Disease Causing Microorganisms
We have heard time and again that we need to keep ‘germs’ away!
‘Germs’ are actually another word for microorganisms or microbes.
These can affect both plants and animals and cause diseases in them.
This is why we need to keep ourselves and surroundings clean. Let’s
read more about the disease causing microorganisms.
What are these ‘germs’?
They are small living organisms that are present everywhere- on us,
inside us and in our surroundings and cannot be seen with the naked
eye. Special devices called the microscope help us see and study them.
However, it is important to note that not all microorganisms are bad.
We can broadly classify these into ‘good’ and ‘bad’ microorganisms.
The ‘good’ microorganisms help in the routine body functions such as
digestion, immunity and coexist inside our body all the time. The
‘bad’ microorganisms are the ones that we need to stay clear of
because they make us fall ill by causing diseases.
In biology, disease-causing micro-organisms can be classified into
four main groups:
● Bacteria
● Virus
● Fungus
● Protozoa
These ‘bad’ micro-organisms or disease causing microorganisms are
always looking for a chance to enter our body and cause a disease.
Most diseases in the world are caused by these micro-organisms, for
example, the common cold and flu, malaria, diarrhoea, pneumonia,
urinary tract infections, chicken pox, Hepatitis, polio etc.
How do these disease causing microorganisms function in the human body?
Disease causing microorganisms outnumber our body cells in a large
way. They are present on the skin and various orifices of our body
through which they can enter into the system such as:
● Respiratory tract
● Genital Tract
● Urinary tract
Once these microbes enter the system, depending on their own
constitution, they look for their target site and attach themselves there.
Once they firmly attach themselves, they release toxins and enzymes
to stay grounded and at the same time start multiplying and increase in
number. The microbes derive nutrition from the host’s body. The
toxins and enzymes released by these microbes make the cells of the
host weak or ‘ill’ or affected. These toxins can even be spilt into the
bloodstream and reach other parts of the body which can also be
affected. This way the microbes are able to make the body they are in
sick! The manifestation of these toxins and enzymes released on the
tissues are varied such as inflammations, swellings, bleeding, wounds,
pustules, fever, sneezing, itching and general weakness in the body.
What does the host’s body do?
If you think the microbes have their way once they are in, then you are
wrong! The human body is designed to keep all disease-causing
elements out of it. The human body always has its defences up even
before the microbes enter. For this reason, keeping ourselves clean,
healthy and alert is essential. By doing so we do not allow close
contact with these microorganisms and so minimise their chances of
entering the system.
But, there are many times when the microbes enter the body and find
their favourite spot. In these cases, the body’s ‘immune system’
consisting of defence cells are activated. From the time of the
microbes entry into the body till the time the body fights it and its
products, the immune system is on high alert. The defence cells of the
body constitute mainly of two types of cells: T-Lymphocytes and B-
Lymphocytes. They both have a different sub-types and modes of
action. Together, they are responsible for eradicating the pathogen as a
whole either by engulfing it (phagocytosis) or releasing their remedial
toxins (antibodies) against the toxins and enzymes of the microbes.
Imagine it to be a battle-field between the disease causing pathogens
and the body’s armed forces -the T and B- Lymphocytes.
The end result depends upon whose defences are higher. A healthy
body which is well nourished is better equipped to fight a microbial
invasion compared to a not-so-healthy body. Therefore, it is essential
to stay fit. When the body isn’t able to fight back on its own, help is
given from outside in the form of antibiotics(for bacteria),
antivirals(viruses), antifungals(fungus) and anti-helminthic(protozoa).
These can be either in the tablet or capsule form or vaccinations.
Transmission
Microbes can be transmitted through different routes: few are
airborne, few are waterborne, some travel on top of other animals,
some are transmitted through human touch, some through touching
contaminated surfaces or objects and some though ingesting
contaminated water and food. Keeping clear of obvious contaminated
or infected areas is important.
In case of plants, there is a host defence mechanism that helps fight
these microorganisms as in the case of animals. But, the
microorganisms that affect plants and animals are very different.
Different species of bacteria, virus and fungi affect plants.
Disease causing pathogens are therefore present everywhere. Whether
they are able to enter our body and cause a disease is in our hands to a
large extent. Advances in medicine have been made to make our
body’s immune system stronger with preventive medicines and
vaccinations. There have been biotechnological advances to protect
plants as well from infestations and plant diseases.
Let’s do our bit daily to stay fit and healthy, as it is absolutely
essential.
Food Preservation
Food preservation is a process by which edible items such as fruits
and vegetables are prevented from getting spoilt. The nutritive value,
flavour and colour of the foods preserved remain intact.This is done to
increase the life of the food product and enable its storage and supply.
(Source: Wikipedia)
What principles is food preservation based on?
The main aim of food preservation is to prevent the food that is being
preserved from decay by microorganisms.
The principles it works on are:
1.Preventing microorganisms in the food that is being preserved i.e
maintaining asepsis.
2. Removal of microorganisms
3. Preventing or hindering the growth of microorganisms by various
methods such as low temperatures, drying, use of chemicals etc.
4. Killing the microorganisms by various methods such as heating and
radiation.
Some food substances can self-decompose due to the enzymes that are
present in them. In these cases, the enzymes are deactivated at the
time of food preservation.
Some foods are also susceptible to insects or animals and so the
utilisation of appropriate chemicals to kill them and prevent them
from destroying the food.
Let’s now look at the methods that are used for food preservation
Food preservation methods are broadly divided into three:
1. Biological
2. Physical
3. Chemical
The commonly used methods of food preservation fall into one of the
above categories. The main purpose of all these methods is to either
prevent or retard spoilage of food items.
1.Filtration
This is done for liquids such as juices. The process applies pressure
while the liquid is passed through a very fine sieve. This results in the
liquid passing through while the microbes cannot and thus the liquid
obtained is sterile.
2.Heat treatments
There are different kinds of heat treatments that can be done such as
boiling at 100 degrees Celsius, boiling above 100 degrees
Celsius(sterilisation)or pasteurisation( as done in case of milk)
3. Low- temperature treatments
The most commonly used method even in households- using a
refrigerator. The refrigerator maintains a low temperature such that it
slows down the growth of microbes and keeps food fresh for longer.
Freezing is another low-temperature method used to preserve food
where the temperature is maintained at -18 degrees Celsius.
4. Using chemicals or preservatives
These are substances that are added to foods to prevent or slow down
their spoilage. The preservatives that are added, need to fulfill certain
criteria before they are deemed fit to be added to foods. Few
properties of preservatives are – they should be able to inhibit a wide
range of microbes, should be safe for human consumption, should not
affect the taste, flavor, color or properties of the food being preserved,
should not activate any other change in the food being preserved.
Commonly used preservatives are sulfites, sorbic acids, sodium
nitrate, and benzoic acid.
5. Acids
Citric acid and Acetic acid are commonly organic acids that are used
to preserve food substances such as pickles, sauces chutneys, and
vegetables. Being acidic, they inhibit the growth of the
micro-organisms and thus are effective food preservatives.
(Source: Wikipedia)
6. Drying
Many foods such as chips, papad, vegetables like methi or ginger are
dried or dehydrated and preserved. By dehydrating, the moisture
inside these substances is removed and thus micro-organisms are
unable to thrive on them, thus, preserving them.
7. Radiation
This method of preservation is used commonly for increasing the shelf
life of meat, seafood and poultry. Irradiating these food substances
helps to kill any pathogens and microbes that are present in them and
prevent the growth of others.
Humans have always tried and preserved their food items and other
perishable items. The methods have either changed or evolved, but the
purpose remains the same.
Look around and observe how many of these methods you have seen
at home or around you.
Solved Example for You
Q: Fruits kept in the refrigerator maintain their flavour and taste for
longer period due to
a. Non-availability of CO2
b. Presence of excess O2
c. Delay in the process of respiration
d. Presence of excess moisture
Solution: The correct answer is option “c”. Freezing is one of the
oldest and most widely used methods of food preservation. Very low
temperatures mean microorganisms cannot grow due to their delayed
metabolic activities like respiration.
Microorganisms and its Uses
The term ‘microorganisms’ include bacteria, fungi, viruses and
protozoa. We almost always presume they are harmful to us. So this
is because we read about how they cause diseases to both plants and
animals including humans. But, it is a fact that microorganisms are
useful to us in many ways. Microorganisms help in the production of
many food items, making medicines, keeping the environment clean,
in manufacturing and in research. Let us learn about microorganisms
and its uses.
(Source: Gallinee)
Microorganisms and its uses
1. Production of dairy products:
Bacteria are the key players here. Bacteria help in fermentation which
helps in making different forms of dairy products from milk like curd,
buttermilk, butter, cheese. Streptococcus is the most common genus of
bacteria that are used in the commercial production of this product.
Learn more about Disease-Causing Microorganisms here in detail.
2. Bread Baking:
A species of Streptococcus is added to the dough before making bread
to bring about the required fermentation.
3. Alcoholic Drinks:
Alcoholic drinks are prepared or manufactured by the process of
fermentation. Each drink is derived from a different starting product
such as potato and grapes. Then it is fermented, distilled and alcohol is
prepared. The commonly used microorganism here is different types
of fungus like yeast. Some even use bacteria and fungus. Alcoholic
drinks include wine, rum, vodka etc.
4. Organic acids:
Organic acids are commercially prepared using fungi. Acetobacter,
Rhizopus, Penicillium are a few fungi that are used to ferment
substrates such as fruits and sugar-containing syrups. Examples of
acids that are derived and manufactured on a large scale using fungi
are acetic acid, citric acid, gluconic acid, fumaric acid and lactic acid.
5. Enzymes:
Many microbes are used in the derivation of enzymes such as lipase,
lactase, protease, peptidase to name a few.
6. Steroid production:
Some bacterial and fungal species are used in the preparation of
steroids that are then injected into the human body for different
purposes.
7. Help in sewage treatment:
Not only are microorganisms helpful to our body, they are also helpful
to the environment. They help in the secondary treatment stage of
sewage treatment.
8. Used as insecticides:
Certain bacterial and fungal species are used to keep certain insects
and pests away from crops.
9. Fertility of soil:
Microorganisms play a very important role in maintaining the fertility
of the soil. They help in the composting process which forms manure.
Also, microorganisms present in the soil help aerate it and enrich the
soil with nitrates and other nutrients. These nutrients are needed by the
crops for an abundant harvest.
Learn how Nitrates are converted to Nitrogen here.
(Source: Noble Research Institute)
10. Production of vitamins:
An essential vitamin that people need for proper digestion is Vitamin
B 12. Fungi are responsible for manufacturing B12.
11. Production of antibiotics and antivirals:
Bacteria and viruses are isolated and their antigens and enzymes are
extracted. These antigens help in the development of antibiotics and
antivirals.
12. Biotechnology and research:
So many labs use bacteria, fungi and especially viruses for research
studies. Non- virulent forms of these microorganisms are injected into
subjects going through clinical trials. This in future helps in the
development of medicines, vaccinations and cure for diseases. And
DNA and RNA studies also make use of them.
It is important for us to know about microorganisms and its uses as
they are both beneficial as well as harmful to other life forms. They
play a crucial role in the ecosystem. Maintaining a balance between
the ‘good’ and ‘bad’ microorganisms is the key to coexisting with
them.
Solved Example for You
Q: From which of the following Antibodies are obtained?
a. Bacteria
b. Viruses
c. Angiosperms
d. Gymnosperms
Solution: The correct answer is option “a”. Antibodies are chemicals
that kill or inhibit the growth of bacteria. They are used to treat
bacterial infections.
Nitrogen Cycle
We are generally under the impression that we only need oxygen to
live. Well, you couldn’t be more wrong! There is a laundry list of
elements that animals need for survival. One such element is Nitrogen.
But we can’t just get nitrogen from the air. It needs to be converted to
nitrates, via a process called nitrogen cycle. So let us learn more about
this fascinating concept.
The air we breathe contains 78% nitrogen, 21% oxygen and remaining
are other trace gases. The nitrogen component of air is inert. So this
means plants and animals cannot use it directly. To be able to use
nitrogen, plants convert atmospheric nitrogen to nitrates, nitrites and
ammonia compounds by a process called the nitrogen cycle. Animals
derive their nitrogen requirements from plants.
What are the steps involved in the nitrogen cycle?
Nitrogen cycle consists of four main steps namely:
1. Nitrogen Fixation
2. Ammonification/ Decay
3. Nitrification
4. De-nitrification
It is important to note that microorganisms play an important role in
each of these steps.
What is the mechanism of each of these steps?
Nitrogen Fixation
This is the first step of the nitrogen cycle. This step is characterized by
the conversion of atmospheric N2 into ammonia (NH3). Bacteria like
Azotobacter and Rhizobium have a major role in this process. They
are harbored in the roots of the leguminous plants and help convert
inert nitrogen to ammonia. Nitrogen fixation can occur in any of the
following ways: atmospheric fixation (involves lightening), industrial
fixation(manufacturing ammonia under high temperature and pressure
condition)
Assimilation
Once the nitrogen has been fixed in the soil, plants can absorb
nitrogen through their roots. This process of absorption is known as
assimilation.
Ammonification
This is another process by which ammonia can be generated. Organic
remains of plants and animals are broken down in the soil by some
bacteria to release ammonia into the soil. These dead and waste matter
is used by these microorganisms as food and they release ammonia
into the soil.
Nitrification
This occurs in two-steps. The first step is in which NH3/NH$+ is
converted to NO3- (nitrates). The bacteria Nitrosomonas and
Nitrococcus present in the soil convert NH3 to NO2-, and another
bacterium, Nitrobacter converts NO2- to NO3-. These bacteria gain
energy through these conversions.
Denitrification
Is the reverse of nitrification that occurs in the deep layers of soil
where the bacteria convert NO3- is converted into N2 and other
gaseous compounds like NO2. This occurs because in deep layers of
soil, oxygen is not available and the soil bacteria use these nitrogen
compounds instead of oxygen.
What are some Essential Mineral Elements?
What is the importance of the nitrogen cycle?
● As we all know by now, the nitrogen cycle helps bring in the
inert nitrogen from the air into the biochemical process in
plants and then to animals.
● Plants need nitrogen to synthesize chlorophyll and so the
nitrogen cycle is absolutely essential for them.
● During the process of ammonification, the bacteria help
degrade decomposing animal and plant matter. This helps in
naturally cleaning up the environment.
● Due to the nitrogen cycle, nitrates and nitrites are released into
the soil which helps in enriching the soil with nutrients needed
for cultivation.
● As plants use nitrogen for their biochemical processes, animals
obtain the nitrogen and nitrogen compounds from plants.
Nitrogen is needed as is an integral part of the cell composition.
It is due to the nitrogen cycle that animals are also able to
utilize the nitrogen present in the air.
Solved Example for You
Q: Nitrates are converted into Nitrogen by
a. Ammonifying Bacteria
b. Denitrifying bacteria
c. Nitrogen-fixing bacteria
d. All of the above
Solution: The correct answer is “b”. Denitrification is the process
where after nutrients are converted back into ammonia, anaerobic
bacteria will convert them back into nitrogen gas.
Heterotroph – Definition, Functions, Types
Heterotrophs refer to an organism that consumes other organisms
available in the food chain. Furthermore, this organism is unable to
create organic substances from inorganic substances. Students can
learn more information about heterotroph here.
Definition and Meaning of Heterotroph
A heterotroph refers to an organism that produces its own food.
Furthermore, such an organism relies on gaining nutrition from other
sources of organic carbon. Moreover, these sources are mostly plant or
animal matter.
Heterotrophs in the food chain are primary, secondary, and tertiary
consumers, but certainly not producers. Moreover, heterotrophs
among the living organisms include all the animals and fungi,
bacteria, and parasitic plants.
Types of Heterotrophs
The various types of heterotrophs are as follows:
● Organotrophs
● Lithotrophs
● Chemotrophs
● Phototrophs
● Photoorganoheterotrophs
● Chemolithoheterotrophs
● Mixotroph
Organotrophs – These heterotrophs indulge in exploiting the carbon
compounds as the electron sources, like fats, proteins, and
carbohydrates from animals and plants.
Lithotrophs – These heterotrophs indulge in the usage of inorganic
compounds. Furthermore, these inorganic compounds are ammonium,
sulfur, and nitrite so as to obtain electron sources.
Chemotrophs – These organisms use the energy which is obtained by
the process of oxidation of chemicals. Furthermore, this energy is
obtained from the environment.
Phototrophs – This refers to heterotrophs that undertake utilization of
light to gain energy and carry out the processes of metabolism.
Photoorganoheterotrophs – These organisms certainly synthesize the
organic compounds by making use of sunlight along with the
oxidation of organic substances, which include elemental sulfur,
thiosulfate, hydrogen sulfide, and molecular hydrogen.
Most noteworthy, some examples of such organisms include
rhodospirillaceae and purple non-sulfur bacteria. Moreover, such
organism uses organic compounds to build the structures.
Furthermore, they do not fix carbon dioxide and do not have the
Calvin cycle.
Chemolithoheterotrophs – These organisms obtain their energy from
the oxidation of the inorganic compounds. A popular example of
Chemolithoheterotrophs is the Oceanithermus profundus.
Mixotroph – This is an organism that uses either organic carbon or
carbon dioxide as carbon dioxide. Moreover, what this means is that
mixotrophs have the ability to use the methods of both autotrophs and
heterotrophs. Consequently, they can grow under both heterotrophic
as well as autotrophic conditions.
Functions of Heterotrophs
There are many heterotrophs that use organic carbon as their source of
carbon. Furthermore, the organic chemicals as their energy and source
for electron.
Heterotrophs certainly function as consumers in the food chain.
Moreover, they get nutrients from parasitic, saprotrophic as well as
holozoic nutrients. Also, they indulge in breaking down complex
organic compounds. Release of energy results by oxidizing carbon and
hydrogen atoms that are available in carbohydrates, lipids, and
proteins.
Heterotrophs catabolize organic compounds by respiration,
fermentation, or both. Fermenting heterotrophs can be facultative or
obligate anaerobes. Furthermore, fermenting heterotrophs carry out
fermentation in environments of low oxygen.
Respiration in heterotrophs is almost always accompanied by
mineralization. Mineralization refers to the process of converting
organic compounds into the forms of inorganic nature. Furthermore,
when the organic nutrient used by the heterotroph contains very
important elements. Moreover, these elements are N, S, P, C, H, and
O.
Htereotrophs allow for dephosphorylation as something which is a
part of decomposition. The conversion of N and S from their organic
form to the inorganic is a vital part of the sulfur and nitrogen cycle.
H2S results from desulfurization which is ultimately oxidized by
lithotrophs and phototrophs.
Solved Question on Heterotrophs
Q1 Which of the following statements is not true in the case
heterotroph?
A. Heterotrophs in the food chain are never primary, secondary, and
tertiary consumers
B. It refers to an organism that produces its own food
C. It refers to an organism which consumes other organisms
D. It refers to an organism which relies on gaining nutrition from other
sources of organic carbon
A1 The correct option is A., which is “heterotrophs in the food chain
are never primary, secondary, and tertiary consumers. This is because,
“heterotrophs in the food chain are certainly always primary,
secondary, and also tertiary consumers.”
Inoculation – Definition and Types of Media Used for Inoculation
Microbiology is a branch of science that deals and focuses on
microorganisms. Microbiology deals with the study of bacteria,
unicellular organisms and viruses. We learn many new terms while
studying microbiology such as inoculation. Inoculation meaning in
microbiology is that transfer from culture for their growth. It is the
direct transfer from the culture of microorganisms to inoculation
needle.
Meaning of Inoculate in Microbiology
In microbiology, the definition of inoculation is different from
common terms such as health, vaccines, and immunology. Inoculation
is the study of introducing microorganisms into environments where
they will grow and reproduce. In other words, we can say that
inoculation means introducing a certain substance into another
substance.
For example, inoculation is adding a certain type of nutrient or
chemical into a suspension of bacteria. We can say that inoculating a
suspension with a particular nutrient or chemical.
This definition is in use in laboratory and researches in which
scientists study the growth of microorganisms in a specific
environment, study certain species and strains of microorganisms.
There is a similarity in the definition of inoculation in microbiology
and in immunology.
For example, a vaccine is a method of injection of pathogens into a
person’s body where they grow and from our immune system. Thus,
in this way, vaccines are able to protect us from pathogens that harm
our body they weaken the foreign pathogens before they grow in our
body.
Types of Media Used for Inoculation
● Agar Plates
● Broth Culture
● Slant culture
● Plate culture
● Stab culture
Agar Plates
Agar plates are some of the most common media which are in use for
growing bacteria and other microorganisms. A mixture of agar and
nutrients necessary for bacterial growth. This is then poured into
circular Petri dishes where the agar solution solidifies. After this,
inoculation of a solution-containing microorganism onto these plates
with the help of streaking.
A small streaking loop is a dip into a solution, which contains
bacterial cells that are used to streak onto the plates with the bacteria.
These plates are stored at the proper temperature for bacterial growth
for further study. We can also inoculate liquid media suspensions of
bacteria to grow and reproduce.
A single culture of microorganism added to a small solution to form a
mixture and pipette into liquid media. For Bacterial growth, we need
media in which the mixture of microorganism and solution contain
nutrients, compounds, and other necessary molecules.
Broth Culture
An inoculation needle used in inoculating a sterile broth culture.
Flaming the open end of the broth will keep it sterile. The broth
moved up to the needle so that the tip of the needle is submerged
while maintaining the original position of the needle.
Swirling of the needle carefully can help the inoculation of the
microorganism from the needle to the sterile broth. The inoculated
broth culture then removed from the needle. With the help of the
Aseptic technique which is applied to the open end of the broth culture
so as to prevent contaminants, and the needle is flamed for
sterilization.
Slant Culture
To inoculate a slant culture in a fishtail inoculation technique we use
inoculation needle. After transferring the microorganisms from the
original microbial culture to the inoculation needle the sterile slant
culture is uncapped. The open end of the uncapped slant culture is
then flamed.
The position of the slant is such that it moves the needle up until the
tip of the inoculation needle comes in contact with the base surface of
the sterile media. A zigzag pattern is formed on the agar surface when
the inoculation needle inoculates the sterilize agar by the manipulation
of the media. To remove the inoculation needle, we use an aseptic
technique.
Plate Culture
Inoculation of a plate culture uses a streaking technique to make a
streak plate. The inoculation needle streaked across the plate in
controlled directions, after lifting the lid so that it hovers above the
sterile agar plate. Microbial aerosols created from the hitting of the
inoculation tip to the sides of the agar plate. The inoculation needle
removed from the inoculated agar plate culture and flamed.
Stab Culture
In inoculating a stab culture, an inoculation needle is an essential tool.
Removal of a sterile stab culture cap is completed and the open end of
the needle is flamed. The needle tip and length of the needle is pushed
into the stab media until the needle reaches 0.5 inches away from the
bottom of the stab media. The inoculation needle is removed from the
media in the same direction and path that it was pushed into the stab
media to prevent the wobbling effect that may disturb the culture. We
can sterilize the needle with the help of a flame.
Solved Questions on Inoculate in Microbiology
Q. What do you mean by Inoculation Needle?
Ans: An inoculation needle is laboratory equipment that is useful in
the field of microbiology to transfer and inoculate living
microorganisms. It is one of the most common tools in a biological
laboratory. It is of two types disposable or re-usable. A reusable
inoculation needle made up of nichrome or platinum wire attached to a
metallic handle whereas disposable inoculation needle made up of
plastic resin.