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The aim in this experiment is to estimate the total number of microbial cells in a culture and estimate the number of living cells. This will be done using a counting chamber and microscope. There will be a total count and a viable count

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Introduction

MC-2 molecules to cells. Estimation of the number of microbial cells Aim The aim in this experiment is to estimate the total number of microbial cells in a culture and estimate the number of living cells. This will be done using a counting chamber and microscope. There will be a total count and a viable count. The Total count will require a microscope to count the number of cells in a sample. These cells are living and dead. A haemocytometer will be used. A haemocytometer has a known volume of chamber and area which is etched on the glass. A cell suspension is able to be above the known area. The chamber is then filled with a yeast suspension then covered with a cover slip. An average number of microbes can then be counted in the ruled area to give the number of yeast cells per cm3. This is a view through a microscope of a grid on a haemocytometer. Most of the cells in the grid are counted other than from the cells that are represented in black. b) In a viable count a set of known dilutions are set up of yeast, tenfold serial solutions are prepared. A sample from each dilution is then added using a pipette onto a labelled area of the agar medium culture where the Miles Misra method is to be used. ...read more.

Middle

The result 10-5 is 5.5* 108 cfu cm �� and 10-6 is 7*108 cfu cm ��. The result for the total count is 1.281*107 cells cm��. There are problems with this method, however. The number of cells in each grid maybe more concentrated or less concentrated as they are not evenly spread over the all the grids. So therefore this makes the results inaccurate as the concentration of cells vary. Also, the cells clump together-this makes it very difficult to count the number of cells. Moreover, there will be human error involved as the cells have to be counted through a microscope. So therefore more or less cells may have been counted. One problem with this technique is you are unable to distinguish between dead and living cell, so the number of living cells cannot be equated. There are advantages and disadvantages with viable and total count technique. Firstly, with the viable technique the advantage of this technique is that it only counts the living cells. The disadvantages of the of viable count are the confluence of cells, this prevents the ability to distinguish colonies. So there could be more or less colonies therefore making the results inaccurate as you are unable to distinguish them. To solve this a drop of each dilution could placed on a agar plate then spread this will then distribute the cells so there is less chance convergence clumping . ...read more.

Conclusion

Both methods enabled me to gain the results that I required. This was not the most accurate way as both methods have error. The techniques would have to be improved. This may mean producing a wider range of dilutions. Another idea would be to pipette a drop of diluted suspension onto its own medium then use the Spread Plate Method this prevents clumping. Producing a greater number of results, would then mean I could produce more accurate mean. References a) Biology seventh edition. Cambell and Reece b) www.uwcsea.edu.sg/bio MC-2 1. This could be due to a number of factors. Using non-sterile equipment could cause contamination. This may affect the growth on the plates. As it may inhibit growth or enhance the growth. Another factor would be the length of time that the culture is left to incubate for. If the plate is left for longer then the cells would grow producing larger colonise. the only limiting factor would be nutrients, so if left to long cells may begin to die. The conditions that the cultures are kept in will affect the growth. If they were left in hot conditions then the rate of reaction would be increased. This there for means increased . Keeping the cultures in cool conditions will restrict the growth of the bacteria. 2. Viable count/total count * 100= percentage of viable count. 3. Yoghurt production Pharmaceutical industry Food testing Shelf life dates. ...read more.

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