FACTORS THAT AFFECT THE GROWTH OF

MICROORGANISM…

MILK ON DAY 1

WHAT HAPPEN TO THE MILK AFTER 3 DAYS?

Dorman microorganism….

• Dormant means inactive because growth and metabolic processes temporarily stopped.

( dormant – tidak aktif kerana pertumbuhan dan proses metabolik berhenti secara sementara.)

• They may dormant until condition are suitable for them to grow and reproduce

Why the milk curdled after 3 days?

• Milk is rich with nutrient like protein.

• Some bacteria use this nutrients to grow and multiply.

• As they grow, they may damage the constituent of milk such as protein.

Condition of milk after day 3Day 1 Day 3

The growth of microorganism spoil the milk

So what can you conclude about the growth of

microorganism?

Factors that affect the growth of microorganism

1.Nutrient

2.Humidity (kelembapan)

3.Light (cahaya)

4.Temperature (suhu)

5.pH

Nutrient • Microorganism need energy for

their life…• Why?• They need energy for growth and

reproduce (membesar dan membiak)

Nutrients that needed by microorganism

• Starch kanji

• Amino acids asid amino

• Fats lemak

• Glucose glukosa

• Inorganic compound sebatian bukan organik

• This nutrient supply (bekal) energy to microorganism

Other microorganism

Microorganism Example Source of nutrient

Parasite Viruses Bacteria

Absorb nutrient from host

Saprotrophics Mould Feed on dead matter

When there are enough nutrient, the growth rate of microorganism is higher

Apabila nutrient mencukupi, kadar pertumbuhan microorganisma adalah tingggi

Other factor?

Condition of bread after 1 week…..

Why its happen like that?

HUMIDITY

• Almost all microorganism live in damp or watery habitats

• They need water to stay alive.• What happen when there is no water?• Microorganism would be inactive and dead.• Moisture content between 25% to 40% is

suitable for microorganism to carry out their normal activity.

Bacteria in a dry condition

• They will become a spores and become inactive.

• That spores can survive with a dry condition.

• The spores would become active again when moisture is available.

Other factor?

Lets dry 2 wet shirt on 2 conditions….

Closed room Under the hot sun

What happen to the shirt A?

What happen to the shirt B?

•Why have mould on shirt A?

•Why no mould on shirt B?

LIGHT for algae

• Some microorganism such algae can live where is an enough light..

• Why they need light?• They need light to conduct

photosynthesis• What happen if there is not

enough light for algae?• Can’t produce food then die

UV light

The sun is the powerful source of UV light….

Light for viruses, bacteria, and fungi

• They can live with or without light.• Why?• Because they did not conduct photosynthesis• But, some bacteria and fungi are grow better in a adark

condition.• Uv rays in sunlight could affect the growth rate of

microorganism or even kill them.

1. hospitals and food shops employ the use of UV (ultraviolet) light to aid in killing microorganisms, specifically bacteria and mold

2. Preventing infection and the spread of airborne diseases is the goal of hospitals.

3. Food shops aim to keep their food products and preparation surfaces free of bacteria and mold spores.

4. UV light can also be used to purify water.

TEMPERATURE

Temperature

• Suitable temperature for microorganism : 35 º - 40 ºC.

• This is the optimum temperature for them to growth.

• 0 ºC microorganism will be inactive..• But there are some bacteria that are still active

when the temperature is below 0 ºC.• When the temperature are more than 50 ºC,

microorganism will form spores and can survive until 120 ºC

pH

EFFECT OF pH on microorganism growth

pH

• Each kind of microorganism is active at a particular pH value. Setiap microorganisma adalah aktif pada pH tertentu

• Neutral pH (7) is the most suitable for microorganism.• The pH value which is too high or low could prevent the

growth of microorganism