Max-X-Bacteria Lab Draft - Max

8/10/2019 Max-X-Bacteria Lab Draft - Max

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Max A. Sutters

The Dirt Report: Microbiomes of Quest University

Purpose:

In this lab we investigated Quest microbiomes by growing and identifying bacteria on often

infrequently washed surfaces from several locations on campus. articipants also drilled general

laboratory protocol and practiced a staining technique for telling apart !ram positive and negative

bacteria.

Methods and Observations:

Plate Preparation:

etri dishes filled with agar growth medium were prepared and mar"ed into four quadrants prior to the

experiment. I chose three surfaces to swab# the belly button$ underside of my left hand$ and the surface

of my laptop "eyboard. I prepared two sterile$ double%ended cotton swabs# three ends for the bacteria%

carrying quadrants$ and a fourth for a negative control &'(). After swabbing$ I gently wiped each end

of the Q%tips in a cross%hatch pattern to cover most of their respective quadrant. *or the order of

samples swabbed$ refer to *igure +. After bacteria collection and labeling the petri dishes were stored at

,-( to incubate for roughly +%/ hours.

Colony Analysis:

0he bacteria present were analy1ed based on the appearance$ form$ and structure of the colonies. 2e

were given a list of terms to describe qualitative data. 3efer to *igure 4 below for raw data gathered. I

estimated the number of colonies for the most populated quadrant by counting colonies in a small area

and assuming colony density remained constant for the rest of the quadrant. I measured colony

diameter from the largest colony present in the quadrant. Staining and viewing under a microscope to

determine shape and gram positivity of bacteria are explained in the next section. (ells in the table

mar"ed with an 567 represent unclear data due to experimental error.

Hmm from students bodies! We didn't collect any

campus samples!

What happened to figure 1?

We incubated them for 48 hours!

Reverse order

What is the limitation with this?


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Max A. Sutters

Sample Belly Button Hand (underside !aptop "eyboard #C

#umber o$ %olonies 899 4/ 4, 4

Diameter (mm 9.8 4 4.: 4

&orm unctiform$circular$irregular

circular circular circular

'levation: flat flat$ convex$ raised flat$ convex convex

Marin: entire$undulate$lobate

entire entire entire

Te)ture moist moist moist moist

Colour dull$ opaque shiny$ opaque dull$ opaque yellow$ opaque

Shape 6 6 6 6

*ram ositive 6 6 6

&iure +: 3aw quantitative and qualitative data gathered for bacteria samples and control.

As seen in the petri dish photograph in *igure +$ the hundreds of cultures incubated from the belly

button sample were largely punctiform$ with few circular and irregular colonies. 0he margins of the

punctiform colonies were entire. I observed undulate and lobate margins on the circular and irregular

colonies. 0he colonies were flat$ dull$ and opaque. 0he 4/ colonies incubated from the underside of my

left hand were all circular in form. Most were flat$ but convex and raised colonies were observed with

some difficulty. ;acteria gathered from the laptop "eyboard formed 4, circular colonies. 0hey were flat

and convex in elevation$ and dully opaque in color. (olonies in all quadrants were moist in texture$ and

all colonies in quadrants +$ ,$ and '( had entire margins. 0he presence of a bacteria colony in the

negative control quadrant could be attributed to accidental contamination of the cotton swab$

condensation dripping onto the quadrant when flipped$ or simply that the Q%tip was not as sterile as the

pac"aging promised.

This is a table not figure


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Max A. Sutters

*ram Stainin:

!ram staining is a useful tool for determining the complexity of a bacteria


4/5

Max A. Sutters

I placed four drops of water on a clean slide with a sterile loop. 3e%sterili1ing the loop in a flame after

each sample$ I gathered bacteria from a variety of colonies within each quadrant and mixed it into the

corresponding droplet of water. =nce the water appeared cloudy in each droplet$ I distributed it thinly

and evenly in a rectangular$ upright smear &*ig. ,). In hindsight the ratio of culture to water was too

high$ a mista"e that became obvious later when bacteria cells were very tightly pac"ed and mostly

unstained. 0he fourth smear on the same slide in particular was prepared with less water and the same

amount of bacteria compared to the previous smears. Swiping the slide through a flame too many times

while heat fixing destroyed cells and further explained the dearth of stained bacteria.

Analysis and Results:

0o streamline the data I standardi1ed qualitative descriptions &e.g. smooth and entire$ coccus>cocci$

etc.) and selected the primary description in qualitative cells with multiple values &e.g.

convex&+)$flat&:) ? flat). 5(leaning7 data that way is very is extremely quic" and dirty$ but it would be

inconsistent and unwor"able otherwise without separate categories for each description &with a yes or

no for each).

&iure -: !ram stained bacteria smears. *rom left to right# belly button$ hand$ laptop "eyboard$ '( &in corner).

Put images after you refer to them in text.

Great idea to take pictures, but visibility

would be enhanced with different colour

background

Not sure what you did here


5/5

Max A. Sutters

Con%lusions:

3 0 test# one continuous variable$ one categorical variable$ only two categories

# confidence interval

Max:

The start of this lab is well written. See

comments throughout to help with clarity andformatting. Unfortunately, you don't have any o

the analyses which was a big component of this

lab or the conclusions/reflections. Please let

me know if you don't understand them, happy to

go over it with you again.

I know you took your 24 hour extension, but I

didn't receive the lab until Monday. This time

won't deduct points for lateness, but in the

future please make sure your emails send!

C

Max-X-Bacteria Lab Draft - Max

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