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Food Microbiology Quiz 1


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what are the characteristics of a gm + bacteria?
1. Have a Cell Wall
2. Cell Wall is Thick
3. Lack an outer membrane
4. Stain purple
what are the characteristics of a gm - bacteria?
1. Have a Thin Cell Wall
2. Has an outer membrane composed of a phospholipid bilayer
3. Stains Pink
what is an aerobic bacteria?
has an O2 based metabolism
what is a facultative anerobe?
are anerobic bacteria, but can grow also when O2 is present. Basically, they grow in both environments
what is an anerobe
grows in environments that lack O2
what are rickettsias?

non-motile, gm -, non-sporeforming bacteria that require a host to grow.

(depend on cytoplasm of euk. host)

example: Rickettsia typhi
what is a cocci bacteria?
spherical shaped

ex. staphylococcus
what is an endospore?
dormant, tough, non reproducing structures that are produced by bacteria for survival in non-optimal environments.

ex: Cloistridium botulinium
what is an example of a gm - endospore forming rod?
what is a thermophilic bacteria?
grows in high temp env.
what is a psychrotropic bacterium?
bacterium that can grow at 0C but prefer 40-70C range. particularly concerning for food spoilage.
what is a thermoduric bacterium?
bacteria that can survive high temperatures, particularly pasteurization.
what is a halotolerant bacteria?
bacterium that can grow best in the absence of NaCl, but can still grow when mod. conc.'s are present.
what is a aciduric bacterium?
bacteria that can tolerate highly acidic environments.
what is a osmophilic bacterium?
bacteria that prefer to grow in env.'s of high osmotic pressure.
Who contradicted spontaneous generation in 1765?
Leuweenhoek. Boiled meat in sealed flask, saw no growth.
Who invented canning in 1804?
Appert. He developed the sealed container therma process (canning). He developed it for a 10000 prize that Napolean offered to prevent food spoilage at war.
Who further refined the canning process to use tin? What year?
Durand, 1819.
Who was JT Snow?
Recognized cholera in 1849. Drinking water issue in britain.
Describe Pasteurs notable discoveries and the years.
1860-fermentation was due to yeast and bact. Disproved spon. generation.

1870- Developed mild heating process for preservation (pasteurization). Originally developed for wine industry.

Postulated GERM THEORY FOR DISEASE--infections due to micro-organisms.

Developed ANTHRAX and RAIBES vaccines.
Describe Koch's major discoveries.
-Isolated Vibrio cholera
-Developed solid media(agar), petri dish, and steam sterilization. (autoclave)

1.Isolate agent from patient
2. Grow in lab
3. Infect healthy subject
4. Subject must develop symptoms
what are the characteristics of prokaryotes?
no nucleus
singular chromosome (DNA)
usually unicellular
describe characteristics of yeast
eukaryotic, cell walls made of glycan

cell size = 2-30um

fungi group

unicellular, oval, spherical, or elongated

describe characteristics of molds

rigid cell walls (made of chitin or cellulose)

lack chloroplasts
describe characteristics of protozoa

quite motile

no cell walls or chloroplasts

usually unicellular
describe characteristics of viruses
made of non-cellular genetic elements

size = 0.1um

obligate parasite - needs cells to replicate viral particles
what are beneficial food microbes?

deleterious? innocuous?
food fermentators


dont do anything relevant
Name all of the Pathogenic Bacteria in Foods
Aeromonas, Arcobacter, Bacillus, Campylobacter, Clostridium, Escherichia, Listeria, Salmonella, Shigella, Staphylococcus, Streptococcus, Vibrio, Yersina
Name a disease associated with the pathogens listed above in food.
Aeromonas - Diarrhea, severe sickness in children

Arcobacter - Campylobater species, diarrhea. Spread through animals

Bacillus - Bacillus cereus, vomiting and diarrhea. Short duration of illness

Campylobacter - Diarrhea

Cloistridium - Botulism, canned foods anerobic, diarrhea, double vision, suffocation, Gm+

Escherichia - diarrhea, kidney disease, meats (cow)

Listeria - Milk prod, immunocompromised adults, causes septicimia, meningitis, monocytogenes is species. Gm+

Salmonella - diarrhea, meats

Shigella - bloody diarrhea (dysentary)

Stapylococcus - aureus, vomiting, diarrheam nausea, Gm+

Streptococcus - pyogenes

Vibrio - seafood (oysters), usually from fecal source. makes. fever, chills, nauseas. Vibrio vulnificus

Yersina - enterocolitica, diarrhea
What is another name for microbial growth?
Binary Fission
What is the equation used for predicting binary growth?
Name all the phases of a microbial growth curve
Lag Phase, Exponential Phase, Stationary Phase, Death
What is Symbiotic, Synergistic and Antagonistic Growth?
Symbiotic=Require each other
Synergistic=Complement Each other, faster together
How do we measure growth?
Generation Time, Specific Growth
Name Intrinsic Factors that Affect Growth.
pH, aW, Nutrient Content, Oxi-Red Potential, Presence of Anti-Microbials
Why can't bacteria grow at a very low pH?
Because the protiens of the bacteria have an optimal pH value to catalyze reactions in order for reproduction. (more H+ diffuses in cell than H+ pump can pump out)
Name differences between yeast and algae
⬢Yeast have no chloroplasts
⬢Yeast are non-motile
⬢Yeast are relevant in food microbiology, algae aren't
Name differences between yeast and mold
Yeasts are mostly unicellular, Molds are usually multicellular
Yeast cell wall made of glycans, molds of chitin
Discuss three differences and two similarities between an ELISA and a lateral-flow device.
⬢ ELISA requires several steps, LFD does not
⬢ ELISA uses enzymes as reporters, LFD does not (use latex particles)
⬢ ELISA is slower than LFD
⬢ LFD is simpler than ELISA
⬢ ELISA is more sensitive than LFD
⬢ Both use at least two set of antibodies
⬢ Both use the sandwich format
⬢ Both are immunoassays
⬢ Both are qualitative methods
7. What are the characteristics that make the 16s RNA genes ideal as a phylogenetic molecule?
Mention at least 3 of the following 4:
⬢It is highly conserved
⬢It is present in all bacteria (universally present)
⬢It is easy to obtain
⬢It has multiple copies
What are the differences between the activated and germinated stage of the sporeformer cycle?
The germination stage has synthesis of amino acids & nucleotides, RNA and protein synthesis, cell wall and membrane synthesis, and DNA replication

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