standard cell growth

8/16/2019 Standard Cell Growth

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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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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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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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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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standard cell growth

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