This document provides information about microbes including their types, growth, and role in the environment. It discusses that microbes are tiny organisms that can only be seen under a microscope. They are found everywhere and play vital roles such as breaking down waste, producing nutrients for plants, and maintaining healthy human microbiomes. The document also describes the different types of microbes based on oxygen needs, temperature tolerance, pH tolerance, and other characteristics. It explains the growth phases of microbes and factors that influence their growth such as nutrients, temperature, oxygen levels and pH. Finally, it discusses the important roles microbes play in environments like producing oxygen, nutrient cycling, supporting agriculture, and maintaining livable climates.
3. Microbes
Are invisible to the naked eye, you need a
powerful microscope to see them.
Are everywhere around us, inside us, on us, in
our food, in our homes, in the air we breathe
and the water we wash in.
Are mostly useful, but some are harmful
Are vital for life on Earth.
4. What do Microbes look like ?
Magnified 1000‘s of times and coloured using
dye, we see -
5. Microbes exist in huge numbers
In one single teaspoon of garden soil, there are
over 100,000 microbes. In 1ltr of
seawater, there are over 1bn microbes.
On your hands there are more microbes than
there are people in the world.
There are so many microbes, that scientists
have only named 0.5% of them.
Microbes outnumber all other species and
make up most of the living matter on the
planet.
6. Microbes live among us
In our food
Cleaning up our waste
Killing pests
Making medicines
In the making of such things as leather, soy
sauce, cheese and paper.
In our bodies.
7. Types of Microbes
Named based on their particular physiological
and nutritional characteristics.
Oxygen Description
Aerobe Capable of using oxygen as a
terminal electron acceptor
Anaerobe Grows in the absence of oxygen
Facultative anaerobe Can grow aerobically or
anaerobically
Microaerophile Capable of oxygen-dependent
growth but only at low oxygen levels
8. Temperature Description
Psychrophile/ Optimal temperature for growth is 15 °C or lower,
facultative maximal temperature is approximately 20 °C, and
psychrophile minimal temperature is 0 °C or lower
Psychrotroph Capable of growing at 5 °C or below, with maximal
temperature generally above 25 °C to 30 °C
Mesophile optimal temperature for growth, which is
approximately 37 °C; frequently grows in the range
from 8 °C to 10 °C and from 45 °C to 50 °C
Thermophile Grows at 50 °C or above
Hyperthermophile Grows at 90 °C or above, although optimal
temperature for growth is generally above 80 °C;
maximal growth of pure cultures occurs between
110 °C and 113 °C,
9. pH Description
Acidophile Grows at pH values less than 2
Alkalophile Grows at pH values greater than 10
Neutrophile Grows best at pH values near 7
Salinity Description
Halophile Requires salt for growth: extreme halophiles (all are archaea), 2.5
M to 5 M salt; moderate halophiles, usually low levels of NaCl as
well as 15 to 20 percent NaCl
Hydrostatic pressure Description
(100 atmospheres per
1,000-m depth)
Barophile Obligate barophiles, no growth at 1 atmosphere
of pressure; barotolerant bacteria, growth at 1
atmosphere but also at higher pressures. (0.987
atm = 1 bar = 0.1 megapascal [Mpa])
10. Nutrition Description
Autotroph Uses carbon dioxide as its sole source of carbon
Heterotroph Unable to use carbon dioxide as its sole source of
carbon and requires one or more organic
compounds
Chemoorganoheterotroph Derives energy from chemical compounds and
uses organic compounds as a source of electrons
Chemolithoautotroph Relies on chemical compounds for energy and uses
inorganic compounds as a source of electrons.
hydrogen bacteria, iron bacteria, sulfur bacteria,
ammonia oxidizers, and nitrite oxidizers.
Mixotroph Capable of growing both
chemoorganoheterotrophically and
chemolithoautotrophically
Oligotroph Can develop at first cultivation on media containing
minimal organic material (1 to 15 micrograms
carbon per liter)
12. Bacteria
Have three main shapes
spiral (boriella) little balls(-cocci) rods (-bacilli)
Can move about on their own
Join up together to form chains
called ‗bio-films‘. As on teeth !
13. Virus
Come in 1000s of different shapes and sizes.
They hang about waiting to meet a ‗host‘ which they
then invade, hijacking the host‘s cells. Beware the air
you breathe and door handles !
14. Fungi
Not just mushrooms –
athlete‘s foot, penicillin, and yeast.
Yeast is used in bread making,
and brewing
15. Algae are also Microbes
Algae photosynthesise – taking their energy
from the sun, and producing oxygen in the
process. Algae are thought to produce over
50% of the oxygen in the world.
16. And finally
Without microbes, life on this planet would be entirely
different – they generate oxygen, are part of the carbon
and nitrogen cycles, and can survive the harshest
conditions.
Without microbes, our bodies would not process the
food we eat.
They drive the chemistry of life, breaking things down
into their parts so that life can being again.
Microbes are small but mighty !
18. Factors that Influence Growth
Growth vs. Tolerance
– ―Growth‖ is generally used to refer to the
acquisition of biomass leading to cell division, or
reproduction
– Many microbes can survive under conditions in
which they cannot grow
19. The suffix ―-phile‖ is often used to describe
conditions permitting growth, whereas the term
―tolerant‖ describes conditions in which the
organisms survive, but don‘t necessarily grow
For example, a ―thermophilic bacterium‖ grows
under conditions of elevated temperature, while a
―thermotolerant bacterium‖ survives elevated
temperature, but grows at a lower temperature
20. Factors that Influence Growth
Obligate (strict) vs. facultative
―Obligate‖ (or ―strict‖) means that a given condition is
required for growth
―Facultative‖ means that the organism can grow under
the condition, but doesn‘t require it
The term ―facultative‖ is often applied to sub-optimal
conditions
For example, an obligate thermophile requires
elevated temperatures for growth, while a facultative
thermophile may grow in either elevated
temperatures or lower temperatures
21. Factors that Influence Growth
Temperature
– psychrophiles (cold loving microbes )
•range 0 C - 20 C
– mesophiles (moderate temp. loving microbes)
•range 20 C - 40 C
– thermophiles (heat loving microbes)
•range 40 C - 100 C
22. Factors that Influence Growth
pH
Most bacteria grow between pH 6.5 - pH 7.5
Very few can grow at below pH 4.0
many foods, such as sauerkraut, pickles, and cheeses are
preserved from spoilage by acids produced during
fermentation
23. Factors that Influence Growth
Salt concentration
Halophiles require elevated salt concentrations
to grow; often require 0.2 M ionic strength or
greater and may some may grow at 1 M or
greater; example, Halobacterium.
Osmotolerant (halotolerant) organisms grow
over a wide range of salt concentrations or ionic
strengths; for example, Staphylococcus aureus.
24. Factors that Influence Growth
Oxygen concentration
– Strict aerobes: Require oxygen for growth (~20%)
– Strict anaerobes: Grow in the absence of oxygen;
cannot grow in the presence of oxygen
– Facultative anaerobes: Grow best in the presence of
oxygen, but are able to grow (at reduced rates) in the
absence of oxygen
– Aerotolerant anaerobes: Can grow equally well in the
presence or absence of oxygen
– Microaerophiles: Require reduced concentrations of
oxygen (~2 – 10%) for growth
25. Osmotic Pressure
Microbes obtain almost all their nutrients in
solution from surrounding water
Tonicity
– isotonic
– hypertonic
– hypotonic
27. Limiting factors in the environment
Lack of food, water or nutrients
space
accumulation of metabolic wastes
lack of oxygen
changes in pH
temperature
28. Phases of Growth
4 Phases
1. Lag Phase
2. Log Phase
3. Stationary Phase
4. Death Phase
30. Lag Phase
Bacteria are first introduced into an
environment or media
Bacteria are ―checking out‖ their surroundings
cells are very active metabolically
no of cells changes very little
1 hour to several days
31. Log Phase
Rapid cell growth (exponential growth)
population doubles every generation
microbes are sensitive to adverse conditions
– antibiotics
– anti-microbial agents
32. Stationary Phase
Death rate = rate of reproduction
cells begin to encounter environmental stress
– lack of nutrients
– lack of water
– not enough space
– metabolic wastes
– oxygen
– pH
Endospores would form now
34. Roles of microbes in environment
Microbes—life forms too tiny to see—play a
surprisingly large role in life on Earth.
Humans depend on microbial communities in
more ways than you can imagine.
35. Make air breathable
Keep us healthy
Provide sources of new drugs
Help us digest food
Clean up hazardous chemicals
Support and protect crops
36. Microbes keep us healthy
Partners for life
Invite a microbe to dinner
Nature‘s master chemists
New possibilities