MicorA report Exp2 (I)

: Norbert Ha How Ong, Norisha bte Othman Name Group : MB0702 Date : 26th April 2007 Module name: MicroBiology A Exp no. : 2 (I) Title Aseptic broth transfer and colony selection Objectives 1. Perform basic bacteriology bacteriology transfer techniques using broth and agar cultures. 2. Handle bacteriolo bacteriology gy cultures cultures aseptically aseptically

Summary of Theory

Media preparation Aseptic technique is a technique to prevent contamination of cultures. Culture media are prepared in either a liquid (broth) or solid form. Meticulous care is taken to provide the proper concentration of nutrients , pH and other factors needed to cultivate microorganisms. Glassware such as test tubes containing media are stoppered with cotton plugs or loosefitting autoclavable plastic or metal caps to p revent the entrance of foreign microorganisms. The tubes with their contents are then sterilized . For Petri dishes , they are sterilized  in the autoclave and media are then poured aseptically into them.

Two general-purpose media are nutrient broth and nutrient agar. The broth preparation contains beef extract and peptone, pep tone, dissolved in distilled water. Nutrient agar contains all of the ingredients found in nutrient broth b roth and the solidifying agent agar. Growth patterns of bacteria Broth media: Bacteria may exhibit a particular form of growth such as clouding of the medium turbidity), accumulations of cells at the tube bottom (sediment  (turbidity), (sediment  ), ), and form a thin pellicle). surface film (pellicle). Agar media: Bacteria form visible accumulations of cells which is known as colonies. The appearance of colonies as to pigmentation, shape , elevation and the patterns of growth.

Procedures A. Broth Transfer 

B. Agar Slant as Sources of Inoculum

C. Inoculation of an Agar Slant

D. Colony Selection

Hypothesis For experiment A, B and D, growth will be expected which causes turbidity of the medium. It will accumulate at the bottom of the tube which will form pellicle.

For experiment C. , growth will be expected as colonies on the agar slant.

Discussions No. 1.

2.  

Sources of error Using both hands to remove the caps from the tubes.

Contamination of inoculating loop.

Improvements Ask help from our partner to remove the cap while one hold the inoculating loop. Sterilize the inoculating loop and keep it close to the flame at all times.

Answers to questions

1. 4 specific characteristics of broth cultures are it is in liquid form, contains beef  extract and dissolves in distilled water. After inoculation of broth media, bacteria may exhibit a particular form of growth.

2. A bacterial colony is a cluster of organisms growing on the surface or within a solid medium, usually cultured from a single cell and are genetically identical. 3. A nutrient broth contains beef extract and peptone dissolved in distilled water.  In which, peptone contains a mixture of amino acids, carbohydrates, mineral salts and polypeptides. A nutrient agar contains all of the ingredients found in the nutrient broth. It also contains a solidifying agent, agar, generally in 1.5 to 2.0% concentration, which makes it different form the nutrient broth. 4. 2 ways to sterilize laboratory media are sterilizing by flaming and sterilizing objects with ethanol.