Lab Exam 1 Flashcards
ubiquitous
microorganisms are always present- ie they are ubiquitous -as they are in the air, surfaces, skin clothing. Because of this, they are always a potential source of contamination during an experiment.
aseptic technique
a series of steps to prevent contamination during manipulations of cultures and sterile culture media, both liquid and solid.
Keeping things clean
culture
a liquid or solid substance that allows the growth or multiplication of microorganisms. The culture has a particular nutritive makeup and the microorganisms are grown in laboratory conditions
media
combination of nutritive substances that can be altered depending on the microorganism that is to be cultured. Different microorganisms may grow on some media but not on others due to specific metabolic or nutritive requirements
-nutrient solutions used to culture microorganisms
-may be prepared as a liquid (broth, planktonic) or solid (agar, colonies)
chemically-defined media
basal (basic) salt solution, which supplies the inorganic requirements of the organism, and organic components that provide a source of carbon and energy. The exact chemical composition of each component is known
Complex media
contain substances that are rich in both inorganic and organic nutrients such as meat or vegetable infusions, blood, and hormones. The exact chemical composition of the media is not known.
Enriched media
are loaded with nutrients and macromolecular monomers to promote the growth of even the most fastidious organisms
Minimal media
Minimal media contain only the most basic nutrients
Fastidious organisms
Are organisms that have specific nutritive requirements in order to grow.
How is culture media sterilized?
In an autoclave. This eliminates any microorganisms that may be present (as they are ubiquitous; found everywhere)
High pressure and high temperature
inoculation
the process of introducing microbes into a culture media so that it reproduces there
incubation
incubated under the desired environmental
conditions
Putting microorganism and the media its in under the desired environmental conditions to promote growth
What is a pure culture?
When there is only one microbial species present on agar or in a broth media.
Colony morphology
shape, surface, elevation, size, pigment, opacity
cellular morphology
cell shape, size, cell arrangement, Gram reaction
colony forming unit
It is assumed that each colony on the spread plate originated from a single organism from the dilution tube, so we call each colony a colony forming unit (CFU) and we measure bacterial concentration as the number of CFUs per ml of original culture
How to enumerate bacteria in a sample from CFUs?
Number of CFUs on the plate x 10 x 10^x (depends on the dilution of the plate you are counting CFUs on)
Selective media
contain compounds that selectively enrich and/or selectively repress the growth of certain organisms while not affecting the growth of others. In selective enrichment, the nutritional or environmental conditions are controlled to favor the growth of a sought-after species. Selective repression involves inhibiting the growth of interfering species while permitting the growth of a sought-after species.
differential media
contain an indicator that differentiates the
occurrence of specific chemical reactions such that groups of bacteria can be differentiated from each other based on their ability to carry out that reaction.
Acid-fast stain (Kinyoun method)
Prepare smear - flood smear with Kinyoun carbolfuchsin -10min -rinse- decolourize with acid alcohol -rinse - flood with Brilliant Green stain for 1 min
acid fast organisms are red, others are blue/green
Endospore stain
The organism is grown on sporulation agar for 48 hours before preparing an endospore stain
2. Prepare a bacterial smear
3. Place the slide on a heating rack in the fume hood. Cover the smear with a piece of paper towel
that just covers the smear and moisten the towel with Malachite Green. Steam gently for 10
minutes, keeping the paper moist with stain.
4. Remove the paper towel with forceps and rinse the slide with water to remove excess stain
5. Counterstain with Safranin for 1 minute. Rinse with water, blot dry, and observe
ENDOSPORES ARE GREEN AND THE REST OF THE CELL IS PINK/RED
protoplast
When the cell wall is removed, a viable protoplast is obtained that consists of a cell membrane and all intracellular components.
Protoplasts are produced from Gram-positive bacteria by removing the cell wall with lysozyme
spheroplast
In Gram-negative bacteria, the lysozyme will act on the peptidoglycan layer, but it does not remove the
lipopolysaccharides and lipoproteins of the outer membrane, which causes remnants of the cell wall to remain associated with the cell. These are called spheroplasts.
Endospores
Differentiated bacterial cells that form due to gradual changes in the nutritional and physical environment of the organism.
highly resistant
Can remain dormant for a long period of time
the location of the endospore in the cell is usually characteristic of the species
only formed in Gram + organisms
carcinogenic compounds
induce increased rates of mutation and as such have the potential to cause cancer
The Ames Test
Developed by Dr. Bruce Ames
The test screens for carcinogenic compounds
It really tests for mutagenicity but also for potentially carcinogenic substances
test chemicals for mutagenesis has been to measure the rate of back mutations
(reversions) in strains of auxotrophic bacteria
auxotrophic Salmonella strain for histidine
mutagenicity
The capacity to cause mutations - correlates with carcinogenesis by 85-90%
