WorksheetsMicro Exam 2 Section 1
Total questions: 94
Worksheet time: 1hrs 5mins
supply of monomers (or precursors of) required by cells for
growth
Nutrients
Macronutrients
Micronutrients
All
nutrients required in large amounts
Nutrients
Macronutrients
Micronutrients
All the Above
nutrients required in minute amounts
trace metals and growth factors
Nutrients
Macronutrients
Micronutrients
All the above
A medium used for growing microbial cultures is composed of all these elements.
Nutrients
Macronutrients
Micronutrients
All the above
-Carbon, Nitrogen
-Hydrogen,
Oxygen
-Phosphorus
-Sulfur
-Potassium
-Magnesium
-Calcium, Sodium
(a)
-Boron, Cobalt
-Copper, Iron
-Magnesium
-Molybdenum
-Selenium, Tungsten
-Vanadium, Zinc
Examples of Macronutrients
Examples of Micronutrients
All the above
None
organic compounds required in small amounts by certain organisms
(Ex: vitamins, amino acids, pyrimidines, purines)
(a)
most frequently required growth factor
most function as coenzymes
amino acides
purines
vitamins
pyrimidines
increase in number of cells
(a)
time required for microbial cells to double in number
Growth
Growth Factor
Generation
Generation Time
What does generation time depend on?
nutritional and genetic factors and temperature
Nutritional Factors
Genetic Factors
Temperature
All the above
During cell division, each daughter cell receives a chromosome and sufficient copies of all other cell constituents to exist as an independent cell.
(a)
Types of Bacterial Growth include?
Binary Fission
Budding
Biofilms
all the above
-Method of Asexual reproduction in bacteria that involves the splitting of a parent cell into two daughter cells
-Cell division follows enlargement of a cell to twice its minimum size and formation of a septum
Binary Fission
Budding
Biofilm
none
Partition between dividing cells, pinches off between two daughter cells
(a)
-results from unequal cell growth, one part of the cell ‘buds off’ and forms totally new daughter cell.
• Some _ bacteria form cytoplasmic extensions such as stalks (Caulobacter), hyphae (Hyphomicrobium), and appendages(Ancalomicrobium).
Binary Fission
Budding
Biofilm
none
are a layer of organic matter and microorganisms formed by the attachment and proliferation of bacteria on the surface of an object
Binary Fission
Budding
Biofilm
None
Types of biofilms
Planktonic Growth
Sessile Growth
Fungi Growth
Bacterial growth
growth as suspension, e.g., algal blooms on surface water
(a)
attached to surface
can develop into biofilms
(a)
multilayered sheets with different organisms in each layer (e.g., hot springs, intertidal regions)
Fits under biofilms
Microbial Mats
Growth factors
Fungi growth
Bacterial Growth
-Different groups laterally compressed into thin (mm to cm) mats
-Vertically stratified
-Support most of major biogeochemical cycles and thus largely self-sufficient
-Often associated with extreme environments
(a)
Layers of a microbial mat include?
sand
cyanobacteria
oxidized iron
purple sulfur bacteria
precipitated iron sulfide
Biofilms prevent harmful chemicals from penetrating, prevent protists from grazing, prevent washing away of cells, easy genetic exchanges with their buddies.
This is a (advantage or disadvantage)
(a)
Biofilms affect human health, water distribution systems
(this is a advantage or disadvantage)
(a)
Microbial growth cycles included?
Continuous
Batch
Both
Neither
a closed-system microbial culture of fixed volume
• Typical growth curve for population of cells grown in a closed system is characterized by four phases.
• lag phase • exponential phase • stationary phase • death phase
Batch
Continuous
an open system microbial culture of fixed volume
Continuous
Batch
Which batch phase is first
Exponential
Stationary
Death
Lag
Which Batch phase is second?
Exponential
Death
Stationary
Lag
Which Batch phase is third?
Exponential
Stationary
Death
Lag
What is the final Batch Phase
Exponential
Stationary
Death
Lag
interval between inoculation of a culture and beginning
of growth
• time needed for biosynthesis of new enzymes and to produce required metabolites before growth can begin
(a)
Cells in this phase are typically in the healthiest state.
(a)
Growth rate of population is zero.
Either an essential nutrient is used up or waste products accumulate.
Metabolism continues at greatly reduced rate.
Some cells grow while others die, balancing
each other.
(a)
If incubation continues after cells reach stationary phase, the cells
will eventually die.
exponential rate
typically much slower than exponential growth
Viable cells remain for months or years.
(a)
most common type of continuous culture device
Chemostat
Remostat
Kemostat
none
(Continuous)
Both growth rate and population density of culture can be
controlled independently and simultaneously, depending on:
Dilution Rate (F/V)
Concentration of a limiting nutrient
both
neither
cell density and substrate concentration do not change over time.
(a)
What are the experimental uses of Continuous Culture?
can maintain exponential growth phase for
weeks/months
used to study physiology, microbial ecology and evolution
enrichment and isolation of bacteria from nature
all the above
it is important to know the nutritional requirements and supply them in proper form and proportions in a culture medium.
(a)
cells can be grown in what two types of media?
mixed
solid
liquid
are prepared by addition of the gelling agent agar to liquid media.
Solid Media
Liquid Media
When grown on solid media, cells form isolated masses called _
(a)
• nutrient solutions used to grow microbes in the laboratory
• typically sterilized in an autoclave
(a)
what are the two broad classes of media
defined
complex
selective
differintiation
exact chemical composition known
(a)
composed of digests of microbial, animal, or plant products (e.g., yeast and meat extracts)
(a)
Other types of media includes?
Enriched
Selective
Differential
All the above
contain complex media plus highly nutritious materials (e.g.,
serum or blood)
used to culture fastidious (nutritionally demanding) microbes
Enriched
Selective
Differential
contain compounds that selectively inhibit growth of some
microbes but not others
Enriched
Selective
Differential
contain an indicator, usually a dye, that detects particular metabolic reactions during growth
Enriched
Selective
Differential
MICROSCOPY – viable + non-viable cells
(Enumeration)
True
False
PLATE COUNTS - viable cell count only
(Enumeration)
False
True
TURBIDOMETRY – total cells in a sample by optical density
(Enumeration)
True
False
observing and enumerating cells present
enumeration
total cell count
microscopic cell count
-Microscopic cell count
-Liquid samples dried on slides
-Counting chambers with squares etched on a slide for liquid samples
(a)
-cant tell difference but dead or live cells without special stains
-precision is difficult to achieve
-small cells can be overlooked
-cells of low density are hard to count (< 10^6)
-motile cells need to be immobilized
-debris can be mistaken as cells
Microscopic Cell Count Advantage
Microscopic Cell Count Disadvantage
-use stains to visualize and provide phylogenetic information or metabolic properties
-DAPI reacts with DNA→ fluorescent nucleic acid stains.
-Other fluorescent stains differentiate live and dead cells.
-Phylogenetic stains can determine proportion of Bacteria or Archaea.
(a)
Direct microscopic counts of natural samples reveal far more organisms than those recoverable on plates.
“The great plate count anomaly”
None
Microscopic methods
both
“The great plate count anomaly”
Direct microscopic counts of natural samples reveal far more organisms than those recoverable on plates.
Why is this?
Microscopic methods count dead cells, whereas viable methods do not.
Different organisms may have vastly different requirements for growth.
Microscopic methods do not count the dead cells
Most organisms have similar requirements for growth.
measurement of living, reproducing population
(a)
What are the two main ways to perform plate counts
spread-plate method
pour-plate method
liquid method
solid method
spread a culture of a microorganism in liquid culture on top of an agar plate
(a)
mix a culture of a microorganism in liquid media with liquefied agar first, mix this and pour this mixture in a petriplate
→ the agar solidifies along with the culture in it.
(a)
When doing viable (plate) counts you must _.
count colonies on plates with 30–300 colonies
To obtain the appropriate colony number, the sample to be counted should always be diluted.
none
colonies must be sterile
An EPA standardized membrane filtration method used for the enumeration of E. coli in different sources- wastewater, drinking water, testing microbial contamination in watersheds.
(a)
This media contains a chromogen which is converted into glucuronic acid. This compound produces red or magenta colonies in the presence of E. coli strains possessing the enzyme beta-D-glucuronidase.
(a)
Cell suspensions are turbid (cloudy) because cells scatter light.
True
False
Most often turbidity is measured with a (a) and measurement is referred to as optical density (OD) at specified wavelength (e.g., OD540 for measurements at 540 nm [green light]).
For unicellular organisms, OD is proportional to cell number within limits.
True
False
To relate a direct cell count to a turbidity value, a standard curve must first be established
False
True
quick and easy
used in food, dairy, medical, and aquatic microbiology, and water analyses
high sensitivity
can target particular species in mixed samples
Applications
Disadvantages
Control of Microbial growth
Heath Sterilization
UV irridiation
Membrane filtration
Chemical methods
is the most widely used method of controlling microbial growth.
heat killing faster as temperature rises
thermal death time: time to kill all cells at a given
temperature; affected by population size
(Endospores can survive heat that would rapidly kill vegetative cells.)
(a)
is a sealed device that uses steam under pressure.
• Operates at a temperature 121°C and pressure of 15 psi.
• killsendospores
Autoclave
Pasteurization
UV
none
is the process of using precisely controlled heat to reduce the microbial load in heat- sensitive liquids.
• does not kill all organisms, so it is different from sterilization
Autoclave
Pasteurization
UV
None
has sufficient energy to cause modifications and breaks in DNA.
Laminar airflow unit is used in labs for UV sterilization
In a laminar flow hood
the air is passed through a HEPA (High Efficiency Particulates Air) filter which removes all airborne contamination to maintain sterile conditions.
UV
Heath
Laminar
killing of bacteria, viruses, and yeasts within seconds
no chemicals need
no ecological damage
method with low maintenance and easy handling
low operating costs, highest reliability
Advantage UV Sterilization
Disadvantage UV Sterilization
The cells may adapt to UV irradiation by developing several repair mechanisms.
This means that permanent deactivation of microorganisms by way of UV systems is impossible.
Such effects must by all means be taken into consideration when designing and operating the system.
Advantage UV Sterilization
Disadvantage
avoids the use of heat on sensitive liquids and gases.
allows for the exclusion of organisms based upon size.
traps contaminants larger than the pore size on the
surface of the membrane.
UV
Heath
Membrane Filtration
Chemical
For greater system flexibility, filters can be added in parallel or series.
True
False
For trapping viruses, we use 0.02 μm filters.
True
False
pores of filter (0.45 and 0.2 μm) are too small for living organisms
(most bacteria) to pass through but do not trap most viruses
False
True
Absolute sterilization - separates particles based on size Used for heat sensitive media or components(e.g. trace
elements) Removal of multiple particle sizes Allows for fairly high throughput
Advantage Membrane Filtration
Disadvantage Membrane Filtration
Each filter has a specific nominal pore size Unable to separate microorganisms that have the same
size May require a high differential pressure
Advantage of Membrane Filtration
Disadvantage Membrane Filtration
are chemicals that kill or inhibit growth.
(a)
kills microorganisms (e.g., bactericidal, fungicidal, viricidal)
(a)
inhibits growth (e.g., bacteriostatic, fungistatic, viristatic)
(a)
used to prevent growth on inanimate surfaces and external body surfaces
sterilants
disinfectants
sanitizers
antiseptics
destroy all microorganisms, including endospores
sterilants
disinfectants
sanitizers
none
are used on surfaces to kill microorganisms but not necessarily endospores
sterilants
disinfectants
sanitizers
none
reduce microbial numbers but do not sterilize
sterilants
disinfectants
sanitizers
antiseptics
(germicides) kill or inhibit microbial growth but are non toxic enough to be applied to living tissue
none
sterilants
disinfectants
antiseptics
