LAB EXAM #1 cont. Flashcards
Psychrophiles:
- Grow between -5C and 20C
- Found in waters of Antarctic and Arctic
Mesophiles:
- Grow between 20C and 50C
- Most common temp range for organisms
Most pathogens grow between:
35C and 40C
Thermophiles:
- Grow between 50C and 80C
- Found in soils or compost piles
Hyperthermophiles:
- Grow above 80C
- Found in thermal vents or where there is volcanic activity
How does temperature effect metabolic factors in a cell? (3)
- Enzyme function or activity
- Cell membrane and transport
- Ribosomes
Neutrophils:
- Neutral pH
- MOST bacteria are neutrophils
- Some can grow over a range of 2-3 pH units
Acidophiles:
- Acidic pH
- Ex: Yeast prefers a pH of 4-6
Alkaliphiles:
- Alkaline pH
- Belong to the genus Bacillus
How does bacteria that grows at the extremes of the pH scale maintain their cytoplasm?
At a neutral pH to help prevent damage
7 physical agents:
- Heat: thermal death point, dry heat, moist heat, pasteurization
- Cold: refrigeration, freezing, freeze-drying
- Radiation: ultraviolet light (UV), ionizing radiation, microwave
- Sonic and ultrasonic waves
- Filtration
- Drying
7`. Osmosis
Thermal death point:
Temp that kills all bacteria in broth in 10 min
Dry heat: (3)
- Oxidizes molecules
- SLOW penetration
- Metal, glassware
Moist heat: (2)
- Denatures proteins
- RAPID penetration
2 mechanisms of moist heat:
- Boiling water: kills vegetative cells not spores
- Autoclave:
- steam under pressure
- kills spores
Cold physical agents:
Slows enzyme controlled reactions- doesn’t kill
Refrigeration:
At (-5C), food is good for a few days
Freezing: (3)
- At (-20C), slows chemical reactions a lot
- At (-78C). stores microbes in glycerol
- Long term storage
Freeze-drying:
- Lyophilization: microbes dried (vacuum) while frozen
- Long term preservation
UV radiation: (3)
- 200 nm range
- Damages DNA
- Poor penetration
Ionizing radiation: (4)
- X-rays, gamma rays
- Damages DNA
- Deep penetration
- Good for plastic
Microwave:
Lower frequence of radiation
Sonic and ultrasonic waves:
- Sonication causes cavitation in cell cytoplasm
- Bacteria killed
Filtration: (4)
- Small pore size: 25um to 0.025um
- Can sterilize
- Good for drugs
- Alternative to pasteurization
Drying: (3)
- Ancient practice
- Sun dried food
- Hot air
Osmotic pressure:
-High sugar and salt-> hyperosmotic conditions
A. Plasmolysis: cell ruptures
Stage:
Knob that supports microscope slide
Lenses:
Oculars, have a magnification of 10X
4 microscope objectives in order:
4X: red, scanning
10X: yellow, low power
40X: blue, high power
100X: white, oil immersion
Condenser:
- Located under stage
- Collects and directs light from the lamp to the slide
Diaphragm:
Controls the amount of light that enters the condenser
Coarse focus knob:
Used with 4x and 10x objectives to bring slide into FOCUS
Fine focus knob:
Used with 40x and 100x objectives to SHARPEN image
Ability to go from one objective to another and not lose sight of the specimen is called:
Parafocal
What parts of the microscope are necessary for cleaning with lens paper?
- oculars
- objectives
- condensers
How to center specimen on microscope?
Mechanical stage knobs
Purpose of oil immersion:
To bend light-> increasing resolution
Where is E. coli found?
Intestines of animals and humans
Where is S. aureus found?
Normal flora of body
As objective magnification goes up:
Field of view decreases
4X diameter of field of view in microns:
5,000
10X diameter of field of view in microns:
2,000
40X diameter of field of view in microns:
500
100X diameter of field of view in microns:
200
What happens to serratia marcescens when it reaches 37C or higher?
Loses its enzyme that produces the red pigment-> it is clear
Ignaz Semmelweis
Observed that hand washing is important in preventing the spread of diseases
3 main groups of the normal flora that inhabit the human skin:
- Diphtheroids
- Staphylococci
- Fungi
Nosocomial infections:
- Hopsital acquired infections
- Ex: Methicillin-resistant S. aureus (MRSA)
Diphetheroids:
- Prefer oily regions of skin
- Degrade fatty secretions in hair follicles
Staphylococci: (4)
- Coagulase-negative
- Salt tolerant
- Grow in dry areas
- Beneficial because they produce antimicrobial compounds
Fungi:
- Nonpathogenic yeast that uses fatty substances
- Found on face as flaky skin around nose
Disinfectants:
Substances that are applied to inanimate objects to kill or reduce microorganisms. Harsh and damaging to living tissue
Antimicrobial:
Agents that kill or inhibit microorganisms
Antibiotic:
Low molecular weight antimicrobials that are produced by microorganism that inhibit or kill other bacteria
First line of defense that battle diseases:
Antimicrobials and antibiotics
Kirby-Bauer method:
Standardized test used to determine the sensitivity or resistance of a bacteria to a antimicrobial agent
How is the Kirby-Bauer method performed?
With Mueller-Hinton agar plates and disks that have specific antibiotics and concentrations
Responsible for observing penicillin species inhibiting the growth of S. aureus?
Alexander Fleming
Responsible for the purification of penicillin:
- Howard Florey
- Norman Heatley
- Ernest Chan
