Food Microbiology Flashcards
A gene with reversed orientation with respect to its regulatory sequence is called?
Antisense gene
A pool of DNA segments that is likely to contain a gene of interest is called a ____?
Genome library
A transgenic organism can be defined as what?
An organism containing foreign DNA
A thermal death curve is a plot of temperature versus log of the process time. What is the slope equal to?
-1/z
Allicin is an antimicrobial compound produced in what vegetable?
Onions/garlic
An enzyme called “coagulase” is produced by this pathogen which is highly correlated with its toxin production?
Staphylococcus aureus
An initial population of 50,000 bacteria grows with a generation time of 30 minutes. About how many bacteria 3 hours later?
3,200,000
A 6D process reduces the population of the target organism by what percent?
99.9999%
Chocolate creams have been known to undergo explosions. What is responsible for this phenomenon?
Clostridium species cause explosions after they enter the chocolate candy through sugars, starch and other ingredients
Clostridium welchhii is more commonly known as what?
Clostridium perfringens
Define “transformation”
The process of genetic transfer where bacteria are induced to accept and incorporate into their genome foreign pieces of cell-less, isolated DNA, often in the form of a plasmid.
Define a food infection.
Ingestion of organism and then the organism invades tissues in the body
What are the end products of a homofermentation by lactic acid bacteria?
Homofermentative - glucose fermented to > 90% lactic acid
Define D Value
Time needed to inactivate 1 log cycle of a population (or a 1 decimal reduction) at a given temperature or time needed to reduce a population to 10% of the original
Define fecal coliforms and indicate the reason that they are often evaluated in foods.
Gram negative, asporogenous rods that ferment lactose to acid and gas at 44.5 to 45.5 C
DNA obtained by cutting and recombining DNA molecules from different sources is called?
rDNA (recombinant DNA)
DNA sequence variations that occur when a single nucleotide in the genome sequence is altered is called what?
Single Nucleotide Polymorphisms (SNPs)
During which phase of microbial growth may bacteria be most easily killed?
Log phase
Enzymes that catalyze the hydrolysis of ester linkages in triacyglycerides are called what?
Lipases
Every microbiology student knows it’s the Bible of Bacterial Taxonomy. What is it?
Bergey’s Manual
For what does BRC stand and what is it?
British Retail Consortium; food safety standards system
For what does MPN stand?
Most Probable Number
Fresh Mexican style cheese was the vehicle for an outbreak in California in 1985 in which 300 persons became ill and almost 100 of them died. What organism, found in the finished product and throughout the plant, was responsible for this outbreak?
Listeria monocytogenes
Give three sites of action for antimicrobials.
Cell wall; cell membrane; genetic mechanism or functions; interfering with enzyme systems; binding essential nutrients
Give two microorganisms responsible for scombroid poisoning (histamine) in seafood?
Morganella spp., especially Morganella morganii; Others include: Proteus spp., Klebsiella pneumoniae, Clostridium perfringens, Hafnia alvei
How does pH negatively affect microorganisms?
Influence availability of metallic ions; cell permeability to cations and anions; affects tRNA and protein synthesis; activities of enzyme systems; products of metabolism of microorganisms
How is fungi differentiated from algae and other higher plants?
Lack of chlorophyll
How many primer(s) is(are) used in a loop-mediated isothermal amplification assay?
4 to 6
How many square centimeters in a standard 9 cm Petri dish?
64 cm2
If a food processor chooses potassium sorbate over sorbic acid it would probably because it is what: less toxic, more heat stable, more water soluble, less water soluble
More Soluble in water than in Sorbic acid
If Salmonella colonies are isolated on an XLD plate, what color will the colonies likely be.
Red with black centers
In 1996 a parasite outbreak was found on strawberries in 3 US states. What was it?
Cyclospora cayetenensis
In Baird-Parker medium, what do Staphylococcus aureus colonies look like?
Black with a clear zone
In relation to HACCP, define the term hazard.
Anything (biological, chemical, physical) that may cause an unacceptable consumer health risk.
In what year was nisin discovered?
1928
Mad Cow disease is also known as BSE, which stands for what?
Bovine Spongiform Encelphalopathy
Messenger RNA is synthesized by what process?
Transcription
Name a foodborne pathogen has the greatest tolerance for low water activity?
Staphylococcus aureus
Name a foodborne pathogen that is linked to the sequela called “Reiter’s Syndrome”
Salmonella, Campylobacter, Shigella, Yersinia
Name a method to evaluate surface bacteria contamination.
Swab and streak SMA plate, direct contact plating
Name the common biological indicator for acceptable autoclave function.
B. stereothermophilus spores
Name the two crops which are clearly considered to be the major sources of dietary aflatoxin in the U.S.
Corn and Peanuts
Name the type of botulism most often associated with fish and which may grown at low temperatures?
Type E
Name three factors that contribute to the preservative action of smoking foods.
Temperature, drying and salt lower water activity, smoke contains antimicrobials and antioxidants
Name three means of genetic material exchange between bacteria?
Transduction, Transformation, conjugation
Name two conditions under which yeasts and molds will out compete most bacteria.
Low aw (0.6-0.7) and pH 9
Name two organisms responsible for pickle fermentation?
Lactobacillus plantarum, Pediococcus cerevisiae (these are the 2 that are most involved), Lactobacillus brevis
Name two species of bacteria that cause human food poisoning by producing a bacterial toxin in the food product.
Staphylococcus aureus, Clostridium botulinum, Bacillus cereus
Name two ways that freezing slows down the growth of microorganisms.
Lowers temperature and slows metabolic processes down and decreases water activity
Of the Staphylococcal enterotoxins, which type is the most frequent cause of food poisoning?
Type A
Organisms whose genetic material has been altered using genetic engineering techniques are called what?
Genetically Modifed Organisms or GMOs
Sauerkraut results from what type of fermentation process?
Lactic Acid
Structures composed of a polymer of glycerol or ribitol joined by phosphate groups and amino acids covalently linked to muramic acid in the cell walls of gram positive bacteria are called what?
Teichoic acids
The Lohman reaction is catalyzed by ATP creatine phosphotransferase. Its function is to replenish ______.
ATP
The manufacture of tempeh requires what two essential ingredients?
Soybeans and mold (Rhizopus oligosporus or Rhizopus oryzae)
The medium used for the detection of Lactic Acid Bacteria goes by the acronym MRS; what does MRS stand for?
deMann, Rogosa, and Sharpe
The oxidase test detects the presence of what enzyme?
Cytochrome C oxidase
The term hyphae refers to: A. a large pipe that carrier water; B. bacterial growth; C. mold growth; D. a packaging machine
mold growth
The toxin from Clostridium botulinum impairs nerve function by blocking release of what?
Acetylcholine
Toxoplasmosis is caused by what microorganism?
Toxoplasma gondii, a coccidian protozoan
Use of a chemical compound to reduce viable pathogenic and spoilage vegetative microorganisms on food contact surfaces or some raw food surfaces is called what?
Sanitization (NOTE: NOT sanitation)
Vibrio vulnificus food poisoning has been associated with what type of seafood product?
Raw oysters and clams
What agency is responsible for maintaining records and reporting foodborne illnesses in the US?
Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia
What antimicrobial food preservative is a macrolide antibiotic
natamycin
What are bacteriocins?
Proteins or protein complexes produced by bacteria with bactericidal activity directed against species closely related to the producer bacteria.
What are haloduric bacteria?
Organisms that can withstand but not grow in high concentrations of salt
What are halophilic bacteria?
Organisms that can grow in the presence of and require high concentrations of salt
What are hemolytic bacteria?
Bacteria which can lyse blood cells
What are osmophilic bacteria?
Bacteria that prefer high osmotic pressures - those that can grow in a relatively higher osmotic environment
What are porins?
Outer membranes proteins that form pores wide enough to allow passage of most small hydrophobic molecules through the cell membrane of bacteria.
What are some viruses that cause foodbome human illnesses?
Hepatitus, Rotavirus, Norwalk virus
What are the 2 distinct syndromes of B. cereus gastroenteritis?
Emetic – intoxication; Diarrheal - toxicoinfection
What are the general water activity limitations for bacteria, yeast, and molds (list 3 separate answers)?
Bacteria: 0.90 Yeasts: 0.88 Molds: 0.80 (Halophilic bacteria can go to 0.75; halophilic yeasts can go to 0.60; and halophilic molds can go to 0.65)
What are the two main types of bacteriophages and how do they operate?
Virulent phage (lyses cells); Temperate phage (inserts genetic material into bacterial cell, which then becomes a carrier)
What are the two methods yeast used to divide?
budding, binary fission
What are the two templates for RPCR and PCR?
RNA, DNA
What are the types of double helix DNA?
A, B, and Z
What are two components that make up the outer cell membrane of gram negative bacteria?
Lipopolysaccharide; porins; lipoproteins; Outer membrane proteins
What bacteria, usually found in powdered milk formulas, is the cause of neonatal necrotizing entercolitis?
Cronobacter sakazakii
What bacterial genus is often the cause of foodborne illness in seafood?
Vibrio spp.
What bacteriocin is produced by Pediococcus and what does it act against?
Pediocin
What bacterium causes flat sour spoilage of canned food?
Bacillus stearothermophilus
What can be described as a bacterial virus that can infect specific strains of bacteria?
Bacteriophage
What causes the “eyes” in Swiss cheese?
CO2 production by Propionibacterium shermanii
What causes the increase in pH associated with microbial spoilage of foods?
Deamination of amino acids, decarboxylation of organic acids
What company introduced CHY-MAX Chymosin and what is its significance?
Pfizer, Inc. introduced CHY-MAX Chymosin, the first product of rDNA technology in the US food supply.
What concept was devised at the Massachusetts Institute of Technology in 1966 that used microorganisms as a food source?
Single Cell Protein (SCP)
What disease on wheat is casued by the fugal species of genus Puccinia?
Rust
What do the initials SDS-PAGE stand for?
Sodium dodecylsulfate polyacrylamide gel electrophoresis
What does an indicator microorganism indicate?
The potential presence of a pathogenic microorganism
What does BT corn stand for?
Bacillus thuringensis corn that is used to control insects. The corn expresses high levels of Bt protein to kill the insects.
What does CFU stand for?
Colony Forming Unit
What does E. stand for in E. coli?
Escherichia
What does ELISA Stand for?
Enzyme Linked Immunosorbent Assay
What does FAD stand for?
Flavin adenine dinucleotide
What does IMVIC stand for?
I=Indole, M=methyl red, V=Voges-Proskauer, C=Citrate - Set of biochemical test used to differentiate coliforms
What does RAD stand for?
Radiation absorbed dose
What does RODAC stand for and describe the method
Replicate organism direct agar count
What does the operator of an operon react with?
A repressor protein
What does the term RT-PCR stand for?
Reverse transcriptase polymerase chain reaction
What Eh range favors anaerobes?
Anaerobes require negative Eh values (reduced)
What equation is used to describe the growth of microorganisms?
Gompertz
What essential oil component in oregano is a naturally occurring antimicrobial?
carvacrol
What foodborne pathogen can cause symptoms similar to appendicitis?
Yersinia enterocolitica
What forms the basis of the difference between coliforms and fecal coliforms?
Coliforms ferment lactose at 35 C, while fecal coliforms ferment lactose at 44.5 C.
What genus of microorganisms is most often involved with spoilage of refrigerated fresh meat, poultry, fish, and eggs?
Pseudomonas
What gram-negative foodborne pathogen has been linked to the syndrome known as Guillain-Barre syndrome?
Campylobacter jejuni
What group of microorganisms has an optimum growth temperature range of 10 to 15C?
Psychrophiles
What group of microorganisms has an optimum growth temperature range of 20 to 30C?
Psychrotrophs
What group of microorganisms has an optimum growth temperature range of 20 to 45C?
Mesophiles
What group of microorganisms has an optimum growth temperature range of 55 to 65C?
Thermophiles
What is a chimera?
Chimera is a recombinant DNA molecule made up of DNA fragments from more than 1 organism, named after the mythological beast.
What is a Roentgen?
A unit of measure used for expressing exposure dose of X-ray or gamma radiation.
What is Agrobacterium tumefaciens used for?
It is a tumor inducing plasmid used to transfer genes into plant genomes.
What is an aerobic or facultatively anaerobic gram-negative non-sporeforming rod shaped bacteria that ferments lactose with the production of gas in 48 hr at 35°C called?
Coliform
What is expressed when some restriction endonuclease are used under the wrong/non-optimal buffer conditions?
Star Activity
What is mutually advantageous association of two or more organisms?
Symbiosis
What is one example of a medium used for Salmonellae preenrichment?
Lactose broth, tryptose broth, brilliant green water, universal pre-enrichment
What is SCP?
Single cell protein
What is the causative agent of typhoid fever?
Salmonella Typhi
What is the chief component of fungal cell walls and shells of insects and crustaceans?
Glucosamine
What is the color of a positive Simmons Citrate Test?
Blue
What is the commercial source of lysozyme for use as an antimicrobial food preservative?
Egg white
What is the complementary mRNA sequence of the following DNA sequence: AGCT?
U-C-G-A
What is the complimentary nucleotide sequence to A-G-C-T?
T-C-G-A
What is the definition of a foodborne disease outbreak?
An incident in which 2 or more persons experience a similar illness after ingesting a common food and epidemiological analysis implicates the food as the source of the illness. Note: For botulism or chemical poisoning, 1 case constitutes an outbreak.
What is the difference between a prokaryotic organism and a eukaryotic?
Prokaryotes - no nucleus, no mitochondria, wide variety of metabolic mechanisms
What is the difference between bacteriostatic and bactericidal?
Bacteriostatic: inhibitory; Bactericidal: lethal, kills microorganism
What is the Fight Back Program?
STEPS?????
What is the first step in detection of Salmonellae in foods using the standard FDA cultural procedure?
Preenrichment
What is the foodborne disease involving cats as obligatory intermediate hosts known as?
Toxoplasmosis
What is the Hurdle Concept?
Reliance on multiple preservation processes to stop or slow growth of microorganisms in foods
What is the indicator organism used to ensure the proper pasteurization of milk?
Coxiella burnetti
What is the main source of Vibrio cholerae?
Shellfish
What is the measurement of the oxygen used in the stabilization of organic matter by microorganisms over a 5-day period at 20 C called?
BOD - Biological Oxygen Demand
What is the medical term or name given to the condition where bacteria are actively multiplying in the blood stream?
Septicemia
What is the minimal water activity for growth for most bacteria?
0.90-0.91
What is the minimal water activity for growth for most molds?
0.70-0.80
What is the mold that produces aflatoxin?
Aspergillus flavus
What is the most common cause of inconsistent acid development in the cheese industry?
Bacteriophage infection
What is the most common matrix used for protein electrophoresis?
Polyacrylamide gels
What is the most frequently reported Salmonella serotype isolated from human and non-human sources?
Salmonella Typhimurium
What is the most radiation resistant pathogenic microorganism in food?
Clostridium botulinum
What is the name for a secondary metabolite produced by fungi that can cause unnatural or deleterious biological changes in plants, animals, humans, or microorganisms?
Mycotoxin
What is the percent RNA and protein in a ribosome?
70% RNA, 30% protein
What is the primary microorganism used for the leavening of bakery products?
Saccharomyces cervisiae (bakers yeast)
What is the primary physical defense of shell eggs?
Shell membrane
What is the principal structural component of the bacterial cell wall?
Peptidoglycan
What is the purpose of a Durham vial in a lactose broth?
To test for gas
What is the range in kilograys of the sterilization treatment known as radappertization?
30-40 Kgy
What is the site of protein synthesis within cells?
Ribosomes
What is the source for the antimicrobial food preservative natamycin?
Streptomyces natalensis
What is the source of catalase?
Bovine liver
What is the temperature danger zone for holding foods?
40-140°F
What is the term for diseases resulting from the invasion of living cells by fungi?
Mycoses
What is the term for the noncoding section of DNA in a gene from eukaryotes?
Intern
What is the term given to the time required to reduce a specific microbial population by 90% at a given temperature?
D value or Decimal Reduction Time
What is the unit for dose rate in ionizing radiation preservation?
Kilogray (1 G = 100 rads; 1 kGy = 105 rads)
What is the USDA temperature recommendation for cooking pork products?
It should attain 170 F (76.7 C).
What is xerophilic?
Dry-loving (e.g., Dry loving molds)
What is zoonosis?
Disease spread to humans from vertebrate animals.
What medium is used to identify the presence of Bacillus cereus in a food?
MYP
What microaerophile causes foodborne gastroenteritis?
Campylobacter jejuni
What microorganism carries out the malolactic fermentation of wines?
Oenococcus oenos
What microorganism causes ropiness of milk?
Alcaligenes viscolactis
What microorganism causes trichinosis?
Nematode - Trichinella spiralis
What microorganism initiates most natural vegetable fermentations?
Leuconostoc mesenteroides
What microorganism is responsible for the “Noble Rot” of late harvest wine grapes?
Botrytis cineria
What microorganisms are the public health parameters of pH 4.6 and aw of 0.85 based on?
pH = 4.6 is Clostridium botulinum; aw = 0.85 is Staphylococcus aureus
What model is used to describe the non-linear inactivation of microorganisms by heat?
Weibull
What mold is hypothesized to be connected with the Salem witch trials?
Claviceps purpea - ergot of wheat
What mold is used in making blue cheese and Roqueforti?
Penicillium roquefortii
What mold is used in making Camembert and Brie cheese?
Penicillium camemberti
What neurotoxin from a bacterial foodborne pathogen may be inactivated by boiling?
Clostridium botulinum toxin
What one bacteriocin is approved for food preservation in US and in what product may it be used?
Nisin–pasteurized process cheese spread (Nisin is produced by Lactococcus lactis)
What organism causes anisakiasis or herring worm disease?
The nematode Anisakis simplex
What organism causes ergotism, also known as St. Anthony’s Fire?
Claviceps purpurea; Caused by eating toxic alkaloids produced by the fungus on wheat, barley, rye, oats, and wild grasses
What organism is a source of cellulase, glucoamylase, pectinase, and glucose oxidase?
Aspergillus niger
What organism is responsible for Q fever?
Coxiella burnetti
What organism is responsible for the ropiness defect?
Bacillus subtilus
What organism is used to determine the nutrient bioavailabilty of some water soluble vitamins?
Lactobacillus plantarum
What organism produces nisin?
Lactococcus lactis ssp. Lactic
What organisms are a source of alpha amylase?
Aspergillus orzae, Bacillus subtilis
What pathogenic bacteria can grow in foods with a water activity of 0.86?
Staphylococcus aureus
What procedure involves the migration of charged molecules in a solution through an electric field?
Electrophoresis
What purpose does the “Howard Mold Counts” serve?
Primarily for the purpose of monitoring molds in tomato products and processing equipment
What regulatory approved food antimicrobial gets its name from the group of bacteria, previously called “Group N Streptococcus,” which produce this peptide?
Nisin
What risk does L. monocytogenes pose to pregnant women?
Abortion
What scientist won a Nobel prize for being the first to deduce the amino acid sequence of insulin, and a second Nobel for being the first to sequence DNA?
Fredrick Sanger - 1955
What surveillance system in use by CDC uses standardized molecular subtyping (or “fingerprinting”) of foodborne disease-causing bacteria by pulsed-field gel electrophoresis (PFGE). To identify outbreaks?
Pulsenet
What template is used when conducting RT-PCR?
ribonucleic acid (RNA)
What term is given to the canned food spoilage that produces a lowered pH but no gas?
Flat-sour
What term is used to describe a process in which chemical changes are brought about in an organic substrate through the action of enzymes and MO?
Fermentation
What the three agents of foodborne illness cause the most cases?
Norwalk-like viruses, Campylobacter jejuni, and Salmonella
What three sugars are included in a triple sugar slant?
Lactose, glucose, and sucrose
What two groups were primarily involved in developing the HACCP system for food?
NASA, Pillsbury
What type of gaseous environment is required for the growth of virtually all species of mold?
Aerobic
What type of gene signals the presence of a DNA sequence of interest?
Reporter gene
What type of microbiological medium is triple sugar iron agar? A. Differential, B. Selective, C. Selective and Differential
A: Differential
What types of organisms are most likely to grow on the surface of a jar of jam?
Yeasts and molds
What types of spoilage organisms are most likely to be found in vacuum packed, refrigerated meats held for several weeks?
Lactic acid bacteria, psychotrophs, microaerophiles
What was the first genetically engineered whole food in the U.S. food supply?
The FLAVR SAVR tomato marketed by Calgene, Inc.
What was the first recombinant DNA food additive sold in the USA?
Calf chymosin produced by microorganisms – first food grade enzyme made by recombinant DNA technology
What was the name of HACCP before it was termed HACCP?
Failure mode effect analysis
When mold growth occurs on a food, will the pH of that food increase or decrease and why?
Increase; molds use organic acid for nutrients
When testing for C. perfringens what is the only negative test result that suggests a positive confirmation?
Motility
Which bacterium promotes tooth decay?
Streptococcus mutans
Which foodborne pathogens produces a heat-stable toxin?
Staphylococcus aureus
Which of the following is a fermented food? a) sweet acidophilus milk b) tofu c) surimi d) miso
d) Miso
Which of the following is a psychrotrophic food poisoning organism? - Campylobacter; E. coli; Salmonella; Yersinia enterocolitica
Yersinia enterocolitica
Which of the following is a psychrotrophic foodborne pathogenic bacterium? A. Campylobacter B. Escherichia coli C. Salmonella D. Yersinia enterocolitica
D. Yersinia enterocolitica
Which organ in the body is the primary site of action of aflatoxin?
The Liver
Which taxonomic scheme has includes over 2000 serovars of Salmonella?
Kauffmann-White
Who discovered lysozyme?
Alexander Fleming
Who discovered the DNA structure?
Watson and Crick
Who first described the “Hurdle Concept” and when?
Lothar Leistner - Federal Center for Meat Research Germany in 1978
Who first investigated nisin for use as a food preservative antimicrobial?
Hirsch
Why are enrichment techniques used when examining food for the presence of Salmonella?
Salmonella are usually present in small numbers. Enrichment allows Salmonella to grow and outcompete non-Salmonella microbes and also allows recovery of injured cells.
Why is mercaptoethanol used in the preparation of protein samples for gel electrophoresis?
It is a reducing agent which dissociates the protein into subunits and reduces disulfide bonds.
Wthin the HACCP model, how is Critical Control Point defined?
A step at which control can be applied and is essential to prevent or eliminate a food safety hazard or reduce it to an acceptable level.
Order the following organic acid antimicrobials with respect to their pKa’s, from highest pKa to lowest. (Benzoic Acid, Sorbic Acid, Propionic Acid, Lactic Acid)
Propionic Acid, Sorbic Acid, Benzoic Acid, Lactic Acid
Define an Intermediate Moisture (IM) Food.
Food preserved by lowering the Aw by solutes; Moisture levels = 15-50%, aw = 0.6 - 0.9
Define vector and shuttle vector.
Vector - DNA molecule, capable of replication in a host organism, into which a gene is inserted to construct a rDNA molecule; Shuttle vector - can replicate in the cells of more than 1 organism (gram + and gram -); goes between the cloning host and target host.
Following is a list of bacterial genera; tell whether they are gram positive or gram negative: Bacillus, Clostridium, Escherichia, Pseudomonas, Erwinia, Staphylococcus
Positive, Positive, Negative, Negative, Negative, Positive
For what do the following stand?
RFLP, RAPD and PFGE
RFLP - Restriction Fragment Length Polymorphism
RAPD - Random Amplified Polymorphic DNA
PFGE- Pulse Field Gel Electrophoresis
Give three examples of Intermediate Moisture (IM) Foods
fig newtons, marshmallows, jams, jellies, molasses, honey, syrups, semimoist pet foods
How is vinegar made?
food product (cider, malt, whey and fruits that have fermentable sugars) fermented by yeast to ethyl alcohol, oxidation of the alcohol to acetic acid by Acetobacter and/or Gluconobacter.
If the thermal death time for C. botulinum spores is 2.5 minutes at a temperature of 250 F with a Z-value of 18, what is the thermal death time at 286F?
0.025 min
In what order are the gram stain reagents added?
Crystal violet, iodine, ethanol, safranin
List 5 genotyping methods
Pulsed Field Gel Electrophoresis(PFGE); Repetitive extragenic palindromic PCR (Rep-PCR); Restriction Endonuclease analysis; Restriction Fragment Length Polymorphism(RFLP); Plasmid Profile Analysis; Ribotyping; Random Amplified Polymorphic DNA(RAPD)-Arbitrary primed PCR; Ribotyping; Sequencing
Name 5 major causes of food deterioration.
1-microorganisms; 2-food enzymes; 3-insects, parasites, and rodents; 4-temperature; 5-moisture/dryness; 6-air/oxygen; 7-light; 8-time
Name four genera of bacteria always considered as lactic acid bacteria.
Lactobacillus, Lactococcus, Leuconostoc, Pediococcus
Name four molecular methods of fingerprinting foodborne organisms.
nucleic acid probes, polymerase chain reaction (PCR), multilocus enzyme electrophoresis, restriction enzyme analysis, random amplication of polymorphic DNA (RAPD), plused field gel electrophoresis (PFGE), restriction fragment length polymorphism (RFLP), ribotyping
Name three factors that affect the heat resistance of microorganisms?
Temperature, pH, variation among strains, fat, protein, carbohydrate content, preservatives, number of cells, age of cells, growth medium
Name two organisms used as starter cultures for Cottage cheese
Lactococcus lactis subsp lactis (or subsp cremoris) and Leuconostoc mesenteroides subsp cremoris
Peptidoglycan is an important structural component of bacterial cell walls. Of what two amino sugars is it composed?
N-acetyl glucosamine (NAG), N-acetyl muramic acid (NAM)
Reiter’s syndrome may be a sequalae of a primary foodborne infection. List two potential bacterial pathogens involved with the syndrome.
Campylobacter, Salmonella, Shigella, Yersinia
The CAMP test is used to identify what foodborne pathogen? What does “CAMP” stand for?
Listeria monocytogenes; Christie, Atkins, Munch, Peterson
The two microorganisms used as the starter culture for yogurt are what?
Streptococcus thermophilus, Lactobacillus bulgaricus (in 1:1 ratio)
What are five uses of ionizing radiation in foods?
Inhibit sprouting, delay ripening, destroy insects and larvae, destroy parasites, eliminate pathogens, reduce the number of viable microbes, commercially sterilize foods
What are the 4 Koch’s postulates and what do they apply to?
The causative microorganism must be present in every individual with the disease; The causative microorganism must be isolated and grown in pure culture; The pure culture must cause the disease when inoculated into an experimental animal; The causative microorganism must be reisolated from the experimental animal and reidentified in pure culture
What are the names of the 3 typical radiation treatments used for foods?
Radappertization; Radicidation (pasteurization); Radurization (disinfestation, sanitization)
What are the seven steps of HACCP?
Hazard Analysis, Identifying CCPs, Establishing Critical Limits, Monitoring CCPs, Corrective Action, Verification, Record Keeping
What are the spore-forming foodborne pathogens?
Bacillus cereus, Clostridium perfringens, Clostridium botulinum
What are the three major genera of mycotoxin producing fungi?
Aspergillus, Penicillium, Fusarium
What are three intrinsic factors that affect the growth of microorganisms in food?
pH, aw, antimicrobial constituents, Eh, nutrient content, biological structures
What are three methods for immobilizing enzymes?
Adsoption, Entrapment, Microencapsulation, Ion exchange, Cross-linking, Copolymerization, Covalent attachment
What are three microbial inhibitors in egg white and how do they work?
Lysozyme - Lysis of cell wall (Gram-positive bacteria); Ovomucoid - Trypsin inhibitor; Conalbumin - Chelates metal ions, especially ferric ions–inhibits growth by extending lag phase; Avidin - Binds biotin; Ovoflavoprotein -Binds or sequesters riboflavin Also high pH
What are two extrinsic factors that affect the growth of microorganisms in food?
Temperature, atomosphere, relative humidity
What do the letters of the IMVIC test stand for?
Indole, methyl-red, vogues proskauer, citrate
What is a plasmid? Name 3 methods for plasmid replication.
A self replicating, usually circular piece of DNA, primarily independent of the host chromosome (extrachromosomal); Replication: 1) unidirectional; 2) bidirectional; 3) rolling circle
What is Taq polymerase and for what is it named?
A. It is a thermostable DNA polymerase; B. Thermus aquaticus (a bacterium)
What is the difference between direct and indirect ELISA?
Indirect ELISA is used to detect or quantitate antibody; Direct or sandwich ELISA is used to detect or quantitate antigen
What is the name of the causative agent that is thought to cause Bovine Spongiform Encephalopathy?
Prion
What organisms do the following media select for and how do the colonies appear? XLD (xylose lysine deoxycholate), VRBA (violet red bile agar), EMB (Eosin methylene blue), Baird Parker, Sorbitol MacConkey
XLD - Salmonella and Shigella. pink colonies with or without black centers; VRBA - enterobacteriacae (coliforms), pink colonies with a halo; EMB - E. coli - metallic green; Baird Parker - black colonies with a halo; SMAC - E. coli O157:H7, colorless
What three organisms are used to make Swiss cheese?
Streptoccus thermophilus and Lactobacillus bulgaricus and Propionibacterium shermanii
Which microorganisms make the following hydrocolloids? Xanthan, Curdlan, Gellan
Xanthan - Xanthomonas campestris; Curdlan - Alcaligenes faecalis var. myxogenes; Gellan - Pseudomonas elodea
What are the end products of a heterofermentation by lactic acid bacteria?
Heterofermentative - glucose fermented to > 50% lactic acid, 25% CO2, 25% ethanol and acetic acid
The interval from exposure to infectious agent until the time of onset of clinical illness is called what?
Incubation period
What are the known types of Hepatitis viruses? Which of them cause foodborne illness?
Hepatitis A, B, C, D and E. Hepatitis A and E are foodborne virus
A substance in oradded to a ready-to-eat product that reduces or eliminates amicroorganisms, including pathogens, is defined by USDA/FSIS as what?
Antimicrobial agent
What does AIB stand for and what do they do?
American Institute of Baking, third party food safety audits.
What is the most common surrogate bacterium used to model the thermal resistance of Clostridium botulinum spores?
Clostridium sporogenes PA 3679
Ready to eat foods containing this Gram positive nonsporeformer are considered adulterated in the United States
Listeria monocytogenes
Violet Red Bile Agar and MacConkey’s Agar are examples of what type of media?
Selective and Differential
- What is the genus of the the fungus known as the “machinery mold”; 2. for what product is it most often associated; 3. what is a microscopic test used to indicate its level of contamination
Geotrichum; tomatoes or tomato juice; Howard mold count
Most foodborne pathogens of the genus Vibrio will not grow unless the growth medium contains at least 0.5-1% of what compound?
NaCl
What genus and species of mold caused sickness among consumers of Chobani greek yogurt in 2013?
Mucor circinelloides
What is the correct order of steps for a single PCR cycle?
denature, anneal , extend
