Experiment to investigate the effect of different antibiotics on the bacteria Bacillus subtilis:

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Biology-Miss Hardy                                                                                                                                                  By Rebecca Kriegbaum

Experiment to investigate the effect of different antibiotics on the bacteria Bacillus subtilis:


To see which antibiotic (Chloramphenicol, Erythromycin, Fusidic Acid, Oxacillin, Novobiocin, Penicillin, Streptomyan and Tetracycline) reacting with the Bacillus subtilis has the largest zone of inhibition in mm (+/- 0.5mm) and so which has the biggest effect on the bacteria.


Gram -positive bacteria are bacteria that are dark blue or violet when gram staining. Gram-positive organisms are able to keep the crystal violet stain because of a high amount of peptidoglycan in the cell wall. This makes up about 90% of the thick, more than 20 layers of peptidoglycan together. Gram-positive organisms normally do not have the outer membrane, whereas Gram-negative organisms do.

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Gram-positive bacteria include many well -known genera like Streptococcus and Bacillus.

Most pathogenic bacteria in humans are Gram-positive organisms and these are used to manufacture antibiotics.

Bacillus subtilis, also known as the hay bacillus or grass bacillus is a Gram- positive bacterium, which is mostly found in soil. Bacillus subtilis is not a human pathogen and it can contaminate food but rarely causes . Bacillus subtilis spores can survive the extreme heat during cooking and Bacillus subtilis is responsible for causing a sticky, stringy consistency in spoiled bread dough.

Antibiotics are among the most frequently prescribed medications in modern medicine.

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**** A very good, interesting scientific study. Although not complete the foundation for an excellent investigation is present. The method needs to be provided which would allow the reader to repeat the experiment. The data collection is excellent and answers the aim of the investigation well. The conclusion does not put enough emphasis on the central question of which antibiotic is most effective and offer a scientific explanation of why this might be.