examining something under a microscope requires 3. Examining something under a m
ID: 189480 • Letter: E
Question
examining something under a microscope requires 3. Examining something under a microscope requires the microbiologist to consider potential problems associated with viewing each specimen, and then to evaluate the pluses and minuses of problems inherent in viewing the specimen. Then consider at least TWO types of microscope that could reasonably be used to view the specimen. Make a table that lists (1) how that particular microscope works, and (2) at least two pluses and two minuses associated with each of your microscope choices. Please confine your answer to types of microscopy we covered in Lecture 4 A. Motile bacterial cells swimming B. Bacteriophage inside host cells C. Bacterial slime layer D. Bacterial biofilm forming on a plant leafExplanation / Answer
A. Problem with motile cells- if cells are heat fixed then motility can not be seen. And if cells are not stained then also it will create a problem to observe
To solve these problems there are two microscopes one is dark field microscope. In this the specimen will be bright against a dark background. So one can see every details of cell morphology and structure. Another one is bright field microscope. To see the motility hanging drop technique is used, so motility can be seen in alive bacteria.
B. Problem with bacteriophage inside host cell- the phage will be inside the cell, so we need to see the interior view of a cell. But usual bright field or dark field microscopes are used to see the exterior. To see the interior we need TEM. Transmission electron microscopy with fluorescence lighting. This helps to see the detailed structure of bacteriophage inside the host cell. Positive point: proper structure can be seen, quick
Negative point specimen preparation is comparatively hard, expensive.
C. Problem with slime layer- bacterial slime layer covers whole bacterial surface, so under normal bright field microscope, we can not differentiate between cell and slime layer. To study slime layer, we can use phase contrast microscope. Positive point, can distinguish between loosely attached slime layer and tightly attached capsule with cell all. Fast.
Negative points, not much details about slime layer can be deducted. for detailed structure we can use electron microscope.
D. Problem with biofilm on leaf- biofilms are several layers deep, contains cells and debris
We can use epifluorescence microscope, scanning electron microscope, or confocal laser scanning electron microscope.
Positivepoints - we can observe upto the depth of 20 micrometer, clear images, detailed morphology
Negative points: expensive, time consuming
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