M
MICROBIOLOGY & PARASITOLOGY
C3
PRELIMS CELL STRUCTURE
CELL STRUCTURE
Types of Living cells According to Structure
Prokaryotes Eukaryotes BACTERIAL SHAPES AND ARRANGEMENTS
Cell membrane Cell membrane Coccus/Cocci
Cytoplasm Cytoplasm Spherical or ellipsoidal; “berries”
One circular Paired chromosomes, in May have the following arrangements:
chromosome, not in a nuclear membrane o Diplococci: pair; divide in 1 plane
membrane o Streptococci: Chains; divide in 1 plane
No histones Histones o Tetrads: Groups of four. Divide in two
No organelles Organelles planes.
Peptidoglycan cell walls Polysaccharide cell o Sarcinae: Groups of eight. Cuboidal.
walls Divide in three planes.
Binary Fission Mitotic spindle o Staphylococci: Grapelike clusters or
Cell membrane Cell membrane bunches. Divide in multiple planes.
Cytoplasm Cytoplasm Typical Arrangements of cocci
Bacteria (Eubacteria) Fungi
Blue Algae protozoa
(microscopic)
Fungi (microscopic) Algae
Protozoa (single-celled) Plants
Virus Animals
THEM US
Relationships Of Microorganisms
Bacillus/ Bacilli
Rod-like or cylindrical.
Most bacilli appear as single rods but you
may see:
o Diplobacilli: pair. Divide in 1 plane.
o Streptobacilli: Chain. Divide in 1 plane
NOTE
Size of living things Coccobacillus: Intermediate shape between
coccus and bacillus. Oval rods.
Arrangements of Bacilli
1 m = 100 cm = 1,000mm
= 1,000,000 µm =
1,000,000,000nm
1mm = 1000 µm =
1000000nm
1 µm = 1000nm
Rod-shaped Bacteria
Bacterial cell size Compared to eukaryotic cells
and viruses
Hannah Adan 1
, M
MICROBIOLOGY & PARASITOLOGY
C3
PRELIMS CELL STRUCTURE
Found in a few groups:
o Corynebacterium
Double stranded helix o Rhizobium
formed by Bacillus Monomorphic
subtilis Maintain a single shape.
Bacillus cells often However environmental factors may affect cell
remain attached to shape.
each other, forming
extended chains STRUCTRURE EXTERNAL TO THE CELL WALL
Gram Stain (1884)
Hans Christian Joachim Gram,
Danish microbiologist
Spiral Bacteria The most useful staining
Have one or more twists; never straight procedure in medical
o Vibrio: comma shaped; curved rods microbiology.
o Spirilla: Helical, corkscrew shaped Distinguishes bacteria of two
bacteria with rigid bodies. large and medically important groups:
Use whiplike external flagella to o Gram-positive bacteria
move. o Gram-negative bacteria
o Spirochetes: Helical bacteria with Provides useful information for disease
flexible bodies. treatment.
Use axial filaments (internal flagella)
to move.
Arrangements of spiral bacteria
UNUASUAL SHAPES OF PROKARYOTES
Star-shaped Stella
Square Haloarcula (halophilic archaea – salt-
loving)
Triangular
Pear-shaped
Disks arranged like stack of coins
Rods with square ends
Trichomes: chain but with larger contact
between adjacent cells
Palisade: cells are lined side by side like
matchsticks & at angles to one another
BACTERIAL APPENDAGES OR CELL EXTENSIONS
CLASSIFICATION OF BACTERIA ACCORDING TO Flagellum/Flagella
NUMBER OF SHAPES ASSUMED Bacterial Propellers
Pleomorphic Bacteria Hairlike
have several possible shapes. Long, thin, helical appendages
Hannah Adan 2
MICROBIOLOGY & PARASITOLOGY
C3
PRELIMS CELL STRUCTURE
CELL STRUCTURE
Types of Living cells According to Structure
Prokaryotes Eukaryotes BACTERIAL SHAPES AND ARRANGEMENTS
Cell membrane Cell membrane Coccus/Cocci
Cytoplasm Cytoplasm Spherical or ellipsoidal; “berries”
One circular Paired chromosomes, in May have the following arrangements:
chromosome, not in a nuclear membrane o Diplococci: pair; divide in 1 plane
membrane o Streptococci: Chains; divide in 1 plane
No histones Histones o Tetrads: Groups of four. Divide in two
No organelles Organelles planes.
Peptidoglycan cell walls Polysaccharide cell o Sarcinae: Groups of eight. Cuboidal.
walls Divide in three planes.
Binary Fission Mitotic spindle o Staphylococci: Grapelike clusters or
Cell membrane Cell membrane bunches. Divide in multiple planes.
Cytoplasm Cytoplasm Typical Arrangements of cocci
Bacteria (Eubacteria) Fungi
Blue Algae protozoa
(microscopic)
Fungi (microscopic) Algae
Protozoa (single-celled) Plants
Virus Animals
THEM US
Relationships Of Microorganisms
Bacillus/ Bacilli
Rod-like or cylindrical.
Most bacilli appear as single rods but you
may see:
o Diplobacilli: pair. Divide in 1 plane.
o Streptobacilli: Chain. Divide in 1 plane
NOTE
Size of living things Coccobacillus: Intermediate shape between
coccus and bacillus. Oval rods.
Arrangements of Bacilli
1 m = 100 cm = 1,000mm
= 1,000,000 µm =
1,000,000,000nm
1mm = 1000 µm =
1000000nm
1 µm = 1000nm
Rod-shaped Bacteria
Bacterial cell size Compared to eukaryotic cells
and viruses
Hannah Adan 1
, M
MICROBIOLOGY & PARASITOLOGY
C3
PRELIMS CELL STRUCTURE
Found in a few groups:
o Corynebacterium
Double stranded helix o Rhizobium
formed by Bacillus Monomorphic
subtilis Maintain a single shape.
Bacillus cells often However environmental factors may affect cell
remain attached to shape.
each other, forming
extended chains STRUCTRURE EXTERNAL TO THE CELL WALL
Gram Stain (1884)
Hans Christian Joachim Gram,
Danish microbiologist
Spiral Bacteria The most useful staining
Have one or more twists; never straight procedure in medical
o Vibrio: comma shaped; curved rods microbiology.
o Spirilla: Helical, corkscrew shaped Distinguishes bacteria of two
bacteria with rigid bodies. large and medically important groups:
Use whiplike external flagella to o Gram-positive bacteria
move. o Gram-negative bacteria
o Spirochetes: Helical bacteria with Provides useful information for disease
flexible bodies. treatment.
Use axial filaments (internal flagella)
to move.
Arrangements of spiral bacteria
UNUASUAL SHAPES OF PROKARYOTES
Star-shaped Stella
Square Haloarcula (halophilic archaea – salt-
loving)
Triangular
Pear-shaped
Disks arranged like stack of coins
Rods with square ends
Trichomes: chain but with larger contact
between adjacent cells
Palisade: cells are lined side by side like
matchsticks & at angles to one another
BACTERIAL APPENDAGES OR CELL EXTENSIONS
CLASSIFICATION OF BACTERIA ACCORDING TO Flagellum/Flagella
NUMBER OF SHAPES ASSUMED Bacterial Propellers
Pleomorphic Bacteria Hairlike
have several possible shapes. Long, thin, helical appendages
Hannah Adan 2
