Lab report-Culture media PDF

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Ashneeta Nand S4555319 RBF2300 MICROBIOLOGY 1 PRACTICAL 2: PREPARATION OF CULTURE MEDIA, MICROSCOPY AND ENUMERATION OF MICROORGANISMS

INTRODUCTION A culture medium is a solid, liquid or semi-solid form designed to support the growth of microorganisms. It is composed of different nutrients that are essential for microbial growth. All microorganisms contain unique properties and therefore require specific nutrients for growth. The main aim of a culture medium is to let microorganisms grow safely in an ensured environment and to protect them against any environmental damage. AIM To prepare successful culture media’s and determine the number of individual viable microbes. MATERIALS a. Light microscope b. Immersion oil c. 70% ethanol, Bunsen burner d. Microscopic slide containing stained microorganisms e. Lens tissue f. Slide micrometer g. Stained preparation of yeast and bacteria h. Microscope fitted with ocular micrometer i. Bacterial cultures labelled A, B, C and D. j. Glass slides k. Crystal violet, iodine, 95% ethanol in a dropper bottle and safranine l. Staining racks

METHOD Exactly as described in RBF2300, Practical 1 Introduction to Microbiology Laboratory 2017. No changes were made during the practical.

Ashneeta Nand S4555319

RESULTS TABLE 1-DIFFERENT TYPES OF BACTERIA OBSERVED UNDER MICROSCOPE

E.coli

-Gram-negative -Rod-shaped - Single cell arrangement

Bacillus cereus

-Gram-positive -Rod-shaped -Arrangement is in chains

Ashneeta Nand S4555319

Clostridium tetani

-Gram positive -Rod-shaped

Staphylococcus aureus

-Gram-positive -Round-shaped -Single cell arrangement

Ashneeta Nand S4555319

TABLE 2-GRAM POSITIVE VS GRAM NEGATIVE BACTERIA GRAM POSITIVE

-Thick (multilayered) - Stain is dark violet or purple -Rod shaped -Arrangement is in chains

GRAM NEGATIVE

-Thin (single-layered) -Stain is red or pink -Streptococcus shaped -Arrangement is in clusters

IMAGE 1- OCULAR MICROMETER VS STAGE MICROMETER UNDER MICRSCOPE

Ashneeta Nand S4555319

IMAGE 2-MOVING MOTILE PROTOZOA UNDER MICROSOPE

CALCULATIONS How many ocular micrometre superimposed with stage micrometer units? 97 OBSERVED 97 X 10 / 100 X 10 10 u = 0.97 μm =0.97 μm Therefore size is (0.1 x 0.97) = 0.097μm

DISCUSSION During this experiment various types of bacteria were observed under a microscope. This practical enhanced students’ knowledge of the different shapes and arrangements of certain bacteria. The shape of gram positive bacteria was observed to be multilayered and the stain colour was dark violet. Specifically the arrangement was in chains of rod like structures. However gram negative bacteria’s shape was single-layered and the stain was red in colour. The arrangement was in clusters specifically consisting of streptococcus like structures. When comparing and contrasting the ocular micrometre with the stage micrometre, both were proven to be similar but had different functions. The ocular micrometer was known to the measure the size of samples, while the stage micrometer was used to calibrate the ocular micrometer. Furthermore students also observed motile protozoa under the

Ashneeta Nand S4555319 microscope. Although it was difficult to observe the motile protozoa due to the small size students were able to successfully identify and record the different structures visible. CONCLUSION Overall during this laboratory practical students were able to thoroughly identify and distinguish gram positive and gram negative bacteria. Many differences were identified between the two types of bacteria therefore making it easier acknowledge the contrasts. Students also learned the difference between an ocular micrometre and a stage micrometre. This practical enhanced our knowledge of bacteria and microscopes such that we could apply these teachings in the upcoming laboratory practicals....