Bacterial cells Quantification - Lab Report Example

Additionally, the information provided by this can be used to discover the effect of an enzyme on bacterial cell count – if an enzyme increases reproduction or lyses cells, this is discoverable by comparison to the absorbance graph created using known concentrations. In this experiment, the activity of lysozyme is studied. Lysozyme is the name of a glycoside hydrolase which damages cell walls by catalysing hydrolysis of the links between two key components of peptidoglycan – N-acetylmuramic acid and N-acetyl-D-glucosamine (Pommerville, 2007).

It is notable that lysozyme is present in many human excretions, such as saliva and tears, and this forms one of the body’s many natural antimicrobial techniques. It is also notable that lysozyme is more effective against Gram-positive cells because the cell walls of these bacteria have a higher concentration of peptidoglycan (Pommerville, 2007). An additional experiment was performed to test the effect of certain antibiotics on bacterial cells. This is always an important test because of the current crisis in clinical practice due to the increasing amount of bacteria that are highly resistant to many or all of the available antibiotics (Neu, 1992).

This can be done in several ways, but antibiotic disc sensitivity testing is particularly useful as it allows a test of several antibiotics on one sample of organism, allowing us to be certain that all the microbes are the same and thus reducing the possibility of false results. Results Antibiotic Effect on Various Bacteria Antibiotic/Dose Escherichia coli (-) Pseudomonas aeruginosa (-) Staphylococcus aureus (+) Bacillus subtilis (+) AP/25?g S R S S GM/10?g S S R S PY/100?g S R S S NA/30?g S R S R NI/50?

g R R S S SM/200?g R R R R T/100?g S R S R TS/25?g S R S S NI at a dose of 50?g is effective only against Gram-positive microbes. TS at a dose of 25?g and T at a dose of 100?g, as well as NA at 30?g, PY at 100?g, GM at 10?g and AP at 25?g all appear to be effective against both Gram-positive and Gram-negative organisms. Micrococcus lysodeikticus Concentration vs. Absorbance at 450nm Micrococcus lysodeikticus (cells/ml) Absorbance at 450nm 0 0.000 6.25 x 106 0.406 1.25 x 107 0.274 2.5 x 107 0.301 5.0 x 107 0.455 1.0 x 108 0.870 Unknown 0.

599 The general trend appears to be that absorbance is higher with a higher concentration of cells per ml. Absorbance = (0.000000008 * cell concentration) + 0.21 We can thus work out the unknown value by rearranging this formula – Absorbance – 0.21 = 0.000000008 * cell concentration Cell concentration = (Absorbance – 0.21)/0.000000008 Unknown = 48625000 or 4.8625 x 107 Effects of Lysozyme Solution on Viable Cell Count – Shown Using Absorbance Time (minutes) Absorbance of the M. Lysodeikticus standard containing 5.

0 x 107 cells/ml 0 0.414 3 0.350 6 0.337 9 0.333 12 0.320 15 0.300 The longer the cells are left in the lysozyme solution, the less absorbance is shown. Discussion As noted in the discussion, lysozyme is more effective as a antimicrobial towards Gram-positive cells due to the larger amounts of peptidoglycan in the cell walls of these organisms. As can be seen here, lysozyme has a very distinct effect on the absorbance measurements from the M. lysodeikticus standard which increase substantially with time, suggesting that there are less viable cells the longer the organism is left in the presence of