investigating fungal growth

Biology Investigation: Fungal Growth

Ylenia Attard, Dorianne Galea & Cristina Zammit

Investigating

fungal

growth

by

Ylenia Attard

Dorianne Galea

Cristina Zammit



The following were taken at the beginning of the investigation. All the greenhouses were

prepared by Dorianne Galea at home.



Does salt prevent fungal growth?

Salt will be used to check if it induces fungal growth or if it inhibits it:

After 6 days there was no fungal growth. After 10 days, there was no fungal growth either.

Why?

What we think:

Salt prevents any fungal growth.

Salt induces osmosis from the food to the outside, thus reducing the amount of moisture.

Lack of moisture decreases fungal growth.



Does acidity induce fungal growth, or will it prevent it?

10 drops of lemon were sprinkled every 3 days on

the food item.

After 6 days, fungal growth was very little. This means that acidity helps to prevent fungal

growth.

The following was observed after 10 days:

It can therefore be concluded that acidity reduces fungal growth.



Do fungi need oxygen to grow?

A small window was cut, to allow circulation of air A little fungal growth was observed after 1 week

After 10 days, slightly more fungal growth was observed. In this case, more growth was

expected since oxygen is essential for fungal growth. However, since the plastic was perforated

to create circulation of air, less humidity was observed. This might explain the slow rate of

fungal growth.



A green house having no air was attempted. This had several sources of error since no vacuum

pump was available, implying that practically air was still present. The greenhouse was further

inserted in another plastic bag, to try and remove all surrounding air. This worked in an adverse

way, since it created more humidity, making the fungi grow rapidly.

This was observed after 6 days. One can see the

humidity trapped within the greenhouse.

The next 2 photos were observed after 10 days:

In this case, the result was not as expected. NO fungi should have grown. This set up had

several sources of error, the main one being that it was not vacuumed, and so was not

completely air free. Moreover, it had a lot of trapped humidity. The 2 main factors essential for

fungal growth were therefore present



Do fungi grow better in a humid or in a dry situation?

Moisture is an essential environmental factor for fungal growth. In this case, water was

sprinkled on the tomatoes regularly. Spores will germinate more in a humid environment, as

can be shown in the following photos, taken after 6 days:

The following was observed after 10 days:

In this case, fungal growth was observed on the outside too. This is because it was regularly

sprinkled with water, enhancing spore germination.



The next set of tomatoes was not sprinkled with water, in an attempt to create a ‘no moisture’

situation. However, the tomato in itself has a lot of water on the inside, thus creating the

perfect environment for fungal growth.

Preparing the set up After 6 days

After 10 days

In this case, the tomato was not the ideal medium to test fungal growth in no moisture! Fungi

do NOT usually grow without moisture. But, the inside of the tomato is very moist, and

therefore has the perfect environment to induce fungal growth. The outside of the tomato is

very well protected by the skin, and therefore not moist; hence lack of fungal growth.



Do fungi grow better in light or in the dark?

In this case 2 carton boxes were used. One was fixed with a bulb on the inside, which was kept

on for 24 hours, throughout the investigation. The other was enclosed within the box, and

therefore exposed to total darkness throughout the investigation. The following was observed

after 6 to 10 days since the investigation was set.

As can be seen, fungal growth was observed in both situations.

This is because fungi do not photosynthesize, and therefore do

not require light.



Does temperature effect fungal growth?

One set of tomatoes was wrapped in a piece of cloth to create extra warmth. The other set was

placed in a refrigerator. The following were observed after 6 days:

As can be observed, warm temperatures induce rapid fungal growth. In a cold temperature, no

fungal growth should be observed.

The following photos show the rate of fungal growth after 10 days:



Conclusion

Factor Growth No Growth

Salt Acidity

Oxygen

No Oxygen Moisture

No Moisture

Light

Darkness

Warm Temperature

Cold Temperature

Therefore, it can be concluded, that in order to avoid fungal growth, a person must store things

in an acidic or salty environment, which has no oxygen and moisture, and at a low temperature.

investigating fungal growth

Documents

little fungal growth

fungal growth ylenia

slow rate of fungal

present biology investigation

circulation of air

surrounding air

air free

following photos