Question

Micrebes in the Environment QUESTIONS What in the advantage of using Petri plate rather thon tet t in mieriogy? 2What are bacteria uaing for nutrienta in satrient agsr What is the perpoe of the agar? CRITICAL THINKING Did all the organiems living in or on the environmente aompled gw on your nutrient agar Briefly explain. 1. 2 How could you determine whether the turbidity in your nutrient broth tube was from a mixture of diferent microbes or from the growth of only one kind of micrebe?" CLINICAL APPLICATION The efectivennas of sanitation procedures in hospitals is determined by sampling surfaces for bacteria, Same can be taken by rubbing a sterile, moistened cotton swab on a surface and inoculating a nutrient agar plate or with a Rodac environmental sampling plate. The 67-mm Rodac plates are designed so that an agar medium can be er Ailled, producing a dome-shaped surface that can be pressed onto a surface for sampling microbes As the sanitadion coatrol officer, you test each method to determine which you will use. What can you conclude from these resulb Number of Plates Inoculated Number of Plates with Colonies 50 Swab onto nutrient agar 40 Rodae plate containing nutrient agar 5 27

Answer 1

Ques 1:

Advantages of using petri- plates over test-tubes are:

1. The risk of contamination from air-borne micro-organisms is less because they are incubated in incubator upside down.
2. The danger of condensation of water droplets on the agar medium is less.
3. It provides large surface area than test-tubes for examination of micro-organisms.
4. Can be stacked on each other to save space in incubator.
5. Petri-Plates allows long examination of micro-organisms as compared to test-tubes.

Ques 2:

Purpose of Agar are :

1. Most of the micro-organisms are not able to enzymatically degrade agar.
2. At boiling temperature agar melts in water.
3. High degrees of transparency.
4. Agar is used as a solidifying agent and have excellent handling property.