Microbes everywhere experiment | Biology homework help

EXPERIMENT: Microbes Everywhere

PHOTOS – Include two digital photos with your lab report, either as separate attachments to an e-mail or paste into your document.

1.    1. Photo #1 – Take a photo of the six nutrient agar tubes AFTER they have been growing for at least two days.  Lay them out so that it might be possible to get close enough to see some growth.

1.    2.Photo #2 – Take a photo of the slides you are treating with the gram stain, at some point during the procedure.  (Preferably while you are flooding them with one of the stains and waiting.)

Exercise 1 – Finding Microbes:

2. Select six sources from your prioritized list that are from different areas of your home.  Set up a data table similar to the one shown below to number your microbes and record information and observations about them for Exercise 1 and Exercise 2 activities.

7.    7.      Use the hand magnifying lens to observe the growths of colonies within the tubes.  Note their shape, size, color, and anything else distinguishing.  Bacteria will grow in small circular colonies, whereas molds will spread out more and may look fuzzy.  Yeasts tend to grow initially in tight, compact colonies and their color is somewhat darker than that of bacteria.  Record what you see in the data table.  Draw what you see for each.  Try to deduce the types of microbes each cultured colony contains: bacteria, mold, or yeast.  Some cultures may contain more than one type of microbe.

7.    8.      If some of the cultures are not yet well developed let all of the cultures continue to incubate for up to three additional days until you see visible growth in them all.  Record final observations for each tube.

Questions:

A.    A.      From which samples did you observe the most and least microbial growth?

A.    B.      Why do you think there were differences in the number and types of microbes at the different sampling sites?

A.    C.      Did microbes from warmer or cooler sites multiply faster?  Hypothesize why.

A.    D.      How could the information gained in this experiment be useful in your home?

Exercise 2 – A Closer Look

Examine the slides under your microscope.  Describe and draw what you see. 

Questions:

A.    A.      Was the structure or arrangement of the colonies of microorganisms different among what you identified as bacteria versus yeast versus mold? 

A.    B.      Four slides are, of course, a very small sample, but regardless of this limitation, what can you hypothesize about differences in the microbe growth patterns?  Does your hypothesis match the descriptions at the beginning of the experiment?

A.    C.      Were you able to see any individual microorganisms?  If so what would you guess they are (e.g., mold, yeast, etc.)?

A.    D.      Do any of the slides appear to have more than one type of microorganism?  Did you determine this by physical appearance of the culture or by color of stain?