Environmental influence on microbial growth
Preliminary
The life of microorganisms is very dependent and influenced by the state of the
environment. There is no environmental factors that greatly affect this activity
of this microorganism,
namely:
1. Physical factors, such as temperature, pH, osmosis pressure, oxygen content,
and others.
2. Chemical factors, such as poison compounds and other chemical compounds
as food.
3. Biological factors, such as interaction with other microorganisms.
This microorganism reaction to its environment is very important to know
because it is very supportive of other processes, for example in controlling the
existence of microbial causes of disease or in the process of making and
preservation of food. Environmental factors that can affect the life of these
microorganisms can be classified as intrinsic factors, such as pH, water content,
light and temperature, and extrinsic factors, such as toxic metabolites, carbon
sources and others.
Temperature
The temperature suitable for the growth of microorganisms varies greatly. The
growth of microorganisms will take place very well at the optimum temperature.
This optimum temperature is usually in accordance with its original habitat
temperature, for example at 37 oC for pathogenic bacteria in animals. We can
distinguish microorganisms to 3 groups based on the optimum temperature of
growth, namely:
a. Psychrothilik: Microorganisms that live at low temperatures (5-30 oC).
breakfast. Mesophilic: Microorganisms that live at moderate temperatures (25-
40 oC).
C.. Thermophilic: Microorganisms that live at high temperatures (45 - 65 oC)
Note: The temperature range above is not a strik like that, because there are
some microbes that can live in a very broad temperature range, so that there are
many overlapping.
Tools
a. Nutrition broth medium equipped with Durham tube.
breakfast. Baisan E. coli, pseudomonas sp., And sarcina lutea.
C.. Incubator.
Work
a. Planting above the nutrient broth medium.
breakfast. Incubation at 5 oC, 20 oC, 40 oC, and 65 oC.
C.. Observe its growth after 2-7 days.
Pengaruh pH
As with temperature, the growth of microorganisms is also greatly influenced by
its environmental pH.
Tools
a. Medium nutritional broth with different pH (3, 5, 7 and 9).
breakfast. Baisan E. coli, Staphylococcus aureus, and S. cerevisiae.
Work
a. Embed each of culture on the medium whose pH is different.
breakfast. Incubation at 30 oC.
C.. After 2 and 7 days, observe the growth of each culture.
Light influence
Microorganisms provide a good response to light (there are positive and
negative ones). Even germination is influenced by light.
Tools
a. Medium na upright
breakfast. Petri sterile dish
C.. Baisan E. coli in the form of suspension (age 24 hours).
Work
a. Pipette 1 ml of the suspension of culture and put it in the petri dish.
breakfast. Melt the NA medium in the bath, and after reaching a temperature of
40 oC, put it in the Petri dish that has contained a suspension.
C.. Shake it evenly distributed, and let it freeze.
d. The treatment of culture was as follows: The first cup of illuminated with the
sun's Cahata for 15-30 minutes, the second cup was illuminated with a light light
for 15-30 minutes and then wrapped in black paper, and the third cup was not
illuminated and immediately closed with black paper.
Hey. The third incubation of Petri dish at 37 oC
f. Observe the growth of culture in the three petri dishes.
Tools
a. A big tube reaction.
breakfast. Distilled water
C.. Filter paper
d. Black paper
Hey. Horse poop
Work
a. Fill in the test tube with distilled water to 10 cm high.
breakfast. Insert filter paper in such a way that the ends are dunted on the
surface of the water
C.. Place horse droppings on the surface of the filter paper.
d. Cover the test tube with black paper, then the paper is fell right on the surface
of horse dung, with a hole size of around 5 x 5 mm.
Hey. Incubate at room temperature in a place that is exposed to sunlight.
f. Observe the growth of fungi in horse dung and pay attention to which growth.
