LAB 1 - MAYA EMIRA BINTI MAD SAAD 111381

1.1   EXAMINATION OF CELLS

INTRODUCTION

Because of their extreme minutes,bacteria are not generally studied with the low-power or high power dry objectives . Instead they are stained and observed with the oil immersion objective.

The wet amount methods enable us to study the sizes of livings microorganisms  .It also enables use determine if the cells are motile. The wet mount method is quick and easy and does not require special treatment.

OBJECTIVE

• To provide an experience in the use of microscope.

•   To illustrate the diversity of cells and microorganisms.

RESULT

1 ) Stained cells

 Penicillium spp.

40x magnification

  

100x magnification

400x magnification

2       ) Wet mount

  Saccharomyces cerevisiae

1000x magnification

Lactobacillus fermentun

1000x magnification

DISCUSSION

A preliminary and easy way to identify unknown bacteria is based on staining method known as gram-stain.The amount of peptidoglycan in the cell walls of the bacteria under study will determine how those bacteria absorbs the dyes with which they are stained,thus the bacteria is either gram positive or gram-negative.Gram-positive have simple cell walls with thick layer of peptidoglycan and stain purple,while gram-negative have more complex cell walls with thin layer of peptidoglycan and stain pink.The outer layer of lipolysaccharide acts as protection to bacteria from the host defense system and resistant to antibiotics.

For Penicillium spp. it can be identify that it has stain with pink color.Thus,it is Gram-negative.
For 40x magnification it can be see that the cell has filamentous structure.

Wet mounts can be made using several different kinds of liquids. Water, immersion oil and glycerin (glycerol) can be used, with water probably being the most commonly used. The source of the water is quite important, especially when observing living specimens. 

Some wet mounts are not made with water, but by using immersion oil. Immersion oil is usually placed on top of the cover glass so that the specimen does not get into contact with the oil. The oil-immersion objective is then rotated directly into the oil for observation.By using this immersion oil,we can see a very tiny specimen with a better view.Other than that,we may see a living and moving specimen. It is also possible to observe certain processes of life, such as feeding, cell division etc.

In the first specimen for wet amount,we can identify that Saccharomyces cerevisiae undergoes asexual reproduction that is budding( axial/polar/random) in different colony areas because of their condition, and sexual reproduction by forming ascospores .Besides that,we can observe that there is formation of karyogamy and plasmogamy .Karyogamy occurs in each ascus.Two haploid nuclei fuse,forming a diploid zygote nucleus.Apart from that, sporulation and meiosis occur because of nitrogen starvation in the presence of a poor carbon source.

Second specimen of wet amout is that Lactobacillus fermentum.It has  rod shape.Sometimes, it form spiral/cocoa under certain condition.It also can be see arranged in chain or oval. Lactobacillus is a genus of Gram-positive facultative bacteria. They are a major part of the Lactic acid bacteria group, named as such because most of its members convert lactose and other monosaccharides to lactic acid. The production of lactic acid makes its environment acidic which inhibits the growth of some harmful bacteria.

Some Lactobacillus species are used industrially for the production of yogurt, sauerkraut, pickles, and other fermented foods, such as silage. Some yogurt drinks contain Lactobacillus bacteria as a dietary supplement. . Many Lactobacilli are unique among living things as they do not require iron for growth and have an extremely high hydrogen peroxide tolerance. Besides that,Lactobacillus fermentum is use as probiotics for human health.

CONCLUSION

By using Gram-staining method we can identify the type of specimen that has been observed.This stain method takes advantages of  the structure of the cell  wall of bacteria.  The Gram-positive bacteria have a thick cell wall of peptidoglycan, which stains purple.  The Gram-negative bacteria have a a thinner cell wall layer (stains pink)  and they also have an outer layer containing lipids . 

Gram-negative bacteria include the proetobacteria, cyanobacteria, spirochaetes, green sulfur and green-no sulfur bacteria.  The group also contains medically relevant Gram-negative cocci, bacilli and many bacteria associated with nosocomial infections.  These organisms stain pink and are the source of endotoxins. Gram-positive bacteria include Bacillus, Staphylococcus, Streptococcus, Enterococcus, Diplococcus pneumoniae, Clostridium and Mycoplasma.  These organisms stain purple.


We use wet amount method because ,it increases the slide's translucency, by letting more light through and it will also make it easier to stain. Not only that, but it will also flatten the organism, which will make it easier to view.A wet mount should be used when we want the microorganisms to remain alive.

REFERENCES

• http://en.wikipedia.org/wiki/Penicillium

• http://www.microbehunter.com

• http://www.ncbi.nlm.nih.gov/pmc/articles/PMC365336/

• http://www.genetics.org/content/189/3/737.abstract

• http://www.sciencedirect.com/science/article/pii/S0923250805001506

• Complete Reference Biology 2,Bah Hock Guan,Tor  Siong Hoon,Sri Nasariya, 2009

• Thomson Brooke/Cole ,Solomon,Berg,Martin ,8th Edition, 2008