Gram Positive and Gram Negative Bacteria Experiment

The goal of this test was to identify between Gram negative and Gram positive bacteria by Gram staining method. In addition, this test allowed us to visualise the morphology and layout of the bacterial cell.

Approach (to attain aim):

In this test, two different staining methods were employed, the monochrome staining method and the Gram staining method. The monochrome staining method is a primary stain that spots the bacteria only using one kind of stain. Gram staining method pays to for classification and id of bacteria. The Gram stain is a differential stain which allows someone to classify bacteria as Gram positive or Gram negative.

Materials and Methods:

Refer to site 4 and 5 for staining methods.

Results:

Table 1 shows the monochrome and Gram Staining of Staphylococcus epidermidis and Escherichia coli

Test

Monochrome Staining

Gram Staining

Bacteria Cells

Staphylococcus epidermidis

Escherichia coli

Staphylococcus epidermidis

Colour

Blue

Blue

Purple

Shape

Cocci

Bacilli

Cocci

Arrangement

Grape-like clusters

Isolated

Grape-like clusters

Results

Both skin cells were stained blue because of the primary staining triggered by Loeffler's methylene blue

Gram positive bacteria

Conclusion and Debate:

In the monochrome staining of S. epidermidis and E. coli, both the bacteria skin cells were stained blue in colour. This was due to the presence of rich nucleic acid and the negatively priced surface receptor substances of the bacterial cell which drawn the cationic stain of methylene blue. Therefore, the cells retained the colour of the methylene blue stain and came out blue.

In the Gram staining of S. epidermidis and E. coli cells, S. epidermidis appeared to be in purple shade. This indicates that S. epidermidis was a Gram positive bacterium. The cell wall structure of Gram positive bacterium experienced a solid peptidoglycan layer which contained magnesium ribonucleate and lacked lipid in the membrane system. During Gram staining process, the crystal violet basic stain made crystal violet-iodine-magnesium ribonucleate organic on the Gram positive bacterium cell wall membrane. Therefore, Gram positive bacteria made an appearance violet in color due to the development of the organic. Regarding E. coli, it was a Gram negative bacterium because it was stained red. The use of 95% ethanol dissolved the lipids in cell walls of Gram negative bacterias, therefore resulting in the outflow of crystal violet from the cell. In addition, the application of carbol fushin stain allowed E. coli to uptake the extra stain and so appearing red during observation.

Under the microscope, S. epidermidis was cocci designed and had grape-like clustered design. On the other hand, E. coli was pole shaped and had isolated layout.

END

Name: Wei Xiao Yang

Question (i. e. Purpose):

The aim of this experiment was to observe bacterial colony characteristics and the merged bacterial culture record in nutritional agar plates.

Approach (to attain aim):

In this experiment, streak dish method was applied to nutritional agar plates to produce isolated colonies of bacteria from blended culture.

Materials and Methods:

Refer to web page 7-9 in the practical manual.

Results:

Table 2 shows the colony characteristics of any and B in stable medium

Mixed Culture

Colony Characteristics

A

Shape

Circular

Size

1-2mm

Chromogenesis

Colourless

Opacity

Translucent

Elevation

Raised

Surface

Dull

Edge

Entire

Texture

Smooth

Emulsifiability

Turbid

Gram nature

Gram negative

Odor

Negative

Consistency

Butyrous

Morphology

Bacilli

Arrangement

Isolated

Conclusion and Discourse:

From the experimental results, bacterial colonies from A were pole designed, gram negative and had isolated kind of arrangement when viewed under the microscope. Enjoying the colony characteristics, the colonies from A appeared round, colourless, translucent, raised, smooth, and possessed a larger size colony. Furthermore, the top of colony A was flat and it got entire ends. Therefore, judging from the colony characteristics, morphology and Gram nature of the bacterias, bacteria from colony A could be possibly be E. coli. On the other hand, bacterias colonies from B were Gram-positive, cocci molded and had grape-like clusters of layout. The colonies from B were round, whitish, opaque, convex, granular and punctiform in size. Thus, bacterias colonies from B were probably S. epidermidis.

END

Name: Wei Xiao Yang

Question (i. e. Goal):

The goal of this experiment was to see the type of progress of different bacteria in liquid medium.

Approach (to achieve aim):

In this experiment, identification of bacteria was based on the physiological properties of the bacterial expansion in liquid medium.

Materials and Methods:

Refer to page 10 of the functional manual.

Results:

Microorganism

  • Escherichia coli

Growth characteristics

Amount of growth

  • Moderate

Surface growth

  • Absent

Turbidity

  • Present (standard)

Sediment

  • Present (disintegrate upon shaking)

Chromogenesis

  • Negative

Gram nature

  • Gram negative

Morphology

  • Bacilli

Arrangement

  • Isolated

Table 3 shows the progress characteristics of Escherichia coli and Pseudomonas aeruginosa in liquid medium.

Conclusion and Dialogue:

From the experimental results, E. coli being a facultative anaerobic bacterium was able to grow in modest quantities as it shows standard turbidity in the liquid medium. The E. coli cells sediments in the bottom of the test tube due to the huge amount accumulation of dead cells. Alternatively, P. aeruginosa being an aerobic bacterium developed pellicle at the liquid-air surface and was turbid towards the surface. This would claim that P. aeruginosa favoured aerobic respiration for growth as the liquid-air surface had higher amount of air content when compared with underneath of the tube. Moreover, P. aeruginosa was able to produce pyocyanin pigments which would diffuse into the medium, turning the liquid medium bluish inexperienced in colour. Beneath the microscope, both E. coli and P. aeruginosa were Gram-negative; rod shaped and experienced isloated agreement.

End

Name: Wei Xiao Yang

Experiment: Biochemical Test

Question (i. e. Purpose)

The goal of this catalase test experiment was to differentiate Staphylococci bacteria from Streptococci bacterias due to the existence of catalase enzyme. The aim of this oxidase test was to detect the occurrence of cytochrome oxidase enzyme in the microorganism.

Approach (to achieve aim):

In the catalase test test, recognition of catalase producing bacterias was done by observing the decomposition of hydrogen peroxide into water and oxygen. Within the oxidase test experiment, the diagnosis of cytochrome oxidase producing bacteria was done by redox result of cytochrome oxidase which changed the oxidase test reagent into crimson colour.

Materials and Methods:

Refer to web page 11-13 of the functional manual

Results:

Table 4 shows the catalase Test outcomes of Staphylococcus aureus and Streptococcus faecalis

Test

Catalase Test

Bacterial Cells

Staphylococcus aureus

Streptococcus faecalis

Observation

Effervescence formed

No Effervescence formed

Results

Positive catalase test

Negative catalase test

Table 5 shows the oxidase Test results of P. aeruginosa and E. coli

Test

Oxidase Test

Bacterial Cells

Pseudomonas aeruginosa

Escherichia coli

Observation

Development of dark purple colour at the website of smear

No coloring change is observed

Results

Positive oxidase test

Negative oxidase test

Conclusion and Talk:

In the experiment of catalase test, S. aureus being catalase positive showed the capability to catalyse the degradation of hydrogen peroxide to air and water, hence producing effervescence. On the other side, S. faecalis being in the streptococci family will not have the catalase enzyme to degrade the hydrogen peroxide. Therefore, there was no effervescence produced. The catalase test allows us to identify between staphylococci species from streptococci species.

In the test of oxidase test, P. aeruginosa being oxidase positive have cytochrome c oxidase which oxidised N, N, N, NHYPERLINK "http://en. wikipedia. org/wiki/Wurster's_blue"-tetramethyl-HYPERLINK "http://en. wikipedia. org/wiki/Wurster's_blue"pHYPERLINK "http://en. wikipedia. org/wiki/Wurster's_blue"-phenylenediamine (an artificial electron donor for cytochrome c) in the oxidase test reagent. The occurrence of cytochrome oxidase catalyses the carry of electrons from NADH to electron acceptors (air) and reduced it to drinking water. Therefore, the oxidation of N, N, N, NHYPERLINK "http://en. wikipedia. org/wiki/Wurster's_blue"-tetramethyl-HYPERLINK "http://en. wikipedia. org/wiki/Wurster's_blue"pHYPERLINK "http://en. wikipedia. org/wiki/Wurster's_blue"-HYPERLINK "http://en. wikipedia. org/wiki/Wurster's_blue"phenylenediamine produced a dark, oxidized product called indophenol blue, turning the oxidase test reagent soaked paper remove into maroon coloring. On the other hand, E. coli showed no color change in the newspaper strip. Hence, this advised that E. coli did not have any cytochrome oxidase activity and was oxidase negative.

Also We Can Offer!

Other services that we offer

If you don’t see the necessary subject, paper type, or topic in our list of available services and examples, don’t worry! We have a number of other academic disciplines to suit the needs of anyone who visits this website looking for help.

How to ...

We made your life easier with putting together a big number of articles and guidelines on how to plan and write different types of assignments (Essay, Research Paper, Dissertation etc)