Proper aseptic technique is crucial to ensuring growth of pure bacterial colonies. what is one experimental way you can test your practices to confirm that you are using proper aseptic technique? (5 points)- in a laboratory setting, what are three ways you can properly sterilize culturing equipment?
- for each inoculation tool, give one scenario in which use of that tool would be appropriate.
- do some research and describe two or three scenarios in which it would be preferable to use a stab tube vs. a growth plate.

(hint: what do bacteria use to them move? can motility be used to identify many medically important pathogenic bacteria such as the enterobacteriaceae? )

1. Aseptic techniques can be tested for their suitability by flaming the loop or by using agar slants.

2. Culturing equipment can be sterilized by three methods and these include wet heat, dry heat and filtration.

3. Inoculating needles are used for transferring bacterial culture to a soft agar medium. Inoculating loops are used to transfer culture into liquid medium or plate.

4. Growth plates or agar plates, Liquid media and Stab-tube media are used for growth of bacterial colonies.

Explanation:

1. A-septic techniques can be tested for their suitability by flaming the loop or by using agar slants. The loop is flamed to an extent that it becomes red-hot and is then cooled before picking up the organisms from the bacterial culture to be transferred. The hot loop is kept into the tube for a few seconds before removing the inoculum so that a bacterial aerosol is not produced.

2. Culturing equipment can be sterilized by three methods and these include wet heat, dry heat and filtration. Wet heat method is the most preferred method for sterilizing culture material using an autoclave. The material is heated using pressurized steam in an autoclave; which is an effective procedure for killing microbes, spores and viruses at 100◦C. However, it is interesting to know that pressurized steam has 7 times more heat than water at 100◦C which allows rapid delivery of heat and good penetration for sterilizing dense materials. High pressured steam hydrolyzes bacterial protein and removes any chances of contamination.  

Dry heat method kill microbes by oxidation of cells thus requires more energy and is conducted at a higher temperature of 121◦C for efficient sterilization.  

Filtration is another method of sterilizing liquids without heating and is performed by passing the solution through a filter with a pore diameter of 0.2 µm. The filter material used for sterilization can be heat-fused glass funnels or cellulose membranes. However, viruses can pass through these filters and filtration is not a preferred sterilization method.  

3. Inoculating needles are used for transferring bacterial culture to a soft agar medium because needles supports appropriate spreading of culture and produces growth along the stab line also.  

Inoculating loops are used to transfer culture into liquid medium or plate because it is free following and adequate spreading of culture is not required.  

4.Growth plates or agar plates are the best bet when morphology of the species is to be identified or a bacterial colony needs to be isolated. In this scenario, growth plates allow the separation of a single clone and aids microscopic analysis.  

In order to expand bacterial culture for the purpose of isolating DNA plasmid, liquid media is used. These liquid cultures allow easy inoculation of growth parameters such as antibiotics, and control of temperature and air pressure.  

Stab tube media is prepared by filling test tube with soft agar and is specifically designed for growth of bacteria in low oxygen conditions. The stab tube allows immersion of inoculation loop into the agar depth where oxygen is extremely low and bacterial colonies can be produced without any shaking of media.