; the filter is then placed on a agar surface that allows development of colonies
Measuring Bacterial Growth: Observation
observation of sample using sight (turbidity)
Measuring Bacterial Growth: Spectrophotometer
- the amount of light that passes through the sample is measured using a detector
- measures how much light goes through the sample
Disadvantage: this method cannot discriminate between live and dead cells
Measuring Bacterial Growth: Coulter Counter
Electronically counts cells as they pass through device; as cells pass through sensing zone they trigger an electronic sensor that registers their numbers
Disadvantage: This method cannot discriminate between live and dead cells
Measuring Bacterial Growth: Petroff Hausser Counting Chamber
manual cell count with a microscope
Disadvantage: This method cannot discriminate between live and dead cells; not possible to give a number for viable cells
Measuring Bacterial Growth: Membrane Filtration Method
Sample is passed through a filter that traps cells; the filter is then placed on a agar surface that allows development of colonies
-A count of the visible colonies on the membrane surface GIVES the number of viable microorganisms
Spread and Pour Plate Methods
Spread= Diluted bacterial suspension is spread (smeared) onto solid agar medium—> incubation—> bacterial colony on surface
Pour= 9mL of molten agar medium–> poured into plate–> incubation–> bacterial colonies on surface and in agar
-A count of the visible colonies gives the number of viable microorganisms
Bacterial Growth
- increase in number of cells
- bacterial growth can be measured either quantitatively (quantity) or qualitatively (type of organism)
Binary Fission
(part of bacterial growth)
- Cell elongates and DNA is replicated
- Cell wall and plasma membrane begin to constrict
- Cross-wall forms, completely separating the two DNA copies
- Cells separate
The Rate of Population Growth: Generation Time
the time it takes for the population to double; genetically determined
ex:
- Salmonella enteritidis and Staphylococcus aureus- double in 30 minutes
- Mycobacterium leprae- double in 10-30 days
Stages In Normal Growth Curve
- Lag Phase- cells are metabolically active, not reproducing yet
- Log Phase- cells are reproducing at exponential rate
- Stationary Phase- rate of cell reproduction is equal to the rate of cells dying (straight line)
- Death Phase- cells dying off at exponential rate
Aerotolerance
Oxygen requirements of bacteria
- Obligate aerobe
- Obligate anaerobe
- Facultative anaerobe
- Aerotolerant anaerobe
- Microaerophile
- Capnophile
Aerotolerance: Obligate aerobe
an organism that cannot grow without oxygen
Aerotolerance: Obligate anaerobe
Not able to grow in the presence of oxygen
-lack the enzymes for processing toxic oxygen, they cannot tolerate any free oxygen. They do not use oxygen for respiration and are not able to grow in the presence of oxygen
Aerotolerance: Facultative anaerobe
does not require oxygen for its metabolism and is capable of growth in the presence of it
Aerotolerance: Aerotolerant anaerobe
do not utilize oxygen but can survive and grow in its presence
Aerotolerance: Microaerophile
does not grow at normal atmospheric concentrations of oxygen but requires a small amount of it (1-15%)
Aerotolerance: Capnophile
grow best at higher CO2 tensions (3%-10%)
Different methods for anaerobic and capnophilic growth:
- GasPak jars
- Specialized media (thioglycolate) (anaerobic environmental chamber)
Thioglycolate broth a Reducing Media
- it helps determine oxygen requirements of isolates
- it allows the growth of anaerobic bacteria
- Thioglycollic acid slows the penetration of oxygen reducing its availability
- Thioglycolate will allow ALL organisms to grow
Thioglycollate Tubes: for measuring oxygen requirements
- Thioglycollate creates a reduced environment in this semi-soft agar, with a small amount of oxygen diffusing in from the top
- organisms with different oxygen requirements will grow in different parts of the tube
Cellular Morphology (bacterial shapes)
- Bacillus (bacilli)- rod-shaped
- Coccus (Cocci)- spherical
- Spirillum- spiral/ loose S
- Spirochete- (corkscrew)
- Vibrio- (coma)
Cellular Morphology: Bacilli Arrangements
- Single or no specific arrangement (random)
- Diplobacillus: pairs
- Streptobacillus: chains
- Coccobacillus
- Palisading: side-by-side
- Snapping: V
Cellular Morphology: Cocci Arrangements
- Singles or no specific arrangement (random)
- Diplococcus: pairs
- Streptococcus: chains
- Tetrad (group of 4s)
- Staphylococcus: grape-like clusters
- Sarcina: cubical packets of 8
Cellular Morphology: Spiral arragements
- Vibrio: one-half spiral turn (comma)
- Spirillum: loosely wound spiral (loose S)
- Spirochete: tightly wound spiral (corkscrew)
Cultural Characteristics in Broth
- Clear (no growth)
- Turbid (cloudy)
- Flocculent (flecks or chunks scattered throughout)
- Pellicle (film of bacteria covering surface)
- Sediment (growth settled to the bottom of tube)
Growth Patterns on Slants
- Filiform (thread-like)
- Arborescent (tree-like)
- Beaded
- Effuse (spreading)
- Rhizoid
- Echinulate (spiny)
Colony Characteristics: Shape
- circular
- rhizoid
- irregular
- filamentous
- spindle
Colony Characteristics: Margin
- Entire
- Undulate
- Lobate
- Curled
- Rhizoid
- Filamentous
Colony Characteristics: Elevation
- flat
- raised
- convex
- pulvinate
- umbonate
Colony Characteristics: Size
- punctiform
- small
- medium
- large
Colony Characteristics: Texture
smooth or rough
Colony Characteristics: Appearance
Glistening (shiny) or dull
Colony Characteristics: Pigmentation
- Nonpigmented (cream, tan, white)
- Pigmented (purple, red, yellow)
Colony Characteristics: Optical Property
Opaque, Translucent, Transparent
The Catalase Test
used to differentiate gram positive cocci
-used to differentiate catalase positive organisms from catalase negative organisms
Catalase Positive: Micrococcus, Staphylococcus
Catalase Negative: Enterococcus, Streptococcus
What the Catalase Test Is
- Hydrogen Peroxide (H2O2) forms as a by-product of aerobic metabolism
- H2O2 is toxic to cells
- The enzyme catalase breaks down H2O2 into water and O2
catalase 2H2O2---->2H2O + O2 -any bubbles should be interpreted as a positive result
