implicit factor

what is the definition of implicit factor

the implicit factor included the property of microbes themself, their interaction with th environment, and how does they interact with each other

how does growth rate affect the microbial flora dominance

• under optimum condition the microbes with the highest growth rate will dominate the microbe flora of the food, and mainly involved in the spoilage of the food

• in general bacteria often have higher growth rate among other microbes

• Hoever, this only applied to the optimum condition

What is the microbial reaction towards the nutrients

• nutrients is a key point in the environment contribute to the microbial growth.

• microbes with lower Ks will have more advantage, since they will have high affinity with the food

• As a result, they will obtain more food, outcompete other microbes in the environment.

How does the physiological state of microbes affect the growth

1. exponential state:

Favorable condition: under this state microbes often grow fast.

If the microbes move to an optimum condition, the growth rate will be maintained, and their growth will continue

Unfavorable condition:They growth fast, but at the same time vulnerable to environmental stress, a small stress will kill them

Therefore, under the environmentally unfavorable condition they will dead faster

1. stationary state

Favorable condition: Under this condition, they will grow slow at the beginning, once they adapt to the environment, they will start to proliferate

Unfavorable condition:   Under stationary phase, microbes are stronger compared with exponential phase

They will adjust themselves to the new environment and start to proliferate.

How does mild environmental stress affect microbes

1. under the mild environmental stress, it may acts as a pre-adaptation to the microbes.

2. it will decrease the damaging effect to the adverse condition in future

How does high environmental stress affect microbes

• it will have 2 affect

1. the cell will injury and take more time to repair before proliferate

2. it will cause endospore formation of the microbes.

what are the beneficial interaction

1. symbiosis: (++) microbes need each to survive

2. mutulism :(++) microbes benefit each other, but it is not obligated for them to be together.

3. succession: (+0), 1 of the 2 microbes will secrete metabolite which benefit the growth of other

what are the detrimental affect to microbe

1. competition(—): both microbes compete for same nutrients

2. outcompete(0-): A will outcompete B

3. antagonist(0-): microbes A will secrete toxic component for B, A will not be affected but B will.

formation of bio-film

1.        Formation of biofilm need time, surface and nutrients, it often occur when the surface is not cleaned

2.        At the beginning only a few cells attached

3.        Then they start to multiply and forma thin-layer of biofilm

4.        Gradually, they will form a extracellular material which internal structure that capture the microbes internally.

5.        Once the biofilm is formed it  becomes resistant to cleaning and disinfection