Powerpoints

Question 1

Bacteria will only grow if provided with specific conditions

Answer 1

1. Temperature
   •2. pH
   •3. Oxygen tension
   •4. Nutrition
   •5. Moisture
   •6. Osmotic pressure

Question 2

For pathogens (disease causing organisms) the range of growth is 20-40°C with an optimum of 37°C. This group is referred to as mesophiles.

Question 3

Aerobes: require oxygen to live

Anaerobes: do not require oxygen and may even be killed by exposure

•Facultative organisms: organisms that survive in the absence of oxygen but growth is limited

Question 4

Nutrients - need sources of carbon, energy, and electrons
•Bacteria vary in their nutritional requirements
•Culture media are chosen based on these requirements
•Bacteria with strict requirements are called fastidious microbes

Question 5

Moisture – most require liquid water to grow. Some tolerant of drying, others very sensitive e.g. Streptococcus species

•Osmotic pressure- usually isotonic in animal body, hypotonic in environment

Question 6

Growth Media Contains:

Answer 6

A mixture of nutrients that the microbes need to live.
•A surface and the necessary moisture and pH to support microbial growth.
•Additionally we provide oxygen or no oxygen

Question 7

Carefully taken Samples will be analysed for the presence of microorganisms.

•How :
•By growing microorganisms from the sample on various types of media.
•By examining this growth and completing additional tests.
•By collating the information and making a preliminary identification.

• We use the six “I’s” and follow a “Routine culture Method”

Question 8

Considerations when incubating
•Temperature?
•Atmosphere?
•Time?

Question 9

Although microbes have adapted to growth at temperatures ranging from freezing to boiling, the usual temperatures used in laboratory propagation fall between 20°C and 40°C

Question 10

Incubators can also control the content of atmospheric gases such as oxygen and carbon dioxide that may be required for the growth of certain microbes.

Question 11

24-48hrs - for most rapid growing bacteria

•48-72hrs - Rapid growing bacteria when plated on selective media(MacConkey/MSA)

Question 12

During the incubation period (ranging from a few hours to several weeks), the microbe multiplies and produces a culture with macroscopically observable growth.

Question 13

Isolation method

Answer 13

Steak or pour plate

Following dilution / serial dilution

Question 14

colony morphology different from
cell morphology!!!!

Question 15

Six Is

Answer 15

Inoculation
Incubation
Isolation
Inspection
Information gathering
Identification