Understanding Bacterial Physiology and Growth

 
BACTERIAL
PHYSIOLOGY
 
Dr
.
 
orub
a
 
Khali
d
 
abbas
Lec.2
 
What 
does physiology 
means 
?
IT’S
 
THE
GROWTH,
NUTRITION,
AND
METABOLISM
 
1-BACTERIAL
 
GROWTH
 
It is 
an 
increase in all the cellular components,
which end in multiplication of the cell leading
to 
an 
increase in
 
population.
 
It involves 
an 
increase in the number of
individual
 
cells.
 
Bacteria divide 
by 
binary
 
fission.
Binary Fission is 
a type of 
Asexual reproduction in single
celled
 
organisms
 
Each cell divides into 
2 
equal sized
 
offspring
Binary
 
Fission
Generation
 
time
 
 
Interval of time between two cell
 
divisions
OR
The time required for 
a 
bacterium to give rise
to 
2 
daughter cells under optimum
conditions
Generatio
n
 
tim
e
 
o
f
 
E.col
i
  
&
 
other
medically important bacteria
 
is 20
 
mins
 
For tubercle 
bacilli is 20
 
hrs
 
For 
lepra bacilli is 20
 
days
 
Colony
by
growing
media.
 
formed
bacteria
on
 
solid
 
Each bacterial
colony represents
a 
clone of cells
derived from 
a
single 
parent
 
cell.
 
FACTORS AFFECTING 
BACTERIAL
 
GROWTH
INCLUDE:
 
1.
Temperature
2.
Atmosphere 
O
2 
&
 
CO
2
3.
H-ion
 
concentration
4.
Moisture 
&
 
drying
5.
Osmotic
 
effects
6.
Radiation
7.
Mechanical 
& 
sonic
 
stress
1-Temperature
 
Bacteria vary in their
 
temperature
requirements.
Temperature range 
growth does not
occur above the maximum or below
 
the
minimum.
Optimum Temperature 
It is the
temperature at which growth occurs
 
best,
it is 
37ºC 
for most pathogenic
 
bacteria
CLASSIFICATION 
BASED 
ON
 
TEMP.
 
Mesophilic 
grows
 
best
between
 
25ºC
 
and
 
40ºC.
e.g. most
 
pathogenic
bacteria
Psychrophilic 
(cold
 
loving)
grows best below
 
20ºC
e.g. 
Flavobacterium
 
spps
Thermophilic 
grows
 
best
at high temp,
 
55-
 
80ºC
 
e.g.
Bacillus
 
sterothermophilus
 
2-OXYGEN
 
2
 
Dependin
g
 
o
n
 
th
e
 
O
divided into
 
:
 
requirement
,
 
bacteri
a
 
are
 
1.
Obligate aerobes
: 
are 
those 
organisms 
that
 
live only 
in the 
presence 
of
oxygen 
with 
its 
atmospheric
 
concentration.
2.
Obligate anaerobes
:
 
are
 
those
 
organisms
 
that
 
live
 
only
 
in
 
the
 
complete
absence
 
of
 oxygen, 
its
 
presence
 
will
 
lead
 
to
 
death
 
of
 
these
 
organisms.
3.
Facultative 
Anaerobes
; 
are 
those 
organisms 
that 
live 
in the
 
presence 
or
absence 
of 
oxygen, 
but 
the 
presence 
oxygen 
will 
inhibit 
the 
anaerobic
system
4.
Microaerophiles
; 
are 
those 
organisms 
that 
live 
aerobically, 
but
 
under
low 
concentration 
of
 
oxygen.
5.
Aerotolerants
; 
are
 
those
 
group
 
of
 
microorganisms
 
that
 
normally
 
live
 
and
grow 
in the 
absence 
of 
oxygen, 
but 
O
2 
presence 
will 
lead 
to 
stop 
its
growth 
without 
killing
 
it.
 
6.
 
7
 
The 
Effect 
of 
Oxygen 
(O2) 
on
 
Growth
3- H-ion
 
Concentration
 
pH 
range,
 
optimum
pH
Majority of
pathogenic bacteria
grow 
best 
at 
neutral
or 
slightly 
alkaline
 
pH
(7.2 
7.6)
 
.
Lactobacilli 
require
acidic
 
pH
Vibrio
 
cholerae
require alkaline
 
pH
4- 
Moisture and
 
drying
 
Wate
r
 
i
s
 
a
n
 
essentia
l
 
ingredien
t
 
of
bacteria. 
Hence 
drying is lethal to
 
cells.
 
Effect 
of drying varies
 
:
Trepanoma pallidum 
are highly 
sensitive
to
 
drying
Staphylococcus 
spp. 
withstand drying for
months
Spore
s
 
ar
e
 
resistan
t
 
t
o
 
dryin
g
 
an
d
 
may
survive 
for 
several
 
decades
 
5- Osmotic
 
effects
 
More tolerant to osmotic variation due
to mechanical 
strength 
of their cell
 
walls.
6-
 
Radiation
X 
rays 
& 
gamma rays exposure 
 
lethal
7- 
Mechanical 
& 
Sonic
 
Stress
May be ruptured by mechanical
 
stress.
MICROBIAL
 
GROWTH
CULTURE MEDIA
CULTURE
 
MEDIUM
 
-
C
u
l
t
u
r
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M
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d
i
u
m
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BACTERIAL 
GROWTH
 
CURVE
 
When a 
bacterium 
is 
added 
to 
a 
suitable
medium 
& 
incubated, 
its 
growth follows 
a
definite
 
course.
 
If 
bacterial counts are 
made 
at intervals after
inoculation 
& 
plotted in relation to time, 
a
growth curve 
is
 
obtained.
 
Growth 
curve shows 
4 
phases 
: 
Lag, Log or
Exponential, 
Stationary 
& 
phase of
Decline
.
PHASES 
OF
 
GROWTH
 
Lag 
phase 
no increase in number but
there 
may be an increase in 
the size 
of
the
 
cell.
 
Log 
or 
Exponential 
phase 
cells 
start
dividing 
and their 
number increases
exponentially.
Stationary phase 
cell division 
stops
due to depletion of nutrients 
&
accumulation of toxic
 
products.
- 
Equilibrium 
exists between dying cells
and the newly formed cells, so viable
count remains
 
stationary
 
Phase of decline 
Population decreases
due to the death of cells 
autolytic
enzymes.
 
BACTERIAL
 
COUNTS
 
Growth in 
numbers 
can 
be
studied 
by 
bacterial
 
counts.
 
2
 
methods 
 
Total cell
 
count
-
 
Viable cell
 
count
 
TOTAL
 
COUNT
 
Total number of cells in 
the sample 
living 
+
 
dead.
Can be obtained by
 
:
1.
Direc
t
 
countin
g
 
unde
r
 
microscope
using counting
 
chambers.
2.
Countin
g
 
i
n
 
a
n
 
electroni
c
 
devic
e
 
Coulter
 
counter.
 
Viable 
Cell
 
Count
 
Measures the number of living
 
cells.
Methods 
Surface colony
 
count
1.
Dilution
 
method
2.
Plating
 
method
Number of colonies that develop after
incubation gives an estimate of the
viable
 
count.
2-Bacterial
 
Nutrition
 
Water constitutes 
80% 
of the total weight of
bacterial
 
cells.
 
Proteins, polysaccharides, lipids, nucleic
acids 
& 
low molecular weight compounds
make up the remaining
 
20%.
 
For 
growth 
& 
multiplication, the minimum
nutritional requirements are water, 
a 
source
of carbon, 
a 
source 
of nitrogen 
& 
some
inorganic
 
salts
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OTHER 
GROWTH
 
 
REQUIREMENTS
 
1.
Vitamin 
B 
complex
 
2.
Thiamine
3.
Riboflavine
4.
Nicotinic
 
acid
5.
Pyridoxine
6.
Folic
 
acid
7.
Vit.B
 
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Bacterial Metabolism
Help us in identifying bacteria by their end
products
Help us in knowing how to inhibit bacteria
Energy Generating Process
 
Sugars formed or obtained - broken down to
release energy
Aerobic respiration
Anaerobic respiration
Fermentation
 
Microbes that use aerobic respiration, detoxify
generated waste:
 
Catalase
:
 H
2
O
2
 -------
 H
2
0 and 0
2
 
Superoxide dismutase
 : oxygen radical -----
 H
2
0 and
O
2
 
 
 
Energy Generating Process
 
Aerobic respiration
:
COMPLETE breakdown of glucose to CO
2
 & H
2
O
Final electron receptor O2
Yield = 
38 ATP
Fermentation:
 Yield = 
2 ATP
 Endproducts: Lactic acid/Alcohol
 Final electron receptor is organic molecule
Anaerobic respiration
:
 Yield 
>2 <38 ATP
 Absence of oxygen
 
THANK
 
YOU
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Bacterial physiology encompasses the growth, nutrition, and metabolism of bacteria. Bacterial growth involves binary fission, generation time, colony formation, and is influenced by various factors such as temperature, atmosphere, moisture, and radiation. Understanding the classification based on temperature requirements of bacteria is essential for studying their behavior and characteristics.


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  1. BACTERIAL PHYSIOLOGY Dr. oruba Khalid abbas Lec.2

  2. What does physiology means ? IT S THE GROWTH, NUTRITION, AND METABOLISM

  3. 1-BACTERIAL GROWTH It is an increase in all the cellular components, which end in multiplication of the cell leading to an increase in population. It involves an increase in the number of individual cells. Bacteria divide by binary fission. Binary Fission is a type of Asexual reproduction in single celled organisms Each cell divides into 2 equal sized offspring

  4. BinaryFission

  5. Generationtime Interval of time between two cell divisions OR The time required for a bacterium to give rise to 2 daughter cells conditions under optimum

  6. Generation time of E.coli & other medically important bacteria is 20 mins For tubercle bacilli is 20 hrs For lepra bacilli is 20 days

  7. Colony by growing media. formed bacteria on solid Each bacterial colony represents a clone derived single parent cell. of from cells a

  8. FACTORS AFFECTING BACTERIAL GROWTH INCLUDE: 1. 2. 3. 4. 5. 6. 7. Temperature Atmosphere O2 & CO2 H-ion concentration Moisture & drying Osmotic effects Radiation Mechanical & sonic stress

  9. 1-Temperature Bacteria vary in theirtemperature requirements. Temperature range growth does not occur above the maximum or below the minimum. Optimum Temperature It is the temperature at which growth occursbest, it is 37 C for most pathogenic bacteria

  10. CLASSIFICATION BASED ONTEMP. Mesophilic growsbest between 25 C and40 C. e.g. mostpathogenic bacteria Psychrophilic (coldloving) grows best below 20 C e.g. Flavobacterium spps Thermophilic growsbest at high temp, 55- 80 C e.g. Bacillus sterothermophilus

  11. 2-OXYGEN requirement, bacteria are Depending on the O divided into : 2 1. Obligate aerobes: are those organisms thatlive only in the presence of oxygen with its atmosphericconcentration. 2. Obligate anaerobes: arethoseorganismsthat live only in the complete absenceof oxygen, its presencewill leadto deathof theseorganisms. 3. Facultative Anaerobes; are those organisms that live in thepresence or absence of oxygen, but the presence oxygen will inhibit the anaerobic system 4. Microaerophiles; are those organisms that live aerobically, butunder low concentration ofoxygen. 5. Aerotolerants; arethosegroup of microorganismsthat normally live and grow in the absence of oxygen, but O2 presence will lead to stop its growth without killingit. 6. 7

  12. The Effect of Oxygen (O2) onGrowth

  13. 3- H-ion Concentration pH range, optimum pH Majority of pathogenic bacteria grow best at neutral or slightly alkaline pH (7.2 7.6) . Lactobacilli require acidic pH Vibrio cholerae require alkaline pH

  14. 4- Moisture and drying Water is an bacteria. Hence drying is lethal to cells. essential ingredient of Effect of drying varies : Trepanoma pallidum are highly sensitive to drying Staphylococcus spp. withstand drying for months Spores are resistant to drying and may survive for several decades

  15. 5- Osmotic effects More tolerant to osmotic variation due to mechanical strength of their cell walls. 6- Radiation X rays & gamma rays exposure lethal 7- Mechanical & Sonic Stress May be ruptured by mechanical stress.

  16. MICROBIAL GROWTH CULTURE MEDIA CULTURE MEDIUM -Culture Medium: Medium containingnutrients that support microbial growth -Sterile: No living microbes -Inoculum: Introduction of microbes into medium -Culture: Microbes growing in/on culture medium Types of Culture Media Enrichment Culture Nutrient media Special media Selective Media Differential Media Selective and Differential Media

  17. BACTERIAL GROWTH CURVE When a bacterium is added to a suitable medium & incubated, its growth follows a definite course. If bacterial counts are made at intervals after inoculation & plotted in relation to time, a growth curve is obtained. Growth curve shows 4 phases : Lag, Log or Exponential, Stationary Decline. & phase of

  18. PHASES OFGROWTH Lag phase no increase in number but there may be an increase in the size of the cell. Log or Exponential phase cells start dividing and their number increases exponentially.

  19. Stationary phase cell division stops due to depletion accumulation of toxic products. - Equilibrium exists between dying cells and the newly formed cells, so viable count remains stationary of nutrients & Phase of decline Population decreases due to the death of cells autolytic enzymes.

  20. BACTERIAL COUNTS Growth in numbers can be studied by bacterial counts. 2 methods Total cellcount - Viable cell count

  21. TOTAL COUNT Total number of cells in the sample living + dead. Can be obtained by : 1. Direct counting under microscope using counting chambers. 2. Counting in an electronic device Coulter counter.

  22. Viable Cell Count Measures the number of living cells. Methods Surface colony count 1. Dilution method 2. Plating method Number of colonies that develop after incubation gives an estimate of the viable count.

  23. 2-Bacterial Nutrition Water constitutes 80% of the total weight of bacterial cells. Proteins, acids & low molecular weight compounds make up the remaining 20%. polysaccharides, lipids, nucleic For growth & multiplication, the minimum nutritional requirements are water, a source of carbon, a source of nitrogen & some inorganic salts

  24. Classification of bacteria based on nutritional requirements Autotrophs are free-living, most of which can use carbon dioxide as their carbon source. The energy can be obtained from: sunlight protoautotrophs (get energy from photochemical reactions) inorganic compounds, chemoautotrophs (get energy from chemical reactions) Heterotrophs are generally parasitic bacteria, requiring more complex organic compounds than carbon dioxide, e.g. sugars, as their source of carbon and energy. by oxidation

  25. OTHER GROWTH REQUIREMENTS 1. 2. Thiamine 3. Riboflavine 4. Nicotinic acid 5. Pyridoxine 6. Folic acid 7. Vit.B 12 Vitamin B complex

  26. Metabolism is the process of building up chemical compounds in the cell and their breaking during activity to receive the required energy and the building elements. Metabolism comprises of anabolism (assimilation) and (dissimilation) down catabolism

  27. Bacterial Metabolism Help us in identifying bacteria by their end products Help us in knowing how to inhibit bacteria

  28. Energy Generating Process Sugars formed or obtained - broken down to release energy Aerobic respiration Anaerobic respiration Fermentation Microbes that use aerobic respiration, detoxify generated waste: Catalase: H2O2 ------- H20 and 02 Superoxide dismutase : oxygen radical ----- O2 H20 and

  29. Energy Generating Process Aerobic respiration: COMPLETE breakdown of glucose to CO2 & H2O Final electron receptor O2 Yield = 38 ATP Fermentation: Yield = 2 ATP Endproducts: Lactic acid/Alcohol Final electron receptor is organic molecule Anaerobic respiration: Yield >2 <38 ATP Absence of oxygen

  30. THANK YOU

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