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51 Cards in this Set

  • Front
  • Back
Name one gram-negative aerobe
Campylobacter, pseudomonas
Name one gram-negative facultative aerobe
Escherichia, Salmonella, Shigella
Name one gram-positive cocci
Streptococcus, Staphylococcus, Lactococus
Name one gram-positive endospore-forming rod
Clostridium, Bacillus
Name one gram-negative endospore-forming rod
Other Clostridium!
Name one gram-positive non-sporulating regular rod
Listeria, Lactobacillus
Name one gram-positive non-sporulating irregular rod
Bacteria Vs Yeasts
Bacteria smaller: 1 micron vs. 2-30
Bacteria prokaryotes/ yeast eukaryotes
Bacteria can be motile/ yeasts are not
Bacteria Vs Mold
Bacteria smaller: 1 micron vs. 20-100
Bacteria prokaryotes/ mold eukaryotes
Bacteria unicellular/ mold form structures (hyphae)
Bateria cell wall = peptidoglycan/ mold = chitin or cellulose
Bacteria vs. Protozoa
Bacteria smaller: 1 micron vs. >10
Bacteria prokaryotes/ protozoa eukaryotes
Bateria cell wall = peptidoglycan/ protozoa = lack rigid cell wall
Bacteria vs Virus?
Bacteria are unicellular: Virus are non-cellular genetic elements
Bacteria are free living/ viruses are obligate parasites
Size: bacteria 1 micron, virus .1mm
Name three common molds is food
Name three common food spoilage microbes
Name a yeast in food
Name three viruses in foods
Hepatitis A
What are some of the sources of Microorganisms in food? (General)
Plants: ephiphytic flora, plant pathogens, soil microorganisms

Animals: Skin, Hair, feathers, etc.; Intestinal tract, poo.
Irrigation and Process H20
Food Ingredients
Equipment, packaging material
Rough estimate of CFU/g in
Meat (raw)
Milk (raw)
Fresh Fruit/Veggies
Ferm. Sausage
Yogurt 10^6-10^7
Meat (raw) 10^4-10^5
Milk (raw) 10^5-10^6
Grains <10^4
Fresh Fruit/Veggies 10^4-10^7
Ferm. Sausage 10^6-10^8
Alfalfa sprouts: 10^9!
pH of:
Milk 6.3
Cheese 5.9
Apple 3.0
Tomato 4.0
Lime 2.0
Beef 5.5
Chicken 6.4
What range of pH can these organisms survive?
Gram + bacteria
Gram -
Gram + 4.0-8.5
- 4.5-9.0
Mold 1.5-9
Yeast 2.0-8.5
What range of aw can these organisms survive? Max??
Bacteria: min .85 - 0.98
Yeast 0.7 - 0.88
Mold 0.6 - 0.85
What are the four main microbiological analysis steps?
1. Sampling
2. Enrichment
3. Detect
4. Confirmation
In step #2 of the four main microbiological analysis steps, what are some options?
Enrichment cultures
In step #3 of the four main microbiological analysis steps, what are some options?
Elisa, Selective media, electrophoresis
In step #4 of the four main microbiological analysis steps, what are some options?
Serotyping, DNA fingerprinting, API strip
What is serotyping?
Method of distinguising between serovars of a species. Phenotypic characterization of strains based on their immunologic reactivity
What is a serovar?
A group of closely related microorganisms distinguished by a characteristic set of antigens. Also called serotype.
What are typical media components? (culture methods)
growth factors
energy source
buffer salt
minerals & metals
Selective agents
Indicator dyes
Gelling agents (base)
What is a major problem with using culture methods?
Does not "detect" VBNC cells that can still make people sick!
List some limitations of culture methods
- Time consuming
- labor intensive
- One cell/colony
- Quantification difficult at times
- Cell injury/cells cannot grow
What are some specific quantitative methods?
Spread, pour plating
Spiral plater
MPN - 3, 5, or 10 reps of each dilutions
Direct Microscope count
What is a specific quantitative biochemical technique? Where is it often used?
Bioluminescence or ATP Measurement:
Used for environmental monitoring / detects ATP bu light emission mediated by luciferin-luciferase; VERY sensitive and instantaneous
What are specific qualitative biochemical techniques?
Ability to grow on selective media
degradation of specific compound
production of specific enzymes
Cell staining
Ability to grow anerobically
What are API strips?
Used for biochemical qualitative analysis:
they're stips w/wells that contain different media/substrates - they react different w/different organisms & the specific color combo tells you what you have
What are immunoassay methods based on?
Specific antibodies bind to specific antigens (i.e. microorganisms).
What are antibodies? What are they made of?
Antibodies are glycoproteins that are produced by Bcells. Mammals can product 1 Billion different ones!! They're produced in response to a specific antigen
Definition of an antigen?
A foreign substance that triggers antibody production as part of an immune repsonse
What are some tests that are based on immunoassay techniques?
Elisa, IMS (immunomagnectic separation), antibody-antigen separation, immunochromatagraphy
What are pregnancy tests based on?
The immunoassay technique: immunochromatography
Describe the structure of an antibody (draw it)
Y shaped - Antigen binding site is at top of "Y" at variable region; it's a glycoprotein held together by S-S bonds
What are qualitative immunoassay techniques?
1. Antibody-antigen precipitation
3. Immunomagnetic separation
4. Immunochromatography (lateral flow device)
Describe antibody-antigen precipitation
Latex bead are covered w/Antibodies (Y). "Latex agglutination" : if specific microbe present, they bind w/antigen and cause precipitation
What are the general priciples behind ELISA?
1. Antigens/Antibodies can be absorped to solid surfaces (surface of well)
2. If not reacted, free reagents washed away
3. Results read in spectophotometer (color)
What are the two types of ELISA?
Direct and Indirect (Sandwich format)
Describe the steps of direct ELISA
1. Antibody absorbed on well surface: antigen added and will react w/antibody
2. Antibody-enzyme complex added - antibody binds to antigen
3. Substrate added that will turn color if enzyme is present (i.e. not washed away) ; Color = antigen present
Describe the steps of indirect ELISA
1. Antibody absorbed on well surface: antigen added and will react w/antibody
2. Antibody #2 added and will bind to antigen (NOTE: in direct, En-AB added here)
3. NOW En-AB added and attached to AB#2. This allows a bunch of Eb-AB to attach.
3. Substrate added that will turn color if enzyme is present (i.e. not washed away) ; Color = antigen present
What is the benefit of indirect vs direct ELISA?
Indirect: generally more En-AB complex can attach and so the color change is more dramatic (i.e. more easily measured)
What are some advantages/Disadvantages of ELISA?
Advantages: quick, cost effective, sensitive, simple, little waste disposal
Dis: Reliability on aqueous media, contaiminants can interfere, more sensitive that reg. standards!
16S "gold standard"
rRNA is the most conserved (least variable) gene in all cells. For this reason, genes that encode the rRNA (rDNA) are sequenced to identify an organism's taxonomic group. The 16S rRNA is used; contained in operon. Some bacteria have duplicates (7 Ecoli)
What is a DNA probe?
It's like a marked primer - generally based on 16S rRna
What is a major difference between PFGE and ribotyping?
With PFGE you need whole DNA; w/ ribotyping, fragments are ok --> prep time is much shorted w/ribotyping
Ribotyping analyzes the DNA that codes for the makeup of the ribosomes

This genetic fingerprint comes from genes that code for ribosomal ribonucleic acids (rRNA)

In ribotyping, restriction enzymes are used to cut the genes coding for rRNA into pieces, and electrophoresis separates the pieces by size through a gel