Post on 05-Jul-2018
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Cell Growth and
Measurements
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Binary fission in bacteria
Scanning electron
micrograph
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Geometric progression
in the number of
bacteria in apopulation resulting
from binary fission
Generation time
length of time it takes
a single bacterium to
double
E. coli 25 minutes
Mycobacterium spp. 1!
days.
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Binary fission re"uires the addition of new
material at the growing sites of bacteria
Gram positi#e cells such as
this coccus$ new materialis added at the di#ision plane
Gram negati#e cells such as
this bacillus$ new material isadded at the di#ision plane and
also throughout the length of
the cell
Bacteria need to synthesi%e the macromolecules that allow for their
growth and reproduction.
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Bacteria need to synthesi%e
macromolecules that allow for their growth
and reproduction & what are bacterial cellsmade up of '
Cells consist of ()*+, and M)C,-M-+C/+S
Macromolecules are made up of smaller monomeric molecules
Small monomeric molecules are made up of atoms
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Macromolecules of the bacterial cell
0roteins —The most abundant class of macromolecules and comprise
most of the structures of the cell as well as enzymes
amino acids —monomeric subunits of proteins
consists of carbon, hydrogen, oxygen, nitrogen, sulfur and
sometimes selenium
amino acids are covalently linked to form a peptide bond
NH3 !!H
H
"
NH3
H
"#
!!H
H
"$!
N
H
%eptide bond
(here ha#e you heard the
word tetrapeptide'
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Macromolecules of the bacterial cell
contd3
0olysaccharides —$nd most abundant of the bacteral macromolecules
sugars &monosaccharides'—monomeric units
consists of arbon, Hydrogen and !xygen atoms at a ratio
of #($(#
individual sugars are linked by a glycosidic bond
%olysaccharides form covalent linkages with other macromolecules
with proteins— glycoproteinswith lipids— glycolipids$ lipopolysaccharides
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Macromolecules of the bacterial cell
contd3• Nucleic )cids
4) —deoxyribonucleic acid
,) —ribonucleic acid
• *ackbone of nucleic acids+ polymer of phosphoribose &"N)'
or phosphodeoxyribose &-N)'
• The sugars are covalently attached to each other by phospho
diester bonds
•*ases are attached to a carbon atom of the sugar moietycytosine$ adenine$ guanine &-N)."N)'/ thymine &-N)'
uracil &"N)'
• omprised of the atoms %hosphorous, arbon, Hydrogen, !xygen
and Nitrogen
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Macromolecules of the bacterial cell
contd3ipids —made up of a long carbon chain— fatty acids —$1
carbons and one carboxylic acid group'
Saturated —Hydrogen atoms attached to most or all carbon
moieties2
/nsaturated —fewer Hydrogen atoms associated with carbons
Comple6 lipids are attached to simple sugars like phoshoglycerol &ie phospholipids' or comple6 polysaccharides &%4'
, H, !, %
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Bacterial utritional ,e"uirements
/*,7*7-((act of supplying microorganisms with the moleculesand atoms they re5uire for the biosynthesis of small molecules
and macromolecules
Macronutrients8 nutrients re5uired in high amounts
arbon, Nitrogen, %hosphorous, 4ulfur )4!
%otassium, 6agnesium, alcium, 4odium
Micronutrients( nutrients re5uired in small or even trace amounts
hromium, obalt, opper, 6anganese, 6olybdenum
Nickel, 4elenium, Tungsten, 7anadium, 8inc, 7ron
Growth 9actors((organic compounds re5uired in very small amounts
7itamins, amino acids, purines and pyrimidines
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Bacterial utritional ,e"uirements
)utotroph( an organism capable of biosynthesizing all cellmaterial from !$ as a sole carbon source
:eterotroph( an organism that re5uires carbon from preexisting
organic material
0hoto8 solar energy converted to chemical energyChemo8 energy derived from chemical compounds
Catabolism8 )ct of breaking down complex molecular materialfor energy or biosynthetic material )nabolism( The act of biosynthesizing complex material from simpler organic compounds
Culture media for artificial cultivation of bacteria in the lab
#2 Comple6 undefined3& enzymatic digests of milk protein
&casein', beef, yeast
$2 Chemically defined —precise amounts of purified organic
and inorganic compounds are added to distilled water
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*ypes of culture media
9astidious*rock, #1th edition
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-ther considerations with respect to
bacterial growth
1. p: —optimum pH of most organisms is 921
2. (ater acti#ity — most bacteria re5uire a water activity
between 12: and #21!. -smolarity —The osmolarity of the bacterial cell cytoplasm
must be greater than that of its environment for cell growth—
turgor pressure
;. -6ygen —bacteria have a great variety of specifications
with respect to the amount of oxygen they re5uire
5. *emperature —most organisms like 39o
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)bout o6ygen
)erobes —capable of growth at full oxygen tensions
Microaerophiles —can only grow when oxygen tensions are lower
than that found in air &soil, water bacteria'
)naerobes — obligate anaerobes —oxygen kills the organism
facultati#e anaerobes —prefer oxygen but can grow in its
absence
aerotolerant anaerobes —can grow in the presence of oxygen but they don;t use it2
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/se of the hemocytometer or 0etroff:ausser
counting chamber direct microscopic count3
4ample added to the surface of
the grid, the whole grid has 25
large s5uares, the total volume
that can be added is >.>2mm!
12 bacteria in one s"uare&assume #$ in each large
s5uare' 12 ? 25 @ !>> bacteria
Total volume held is >.>2 mm!
!>>A.>2 @ 15>>> or 1.5 ? 1>;
Bacteria per mm!
1cm! @ 1>>>mm! x #1 x #1'
1.5 ? 1>; 6 1>>> @ 1.5 ? 1>Acm! or m
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/se of dilution and direct plating to measure
#iable bacteria #iable cell count3
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/se of the spectrophotometer to "uantify
bacteria in a population
-4@ og 7oA77o incident light
7 unscattered light
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/se of the spectrophotometer in measuring
the number of cells in a population
*y using both spectro
photometry and dilutions
and plate counts one can
make a good correlation
between optical density
and cell population numbers
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Stages of bacterial growth88typical growth
cur#e
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Biphasic Growth Cur#e
0remature stationary phase
cells ha#e e6hausted a#ailableglucose
2nd stationary phase
cells ha#e e6hausted
lactose2nd log phase$ cells prepare
en%ymes re"uired for the
catabolism of lactose
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