Download Microbiology

Chair of Medical Biology, Microbiology,
Virology, and Immunology
THE PHYSIOLOGY OF
MICROORGANISMS.
Lecturer As. Prof. O. Pokryshko
Lecture schedule
1.
2.
3.
Growth of bacteria.
Reproduction of bacteria.
Respiration of bacteria.
Nutritional Types
Carbon sources


Heterotroph – must obtain carbon in an
organic form made by other living organisms
such as proteins, carbohydrates, lipids and
nucleic acids
Autotroph - an organism that uses CO2, an
inorganic gas as its carbon source

not nutritionally dependent on other living things
3
Nitrogen Sources
Main reservoir is nitrogen gas (N2);
79% of earth’s atmosphere is N2.
 Nitrogen is part of the structure of
proteins, DNA, RNA & ATP – these
are the primary source of N for
heterotrophs.

4
Nitrogen Sources
Some bacteria & algae use inorganic N
nutrients (NO3 , NO2 , or NH3).
 Some bacteria can fix N2.
 Regardless of how N enters the cell, it
must be converted to NH3, the only
form that can be combined with carbon
to synthesis amino acids, etc.

5
Nutritional Types
Energy source
– gain energy from
chemical compounds
phototrophs – gain energy through
photosynthesis
chemotroph
6
Transport: Movement of Chemicals
Across the Cell Membrane

Passive transport –does not require energy;
substances exist in a gradient and move from
areas of higher concentration towards areas of
lower concentration
 diffusion
 osmosis – diffusion of water
 facilitated diffusion – requires a carrier
7
Transport: Movement of Chemicals
Across the Cell Membrane

Active transport – requires energy and carrier
proteins; gradient independent
 active transport
 group translocation – transported molecule
chemically altered
8
9
10
Gas Requirements
Oxygen
 As oxygen is utilized it is transformed into
several toxic products:


Most cells have developed enzymes that
neutralize these chemicals:


singlet oxygen (O2), superoxide ion (O2-), peroxide
(H2O2), and hydroxyl radicals (OH-)
superoxide dismutase, catalase
If a microbe is not capable of dealing with toxic
oxygen, it is forced to live in oxygen free
habitats.
11
Categories of Oxygen Requirement




Aerobe – utilizes oxygen and can detoxify
it
obligate aerobe - cannot grow without
oxygen
facultative anaerobe – utilizes oxygen
but can also grow in its absence
microaerophylic – requires only a small
amount of oxygen
12
Categories of Oxygen Requirement



Anaerobe – does not utilize oxygen
obligate anaerobe - lacks the enzymes to
detoxify oxygen so cannot survive in an
oxygen environment
aerotolerance anaerobes – do no utilize
oxygen but can survive and grow in its
presence
13
Carbon Dioxide Requirement
All microbes require some carbon dioxide in
their metabolism.
 capneic – grows best at higher CO2
tensions than normally present in the
atmosphere
14
Oxygen requirements
1.
2.
1.
2.
1.
2.
3.
4.
3.
4.
3.
4.
Aerobic culture
Anaerobic culture
1.
2.
3.
4.
1.
2.
3.
4.
Microaerobic culture
Obligate anaerobe
Facultative anaerobe
Microaerophile
Obligate aerobe
Growth requirements
 Temperature
 Pyschrophiles
4-20°C
 Mesophiles
15-48°C
 Thermophiles
42-68°C
 Extreme thermophiles >68°C
17
Effects of pH



Majority of microorganisms grow at a pH
between 6 and 8
Obligate acidophiles – grow at extreme
acid pH
Alkalinophiles – grow at extreme
alkaline pH
18
The Population Growth Curve
In laboratory studies, populations typically display
a predictable pattern over time – growth curve.
The Population Growth Curve
Stages in the normal growth
curve:
1.
2.
______phase – “flat” period of adjustment,
enlargement; little growth
_____________________ phase – a period
of maximum growth will continue as long
as cells have adequate nutrients and a
favorable environment
20
The Population Growth Curve
Stages in the normal growth curve:
1.
2.
_________ phase – rate of cell growth equals
rate of cell death caused by depleted nutrients
and O2, excretion of organic acids and
pollutants
_________ phase – as limiting factors
intensify, cells die exponentially in their own
wastes
21
Nutrient media




Ordinary (simple) media
Special media (serum agar, serum broth,
coagulated serum, potatoes, blood agar,
blood broth, etc.).
Elective media
Enriched media
Nutrient media





Differential diagnostic media: (1)
proteolytic action;
(2) fermentation of carbohydrates (Hiss
media);
(3) haemolytic activity (blood agar);
(4) reductive activity of micro-organisms;
(5) media containing substances assimilated
only by certain microbes.
Biochemical properties
Colonies
Colonies
Colonies
Pure Cultures Isolation
Isolated colonies obtaining