Coccobacilli is a transitional shape between coccus and bacillus. It has the rounded ends of a coccus but is rod-shaped like a bacillus. Bacillus do not form tetrads or clusters because their shape does not allow them to divide in more than one plane like cocci can. As rods, bacilli can only divide by binary fission in one plane, so they remain as single cells or short chains rather than clustering.

1. Bacterial Cytology & Physiology
Bacterial Taxonomy
Parts of a bacterial cell
Specialized structures in bacteria

2. Taxonomical Ladder
• Kingdom Monera • Kingdom Plantae
• Phylum • Kingdom Animalia
• Class • Kingdom Protista
• Order • Kingdom Fungi
• Family • Kingdom Monera
• Genus
• Specie - Type &
Strain

5. New Classification:
• Carl Woese – based on cellular organization (Domain
above Kingdom)
– Bacteria – cell wall w/ peptidoglycan
– Archaea – cell walls, if present lack peptidoglycan
– Eukarya – Protista, Fungus, Plants, Animals

6. Characters used to classify Bacteria
• Morphology- cell • Percentage of DNA
shapes & struc. base pairs
• Biochemistry & • DNA sequence
Physiology - condi- • DNA hybridization
tions & process • sequence of amino
• Serology - FAT & acids in proteins
slide agglutination • protein profiles
• Phage typing • sequence of rRNA

7. Prokaryote VS. Eucaryote

8. Procaryotes
• appendages: pili, flagella, • presence of plasma
axial filaments in membrane
spirochetes • undiff. cytoplasm
• Usually glycocalyx is • non-membrane
present bound organelles
• outer membrane present • 1 circular DNA
in gram (-)
• binary fission
• cell wall in all eubacteria
• 1 to few u

10. Eucaryotes
• different flagella from
• cytoskeleton &
procaryotes
cytoplasmic streaming
• very few has glycocalyx
• membrane bound
• no outer memb. organelles
• no cell wall • paired chromosome
• plasma membrane- • mitosis & meiosis
phospholipid bilayer
• no endospores
• > than 10 u

12. Bacterial Cytology
• Structures external to the cell wall
• The cell Wall
• Structures internal to the cell wall
• General Structures
• Specialized structures

13. External to the cell wall:
• Glycocalyx – sugar coat
– Viscous, gelatinous polymer on the external of the
cell, composed of polysaccharide, polypeptide or
both
• Capsule – If Glycocalyx is organized and firmly
attached to the cell wall, capsule is formed
– Determines virulence of the cell
– Negative Staining

14. • Slime layer - If the substance is unorganized &
loosely attached to cell wall.
• EPS ( Extracellular polysaccharide ) –
– Glycocalyx made of sugar- enables the bacteria to
attach to various surfaces in the natural
environment in order to survive.
• Flagella/Flagellum ( whip )
– Long filamentous appendages that propel bacteria

16. Arrangements of flagella:
• Monotrichous – single polar
• Amphitrichous – tuft at each end
• Lophotricous – 2 or more at one end
• Peritrichous – entire cell
• Atricous – no flagella
• Flagellar rotation depend on cells continuous generation
of energy
• Flagellar motion – run, swim, tumble, swarm

18. • Axial Filaments
– Unique in spirochetes, also called endoflagella,
which are bundles of fibrils that arise at the
ends of the cell beneath an outer sheath and
spiral around the cell.
– Propulsion causes spiral motion or corkscrew
movement

19. Fimbriae & Pili:
• Fimbriae/Fimbria
– can occur at the poles of the cell or evenly
distributed all over
– Functions for cell attachment/ in the absence
colonization cannot happen so no disease
ensues
• Pili/Pilus
– Longer than fimbriae, only 1 – 2 per cell
– Preparation for DNA transfer – sex pili

20. The Cell Wall
• Complex, semi rigid structure responsible
for the shape of the cell
• Composed of peptidoglycan (also known as
murein) made up of NAG ( N-
acetylglucosamine) and NAM (N-acetyl
muramic acid).
– Structures on the disaccharide portion is
repeating.

21. Gram + & - cell walls:
• Most gram (+) bacteria have many layers of peptidoglycan in the
cell wall forming a thick rigid structure while gram (-) only
contain 1 thin layer of peptidoglycan.
• Gram (+) contains teichoic acid consisting primarily of an alcohol
& phosphate
– Lipoteichoic Acid
– Wall teichoic Acid
• Gram (-) cell walls are susceptible to mechanical breakage
because they contain only small amount of peptidoglycan

22. Internal to the Cell Wall:
• Plasma Membrane/Bacterial Membrane
• Cytoplasm
• The Nucleus
• Ribosomes
• Inclusions
– Metachromatic granules
– Magnetosomes
• Endospores

23. Bacterial Membrane
• Functions: • Demonstrated by:
– osmosis & – Plasmolysis
permeability – Stain - Victoria
– cell division Blue
– primer for – Isolation - Diff.
biosynthesis centrifuge
– site of Ag – Ultrathin sections
determinant

27. Bacterial shapes & arrangements
• Coccus -
• Spirillus
– single, diplo, tetrad,
– wavy, corkscrew,
sarcinae, strepto ,
comma-shaped
staphylo.
– Spiral bacteria may
• Bacillus -
have 1 or more
– single, diplo, strepto
twists

28. Additional Shapes
• Star shaped cells – Genus Stella
• Rectangular flat cells – halophilic Genus Haloarcula
• Triangular shaped cells

29. Basis of Shape:
• Shape of the bacterium is primarily
dependent on heredity.
• Generally bacteria are monomorphic,
maintain 1 single shape
• Due to environmental conditions, some
bacteria tend to become pleomorphic
which makes identification difficult. I.e.
Rhizobium & Corynebacterium

30. Trivia:
• Is coccobacilli a coccus or a bacilli? Maybe both or
neither of the two?
• Why do bacillus not have tetrads or clusters?