final lab quiz study guide

we know that Salmonella reduces sulfur. what two tests can you inoculate to show this metabolic activity? name the test and how Salmonella growth will look after overnight incubation?

-HE plate: black precipitate / dots -SIM tube: black

please predict how the following tests will look after you inoculate with the given bacteria -Proteus vulgaris on a HE plate -Micrococcus luteus on a catalase test

-Proteus vulgaris on a HE plate: black precipitate -Micrococcus on a catalase test: positive = bubbles

what techniques kill bacteria?

-flaming (15 secs) -oven heat (1-2 hours) -steam / autoclave (15 mins) -boiling (20 mins)

describe 3 tests you could use to show that culture contains Proteus vulgaris. please explain why you chose these tests - write the name of the specific test and then explain why you picked it

-gram stain: to confirm gram negative bacilli -EMB plate: test for lactose fermentation -SIM tube: test for sulfate reduction + indole production

Pseudomonas aeruginosa is a human pathogen that is capable of forming biofilms in the lungs of cystic fibrosis patients. what is the term to describe the temperature range this organism is likely to grow at? this organism lives in the oxygen environment, name one enzyme this organism will produce to survive the reactive oxygen species in the. lung environment?

-mesophile (12-45C; optimal = 37C) -SOD + catalase will detox oxygen

how do cells become resistant?

-mutations of bacteria -development of mechanisms of resistance

explain what is selective about the HE plate. explain what is differential about the HE plate.

-selective: bile salt -differential: lactose, iron (ferric ammonium), bromothymol blue dye

what are the selective components of the MSA plate? what are the differential components of the MSA plate?

-selective: salt -differential: mannitol, phenol red

what are specific ways that bacteria can become resistant to beta lactam antibiotics?

-spontaneous mutation -horizontal gene transfer

when you have a separated and isolated colony as a result from performing an isolation streak plate, how many bacteria started each colony?

1 bacteria started 1 colony

please put in order the steps to identifying an unknown organisms -use metabolic tests results and a dichotomous key to determine the identity of the unknown bacteria -perform follow up metabolic tests like the catalase test or other follow up tests such as SIM or blood agar plates -streak an isolation streak plate from a patient sample or unknown food or water sample-use aseptic technique to select a sample of the unknown bacterial colony from an isolation streak plate -gram stain -inoculate a set of metabolic plates (using shape, arrangement, and gram stain result info)

1.) streak an isolation streak plate from a patient sample or unknown food or water sample 2.) use aseptic technique to select a sample of the unknown bacterial colony from an isolation streak plate 3.) gram stain 4.) inoculate a set of metabolic plates (using shape, arrangement, and gram stain result info) 5.) perform follow up metabolic tests like the catalase test or other follow up tests such as SIM or blood agar plates 6.) use metabolic tests results and a dichotomous key to determine the identity of the unknown bacteria

what would be the dilution if 96 mL of diluent is added to 4 mL of a bacterial suspension?

1/25

how many micrometers are equal to 1 milimeter?

1000

what is the total magnification if you are using 100X lens?

1000X

which of the following total magnification would be used to best view a gram stained specimen of bacteria? -10X -40X -400X -1000X

1000X

plating 0.1 mL of a sample diluted by a factor of 1/1000 produced 43 colonies, what was the OCD?

43,000

if you transferred 1 mL of a sample that was previously diluted by a factor of 1/1000 and that plate produced 56 colonies, what was the original cell density?

56,000

a microbiology student investigates a potential contamination of a juice box product. the student dilutes the original sample to 1/100,000 in a dilution bottle and then plates 0.1 mL in nutrient agar. 78 CFUs are counted the next day. what is the SPC result?

78,000,000 CFU/mL

please determine the results of this blood typing. agglutination in both A and D samples

A+

which blood type in the following is the universal recipient, ignoring the D antigen? -O -A -B -AB

AB

which blood type in the following list can receive the most blood types? -O+ -A- -B- -AB+

AB+

what is the biosafety level rating for working with pond water?

BSL 1 because it doesn't contain any possible dangerous pathogens and PPE is not required

Ciprofloxacin inhibits ___________

DNA replication

the EMB plate is selective for what type of bacteria (what gram character)? explain why

EMB is selective for gram negative bacteria because gram negative species can ferment lactose, the selective ingredient in EMB plates. also, eosin and methylene blue dyes inhibit gram positive species

what is the correct way to represent the name of a bacteria? -Escherichia coli (italicized) -E. coli (non italicized) -Escherichia Coli (non italicized) -Escherichia Coli (italicized)

Escherichia coli (italicized)

the pregnancy test results in a positive result if ________ is present in the urine

HCG

what is the component in urine that would reveal a positive result in a pregnancy test?

HCG

what would be the biochemical test you would perform to confirm a hypothesis that an unknown bacterial species causing a skin infection is MRSA or methicillin resistant Staphylococcus aureus? -MSA plate, catalase and followed by a kirby bauer test -EMB, blood agar and lactose durham -MSA followed by a SIM tube -SIM tube and HE plate

MSA plate, catalase and followed by a kirby bauer test

what are 2 enzymes that detox oxygen?

SOD (superoxide) & catalase (peroxide)

what does SODIS stand for and what lab test could we perform to test to see if this process 'worked'?

SODIS is the process of killing bacteria in water by using solar energy/UV light. a water filtration and EMB test would be able to tell us if the process was successful or not

we exposed Clostridium difficile to UV light for 15 minutes in water in a plastic bottle. how does UV light kill bacteria?

UV light creates thymine dimers that break DNA bonds and stops replication

define a coliform. why it is important to know and quantify how many coliforms are in water or food samples?

a gram negative bacilli that ferments lactose and produces acid and gas. coliforms are indicator species for fecal contamination in food and drinks

what is agar? -food for bacteria -a solidifying ingredient that is heat stable, solid at room temperature, and most bacteria do not break it down (metabolize it) -a salt -the same as a petri dish and never in a tube

a solidifying ingredient that is heat stable, solid at room temperature, and most bacteria do not break it down (metabolize it)

an anaerobic bacteria or facultative aerobe microbe is likely used to brew beer or make yogurt, you know this because ..... -strict aerobes perform cellular respiration -facultative anaerobes can use oxygen -catalase is present in strict aerobes -acid and alcohol are often byproducts of fermentation, an anaerobic process

acid and alcohol are often byproducts of fermentation, an anaerobic process

what is the purpose of iodine during differential stain?

adhere

which of the following blood type(s) is compatible with a patient that is AB+ and needs a transfusion? -A+ -B+ -O- -all of the above

all of the above

what is augmentin?

an antibiotic like amoxicillin, that is used if penicillin doesn't work to kill bacteria. augmentin is not inhibited by beta lactams

what opportunistic pathogen can be identified by MSA plate? explain why

any staph- and strep- species can be identified on an MSA plate because it selects for gram positive species

what is the difference between sterile and aspetic?

aseptic is to avoid contamination and sterile is the complete absence of microbes

which tests would you perform to identify Streptococcus pyogenes? -blood agar -EMB -SIM tube -Durham fermentation tube

blood agar

describe one method that can be used to decrease bacteria in foods?

boiling

what major cell component may be sensitive to high temperatures?

cell membrane in gram negative bacteria

what 2 types of acids help preserve food?

citric acid + ascorbic acid

please interpret the blood type image below (what is the blood type of the patient and how do you know?) *agglutination in Anti-A and Anti-D samples

clumping of blood, like in anti-a and anti-d means that the blood sample contains those antigens. this person has A+ blood

what kind of microscope do we use in lab?

compound microscope

what does the iris do?

contrasts light coming through

what is the purpose of the HE plate? -differentiate enterics, provides evidence of the Salmonella -ID Staphylococcus species -detect lactose fermenters found on the skin -none of the above

differentiate enterics, provides evidence of the Salmonella

describe the two ingredients in durham tubes and explain if these ingredients are selective or differential

durham tubes are only differential and not selective. the ingredients phenol red and lactose are both differential

OCD = CFU / orignial sample volume which of the following sentences best describe the equation above? -to determine the original cell density of the unknown sample, one must multiply the number of counted colonies on a valid by the cumulative dilution of the final serial diluted sample and then divide by the amount transferred to the plate in milliliters -to determine the original cell density of the unknown sample, one must multiply the number of counted colonies on a valid times the total cumulative dilution factor of the original sample -count every plate and multiply the CFUs -either A or B

either A or B

which dyes are in the EMB plate? -phenol red + neutral red -eosin + methlyene blue -salt + neutral red -bile + crystal violet

eosin + methlyene blue

you inoculated an agar deep stab tube and loosened the lid. after 24 hours there was growth along the stab line and on the top of the agar. what was the category of oxygen requirement for your organism?

facultative anaerobe

true or false: gel electrophoresis actually sequences DNA

false

true or false: slight temperature changes do not affect bacterial growth in any way

false

true or false: testing for indole production is demonstrated by the durham fermentation tubes

false

true or false: the mode of actions of penicillin, ciproflaxacin, and clindamycin are all: the synthesis of peptidoglycan in the bacterial cell wall

false

how do bacterial cells generate ATP during fermentation?

glucose and other sugars are converted to pyruvate and undergo fermentation to produce products like acid or gas

how do bacterial cells generate ATP during aerobic respiration?

glucose broken into CO2 and water using an ETC that contains enzymes like 'oxidase' and other enzymes like catalase are present

how do bacterial cells generate ATP during anaerobic respiration?

glucose broken into CO2 and water using an ETC that uses enzymes and something other than O2 producing sulfate or nitrate

what is the definition of a coliform?

gram negative, rod shaped bacilli that ferments lactose to produce acid and gas

predict the effect of the following mistake on a gram stain image of S. aureus (a known gram positive cocci bacteria): over-decolorizing -gram positive cells falsely look gram negative/pink -no change in results -all cells look purple -cell shapes are changed to appear rod

gram positive cells falsely look gram negative/pink

the following result demonstrates a non-lactose fermenting gram negative species on the HE plate -growth with a red or purple color change -growth with no color change to orange in media and maybe blueish color of colonies -no growth -poor growth

growth with no color change to orange in media and maybe blueish color of colonies

how does the HE plate select for gram negative 'enteric' bacteria? -has the ingredient crystal violet -has the ingredient bile salts -has neutral red -answer 1 and 2

has the ingredient bile salt

explain what a positive result of a catalase test tells us

if a bacterium produces the enzyme catalase, making it either facultative anaerobe or an anaerobe

what information does the durham fermentation tube tell us that cannot be determined by a plate?

if gas is produced

what is the mechanism of action of penicillin?

inhibits the formation of peptidoglycan in the cell wall by blocking transpeptidase

explain the term opportunistic pathogen

it doesn't attack healthy cells unless provoked or given the opportunity, like a weak immune system

what is the purpose of heat fixing?

kill + adhere

what does cooking with heat do to control microbes?

kills them

diagnosis of transmissible viral disease based based on PCR or RT-PCR, restriction enzymes and other molecular biology tools is due to _______ -variations in human DNA -known genetic sequence information on pathogens and viruses -the fact that all viruses have RNA -none of the above

known genetic sequence information on pathogens and viruses

list all the PPE that we should use if we are working with BSL2 level organisms

lab coat, goggles, gloves

compare the terms leukocyte and lymphocyte

leukocyte is another term for white blood cells. lymphocyte is a type of white blood cell. there are B lymphocytes and L lymphocytes

why are metabolic tests used to identify unknown species? -not all bacteria ferment -metabolic outputs can be related to fermentation and exoenzyme production which help relate to particular species that use those metabolic processes -acid is produced in all bacterial organisms -oxygen requirements can be determined

metabolic outputs can be related to fermentation and exoenzyme production which help relate to particular species that use those metabolic processes

what is cardinal temperature of bacteria?

minimum, maximum and optimal temperatures bacteria is able to grow

why is it less likely that acidic foods like tomatoes (pH 3.5 - 4.7) are less likely to be contaminated with food borne pathogens like Salmonella than fresh raw vegetables or meats (pH 6-7)? -they are not processed with heat during canning or pasteurization of any kind -most bacterial pathogens do not thrive in acidic environments -acid tolerant bacteria are those responsible for lactic acid fermentation -harsh environments break down endospores

most bacterial pathogens do not thrive in acidic environments

which white blood cell is the most prevalent in the blood?

neutrophil

which leukocytes, white blood cells, are most prevalent in your blood?

neutrophils

describe the role of nitrogen fixing bacteria in the nitrogen cycle. please name one nitrogen fixing species

nitrogen fixing bacteria like Rhizobium, converts atmospheric nitrogen into fixed nitrogen or ammonia, so the plants can then use it

does freezing kill bacteria?

no

there is a national lab standardization of the kirby bauer test and a statistically validated interpretative table that helps lab scientists determine if a pathogen is truly resistant to an antibiotic. would a zone of inhibition that measured 25mm for penicillin against S. aureus, likely measure the same for E. coli?

no - E. coli is innately resistant to penicillin due to the difference in cell wall structures for gram positive and gram negative cells

wright stain is used to differentiate types of white blood cells in the blood and so WBC counts can be used to diagnose or determine disease states. the below report demonstrates an abnormal WBC count from a differential stain, please explain why it is considered abnormal. wright stain results after counting 100 cells -neutrophils: 50 -lymphocytes: 20 -monocytes: 3 -eosinophils: 2 -basophils: 27

normal amounts: -neutrophils: 50-70% -lymphocytes: 20-30% -monocytes: 2-6% -eosinophils: 1-5% -basophils: <1% the basophil count is higher than normal, which could mean the person has an allergic reaction or parasitic infection

which of the following protocol mistakes would result in a calculation of less CFU/ml than were actually in the original sample? -not properly vortexing a sample during one of the dilution steps -when pippetting, improperly plunging to the second step when transferring sample to a dilution -not changing pippetter tips -adding too much agar to the plate

not properly vortexing a sample during one of the dilution steps

please describe what obligate aerobes require for the production of ATP?

obligate aerobes require oxygen for the production of ATP. these types of organisms can only grow if oxygen is present

describe the protocol of using the oil immersion lens

oil is used with the 100X lens to help bend the light so you can see the slide clearly

penicillin inhibits ________

peptidoglycan synthesis

describe what you learned about phage therapy or ways that researchers are investigating how phage can be harnessed to benefit humans

phage therapy uses viruses to treat bacterial infections. for example, a scientist found a certain phage that attacks the Pseudomonas aeruginosa, the bacterium that causes cystic fibrosis but does not attack good and healthy human cells

define and describe the term phage. why is discovery of new phage therapies needed?

phages are viruses used to fight bacterial infections. some bacterial infections are too severe and resistant to antibacterial medications so new treatment options like phages are required

predict the effect of the following mistake on a gram stain image of S. aureus (a known gram positive cocci bacteria): skipping the iodine step -pink cells at the end of the staining process, mistakenly showing gram negative result -no change in results -very small cells -purple cells in the result

pink cells at the end of the staining process, mistakenly showing gram negative result

which assay is used to quantify bacteriophages in a sewage sample? -spectrophotometry -wright staining -plaque assay -SPC

plaque assay

milk was tested for contamination. the students used serial dilutions to dilute milk (1/10,000) and plated this dilution on two plates: 1 ml (plate 1) and 0.1 ml (plate 2). the next day, the students calculated the results. plate 1 had 295 colonies and plate 2 had 36 colonies. please calculate OCD of milk

plate 1: 295 CFU x 10,000 / 1 ml = 2.95 x 10^6 CFU/ml plate 2: 36 CFU x 10,000 / 0.1 ml = 3.6 x 10^6 CFU/ml

which technique is utilized to amplify/make copes of DNA? -SDS-PAGE -southern blotting -polymerase chain reaction (PCR) -gram staining

polymerase chain reaction (PCR)

lowering pH can _______ food

preserve

why are raisins more protected against bacterial contamination and spoilage than fresh grapes?

raisins are dried and therefore have little to no moisture for microbes to grow unlike fresh grapes

what is the purpose of alcohol during differential stain?

removes crystal violet stain from gram negative cells

what molecular biology tool/step can be used to cut DNA at specific sites? -TE buffer -toxins -taq polymerase -restriction enzymes

restriction enzymes

what is the name of the counterstain used and its purpose?

safranin; stains gram negative cells pink/red

in the MSA plate, the role of NaCl is to _________ -provide carbon -select for salt tolerant species, like the Staphylococcus group -act as pH indicator -differentiate Staphylococcus epidermidis from other species

select for salt tolerant species, like the Staphylococcus group

what can we learn from a simple stain?

shape, size, arrangement

choose by which component gel electrophoresis allows us to separate DNA? -abundance of fragments -size of fragments -sequence of ATCG -order of ATCG

size of fragments

what can we learn from differential stain?

size, shape, arrangement AND cell wall structure

why is the zone of inhibition a circle?

the drug moves through the agar establishing a concentration gradient, if the organism is susceptible to it, a clear zone appears around the disk

please explain why a bacterial specimen from a patients infection (human body sample) should first be inoculated on an isolation streak plate

the goal of an isolated streak plate is to isolate a single colony of bacterium so you can start to identify it by colonial morphology and performing further metabolic tests

how can it be explained that there are some colonies within the zone of inhibition?

the individual cells that began those colonies had a mutation that allowed them to be resistant to that concentration of antibiotic

how does soap work to remove bacteria from hands?

the micells in the soap trap bacteria on your hands and then are removed when you rinse your hands wit water

what are some explanations if you have no growth in the stab tube at all after 48 hours of incubation? -the cultures cannot grow in any aerobic or anaerobic conditions -the nutrients in the agar were not suited to any of the organisms inoculated -bacteria will not adhere to wire straight, only a loop can collect bacteria

the nutrients in the agar were not suited to any of the organisms inoculated

describe or draw how the clear zones are formed on the plate above (phage sample plate)

the plate contains a bacterial lawn and then phages were added, creating the clear zones showed in the picture. clear zones are created because the bacteria is not resistant to the phage, meaning the phage killed the bacteria in those zones

what is colonial morphology?

the size, shape and elevation of a colony on a cultured media

name the universal blood donor type and why is it so important to understand blood types for blood transfusion procedures

the universal blood donor type is O-. if a doctor gives a patient the wrong blood type, it could cause the patient to obtain a blood disease or infection

a standard plate count involves a serial dilution because _______

the unknown sample has an unknown population density and it is expected to be very high

why would a gram stain have limitations when it comes to identifying bacterial species? -there are thousands of known gram positive bacteria and thousands of known gram negatives, more information is needed to identify a species -gram stains take complicated technology to perform -only professionals can perform gram stains as it requires harsh and safety limiting chemicals -gram staining is only for visualizing size of cells, shape and arrangement and provide no other information about the cell characteristics

there are thousands of known gram positive bacteria and thousands of known gram negatives, more information is needed to identify a species

what are some potential reasons that a false negative may result in a pregnancy test, which is typically marketed to be only 0.1% of the time?

there isn't enough HCG in the females urine yet to be detected

what is the purpose of aseptic technique?

to avoid contamination when transferring microbes

using the terms antibodies, antigens, and agglutination, describe in detail blood typing procedure

to find a person's blood type you take a blood sample, then mix the blood samples with antibodies A, B and D. if the blood sample starts to form clots, you can determine the blood type. Agglutination in any sample (A, B and D) means that person's blood contains those specific antigens. for example, if the sample with antibody A clots, and the sample with antibody D lots, that person is A+

what does it mean to 'incubate' a nutrient agar?

to let a cultured media to sit at 37C to allow microbes to grow

what is the role of mannitol in the MSA plate? -to provide a pH indicator -to inhibit gram negative bacteria -to provide a carbon/sugar source to be available for fermentation -select for gram negatives

to provide a carbon/sugar source to be available for fermentation

what is the mechanism/mode of action of ciprofloxacin?

to target the DNA replication process

what does it mean to 'inoculate' microbiological media?

to transfer microbes from a culture to a sterile media

what is the purpose of the alcohol (ethanol) step of the gram stain process?

to wash away the crystal violet from gram negative cells

what do BHIA deep stab tubes demonstrate in the lab? -pH tolerance -acidophiles -tolerance of microbes to oxygen -osmotic pressure

tolerance of microbes to oxygen

true or false: a coliform is a gram negative rod shaped bacteria that ferments lactose producing acid and gas

true

true or false: a lactose fermenter is an organism that splits lactose into monosaccharides, then ferments those monosaccharides

true

true or false: selective media are designed to enhance the growth of some organisms and inhibits the growth of others

true

true or false: the SIM tubes test for indole production, motility, and the ability to produce hydrogen sulfide

true

true or false: the wright stain is used to differentiate types of white blood cells in blood and so WBC counts can be used to diagnose or determine disease states

true

a plaque assay of an unknown sewer water sample revealed 200 plaques on a bacterial lawn of E. coli. what species of bacteria is this bacteriophage likely specific to? -virus -Staphylococcus aureus -all human skin microbiota -E. coli

virus

what is the role of neutrophils?

white blood cells that are stimulated when there is a bacterial infection, they are phagocytic

what does refrigeration do to control microbes?

wont allow some bacteria to grow in low temperatures

the positive result of a lactose tube with a durham tube is: -green -yellow color change for acid and bubbles in the small tube for gas production -blue -black turbidity

yellow color change for acid and bubbles in the small tube for gas production

you inoculated EMB plate with E. coli. after incubating at 37 C you see colonies with metallic green sheen. does this result make sense, and why?

yes because E. coli ferments lactose which will lower the pH and cause a color change on the plate. metallic green is an indicator of a strong fermenter

are dry foods more shelf stable than fresh foods?

yes because dry foods have no moisture for microorganisms / bacteria to grow

describe one fermented food with lots of living bacteria and what carbon source those microbes metabolize and what byproduct of fermentation protects the food from spoilage

yogurt is a fermented food. citric and absorbic acids help protect yogurt