silkysalem

Salem's Den Journal
Ad 2:
2003-06-17 23:11:06 (UTC)

Lab

Identification of unknown bacteria

My bacteria were bacilli. They occurred mostly singly,
sometimes grouped together, like staphylo, but bacilli do
not form in staphylo, and they were more as if they were
there because that was how the slide stuck them rather than
that they live that way. They also had fast growth and
colonies. They were aerobic, growing well without oxygen
and not so well without oxygen. The gram reaction of my
bacteria was gram positive, or purple. I used a simple
stain to determine the shape and aggregational
characteristics of my bacteria. I looked at my petri
dishes to determine aerobic vs. anaerobic and colony sizes
and growth. I used a gram stain to determine the gram
reaction of my bacteria.
The possible bacterial species for the unknown were
Bacillus subtilis, Sarcina lutea, Serratia marcescens,
Escherichia coli, Enterobacter aerogenes, Rhodospirillum
rubrum, Agrobacterium tumefaciens, Proteus mirabilis, and
Neisseria mucosa. Based on my gram stain of positive, I
was able to cross off all the gram-negative bacteria.
(Serratia marcescens, Escherichia coli, Enterobacter
aerogenes, Rhodospirillum rubrum, Agrobacterium
tumefaciens, Proteus mirabilis, and Neisseria mucosa.)
This left me with Bacillus subtilis, Sarcina lutea, and
Lactobacillus acidophilus. I then looked at the visual
characteristics of my bacteria. My bacteria were
definitely not in the square/cube shape of a sarcinae, so
Sarcina lutea fell off my list. I was then left with
Bacillus subtilis and Lactobacillus acidophilus. Bacillus
subtilis comes mainly in chains, strepto, but my bacteria
seemed mostly singular. Therefore, I decided that my
bacteria must be Lactobacillus acidophilus by process of
elimination.
There were other reasons why some of the other bacteria
could not be mine. Petri dishes streaked with Serratia
marcescens turns red. My bacteria did not turn red as the
colonies grew. My experiment could also have had errors.
My gram stains revealed two bacteria in the beginning. One
bacterium did not show up on all my slides, and in lesser
quantity, so I assumed that my bacteria were the one in
greater quantity and on all slides. I still believe my
identification is correct, because I have followed all the
procedures as correctly as possible, and interpreted my
data to the best of my knowledge. I have viewed images on
reliable websites on the internet of Lactobacillus
acidophilus, along with images of other bacteria, and the
bacteria on my slide appears identical to the images of
gram stains of Lactobacillus acidophilus that are available
for viewing.


Ad:2