Laboratory Notes
Activities 11-16
Activity No. 11: DISEASE CAUSING BACTERIA
A. STAPHYLOCOCCUS
The genus Staphylococcus is comprised of both
pathogenic and non-pathogenic organisms. They are
gram positive cocci that occur most commonly as
irregular clusters of spherical cells. They are mesophilic,
non-spore formers. However, they thrive in organic
matter such as blood, pus and tissue fluids.
• The three major’s species include: Staphylococcus
aureus
Staphylococcus saprophyticus
Staphylococcus epidermides
Infections
are
primarily
associated
with
Staphylococcus aureus, pathogenic strains that are
responsible for pus, other infections staphylococcal
enteritis due to enteroxin contamination of food.
B. SALMONELLA TYPI
Salmonella typhi has also been
called Ebertholla or the typhoid fever
bacillus. It develops chiefly in the
human body but can survive in the
outside world in water and foods
which are polluted by the excreta of
typhoid patients or carriers. They are
gram negative, straight rods, nonspore forming, facultative aerobes,
motile and peritrichous. They can
resist cold but are easily killed by heat
and disinfectant.
Activity No.12: STERILIZATION
1. Sterilization - is the process of eliminating living microorganisms using
physical and chemical microbiological procedures.
2. Disinfectants - are antimicrobial agents that are applied to non-living
objects to destroy microorganisms, the process of which is known as
disinfection. Disinfectants should generally be distinguished from
antibiotics that destroy microorganisms within the body.
3. Antiseptics - which destroy microorganisms on living tissue.
4. Sanitizers - are substances that reduce the number of microorganisms
to a safe level. One official and legal version states that a sanitizer must
be capable of killing 99.999%, known as a 5 log reduction, of a specific
bacterial test population, and to do so within 30 seconds. The main
difference between a sanitizer and a disinfectant is that at a specified use
dilution, the disinfectant must have a higher kill capability for pathogenic
bacteria compared to that of a sanitizer.
PHYSICAL STERILIZERS
1.
Heat – can be dry heat or moist heat.
 Heat sterilization is vital in hospital instruments where contaminated
materials must be sterilized so that they be used again; and for
surgical procedures
 At home, boiling the utensils is used to kill the microorganisms.
 Brief exposure of milk to heat will kill the microorganisms in milk.
A. Dry Heat – kills by oxidation
 glassware or other item requires higher temperature like 170 0C for 2 hours of heating inside the oven.
 this requires longer period of heating than moist heat
 incineration is an example of dry heat that effectively sterilize and dispose contaminated cups, bags and dressings
B. Moist Heat – is more effective that dry heat in killing microorganisms for it disrupts the hydrogen bonds that hold the proteins in their threedimensional
structure
 steam sterilization for 15 minutes requires 121 0C to effectively eliminate the microorganisms including the endospores
 autoclave is an example of moist heat that uses steam under
pressure
 the materials to be sterilized are the instruments, wire loop, culture
media, etc
2. Low Temperatures – this limits the production or multiplication of microorganisms,
 refrigeration and freezing are used to inhibit the microbial growth
 most of the pathogenic microbes are unable to grow at refrigerator temperature of 5 0C
 freezing temperature which is at -20 0C lowers the production of
microbes in food therefore the shelf life of food will be longer
3. Radiation – it may cause microbial mutations, induces the formation of toxic free radicals which increases the death rates of microbes
 gamma radiation, x-radiation, and ultraviolet radiation are examples of radiation which kills microorganisms by disrupting their DNA
CHEMICAL STERILIZERS
1. Alcohols
Alcohols, usually ethanol or isopropanol, are sometimes used as a disinfectant,
but more often as an antiseptic (the distinction being that alcohol tends to be used
on living tissue rather than nonliving surfaces). They have wide microbicidal activity,
are non corrosive, but can be a fire hazard. They also have limited residual activity
due to evaporation, which results in brief contact times, and have a limited activity
in the presence of organic material. Alcohols are more effective combined with
purified water—70% isopropyl alcohol or 62% ethyl alcohol is more effective than
95% alcohol, because the alcohol gets inside the cell better.
2. Aldehydes
Aldehydes, such as have a wide microbiocidal activity and are sporocidal and
fungicidal. They are partly in Glutaraldehyde, activated by organic matter and have
slight residual activity.
3. Oxidizing agents
Oxidizing agents act by oxidizing the cell membrane of microorganisms, which results in a loss of structure and leads to cell lysis and death. A large number
of disinfectants operate in this way. Chlorine and oxygen are strong oxidizers.
•Sodium hypochlorite - common household bleach is a sodium hypochlorite solution and is used at home to disinfect drains, toilets, and other surfaces. In
more dilute form, it is used in swimming pools, and in still more dilute form, it is used in drinking water. When pools and drinking water are said to be
chlorinated, it is actually sodium hypochlorite or a related compound, not pure chlorine, which is being used.
•Chloramine is often used in drinking water treatment instead of chlorine because it produces fewer disinfection byproducts, which can be harmful.
•Chlorine dioxide is used as an advanced disinfectant for drinking water to reduce waterborne diseases. In certain parts of the world, it has largely
replaced chlorine because it forms fewer byproducts. Sodium chlorite, sodium chlorate, and potassium chlorate are used as precursors for generating
chlorine dioxide.
•Hydrogen peroxide is used in hospitals to disinfect surfaces. It is sometimes mixed with colloidal silver. It is often preferred because it causes far fewer
allergic reactions than alternative disinfectants. Also used in the food packaging industry to disinfect foil containers. A 3% solution is also used as an
antiseptic. When hydrogen peroxide comes into contact with the catalase enzyme in cells it is broken down into water and a hydroxyl free radical. It is the
damage caused by the oxygen free radical that kills bacteria. However, recent studies have shown hydrogen peroxide to be toxic to growing cells as well as
bacteria; its use as an antiseptic is no longer recommended.
•Iodine is usually dissolved in an organic solvent or as Lugol's iodine solution. It is used in the poultry industry. It is added to the birds' drinking water.
Although no longer recommended because it increases scar tissue formation and increases healing time, tincture of iodine has also been used as an
antiseptic for skin cuts and scrapes.
•Ozone is a gas that can be added to water for sanitation.
•Potassium permanganate (KMnO4) is a red crystalline powder that colors everything it touches, and is used to disinfect aquariums. It is also used widely
in community swimming pools to disinfect ones feet before entering the pool. Typically, a large shallow basin of KMnO4 water solution is kept near the
pool ladder. Participants are required to step in the basin and then go into the pool. Additionally, it is widely used to disinfect community water ponds and
wells in tropical countries, as well as to disinfect the mouth before pulling out teeth. It can be applied to wounds in dilute solution; potassium
permanganate is a very useful disinfectant.
4. Phenolics
Phenolics are active ingredients in some household disinfectants.
They are also found in some mouthwashes and in disinfectant soap
and hand washes.
Phenol is probably the oldest known disinfectant as it was first
used by Lister, when it was called carbolic acid. It is rather corrosive
to the skin and sometimes toxic to sensitive people.
O-phenylphenol is often used instead of Phenol, since it is
somewhat less corrosive.
Hexachlorophene is a phenolic that was once used as a germicidal
additive to some household products but was banned due to
suspected harmful effects.



5. Quaternary ammonium compounds
Quaternary ammonium compounds (Quats), such as benzalkonium chloride, are a large group of
related compounds. Some have been used as low level disinfectants. They are effective against bacteria,
but not against some species of Pseudomonas bacteria or bacterial spores. Quats are biocides which also
kill algae and are used as an additive in large-scale industrial water systems to minimize undesired
biological growth. Quaternary ammonium compounds can also be effective disinfectants against
enveloped viruses.
6. Acids
Organic acids can control microbial growth and are frequently used as preservatives.

Sorbic, benzoic, lactic, and propionic acids are used to preserve foods and pharmaceuticals.

Benzoic, salicylic, and undecylenic acids are used to contol fungi that cause diseases such as athlete’s
foot.
7. Heavy Metals
Heavy metals used in disinfectant and antiseptic formulations, examples- silver, copper, mercury and
zinc have antimicrobial properties.

Silver nitrate is used to prevent gonococcal eye infections

Mercurochrome and merthiolate are applied on the skin after minor wounds

Zinc is used as antifungal antiseptics

Copper sulfate is used as an algicide
Activity No. 12: PHYSICAL AGENTS OF STERILIZATION
PHYSICAL AGENTS
A.



HEAT
1.Moist Heat Sterilization
Boiling
Steam under Pressure
Pasteurization



2. Dry Heat Sterilization
Direct Flaming
Incineration
Hot Air Sterilization
B. FILTRATION
C. LOW TEMPERATURE
1. Low Temperature
2. Deep Freezing
D. DESSICATION/DEHYDRATION
E. OSMOTIC PRESSURE/PLASMOLYSIS
F. RADIATION
MECHANISM OF ACTION
FUNGI
Fungi are spore-producing organisms; a single-celled or multicellular organism without
chlorophyll that reproduces by spores and lives by absorbing nutrients from organic matter. They are
classified as eukaryotes, i.e., they have a diploid number of chromosomes and a nuclear membrane
and have sterols in their plasma membrane. Genetic complexity allows morphologic complexity and
thus these organisms have complex structural features that are used in speciation.
Fungi are neither plant nor animal, but have some characteristics of each. They cannot move
about like an animal, do consume organic matter, have no chlorophyll as do plants, and cannot
manufacture their own energy. They have a true nucleus in their cells and are able to sexually
reproduce by combining like strains of nucleus. They can also reproduce by spores similar to some
of the more primitive plants e.g. Ferns, Liverworts and Mosses. Modern molecular studies have
shown that fungi are more closely related to animals than to plants.
The structures of fungi are microscopic and not visible to the naked eye. Some are unicellular
like yeast, but most string their cells together in long, thread-like strands called hypha. Most fungi
produce an extensive system of hyphae, which may be visible when growing thickly in a mass called
mycelium (commonly referred to as mold). Mycelium can be of any size from tiny clusters to massive
acre wide systems, which effectively form the feeding and growing body of the fungus.
Fungi are divided into two groups:
1.
2.
Microscopic fungi
a) molds
b) Yeasts
Macroscopic fungi
a) mushroom
b) puffballs
c) gill fungi
YEASTS are eukaryotic microorganisms with round to
oval shape; with about 1,500 species currently described;
they dominate fungal diversity in the oceans. Most reproduce
asexually by budding, although a few do so by binary fission.
Yeasts are unicellular, although some species with yeast
forms may become multicellular through the formation of a
string of connected budding cells known as pseudohyphae, or
false hyphae as seen in most molds. Yeast size can vary
greatly depending on the species, typically measuring 3–4 µm
in diameter, although some yeasts can reach over 40 µm.
The yeast species Saccharomyces cerevisiae has been
used in baking and fermenting alcoholic beverages for
thousands of years. Other species of yeast, such as Candida
albicans, are opportunistic pathogens and can cause infection
in humans.
Growth and nutrition
Yeasts are chemoorganotrophs as they use organic
compounds as a source of energy and do not require sunlight to
grow. The main source of carbon is obtained by hexose sugars
such as glucose and fructose, or disaccharides such as sucrose
and maltose. Some species can metabolize pentose sugars like
ribose, alcohols, and organic acids. Yeast species either require
oxygen for aerobic cellular respiration (obligate aerobes), or are
anaerobic but also have aerobic methods of energy production
(facultative anaerobes). Unlike bacteria, there are no known
yeast species that grow only anaerobically (obligate anaerobes).
Yeasts grow best in a neutral or slightly acidic pH environment.
Yeasts will grow over a temperature range of 10°-37°C (50°98.6°F), with an optimal temperature range of 30°-37°C (86°98.6°F), depending on the type of species (S. cerevisiae works
best at about 30°C(86°F)). Above 37°C (98.6°F) yeast cells
become stressed and will not divide properly. Most yeast cells
die above 50°C (122°F). If the solution reaches 105°C (221°F) the
yeast will disintegrate. There is little activity in the range of 0°10°C (32°-50°F). The cells can survive freezing under certain
conditions, with viability decreasing over time.
Activity No. 13: MOLDS
MOLDS include all species of microscopic fungi that grow in the form of
multicellular filaments, called hyphae. In contrast, microscopic fungi that grow as
single cells are called yeasts. A connected network of these tubular branching
hyphae has multiple, genetically identical nuclei and is considered a single
organism, referred to as a colony or in more technical terms a mycelium.
Molds do not form a specific taxonomic or phylogenetic grouping, but can
be found in the divisions Zygomycota, Deuteromycota and Ascomycota. Although
some molds cause disease or food spoilage, others are useful for their role in
biodegradation or in the production of various foods, beverages, antibiotics and
enzymes.
Although molds grow on dead organic matter everywhere in nature, their
presence is only visible to the unaided eye when mold colonies grow. A mold
colony does not comprise discrete organisms, but an interconnected network of
hyphae called a mycelium. Nutrients and in some cases organelles may be
transported throughout the mycelium. In artificial environments like buildings,
humidity and temperature are often stable enough to foster the growth of mold
colonies, commonly seen as a downy or furry coating growing on food or other
surfaces.
Some molds can begin growing at temperatures as low as 2°C. When
conditions do not enable growth, molds may remain alive in a dormant state
depending on the species, within a large range of temperatures before they die.
Common molds









Acremonium
Aspergillus
Cladosporium
Fusarium
Mucor
Penicillium
Rhizopus
Stachybotrys
Trichoderma
Activity No. 14: FACTORS THAT AFFECT YEAST GROWTH
Yeasts are microscopic organisms that exist naturally on
the surface of the earth. They are noted for their ability to
ferment carbohydrates to produce various food products,
including bread, beer, wine, and cheese.
During fermentation, yeast cells break down complex sugars
into simple sugars, which are further hydrolyzed into CO2 and
ethyl alcohol (ethanol).
Yeast growth is affected by several, including temperature,
pH, and nutrient content.
There are several factors which affect the growth of
yeast. Yeast has been used in the fermentation of foods like
bread, wine, and beer. The by-products of the fermentation
process are carbon dioxide and ethanol.
Activity No. 15: VIRUS: THE MODEL
COVID-19 is the disease caused by SARS-CoV-2, the coronavirus
that emerged in December 2019. COVID-19 can be severe, and
has caused millions of deaths around the world as well as
lasting health problems in some who have survived the illness.
The coronavirus can be spread from person to person
The coronavirus particles are organized with long RNA
polymers tightly packed into the center of the particle, and
surrounded by a protective capsid, which is a lattice of
repeated protein molecules referred to as coat or capsid
proteins. In coronavirus, these proteins are called nucleocapsid
(N)
Activity No. 16: PARASITOLOGY
Organism
1. Escherichia coli
Description
Escherichia coli (E. coli) is a Gram-negative, rodshaped, facultative anaerobic bacterium. This
microorganism was first described by Theodor Escherich in
1885.
The non-parasitic form is excreted via stools and can live as
commensals in the large intestine.
2. Entamoeba coli
3. Entamoeba histolytica
4. Balantidium coli
5. Ascaris lumbricoides/Roundworm/Adult
6. Enterobius vermicularis/Pinworm/Adult
7. Necator americanus/Hookworm/Adult
8. Adult Flatworm/Tapeworms (Scolex and Proglottid)
T saginata “Beef Tapeworm”
T solium “Pork Tapeworm”
Classification
(R Whittaker)
Monera
Unicellular
Prokaryotic Cell