Microbiology Lab practical 2

is plaque formation better determined at a higher or lower concentration of phage? why?

lower concentration of phage makes for better plaque formation, makes less plaques and makes them easier to count

what types of microbe(s) does mENDO select and differentiate for?

***SELECTS FOR COLIFORMS*** bacteria like E. coli, fecal matter differential we didn't get results *had coliforms but we didn't get E. coli specifically because it would be gold*

be able to calculate CFUs/ml in an original water sample based on how many colonies grow on a spread or filter plate (nutrient agar, or mEndo)

*CFU= colony forming units *point of a dilution = too much growth that you couldnt count 18 X 10^3(# of tubes) X 10 = 18 X 10^4 = 1.8 X 10^5 CFUs/ml membrane filter- 100ml sample, count the colonies CFUs can be counted for the original 100ml sample

what is a plague?

*opposite of colonie, covered lawn with clear zones (circles) = plaque -each plaque is one virus is one that got into the bacteria, then moves out to kill more

what is a zone of inhibition? and be able to correctly measure one.

- an area of no growth of the microbe, around the antimicrobial -measure the whole diameter in mm or cm

how does preservatives affect food spoilage?

-citric acid (vitamin C) is commonly used *acid stops bacterial growth -condiments really don't go bad *a lot of salt or sugar are good preservatives (bacteria cannot grow)

what are coliforms and what types of water samples might you expect to find them in? why?

-coliforms gram negative rods usually found in the intestine and typified by E. coli. usually found in the intestine after drinking water that has been contaminated by fecal matter

what type of growth arose on each type of plate, and how could you tell? how do you tell how many different species of microbes you might have

-fungas= fuzzy *bacteria is never fuzzy -yeast may look like bacteria *malt agar --> slime, not fuzzy = unicellular yeast -apperance- looks different = different types of bacteria (dont base on colonies)

what is the membrane filter technique for water sampling, and how does it work?

-it concentrates all the bacteria in the solution onto the same surface (filtering)

how does oxygen affect food spoilage?

-mostly airobes= need oxygen to grow -remove O2 --> less growth *bacteria that don't need O2 are more rare

how does pH affect food spoilage?

-neutral pH=best growth -very acidic or very basic --> not much growth. *yeast can grow in acidic environment

what types of media were used for water testing, and why?

-nutrient agar (clear), mEndo ( selective and differential)

what types of plates were used to test foods, and why?

-nutrient agar because it allowed the growth of many different types of microbes such as bacterias -malt agar because it is selective and allowed growth of yeasts instead of overload of bacteria

know how to interpret the p-values from a t-test

-you want a lower p-value = .05 *.o5= 5% chance it wouldnt happen again, that it was random; 95% positive that it would happen everytime *.01=99% positive *.001= 99.9% positive -anything below 0.05 is good

what 4 microbes did we use, and why did we use all four?

1.) escherichia coli - a gram negative bacillus 2.) Bacillus cereus - a gram positive, bacillus spore former 3.) Staphylococcus aureus - a gram positive coccus 4.) Saccharomyces cerevisiae - a yeast, on malt agar *we used all four because all antimicrobials work differently, and protect against certain bacteria or yeast more, so we test them all to know how they work against several microbes

what are fermented foods?

Food or food ingredients that rely on microbial growth as part of their processing or production.. *beer and wine (yeast) *cheese and yogurt (bacteria)

what are probiotics, and what are used for?

inculation of a good bacteria to keep you healthy or stave away the bad bacteria *example yogurt.

Plate growth (LB, LB-AMP)

LB growth- a lot of growth (both positive and negative) LB-AMP - growth only sucessful transformation -positive- growth (green) - negative - no growth

-T4 vs T4r coliphages and the difference in their plaques

T4--> solid circular, fuzzy outline, smaller T4r--> larger, hard outline *r stands for rapid growth. lyse, kills everything, kills faster

what is a negative control?

a negative control is something that you would know didn't stop anything from growing, like water *expected no result

what is a positive control?

a positive control is something that you would know would stop growth, like 100% ethanol *expected result

lysogenic cycle

copyed within cells, the immune system doesn't know that it is there. *examples, HIV or cervical cancer

how does temperature affect food spoilage?

increased temperature=more growth -microbes grow as fast as the temperature will let them -increased temperature--> faster they move --> increased growth

how does moisture affect food spoilage?

increased water/moisture=increased growth *dry=no growth, (best way to stop spoilage)

transformation efficiency equation

number of colonies/mass of DNA

what types of plates did we use for the antimicrobial lab and why?

nutrient agar- grows all bacteria malt agar- is selective, it inhibits the growth of bacteria, and allow the growth of yeast. *the malt agar plates looked better because there was no bacterial contamination = better results *malt agar= lower pH (5-5.5) so its too acidic for abcteria

what is the pGreen plasmid? what is the name of the gene that allows transformed calls to glow, and where does it come from?

pGreen plasmid- small circular DNA contrains GFP (green florescent protein) gene and ampicillin which comes from jellyfish

lytic cycle

process of making more viruses takes up too much space and bursts the cells (sick)

what does calcium chloride and the heat shock in the procedure do?

the calcium chloride clumps the DNA, and the heat shock opens the pores to allow the plasmid into the cell

what is transformation?

transformation is the uptake of free DNA by a bacterial cell

what are phages, and how do they reproduce (know the life cycle)?

virus that infects bacteria

what is a coliphage?

virus that infects certain bacteria called coliforms

how do you tell which antimicrobial was most/least effective?

you measure the zone of inhibition. the most effective has a bigger zone of inhibition the least effective has a smaller zone of inhibition