- Mr. Zybrinskie Bangcado

1. THE BASES FOR CLASSIFYING
BACTERIA
BACTERIA

2. PROKARYOTIC CELL CHARACTERISTICS
• Unicellular
• Bacteria and Archaea
• Different in chemical composition.
• Differentiated by many factors including:
• A. Morphology (shape)
• B. Chemical composition (often detected by
staining reactions)
• C. Nutritional requirements
• D. Biochemical activities
• E. Source of energy (sunlight or chemicals)

3. THE SIZE SHAPE AND ARRANGEMENT OF
BACTERIAL CELLS
• Range from 0.2 to 2.0 um in diameter.
• 2 to 8 um in length.
• Few basic shapes:
• A. Coccus (berries ) – spherical
• B. Bacillus ( little staff) – rod-shaped
• C. Spiral

4. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS
• Cocci are usually round but can be oval, elongated
or flattened on one side.
• Diplococci – remain in pairs after dividing.
• Streptococci – divide and remain attached in
chainlike patterns.
• Tetrads – divide in 2 planes and remain in groups
of 4.
• Sarcinae - divide in three planes and remain
attached in cubelike groups of eight.
• Staphylococci – divide in multiple planes and
form grapelike structures.
• Frequently helps in the identification of cocci.

5. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS

6. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS

7. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS

8. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS
• Bacilli divide only across their short axis.
• Most bacilli are single rods.
• Diplobacilli - appear as pairs after division.
• Streptobacilli – occur in chains.
• Coccobacilli – oval and look so much like
cocci.
• Others are like straws and others are like cigars
with tapered ends.

9. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS

10. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS
• “Bacillus has two meanings.
• Refers to a bacterial shape.
• Refers to a genus.
• E.g. Bacillus anthracis
• Bacillus often form long and twisted chains of
cells.

11. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS
• Spiral bacteria have one or more twist they are
never straight.
• Vibrio – curved rods.
• Spirilla – have helical shape like a cork screw
and fairly rigid bodies with flagella.
• Spirochetes – helical and flexible with axial
filaments.

12. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS

13. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS
• In addition to the three basic shapes:
• Genus Stella – star shaped.
• Genus Holoarcula – Halophilic Archaea with
rectangular, flat cells.
• Some Genera are triangular.
• Most bacteria are
• Monomorphic – maintain a single shape.
• Environmental conditions could alter shape.
• Some bacteria are
• Pleomorphic – they have many shapes not just
one.

14. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS

15. THE SIZE, SHAPE AND ARRANGEMENT
OF BACTERIAL CELLS

16. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• POSSIBLE STRUCTURES EXTERNAL TO
THE CELL WALL.
• Glycocalyx – is a viscous, gelatinous polymer that
is external to the cell wall.
• Composed of polysaccharide, polypeptide or both.
• Capsule – organized and firmly attached
glycocalyx.
• Presence determined by staining.
• Slime layer – unorganized and loosely attached
glycocalyx.

17. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• POSSIBLE STRUCTURES EXTERNAL TO
THE CELL WALL.
• Capsules – important in contributing to
bacterial virulence.
• Protect the pathogenic bacteria from
phagocytosis.
• Bacillus anthracis secretes a capsule of D-
glutamic acid.

18. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• POSSIBLE STRUCTURES EXTERNAL TO
THE CELL WALL.
• Extracellular Polysaccharide (EPS)
• Glycocalyx made of sugars.
• Enables bacterium to attach to various surfaces
in its natural environment.
• E.g. rocks in fast moving streams, human
teeth, medical implants and etc.
• Streptococcus mutans – attaches to teeth
and causes dental caries.

19. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• POSSIBLE STRUCTURES EXTERNAL TO
THE CELL WALL.
• Glycocalyx can be broken down and serve as
nutritional source.
• Can protect the cell against dehydration.
• Its viscosity may inhibit the movement of
nutrients out of the cell.

20. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• POSSIBLE STRUCTURES EXTERNAL TO THE
CELL WALL.
• Flagella – Long filamentous appendages that propel
bacteria.
• Atrichous – Bacteria that lack flagella.
• Bacteria that have flagella are:
• A. Monotrichous – a single polar flagellum.
• B. Amphitrichous – a tuft of flagella at each end of the
cell.
• C. Lophotrichous – two or more flagella at one or
both ends of the cell.
• D. Peritrichous – flagella distributed over the entire
cell.

21. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• A flagellum has three basic parts.
• Filament – the long outermost region.
• Constant in diameter and contains the globular
protein flagellin.
• Arranged as intertwining chains that form a
helix around a hollow core.
• Hook – where filament is attached.
• Basal body – Anchors the flagellum to the cell
wall and plasma membrane.

22. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• Prokaryotic flagellum – semirigid, helical
structure that moves the cell by rotating the
basal body.
• Either clockwise or counterclockwise along its
axis.
• Movement due to rotation of the basal body.
• Flagellar rotation depends on continuous supply
of energy.

23. THE STRUCTURES EXTERNAL TO THE
CELL WALL

24. THE STRUCTURES EXTERNAL TO THE
CELL WALL

25. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• Motility – the ability of an organism to move by
itself.
• Run – moves in one direction for a length of
time.
• Tumble – random changes in direction.
• Swarm – show rapid wavelike movement across
a solid culture medium.
• E.g. Proteus

26. THE STRUTURES EXTERNAL TO THE
CELL WALL

27. THE STRUCTURES EXTERNAL TO THE
CELL WALL

28. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• Motility enables bacteria to move toward a
favorable environment.
• Taxis – the movement of a bacteria toward or
away from a particular stimulus.
• Chemotaxis – chemicals like oxygen, ribose and
galactose.
• Phototaxis – light.
• Attractant – positive chemotactic signal.
• Repellent - negative chemotactic signal.

29. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• H antigen – flagellar protein useful for
distinguishing serovars.
• Serovars – Variations within a species of gram
negative bacteria.
• E.g.
• E. coli. has at least 50 different H antigens.
• Serovar E. coli. o157:H7 are associated with
foodborne epidemics.

30. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• AXIAL FILAMENTS
• Anchored at one end of the spirochete.
• Have a structure similar to flagella.
• Filament rotation produces a movement of the
outer sheath.
• Propels the bacteria in a spiral motion
(corkscrew motion).
• E.g. Treponema pallidum – syphilis
• Borrelia burgdorferi – Lyme disease

31. THE STRUCTURES EXTERNAL TO THE
CELL WALL

32. THE STRUCTURES EXTERNAL TO THE
CELL WALL

33. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• FIMBRIAE AND PILI
• Many gram negative bacteria contain hairlike
appendages.
• Used for attachment and transfer of DNA.
• Consists of a protein called pilin arranged
helically around a central core.

34. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• Fimbriae – can occur at the poles of the
bacterial cell.
• Or evenly distributed over the entire cell surface.
• Number to few or several hundred per cell.
• Enable cell to attach to surfaces including other
cells.
• E.g. Neisseria gonorrhoeae – colonizes mucus
membrane.

35. THE STRUCTURES EXTERNAL TO THE
CELL WALL

36. THE STRUCTURES EXTERNAL TO THE
CELL WALL
• Pili – usually longer than fimbriae.
• Number only to one or two per cell.
• Conjugation – Transfer of DNA from one
bacterial cell to another.
• Pili for these are called conjugation pili.

37. THE CELL WALL
• Cell wall – a complex, semirigid structure
responsible for the shape of the cell.
• Protects cell from adverse changes in the outside
environment.
• Almost all prokaryotes have cell walls.
• Major function is to prevent bacterial cells from
rupturing.
• Maintain the shape of the bacterium.
• Serve as point of anchorage for flagella.

38. THE CELL WALL
• Clinical importance
• Contributes to Pathogenecity
• Site of action of some antibiotics.
• Cell wall composition used to differentiate major
types of bacteria.

39. THE CELL WALL
• COMPOSITION AND CHARACTERISTICS
• Peptidoglycan – Macromolecular network
that composes cell wall.
• Peptidoglycan is also known as murein.
• Present either alone or in combination with
other substances.
• Peptidoglycan consists of a repeating
disaccharide unit attached by polypeptides.
• It forms a lattice that surrounds the entire cell.

40. THE CELL WALL
• Disaccharide portion is made up of N-
acetylglucosamine (NAG) and N-acetylmuramic
acid (NAM).
• NAM and NAG molecules are linked in rows of
10 to 65 sugars to form the carbohydrate
backbone.
• Adjacent rows are linked by polypeptides.
• The polypeptides could either be a tetrapeptide
side chain or peptide crossbridge.

41. THE CELL WALL
• Penicillin interferes with the final linking of the
peptidoglycan rows by peptide crossbridges.
• The cell wall is greatly weakened and the cell
undergoes lysis.
• Lysis – is the destruction of caused by rupture of
the plasma membrane and the loss of cytoplasm.

42. GRAM POSITIVE CELL WALLS
• Thick rigid structure of peptidoglycan layers.
• Gram-positive bacteria also contain teichoic
acids.
• Teichoic acids primarily consist of alcohol and
phosphate.
• Alcohol could be ribitol and glycerol.

43. GRAM POSITIVE CELL WALLS
• Teichoic acids could be
• A. Lipoteichoic acids – span the peptidoglycan
layer and is linked to plasma membrane.
• B. Wall teichoic acids – linked to the
peptidoglycan layer.
• Teichoic acid may have a role in binding and
regulating movement of cations and prevents
extensive cell wall breakdown and lysis.

44. GRAM POSITIVE CELL WALLS
• Teichoic acids provide much of the wall’s
antigenic specificity.
• Makes it possible to identify bacteria.
• Gram-positive cell walls covered with
polysaccharides allow them to be grouped to
significant types.

45. GRAM NEGATIVES CELL WALLS
• Cell wall consists of one or a very few layers of
peptidoglycan and an outer membrane.
• Peptidoglycan is bonded to lipoproteins.
• Lipoproteins are located in the outer membrane
and in the periplasm.
• Periplasm contains a lot of degradative enzymes
and transports proteins.
• Gram-negative having small amount of
peptidoglycan means they are more susceptible
to mechanical breakage.

46. GRAM NEGATIVE CELL WALLS
• Outer membrane of the gram-negative cell
consists of LPS, Lipoproteins, and
phospholipids.
• Outer membrane specialized functions:
• Strong negative charge evades phagocytosis and
complement.
• Barriers against antibiotic, digestive
enzymes, detergents and etc.

47. GRAM NEGATIVE CELL WALLS
• The gram-positive cell wall has porins.
• Porins are protein channels.
• It allows the entrance of molecules like
nucleotides, disaccharides, amino acids, vitamin B12
and iron.
• LPS has O polysaccharides that function as antigen
and is important for distinguishing species of gram-
negative bacterium.
• Lipid portion of LPS called lipid A is an endotoxin.
• Endotoxin is toxic to bloodstream and GIT.
• Causes fever and shock.

48. CELL WALLS

49. CELL WALL