Microbiology Exam 3

doubling time

from this equation, what is Td?

growth rate

from this equation, what is u?

growth rate

this depends on bacterial species, amount of nutrients, and environmental conditions

number of bacteria

in this equation, what is N?

original number of bacteria

in this equation, what is No?

time

in this equation, what is T?

1.2 × 10^6

If you start with 1 × 10⁴ bacteria, how many bacteria will you have after 24 hrs if the growth rate is 0.2h^-1 at 37°C?

growth rate

will altering growth rate or reducing initial microbial load have a greater impact on the final number of bacteria?

368 hrs/15 days

If the manufacturer considers an initial microbial load of 104 reasonable, how long can you hold the bacteria at 4°C if the growth rate at this time is 0.025h-1 and 108 bacteria is considered the spoilage point?

d value

the time it takes to reduce bacteria 1 log/10 fold

12D

many food manufactures use the ___ concept based on botulism spores to provide a large safety margin against contamination

96 min

How long would you need to incubate the food to achieve a 12 D process if the D value was 8 min at 90°C?

-0.29

what is the slope from this data?

3.4

what is the D-value if the slope is -0.29?

41.4 min

To ensure there are absolutely no traces of Bacillus spores, you recommend using the 12D concept. How long would you need to hold the product at 90°C to achieve this?

D-value: 3.4 min

z-value

the change in conditions required to change the D-value tenfold

9.9×10^5, 8.34 days

1) Your company makes a pasteurized juice product with an initial microbial load of 105 CFU/ml. Storage studies show that after 5 days at 35C, the microbial load is 108 CFU/ml. Your process engineer finds that by increasing the pasteurization temperature a few degrees, the initial microbial load can be lowered to 103 CFU/ml. If this process were used, what would the final microbial load be after 5 days at 35C assuming all other conditions are identical?

2) Using the problem above, if you started with the lowered microbial load of 103 CFU/ml and all other growing conditions were identical, now how long could you now store the juice before it reaches the spoilage point of 108 CFU/ml

b. 7.7

c. 120

You are determining the D value for organisms in a given solution. You have one at 90C and another at 80C. You periodically take out samples and determine microbial load by serial dilution and plating.

a) Using the data above, what is the D value at 80C?

b) Using the data above, what is the D value for 90C?

c) Many food manufacturers use the 12D concept to provide a large safety margin against contamination. Using the data from the previous question, how long would you need to incubate the food at 90C to achieve this process?

15 C

If an organism has a D80C of 20 min; a D95C of 2 min; and a D 110C of 0.2 min; what is the Z value?

vertical gene transfer

the transmission of genetic material from parent to offspring through reproduction

horizontal gene transfer

movement of genetic materials between organisms other than parent to off spring inheritance

bacterial transformation

the uptake of “naked”/free-floating DNA from the environment

smooth

if a bacteria has a capsule it is described as ___

rough

if a bacteria has no capsule, it is described as ___

competent

cells must be __ to do bacterial transformation

quorum sensing

what is bacterial transformation regulated by?

homologous

in microbiology, meaning similar DNA sequence

homologous recombination

the process in which similar or identical DNA sequences exchange genetic material

heteroduplex

original strand of DNA

natural transformation

__ __ can be used to vary surface antigens of microbes as a way to avoid our immune system

bacterial conjugation

the exchange of plasmid DNA

cell to cell contact/mating pair formation

what is required for bacterial conjugation?

plasmid

small DNA that is non-essential, includes “bonus” genes

false

true or false: all plasmids do conjugation

1

how many strands of DNA are transferred in bacterial conjugation?

can cross species and genus

what is “scary” about bacterial conjugation?

transconjugant

the recipient cell that has successfully acquired genetic material from a donor through the process of conjugation

transduction

the transfer of DNA by phage/virus

generalized

which type of transduction uses the lytic cycle?

specialized

which type of transduction uses the lysogenic cycle?

generalized transduction

this is all based on a mistake in the packaging

homologous recombination

what process does generalized transduction use?

specialized transduction

results from a mistake during excision when some chromosome DNA is pulled with the viral DNA

specialized

which type of transduction is easier to track?

prototrophic bacteria

bacteria that can grow in minimal media because they have the genes required to make everything else

auxotrophic bacteria

bacteria that lack gene encoding enzymes required for synthesis of amino acids, nucleotides, or another substance

conjugation

blocking cell to cell contact would prevent ____

transformation

the addition of DNAse to a mixture tube would be used to rule out ___

pathogen

any organism that causes a disease

bacteria that live in us and on us

what does the human microbiome consist of?

commensals

the organisms that live with us and on us

holobiont

host and the many other species living in or around it which together form a discrete ecological unit

germ-free

have zero detectable microorganisms

gnotobiotic

animals that may start germ-free but are then intentionally colonized with a defined, known set of microbes or single strains of bacteria

germ-free

do germ free or gnotobiotic animals require a greater amount of food to reach normal weight?

short chain fatty acids

most carbohydrates are digestible only by bacteria resulting in the production of __ __ __ __

short chain fatty acids

all of the following are positive functions of what?

• proper growth, maturation, differentiation of intestinal cells and hepatocytes

• maintain intestinal integrity

• regulate glucose and lipid metabolism

• lower pH aids in absorption of minerals and impedes growth of harmful bacteria

• produce signals that: inhibit fat accumulation, provide feeling of satiety, aid in insulin sensitivity

firmicutes and Bacteroidetes

what are the two bacteria that are most common in the adult gut microbiome?

obesity

the ratio of firmicutes to Bacteroidetes strongly correlates with __

obese

and increase in firmicutes results in ___ humans and animals

weight loss

an increase in Bacteroidetes in individuals results in what?

probiotic

live organism that when consumed results in a health benefit

prebiotic

a polysaccharide that when consumed, results in a health benefit

vaginal

which type of child delivery resulted in more beneficial probiotic bacteria?

breast milk

this also contains a diverse group of microbes and unique carbohydrates associated with an increase in beneficial probiotic bacteria in newborns

antibiotics

these at low doses were found to increase adiposity and changes in hormone levels related to metabolism in young mice

estrogen

the microbiome can help regulate the bioavailability of ___ which is also a potent driver of tumor progression

infection

invasion and multiplication of a microorganism in or on body tissue resulting in harm to the host

commensalism

microbes living in an on us without causing harm, may cause opportunistic infections (depending on location)

disease

symptoms of infection as a result of the interplay between pathogen and host immune response

pathogenicity

the ability to cause disease

virulence

the degree of pathogenicity

same

Koch’s Postulate 1 says: the __ microorganisms are present in every case of the disease

pure

Koch’s postulate 2 says: the microorganisms are isolated from the tissues of a dead animal and a __ culture is prepared

3

which of Koch’s postulates say the microorganisms from the pure culture are inoculated into a healthy, susceptible animals, the disease is reproduced

4

which of Koch’s postulates says the identical microorganisms are isolated and recultivated from the tissue specimens of the experimental animal?

equally

one problem of Koch’s postulates is that it implies that all strains of a species are __ virulent when actually many vary in severity or may cause different symptoms depending on types of virulence genes

attachment, invasion of tissue, avoid escape from immune system, produce toxic compounds that damage tissue

what are the 4 “weapons” that microbes have?

bacteria

Koch’s postulates imply that virulence/disease is a trait of ___ only and is independent of host, but you must consider the balancing act between host and microbes and location

opportunistic pathogens

this is demonstrated by less virulent organisms causing illness in immunocompromised patients

outbreak

a smaller, more contained period of time or location where a disease is occuring

epidemic

a larger, longer period of time and location that a disease is occurring

suspected case

a person for whom there is suspicion of the disease but no strong evidence or lab confirmation

probable case

a case is whom there is strong circumstantial evidence of infection

confirmed case

a person for whom there is definitive clinical or lab confirmation that they are a case

sensitivity

looks at ensuring those that test positive truly have the disease

specificity

looks at ensuring those that test negative do not have the disease

relative risk

a measure of association between two variables

1

a relative risk greater than __ means exposure is associated with the disease

attack rate

the number of people in a group who developed the disease divided by the total number of people at risk for infection

33.3%, 16.7%, 2

what is the attack rate in exposed children?

what is the attack rate in unexposed children?

what is the relative risk?

dose-response relationship

an increase in attack rate with an increase in exposure

basic reproductive number/Ro

the number of people infected by a single infectious individual in a fully susceptible population

transmissibility

what does the basic reproductive number measure?

spread

an Ro value greater than 1 means the infection will __

die out

a Ro value less than one means the infection will __ __

susceptible

Ro values will be dependent on the percentage of the population that is ____

herd immunity

a state where a significant proportion of the population is immune to an infection leaving few people susceptible to being infected and transmitting on the infection

natural immunity

immunity due to having the disease before and now being immune to it

vaccinate/treat infected/quarantine/isolation/active monitoring/decrease insect vectors/mask/social distance

what are some interventions to try and decrease the Ro value?