very usefull for microbiology students

1. PRESENTATION ON
EFFECT OF PHYSICAL CHEMICAL AND
ENVIRONMENTAL FACTORS ON GROWTH
OF MICROORGANISMS
SUBMITTED TO: DR. (MRS.) SUNITA DEVI
PRESENTED BY: PUNEET KUMAR
M.Sc. MICROBIOLOGY 1ST YEAR
(F-2021-43-M)
COURSE CODE: MICRO 503
COURSE TITLE: MICROBIAL PHYSIOLOGY AND METABOLISM

2. INTRODUCTION
 MICROBES
 MICROBIAL GROWTH
 DIFFERENT FACTORS AFFECTS THE GROWTH
 PHYSICAL FACTORS
 CHEMICAL FACTORS
 ENVIROMENTAL FACTORS

3.  Introduction to Microoganisms
 An organism that can be seen only through a
microscope. Microorganisms include bacteria, protozoa,
algae, and fungi. Although viruses are not considered living
organisms, they are sometimes classified as
microorganisms.
 Types of Microorganisms
 Bacteria
 Archaea
 Protozoa
 Fungi
 Mold
 Algae
 Animals

4.  Bacteria
Bacteria – now sometimes called “eubacteria” or “true bacteria” to
differentiate them from archaebacteria – are the type of microorganism
you probably hear about the most
This is because they’re the type most likely to make you sick. Bacteria
are the cause of most skin infections, and can also cause food
poisoning, pneumonia, strep throat, and many other illnesses.
However, bacteria are also very helpful to humans. “Good bacteria” in
our digestive tracts help us to extract nutrients from our food, and help
to fight pathogens that could hurt us
Example :- E.coli, Salmonella sp., Pseudomonas sp., Clostridium sp.,etc

5.  Archaea
 Archaea, or archaebacteria, were once thought to be part of the
bacteria family
 Archaea can be found in many of the same places as bacteria – in
water, in soil, and inside our digestive tracts, where they help us to stay
healthy.
 However, archaebacteria can also be found in some unusual places –
many are able to live in environments that are very hot, very cold, very
acidic, or very salty.
 This makes them a common finding inside hot springs and other
places where other organisms cannot easily survive.
Example:- Methanosarcina sp. , Hyperthermus butylicus,
Staphylothermus sp. , Thermococcus sp. etc.

6.  Protozoa
 Protozoa are a diverse group of unicellular eukaryotic organisms.
Like bacteria and archaea, they are single-celled; but their cells
resemble those of animals and plants more than those of bacteria or
archaea.
 Several dangerous human diseases including malaria, toxoplasmosis,
giardia, African “sleeping sickness,” and Chagas disease are caused by
protozoa.
 Example:- Amoeba , Paramoecium , Euglena ,Trypanosoma ,
Plasmodium.

7.  Fungi
 Though some microscopic fungi can infect humans just like bacteria or
protozoa, there’s one microscopic fungus that most humans like a lot:
yeast.
 Yeast is the fungus that is responsible for making baked goods rise;
and for producing alcoholic beverages such as beer, wine, and liquor.
 Yeast feeds on sugars found in foods and converts it into carbon
dioxide – and ethyl alcohol.
 The carbon dioxide can make our breads and cakes fluffy.
 Example:- yeasts, mildews, molds, and mushrooms.

8.  Molds
 Molds are microorganisms that share some properties of fungi, but are
not true fungi.
 These include pathogenic molds that infect plants and have caused
devastating crop failures such as the Great Irish Famine of the 1840s.
 They also include the fantastically weird class of slime molds – single-
celled organisms that are capable of cooperation so impressive that,
during one stage of their life cycle, many slime mold cells gather
together and operate like a single organism.
 Slime mold intercellular cooperation is so impressive that scientists
have been using slime molds to study intelligence and problem-solving.
 Example:- Rhizopus sp. , Alternaria sp., Aspergillus sp.,
Fusarium sp., Penicillium sp. Etc

9.  Algae
 Microscopic algae were once thought to be plants, but recent studies
have shown that algae don’t fit into the plant family. Instead, these
single-celled photosynthetic organisms are thought to be relatives of
the lineage that led to land plants.
 Throughout history, algae have been important photosynthesizers. They
likely evolved before land plants did, and helped to pump oxygen into
Earth’s atmosphere along with their ancestors, the cyanobacteria.
 Today algae can both help and hurt humans – some species clean
water and produce oxygen, while others produce dangerous toxins that
can end up in our seafood and drinking water.
 Example:- Chlorophyta , Rhodophyta , Xanthophyta

10.  Animals
 Several types of animals come in microscopic varieties,
including:
 Arthropods (dust mites, spider mites)
 Rotifers (a type of zooplankton)
 Nematodes

11.  GROWTH
 An Orderly increase in the quantity of all the cellular constituents.
 The growth of microorganisms is influenced by various physical and
chemical factors of their environment.
 Physical factors- Temperature ,pH, osmotic pressure,
hydrostatic pressure and radiation.
 Chemical factors- Oxygen, carbon, nitrogen, phosphorus,
sulfur, etc.

12.  Microbial Growth
 Culture Medium : Nutrient material prepared for microbial
growth in the laboratory.
 Requirements:
 Must be sterile
 Contain appropriate nutrients
 Must be incubated at appropriate temperature
 Culture: Microbes that grow and multiply in or on a culture
medium.

13.  Solid Media: Nutrient material that contains a
solidifying agent (plates, slants, deeps).
 The most common solidifier is agar, first used by Robert Koch.
Unique Properties of Agar:
 Melts above 95*C.
 Once melted, does not solidify until it reaches 40*C.
 Cannot be degraded by most bacteria.
 Polysaccharide made by red algae.
 Originally used as food thickener (Fannie Hesse)

14. Chemically Defined Media: Nutrient material
whose exact chemical composition is known.
• For chemoheterotrophs, must contain organic source
of carbon and energy (e.g.: glucose, starch, etc.).
• May also contain amino acids, vitamins, and other
important building blocks required by microbe.
• Not widely used.
• Expensive.

15.  Complex Media: Nutrient material whose exact chemical
composition is not known.
 Widely used for heterotrophic bacteria and fungi.
 Made of extracts from yeast, meat, plants, protein digests, etc.
 Composition may vary slightly from batch to batch.
 Energy, carbon, nitrogen, and sulfur requirements are primarily met
by protein fragments (peptones).
 Vitamins and organic growth factors provided by meat and yeast
extracts.
 Two forms of complex media:
 • Nutrient broth: Liquid media
 • Nutrient agar: Solid media

16.  Selective Media: Used to suppress the growth of unwanted
bacteria and encourage the growth of desired microbes.
 Saboraud’s Dextrose Agar: pH of 5.6 discourages bacterial
growth. Used to isolate fungi.
 Brilliant Green Agar: Green dye selectively inhibits gram-positive
bacteria. Used to isolate gram-negative Salmonella .
 Bismuth Sulfite Agar: Used to isolate Salmonella typhi. Inhibits
growth of most other bacteria.

17. Microbial Growth Phases.

18.  DIAUXIC GROWTH

19. DIFFERENT FACTORS AFFECT
THE GROWTH OF MICROBS
• PHYSICAL FACTORS
• CHEMICAL FACTORS
• ENVIROMENTAL FACTORS

20. Physical factors influencing the
growth of microorganisms
Temperature pH
Osmotic
Pressure
Hydrostatic
Pressure
Radiation

21. Temperature
 Temperature is the most important factor that determines
the rate of growth, multiplication, survival, and death of
all living organisms.
 High temperatures damage microbes by denaturing
enzymes, transport carriers, and other proteins
 Microbial membrane are disrupted by temperature
extremes.
 At very low temperatures membranes also solidify and
enzymes also do not function properly.

22. Types of temperature
Minimum
growth
temperature
Maximum
growth
Temperature
Optimum
growth
temperature

23. 1. Minimum growth temperature
The lowest temperature at which organisms grow is the minimum
growth temperature.
2. Optimum growth temperature
The temperature at which the most rapid rate of multiplication occurs.
3. Maximum growth temperature
The highest temperature at which growth occurs.
A temperature only slightly above this point frequently kills the
microorganisms by inactivating critical enzymes.

33.  Most bacteria prefer neutral pH (6.5-7.5).
 Molds and yeast grow in wider pH range, but prefer pH
between 5 and 6.
 Acidity inhibits most microbial growth and is used
frequently for food preservation (e.g.: pickling).
 Alkalinity inhibits microbial growth, but not commonly
used for food preservation.
 Acidic products of bacterial metabolism interfere with
growth.
 Buffers can be used to stabilize pH .

37. Osmotic Pressure : Cells are 80 to 90% water.
A. Hypertonicsolutions : High osmotic pressure
removes water from cell, causing shrinkage of cell
membrane (plasmolysis).
Used to control spoilage and microbial growth.
Sugar in jelly.
Salt on meat.
B. Hypotonicsolutions : Low osmotic pressure causes
water to enter the cell. In most cases cell wall prevents
excessive entry of water.
Microbe may lyse or burst if cell wall is weak

41.  Chemical factors influencing the growth
of microorganisms
Carbon
Nitrogen
Sulfur
Oxygen
Phosphorus

42. Carbon: Makes up 50% of dry weight of cell.
 Structural backbone of all organic compounds.
 Chemoheterotrophs: Obtain carbon from their energy
source: lipids, proteins, and carbohydrates.
 Chemoautotrophs and Photoautotrophs: Obtain
carbon from carbon dioxide.

43.  Nitrogen:
 Nitrogen: Makes up 14% of dry cell weight. Used to form
amino acids, DNA, and RNA.
 Sources of nitrogen:
 Protein: Most bacteria
 Ammonium : Found in organic matter
 Nitrogen gas (N2 ): Obtain N directly from atmosphere.
Important nitrogen fixing bacteria, live free in soil or
associated with legumes (peas, beans, alfalfa, clover,
etc.). Legume cultivation is used to fertilize soil naturally.
 Nitrates: Salts that dissociate to give NO3-

44.  Sulfur: Used to form proteins and some vitamins
(thiamine and biotin).
Sources of sulfur:
 Protein: Most bacteria
 Hydrogen sulfide
 Sulfates: Salts that dissociate to give SO4
2-
 Phosphorus: Used to form DNA, RNA, ATP, and
phospholipids.
Sources: Mainly inorganic phosphate salts and buffers.
Oxygen: Organisms that use molecular oxygen (O2),
produce more energy from nutrients than anaerobes.
Can classify microorganism based on their oxygen
requirements:

45.  Obligate Aerobes: Require oxygen to live.
 Disadvantage : Oxygen dissolves poorly in water.
Example: Pseudomonas, common nosocomial pathogen.
 Facultative Anaerobes: Can use oxygen, but can grow in its absence.
Have complex set of enzymes.
Examples: E. coli, Staphylococcus, yeasts, and many intestinal bacteria.
 Obligate Anaerobes: Cannot use oxygen and are harmed by the presence
of toxic forms of oxygen.
Examples: Clostridium bacteria that cause tetanus and botulism.
 Aerotolerant Anaerobes: Can’t use oxygen, but tolerate its presence.
Can break down toxic forms of oxygen.
Example: Lactobacillus carries out fermentation regardless of oxygen
presence.
 Microaerophiles: Require oxygen, but at low concentrations. Sensitive to
toxic forms of oxygen.
Example: Campylobacter.

46. Toxic Forms of Oxygen:
 Singlet Oxygen
 Superoxide Free Radicals (O2-)
 Hydrogen Peroxide (H2O2)

47.  Other Elements: Potassium, magnesium, and calcium
are often required as enzyme cofactors. Calcium is
required for cell wall synthesis in Gram positive bacteria.
 Trace Elements: Many are used as enzyme
cofactors.
Commonly found in tap water.
Iron
Copper
Molybdenum
Zinc

48.  Environmental factors influencing the
growth of microorganisms
Moisture
Temperature
Oxygen pH
Carbon
Dioxide
Light

49.  Moisture:
 Water is an essential component for the growth of the bacteria.
 80% of the bacterial cell is made up of water.
 Therefore, the presence of a free water molecule is important
for the optimum growth of the microorganism.
 Apart from that desiccation or drying has a severe effect on
microbes.
 For example Treponema pallidum, Neisseria gonorrhoeae can
die easily due to desiccation
 While bacterial pathogens like M. tuberculosis, S. aureus can
survive desiccation for several weeks

50.  Temperature
 It is an essential environmental factor that can influence the
growth of the organisms. Most of the pathogens grow at
37 0 C (body temperature). Bacteria are categorized under
three groups on the basis of the optimum temperature
range
• Mesophile: The optimum temperature range for
mesophiles is 250C to 400C Most of the pathogenic bacteria
come under this group.
• Psychrophile: The optimum temperature for
psychrophiles is below 200C
• Thermophile: The optimum temperature range for
thermophiles is 550C to 800C Eg: Bacillus
stearothermophilus.

51.  Carbon Dioxide
 Most of the bacteria require a small amount of carbon
dioxide for growth. This carbon dioxide is usually provided
by the environment or it can be produced by the bacteria
due to cellular metabolism.
 Bacteria that require a high level of Carbon dioxide for
growth are known as capnophilic bacteria.

52.  Oxygen
On the basis of requirement of oxygen, bacteria are classified
under three groups
 Aerobes: Oxygen is strictly required for the growth of these
bacteria. Eg : Pseudomonas aeruginosa.
 Facultative Anaerobes: These are the group of bacteria that
can grow both under the presence and absence of oxygen. Most
of the pathogenic bacteria are facultative anaerobes. Eg: E. coli.
 Anaerobes: These are also known as obligate anaerobes as
they can’t grow in the presence of oxygen at the environment.
Eg: Clostridium tetani.
 Apart from these, there is another group called microaerophilic
which grows in the presence of a trace amount of oxygen.
Eg: Helicobacter pylori.

53. pH
 pH is an essential factor for the growth of the microbes.
 May bacteria are able to produce several organic acids
which reduce the pH of the medium and also restrict the
growth of other bacteria.
 Apart from that some media constituents can be affected
by low pH.
 Therefore, maintain the optimum pH is highly important to
obtain adequate growth of the organisms.
 Pathogens are mostly requiring neutral pH (7.2).
 However, industrially important bacteria such
as Lactobacillus lactis requires a lower pH for optimum
growth.

54.  Light
 Phototrophic bacteria require light for the growth. However,
most of the bacteria can grow well in darkness.
 The presence of ultraviolet rays and radiation can
reduce bacterial growth.
 Photochromogenic mycobacterium is a unique
species that produce pigments only at the presence of light.