BLE - intro to microbiology

what is a microbe?

tiny organisms that are too small to see with the naked eye

includes bacteria, fungi and protists

what physical factors affect the growth of microbes

• temperature

• oxygen

• concentration

• pH

• Osmotic pressure

what nutritional factors affect the growth of microbes

• energy

• carbon, nitrogen and phosphorus

• trace elements

how are nutrients provided to microbes in a lab?

in the form of media

name three forms of media

• liquid

• semi-solid

• solid

what does semi-solid and solid media have that liquid doesn’t?

solidifying agent - agar

two reasons to use solid media instead of liquid media?

• solid media allow individual bacterial colonies to form which makes it possible to isolate pure cultures

• Solid media enables the study of colony characteristics such as size, shape, color, and texture,

define sterilization

the complete elimination of all forms of microorganisms

example of method of sterilization includes distillation, dry-heat and autoclaving

Autoclaving

media is exposed to 121 degrees and 15 pounds per square inch for 15 minutes in order to destroy microorganisms and their endospores

used for media and instruments

adhesive tape used

Dry-heat sterilization

used on glassware and lab equipment where they are exposed to 160 degrees in an electric oven for 60 minutes

filtration

used for certain media that are heat sensitive and therefore must be removing another way, by filtration

removes all microorganisms by filtering the media through a bacteriological filter which physically removes microbes

involves the use of a 0.2μm filter

why is autoclave tape attached to the Duran bottle/flask before autoclaving the media?

to identify when the Duran bottle has reached 121 degrees in the autoclave for sterilization

why ensure the lid of the Duran bottle is slightly opened before autoclaving

to prevent the bottle becoming over pressured during autoclaving

why are agar plates placed upside down before inccubation?

to avoid condensation on the agar which could contaminate the growth of microorganisms

what temperature will the place be incubated in and why

37 degrees

this is the optimum temperature for the growth of many microorganisms

the plates are incubated for 24 hours and then stored at 4 degrees. Why?

incubation for 24 hours allows visible colonies to form at a optimum temperature

storage at 4 degrees halts the microbial growth and preserves the colonies formed