• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Comparison of traditional and modern approaches to the identification of bacteria

Extracts from this document...

Introduction

Comparison of traditional and modern approaches to the identification of bacteria The traditional techniques of biochemical testing in the form of API strips was compared to modern techniques of Polymerase Chain Reaction (PCR) for the accurate identification of bacteria. The PCR technique would make use of 16S rRNA databases from Internet search sites. It was found that both techniques were, in most cases, able to identify each bacterium to at least the genus level. INTRODUCTION Identifying a particular strain of bacteria is very useful since it opens up a wealth of knowledge about it. For instance, if one knows that the bacteria is a member of the genus Micrococcus of the Actinobacteria class, then one would be able to find that it is; Gram-Positive, non-motile, has a G + C content of 70%, is aerobic, it is found mainly on mammalian skin etc. If the bacterium was pathogenic, such as Streptococcus pneumoniae, then one could find that it has the potential to cause meningitis, so one could take precautions against this. Identification of a bacterium can also establish the bacteria's position on a phylogenic tree, and thus decipher the immediate relatives. The traditional methods for identification of bacteria generally required the isolation and growth of bacteria. Bacterial growth is usually characterised by the appearance of colonies on media. Then isolation of the bacteria required can be achieved using selective media. ...read more.

Middle

This enables a large quantity of DNA to be sequenced (more than 1x106) in less than a few hours since each cycle produces an exponential increase for sequenced DNA. The sequences can then be compared to the thousands of already sequenced 16s rRNA genes from the databases available. The result will be displayed with a percentage match next to the name of a bacteria strain, for instance Staphylococcus auerus 91.48%. This would mean that the DNA inputted into the system from the strain analysed had a 91.48% match with the DNA in the database. This suggests one could be quite confident that this was Staphylococcus auerus and almost positive that it was from the Staphylococcus genus. METHODS Preparation of unknown bacteria. A known strain of bacteria was isolated and grown into colonies. Each colony is grown from a single bacterium and is thus a clone of this bacterium. This was prepared by the demonstrators such that they knew what each of the strains was, but I was not informed until the end. Preparation of API strip. API 20E (BioMerieux) strip was inoculated with a test strain by using a pipette to remove a single colony from a pre-made agar containing one species of unknown bacteria. The colony was then mixed into a universal tube containing 5 ml of sterile saline by rubbing the pipette on the wall of the tube. ...read more.

Conclusion

As Dr J. Lodge instructed the class what each strain was, it was then known that this was incorrect, but it demonstrates how 16S rRNA is highly conserved across the microbial world. Therefore, caution must be taken not to accept the highest match given on face value, but to compare to that of the second and third matches. Overall, this method is a useful taxonomic tool. PCR of the 16S rRNA can be performed relatively quickly, with only small amounts of DNA As little as, 10-9g is needed. This technique is now automated in many laboratories and the DNA can be amplified up in less than one hour.This means that many 16S rRNA molecules can be compared in anyone day and thus it is a very quick and reliable method of classifying organisms. Strain Name Score A Enterobacter clocae 16S rRNA gene 0.803 A Enterobacter clocae 256-36 0.797 A Seratia marcescens 16S rRNA gene 0.792 B Pseudomonas aeroginosa 16S rRNA gene 0.831 B Pseudomonas sp. 16S rRNA gene 0.831 F Citrobacter freundi 16S rRNA gene 0.876 F Citrobacter freundi CDC 621-64 0.823 F Citrobacter freundi DSM 300 39 0.823 Figure 3. The scores above refer to how good the match is, with 1.000 a perfect base pair to base pair match and 0.000 being no match at all. Therefore, the highest score for each strain should be the closest match that the database can come up with. In each case the database identified the correct genus, i.e., A: Enterobacter; B: Pseudomonas; F: Citrobacter. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Living Things in their Environment section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Living Things in their Environment essays

  1. Marked by a teacher

    Taxonomy is the branch of biology that deals with the identification and naming of ...

    5 star(s)

    In biology the system is "binomial", meaning that two names are used to specifically identify every organism - genus and species. The binomial system uses a two word Latin name. For example, the binomial name for humans is Homo sapiens.

  2. Marked by a teacher

    Animal Testing

    4 star(s)

    When a certain protein was added the number of follicles that grew back doubled and there was less scarring (9). It could be said that this test was unnecessary as baldness is nothing to cure. It is not a life-threatening disease that can kill humans so there is no need to cure baldness and harm animals.

  1. Using the streak plate method, compare the effect of two different brands of toothpaste ...

    Then using the prepared set agar plate, I opened the lid and swiped the loop over the set jelly without breaking it. I swiped the loop down the middle only third of the way. Then I swiped it across so the jelly was covered.

  2. Introduction to bacteria

    and they are produced by some bacteria to prevent other bacteria from growing near them and using up their food. Over 8000 antibiotics are known to science, but we are always looking for more and currently about 200-300 more are discovered each year.

  1. The comparison of bacterial content in a range of milks.

    They usually are not pathogenic. Lactobacilli also create problems. They sometimes are responsible for spoilage of beer, milk and meat. A variety of gram-positive bacteria produce lactic acid as their major or sole fermentation product and are sometimes collectively called lactic acid bacteria.

  2. Investigation of Ecology on Four Sites on the River Nar

    After the sample was collected, it was carried up to the tray and the contents emptied into the tray by inverting the net. The thermometer was then place into the tray and the temperature recorded. The species in the tray were then identified and their frequency recorded.

  1. Investigating the effect of four antibiotic agents on gram positive and gram negative bacteria.

    This outer membrane also contains porins, which are proteins that form pores in the membrane and allow small hydrophilic molecules to pass into or out of the cell. Hydrophobic and larger molecules cannot pass through the porins and this is how the Gram Stain is prevented from reaching the peptidoglycan layer to colour it.

  2. Culturing Bacteria.

    The glass container's neck is sterilised again and lid place back on. The inoculating loop is then run almost horizontally over the surface of the solid agar plate, in different patterns of streaking (see method section). The lid is placed over the agar plate, and it is incubated upside down

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work