BACTERIA

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MICROBIAL MORPHOLOGY AND STRUCTURE
 MORPHOLOGY AND STRUCTURE OF BACTERIA
¢Microorganisms are generally regarded as living forms that are microscopically in size and relatively very simple, usually unicellular.
¢The smallest body a naked eye can see is about 100ยตm (0.1mm) in diameter.
Most of the microorganisms are smaller than this and therefore a microscope is necessary for their visualization
¢The basic living material is called protoplasm and is organized in units known as cells
¢The cell is enclosed by a thin semi permeable membrane called cytoplasmic or plasma membrane.
¢The plasma membrane is usually enclosed by a relative rigid cell wall.
¢The major parts of the protoplast are the cell wall, cytoplasm and the nucleus
¢Cell are usually divided into two distinctive forms; the relatively primitive cells called prokaryotes and relatively advanced ones called eukaryotes.
¢Prokaryotes include the so called “true” bacteria (eubacteria or simply bacteria) and archaeabacteria or simply archaea
¢Eubacteria include all bacteria that infect human, while archaebacteria are bacteria that are free living in the environment.
Eukaryotic cell
Prokaryotic cell


DIFFERENCES BETWEEN 

PROKARYOTES AND             

EUKARYOTES.

1.Unlike eukaryotic cells, the prokaryotic organelles are not compartmentalized.
2. Prokaryotes have a nucleus that is simple, has no nuclear membrane, no nucleolus, no spindles. It is therefore called a nucleoid.
—Nuclear membranes, endoplasmic reticulum, golgi body, are not present.

3. Prokaryotic ribosome’s are 70S (S stands for Svedberg unit) where as eukaryotic ribosome’s are large 80S
—70S or 80s refers to the rate of sedimentation of the ribosome in a centrifuge
¢Prokaryotic ribosomal subunits are 30S and 
50S and for eukaryotes subunits are 40S and 
60S

 70S RIBOSOMES IN PROKARYOTES?
¢70S refers to the rate of sedimentation of the 
ribosome in a centrifuge. You can almost think of it as 
a unit of size. The "S" is a unit of measurement called 
the Svedberg unit. Ribosomes contain two subunits. In 
prokaryotes, these subunits are 50S (large) and 30S 
(small). The total ribosome with both subunits is 70S in 
prokaryotes. (Notice that 30 + 50 = 80 and not 70. 
Remember this is not size and the rate of 
sedimentation is less when the subunits are boundthen 
when they are separated.) Eukaryotic cells have 80S 
ribosomes: 60S (large) and 40S (small) subunits.


PROKARYOTES VS. 

EUKARYOTES

¢Cell Wall
¢Teichoic Acids
¢LPS
¢Endospores
¢Circular DNA
¢Plasmids

SIZE OF BACTERIA
¢Unit for measurement :                Micron or  micrometer,ฮผm: 1ฮผm=10-3mm
¢Siz


SHAPES OF BACTERIA
   ¢Coccus
—Chain = Streptoccus
—Cluster = Staphylococcus
¢Bacillus
—Chain = Streptobacillus
¢Coccobacillus
¢Vibrio = curved
¢Spirillum
¢Spirochete
¢Square
¢Star

STRUCTURE OF 

BACTERIA


BACTERIAL

 STRUCTURES
¢Flagella 
¢Pili
¢Capsule
¢Plasma Membrane
¢Cytoplasm
¢Cell Wall
¢Lipopolysaccharides
¢Teichoic Acids
¢Inclusions
¢SporesVaries with kinds of bacteria, and also related to their age 
CELL WALL
¢This encases the protoplast and lay immediately external to the cytoplasmic membrane
¢It is thick, strong, rigid and porous.
¢The chemical composition of the cell wall differs with bacterial spp
¢But in all spp the main strengthening component is a substance called peptidoglycan or mucopeptide 
ex
BACTERIAL CELL WALLt
\
General structure: 
Mucopolysaccharide i.e. peptidoglycan. 
It is made by  N-acetylglucosamine and 
N-acetylmuramic acid. tetrapeptide ( L-
alanine- isoglutamine-lysine-alanine)  is 
attached. 
The entire cell wall structure is cross 
linked by covalent bonds.  This provide 
the rigidity necessary to maintain the 
integrity of the cell.
N-acetylmuramic acid is unique to 
prokaryotic cell.


 CELL WALL

¢Peptido-glycan Polymer (amino acids +
sugars)
¢Unique to bacteria
¢Sugars; NAG & NAM
—N-acetylglucosamine
—N-acetymuramic acid
¢D form of Amino acids used not L form
—Hard to break down D form
¢Amino acids cross link NAG & NAM
\
CELL WALL-COMPONENTS
¢Peptidoglycan
Backbone: alternating N-
acetylmuramic acid (NAM) and N-
acetylglucosamine (NAG)
A set of identical tetrapeptide side chains
 
A set of identical pentapeptide 
cross bridges(G+) 

Biology 101 Study Guide For Lab Quiz #2



Prokaryotic Cell Structure







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