Module 13 Flashcards
What are physical parameters that control growth? How does each physical parameter inhibit growth?
Temperature-denature the enzymes and proteins when too high; affects membrane fluidity; slows down enzyme activity when too cool
pH-proteins and enzymes denature at both; affects hydrogen bonding
Osmotic pressure-draws water out retarding growth; draws water in and cells swell and possibly burst
Describe the categories for prokaryotes for temp growth
Psychrophiles-cold loving
Psychotrophs-higher optimum
mesophiles-the most numerous group with moderate temp
thermophiles-heat loving
extreme thermophiles-archaea, hot springs and deep sea thermal vents
Describe the categories for prokaryotes for pH growth
Acidophiles- 0-5.5 pH
Neutrophiles- 5.5-8.0 pH
Alkalophile- 8.0-11.5 pH
Describe the categories for prokaryotes for osmotic pressure and growth
Hypotonic- water moves into the cell
Hypertonic- food preservation- causes plasmolysis, water moves out of the cell
Isotonic- no net gain or loss of water
What is the main difference between a halotolerant (facultative halophile) bacteria and an extreme (obligate) halophile?
extreme halophile
-In archaea (domain)
-High salt only 30-40%
Facultative halophile
-In bacteria (domain)
-Grow over a huge range- up to 15%
What is plasmolysis? Under what conditions does plasmolysis occur? Why does this condition inhibit the growth of a bacterium?
The shrinkage of the protoplasm away from the cell wall
Caused by the loss of water in the cell- due to being placed in hypertonic solution, exposed to increased salinity or chemicals
draws water out of the cell retarding growth
What elements are necessary for growth?
Carbon
-Backbone of all living matter (organic life)
Nitrogen
-14% dry weight of cell (protein and nucleic acid synthesis)
Oxygen and hydrogen
-Found in all components of cell
Sulfur and phosphorus
-4% dry weight of cell (cysteine and nucleic acid synthesis)
What is a trace element? Why are trace elements important to prokaryotes?
Small amounts of minerals
Important as cofactors for enzymes
Iron, copper, zinc
What are the 5 categories bacteria are divided into based upon the effects of oxygen on their growth? Be able to explain and recognize the growth pattern of each in a test tube.
Obligate aerobe
-Grow only in the presence of O2
Obligate anaerobe
-Killed by O2
Facultative anaerobe
-Organisms grow with or without the presence of O2 but prefer it
Aerotolerant anaerobe
-Don’t use O2 for growth, and not harmed either
Microaerophile
-Less than atmospheric concentrations of O2
What is the difference between a complex media and a chemically defined media? What is a fastidious bacterium? Which media will a fastidious bacterium grow on?
Chemically
-Know the exact amounts of every substance in the media
-Fastidious bacteria grow- require several different growth factors
Complex
-Composed of extracts which vary from batch to batch
-High in amino acids, vitamins, minerals
Where do you find anaerobic bacteria? How would you grow an anaerobic bacterium?
No oxygen or low oxygen environments
-Reducing media- deplete oxygen in the media
-Anaerobic jar
-Capnophiles- like CO2 environment
How does a selective media differ from a differential media? What is an enrichment culture? When would you use any of these three types of media?
Selective media- inhibits the growth of unwanted bacteria
Differential media- different types of bacteria will appear differently on the plate
Enrichment culture- designed to increase specific bacteria
—Allows for the isolation and identification of specific microorganisms from a mixed culture
What is binary fission? What is a generation time?
Type of asexual reproduction where a parent cell divides into two identical cells.
The time required for a cell to divide
Example problem: If you start with one bacterium that has a generation time of 15 minutes, how many bacteria will you have in 2 hours?
8 GT
1-2-4-8-16-32-64-128-256
256 bacteria
What does the growth curve of a bacterium look like? What does each phase of the graph represent (what is it called)? What is occurring at each phase?
- Lag phase
-Little or no cell division
-Period of synthesis - Log phase
-Exponential growth phase
-Generation time reaches a constant
-Cells most metabolically active
-Most sensitive to antibiotics - Stationary phase
-Death=division
-Constant number of cells
-Run out of nutrients or pH changed - Death phase
-Death greater than division
-No nutrients or extreme pH
How are scientists able to count bacteria? List and describe the techniques. When will each technique be useful?
1.Variable plate counts
Counts live cells
Serial dilutions done
- Filtration
Only for a small number of cells
Concentrate bacteria with a filter-> plate
Used for coliforms (enteric bacteria from sewage)
3.Most probable number
Counting bacteria that don’t grow on their own using statistics
Dilute sample in nutrient broth-> to no cells
Used for bacteria that don’t grow in isolated colonies on plates
Statistical count
- Microscopy
Direct counts-live and dead cells
Petroff-Hausser counter used - Turbidity- cloudiness
Spectrophotometer- how uch light is absorbed or transmitted by the solution
Indirect count
Have to have a viable plate count or microscope count with it - Metabolic activity- measure CO2 or acid released
- Dry weight
Cells 70-80% water
Have to know the number of cells or weight of one cell
What is a biofilm? How are they important in health care?
Bacteria live in communities or groups which is surrounded by a matrix of polysaccharides with DNA and proteins- slime or hydrogel
1000 times more resistant to microbiocides
Most HAIs due to this
Research prevent formation of block quorum sensing
What is quorum sensing?
The cell to cell chemical communication that allows communication- communication system of biofilms
