[Example of a “poor” Report]
this lab we are to gather different samples from the typical habitats of
is an important point. You need to expand on this to really “send
it” to the reader. It is the first selective pressure in your isolation
The samples ranged from soils, muds, ponds, fish sauce, sea water, and sea
weed. From these samples we carried out enrichments and selection procedures
which would yield certain organisms. Then by continuing with experiments we
can obtain pure cultures of the organisms. Even more experiments done on the
pure cultures can confirm their identities. Through all of this we learn how
to find and eventually isolate various microorganisms.
it’s what you did. But you need to introduce the lab. What is the
purpose? Tell me something about why organisms live in different environments.]
MANUAL FOR INITIAL TESTS FOR ISOLATING PURE COLONIES
gram staining of Azobacter, Pseudomonads, Thermophiles, and Halophiles. Heat
treatment to see if spores existed for Thermophiles and Halophiles.
should not combine these sections. There is a distinct purpose to each section
and it is easier for the reader to understand your work when presented
the Escherichi coli
or italicize genus and species names.]
were given pond water
order to get cultures of the E. coli. I
person past tense in Scientific writing.]
had tried to grow the E. coli in a tube of lactose-peptone broth. Nothing
grew however. What may have happened is that there was not enough E. coli in
the water where the sample was taken from. (The sample came from Mirror Lake.)
The amount of fecal matter in the water was not great enough, probably because
the Canadian geese had flown south for the winter and had not returned when the
sample was taken
water temp still very low so low bacterial numbers.] [So if this was the
results section too....what was the gram stain? Cell morphology? Still report
next bacteria that I had grown was a Thermophile. I had gone through the
experiments to the point where I had isolated pure cultures and streaked them
on nutrient agar slants which were being refrigerated for the weekend.
how did you isolate them. Tell me how you selected for these particular
organisms, it wasn’t the agar, but instead the temp!]
I returned to the lab after the weekend I was not able to find the slants with
my Thermophiles. I believe that
were either broken or stolen. To complete this organism I borrowed data from
another student in the lab.
but you need to cite him/her, initials are fine]
He had received gram positive rods.
of Gram positive Thermophiles that were colored red. There were no labels on
positive is Red? Any endospores? Label pictures! What power 40x? 100x?]
as can see there were no spores found among the rods. Therefore he did not
have to do a heat treatment to confirm that the organism was a bacillus.
Thermophiles can grow at temperatures of 55 degrees Celsius or higher, their
growth minimum is usually around 45 degrees Celsius. This is why we place the
thermophiles in an incubator so that we will be sure that thermophiles will
grow while other bacteria will not. Thermophiles have heat-stable enzymes and
protein synthesis systems able to function at higher temperatures. Their
membranes lipids are very saturated and have higher melting points as their
membranes will remain intact at higher temperatures.
but this is the problem with combining the results and discussion sections. I
was looking for this information earlier, but if the sections were separate I
would not have.]
had Actinomycetes isolated onto nutrient agar slants.
where? Do they grow naturally on NA slants? Is this their natural habitat?
NO! you must have started with soil at some point! Tell me about your
Then I streaked a GLA plate with the actinomycetes. GLA medium possesses low
concentration of a variety of compounds and Actinomycetes are able to grow in
these low concentrations. GLA medium also inhibit fungal growth with an
this part of your isolation procedure or are you now telling me about the
growth had occurred I smelled the plate. The odor coming form the plate could
only be described as a strong smelling soil or dirt. Then by streaking
Actinomycetes onto a plate of nutrient agar which had a layer of mixed lawn
growth and soft agar on its surface. The Actinomycetes grew and produced many
this term is reserved for phage assay. Where a clearing zone is the result of
bacterial cell death caused by bacteriophage infection. Also who told you to
do the assay this way or provided you with the materials to do it. We
(TA’s) instructed you to do this a different way in class we did a cross
streak technique to look for inhibition. This other technique you describe was
only used in years past?????]
organization of this paragraph is very poor. Are you testing the organism post
isolation? If so how about telling me about the isolation!]
plaques proved that the Actinomycetes were producing some kind of antibiotics
which were inhibiting the growth of the lawn organisms. After gram staining a
colony of Actinomycetes I found that they are gram positive bacteria
morphology? Usually filaments not individual cells.]
which contain spores.
don’t contain endospores like Bacilluscereus; the spores develop at the
end of the filaments]
are also aerobic bacteria. By observing the margins of the Actinomycete
colonies they appear to be very filamentous. This is because Actinomycetes
have branching filaments which contain spores. Most of the spores are not
particularly heat-resistant but are very adaptive otherwise.
the next organism I received
negative Azobactor in the form of bacillus.
was rod shaped.]
or underline genus names. When no particular species is isolated or further
characterization is not done follow genus name with the abbreviation sp. for
appear to look much like water droplets. Azobacter are nitrogen fixing
bacteria. Only nitrogen fixing bacteria can survie on mannitol medium with
– very important]
this is how we can isolate Azobacter colonies. By observing the margins of
these I could tell as to whether the colonies were Azobacter or Actinomycetes.
The margins were undulate while the margins of the Actinomycetes are
was the color of it? and was it hard like actinomycetes or gummy?]
isolated pure colonies of the Pseudomonads are gram negative rods.
Pseudomonads can be isolated on media that contain carbon sources that can only
be oxidized by a few organisms, this is why benzoate is used as the only source
agar slants that I had stored them on were poor in iron content so when the
Pseudomonad colonies grew on the agar they produced a dark yellowish pigment.
We did not provide you with this medium so there is no way you could have done
this. The lab manual does mention this so I’ll assume you just copied it
out of there. Don’t
report something you did not do.]
can degrade an exceptionally wide variety of organic molecules making them
important in the mineralization process in nature and in sewage treatment.
final organism I had grown was an Extreme Halophile. The halophiles grow in
environments of high salt concentrations where other organisms cannot and this
is how to isolate them. I had tried to grown halophiles from fish sauce and
also from a salt water solution. On the halophile medium I received many dark
shaded colonies. Upon gram staining I received gram negative cocci that did
not produce spores.
by the fact that none of the other 130 students were able to isolate this
organism or get any thing out of their enrichment and that you don’t have
it signed off, I highly doubt you did this isolation. Again, don’t ever
report something you didn’t do]
I did not have enough time to finish my experiments on the halophiles. But
what I would have continued with would have been to streak the halophiles onto
plates of varying salt concentration and observe whether the halophiles grew or
not. The halophiles should have grown on plates with high salt concentrations
but not on plates with concentrations of lower than 1.5M (or molar) salt.
Halophiles accumulate great amounts of potassium in order to stay hypertonic to
their environment. The enzymes, ribosomes, and transport proteins of
Halophiles require high levels of potassium for stability and activity. I also
would have use motility agar to tell whether the organism was motile, but
halophiles are non-motile.
when I received what I now know as being the signing sheet. I thought that it
was a check off list as in the unknown lab. I was not aware until the final
lab period that I was supposed to have gotten the sheet signed whenever I had
completed a step. I have included the sheet with my checks of each step with
you were in the lab at all when other students were in there working on this
lab during the four week period you would have known.....]
of Microbiology: Laboratory Manual
University of Connecticut, Jan. 1999.
Lansing M., Harley, John P., Klein, Donald A.
combination of writing this lab the night before and doing very little work in
the lab made for a report that was poorly organized, hard to read and littered
with suspect data. Please make note of the comments for the next lab report. .
.If you have any questions, please come see me.]