Lab Report 6

Lab Report 6
The Effect of Physical & Chemical Agents

On Bacterial Growth
- BIO 223 L -
Student Name: Sara Alabdulkarim

Student ID: 201136
Submission date: October 31, 2021
Abstract:
The structural and physiological properties of bacteria are greatly affected by high
temperatures. Heat kills most of the harmful microorganisms. There are two types of heat
that can be used: humidity and dry heat. This procedure uses a water bath to detect
bacterial growth (E. coli) at different temperatures. The findings showed that the control
bacteria grew rapidly at 40 ° C, some at 80 ° C, and no at 100 ° C. Other experiments have
shown the effects of disinfectants and hand washing on the surface of the skin. The result
was clear. There were many colonies before hand hygiene and disinfection, and much less
colonies after hand hygiene and disinfection. Various chemicals can prevent the growth of
bacteria. Preservatives and disinfectants are still the best known and are used in medicine,
industry, and home. For the prevention and control of microorganisms, a wide range of
antiseptics and disinfectants are available. Disinfectants are often used on inanimate items
such as tabletops, equipment, and tools, whereas antiseptics are typically applied on the
skin's surface. To explore the impact of chemical compounds on bacteria, the paper disk
method is being employed. Chemicals are adsorbed onto specified paper disks before being
placed in an infected growing medium. The presence of an inhibition zone where the
chemical agent was administered implies that germs were destroyed. The ZOI measurement
result in millimeters is presented. S. aurues is sensitive to Detol and Harpic, resistant to
Clorox, and in the middle of the alcohol spectrum. E. coli was intermediate to Detol and
susceptable to Clorox, intermediate to alcohol, and intermediate to Harpic.
Objective:
Determine which bacteria are susceptible to different disinfectants and antiseptics.

Introduction:
Microorganism control is critical for preventing disease transmission and infection,

stopping decomposition and spoilage, and avoiding undesirable microbial contamination.
Physical and chemical agents are used to keep microorganisms in check. High or low
temperature, desiccation, osmotic pressure, radiation, and filtration are examples of
physical agents. Disinfectants, antiseptics, antibiotics, and chemotherapeutic antimicrobial
compounds are all examples of chemical control. The following are some of the most
common terminology used while addressing the control of microorganisms:
Controlling microbial growth entails preventing or inhibiting the growth of

microorganisms. This control is achieved in two ways:
1) By killing bacteria.
2) By preventing microbe growth.
To add, there are specific agents used to control microbial growth:

1) Physical agents include heat, irradiation, filtration and osmotic pressure.
o Temperature:
For microorganisms to grow, there is a minimum, an optimal, and a maximum temperature.
Microorganisms are frequently frozen at temperatures below the freezing point. They slow
microbial metabolism, which inhibits growth but may not always kill the organism.
Temperatures over the maximum have a cidal effect because bacteria enzymes and other
proteins are denatured. Temperature control is a popular and effective method of
microorganism control
- High temperature:
There are two forms of heat that can be used:
Moist heat, such as that generated by hot water, boiling water, or steam, denatures proteins
more quickly than dry heat, halting microbial metabolism and resulting in death.
Dry heat, which comes from heated air with little moisture, such as that found in ovens,
dehydrates microbial cells and causes protein denaturation.
- Low temperature:
Microorganisms' growth is slowed. Enzymatic reactions are slowed by them. They are not
capable of killing.
o Ultra violate radiation:

Microorganisms' chromosomal DNA is affected by light with a wavelength of about 265 nm,
causing mutations. It is used to disinfect but not to sterilize. However, Poor penetration,
long-term damaging effects on human tissues, retinal impairment, and cancer are the
principal drawbacks.
o Filteration:
Sterilize liquids with this device. The liquid is filtered by membrane filters.
Filters come in a variety of pore diameters. Microorganisms cannot travel through the filter
because the pores are too small.
o Osmotic pressure:
For years, it has been employed in food preservation.
Food preservation uses high quantities of salt, sugar, or other ingredients because it creates
a hypertonic medium.
It robs the organisms of their water.
2) Chemical agents involve the use of microbial chemicals Disinfectant and Antiseptic,
Soap and Detergent, Heavy Metals, Antibiotics, Chemical Food Preservatives.
o A disinfectant is a chemical that is used to disinfect inanimate items or surfaces but

is too hazardous to be utilized on human tissues.
o An antiseptic is a bacteria-killing or microbe-inhibiting chemical that is safe to use
on human tissue.
o A sanitizer is a substance that decreases, but does not remove, bacteria populations
to a safe level.
Disinfectants and antiseptics' antimicrobial effect is influenced by a number of factors,

including:
1) The chemical agent's concentration.

2) The agent's operating temperature. The longer it takes to clean or sanitize, the lower
the temperature.
3) The microorganisms that are present. Bacillus species, Clostridium species, and
acid-fast bacteria like Mycobacterium TB are more difficult to eradicate.
4) The total number of microorganisms in the sample. The greater the number of
germs present, the more difficult it is to disinfect or cleanse the area.
5) The microorganism-bearing material's composition. Organic matter, such as dirt
and excrement, obstructs the action of various agents.
Materials:
o Bubble bath
o Bacterial Tubes
o Two selected bacterial species
o Nutrient agar plates
o Beakers of various disinfectants and antiseptics
o Sterile paper disks
o Forceps in beaker of Alcohol
o Millimeter ruler
o Soap
o Sanitizer
Procedure:
Part 1:
Test the effectiveness of different temperatures on bacterial growth:
1) Obtain the bacterial broth culture (E.colie).

2) Obtain a nutrient agar plate and on the bottom side, divide the plate into 4 sections
each for specific temperature that will be tested.
3) Using aseptic technique, take a loopful of bacterial broth and streak a single-line on
section (1). This will be your control.
4) Expose the bacterial broth culture to temperatures of 40°C, 80°C, and 100°C for 15
minutes.
5) After 15 min, using aseptic technique ,take a loopful of bacterial broth exposed
to 40°C and inoculate section (2).
6) Repeat step 4 and inoculate section (3) and (4) with its correspond temperature.
7) After you finish, incubate your plate for 48 hours.
Part 2:
Test the effectiveness of Disinfectant and hand washing on the skin surface:
1) Obtain a nutrient agar plate, label the bottom side with group # and date.
2) Divide the plate in half and make a five-finger impression by touching the fingers
of one hand to one-half of the plate. This represents the control area.
3) Wash the same hand with soap for 1 Min and then use a sanitizer.
4) Allow the fingers to air-dry and then touch the second-half of the plate, making
another five-finger Impression.
5) When you are done, incubate your plate at 37°C for 48 hours.
Part 3:
1) Using aseptic technique, Inoculate nutrient agar plates with bacteria.

2) Dip sterile disks into various chemical agents.
3) Place disks on the agar surface, leave enough space between them.
4) When you are done, incubate your plates at 37 degree for 24h.
5) Observe your results and measure the Zone of inhibition.
Results:
Figure 1: Bacteria in hands before Figure 2: E.coli heated by three different

and after washing and sanitizing. temperatures with control. Physical agent: Heat.
Chemical agent: soap and sanitizer.
Figure 3: E.coli growth after disks dipped Figure 4: Staph aureus growth after disks dipped in
in chemical agents. Chemical agents: chemical agents. Chemical agents: Disinfectants and
Disinfectants and Antiseptics. Antiseptics.
Discussion:
As stated in the table, the observations are hypothetical and ideal. Heating E. coli at 100°C is
most effective, although heating at 40°C has the least effect because there is almost no
bacterial growth on the plate. At 80°C, the results are at a moderate level, with an increase
in E. coli. This shows that boiling water is the safest choice.
By eliminating E. coli. The hand cleaning and disinfection effect is very good, there are only
a few colonies on the agar plate. A small amount of microorganisms on the plate can be
produced by bacteria in the air or tissues used to dry hands. In terms of chemicals, E. coli
and Staphylococcus aureus react differently to various compounds. Among the tested
substances, alcohol had the worst effect. Clorox has little effect on killing Staphylococcus
aureus, but it is most effective against E. coli.
References:
o Lab manual
o Lab ppt
o https://learn.genetics.utah.edu

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Lab Report 6

The Effect of Physical & Chemical Agents

Student Name: Sara Alabdulkarim

Determine which bacteria are susceptible to different disinfectants and antiseptics.

Microorganism control is critical for preventing disease transmission and infection,

Controlling microbial growth entails preventing or inhibiting the growth of

To add, there are specific agents used to control microbial growth:

o Ultra violate radiation:

o A disinfectant is a chemical that is used to disinfect inanimate items or surfaces but

Disinfectants and antiseptics' antimicrobial effect is influenced by a number of factors,

1) The chemical agent's concentration.

1) Obtain the bacterial broth culture (E.colie).

1) Using aseptic technique, Inoculate nutrient agar plates with bacteria.

Figure 1: Bacteria in hands before Figure 2: E.coli heated by three different

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