The document discusses the morphology of bacteria, highlighting the size range of prokaryotic cells and their efficient nutrient exchange mechanisms, which are influenced by surface area to volume ratios. It categorizes different shapes of bacteria, such as cocci, bacilli, vibrio, and spiral forms, and describes their growth patterns and arrangements. Additionally, it mentions specialized structures like endoflagella in spirochetes and the filamentous nature of actinomycetes.

1. Morphology of Bacteria

2. Size
PROKARYOTES
• Cells of width as small as 0.1-0.2 µm to more than 50 µm in diameter
• Very large prokaryotes, such as surgeonfish symbiont Epulopiscium fishelsoni,
are up to 50 µm in diameter and can be more than 0.5 mm (500 µm) in
length.
• However, the dimensions of an average rod-shaped prokaryote, the bacterium
Escherichia coli, for example, are about 1 x 3 µm
EUKARYOTES
• Typical cells may be 2 µm to more than 200 µm in diameter.

3. SIZE VS BIOLOGICAL
PROPERTIES
• The rate at which nutrients and waste products pass into and out of a cell, a
factor that can greatly affect cellular metabolic rates and growth rates, is in
general inversely proportional to cell size.
WHY
• This is because transport rates are to some degree a function of the
amount of membrane surface area available relative to cell volume, and
small cells have more surface available than do large cells.
• Most readily explained mathematically in case of a spherical cell:
– Volume (V) = 4/3πr3
whereas
– surface Area (SA) = 4πr2
• Thus surface are to volume ratio in a spherical cell is 3/r.
• Thus a cell with a smaller r value has a higher SA/V than a larger cell and
thus can have a more efficient nutrient exchange with its surroundings
than a larger cell.
• Higher growth and metabolic rate in turn can cause major physicochemical
changes in an ecosystem over a relatively short period of time.

5. Coccus
• Coccus (0.5 -1.0 μ dia.)
- Individual cell
- Pair
- Chain
- Irregular grapelike clumps
- Square group of four cells forming
tetrads
- Cubical packets of eight cells

6. Individual cells
Cells divide and completely
separates from each other
eg. Chlamydia trachomatis

7. Pair
Cells divide in single plane
and two cells remain attached
In pairs as a result of incomplete
Separation.
eg. Moraxella catarrhalis,
Neisseria gonorrhoeae
Neisseria meningitidis

8. Chain
Cells divide in single plane and
adhere after repeated divisions
eg. Streptococcus pyogenes,
S. mutans,
S. lactis,
Enterococcus faecalis
Lactococcus lactis

10. Irregular clumps
Cells divide in random planes
to generate irregular
grape-like clumps
eg. Staphylococcus aureus

12. Tetrads
Cells divide in two planes to
form square group of four
cells called tetrads
Micrococcus luteus

14. Cubical
Cells divide in three planes to
produce cubical packets of
eight cells called Sarcina
eg. Sarcina marcesens

15. Bacillus
• Bacillus (0.5 to 20 μ long)
- Pair = Diplobacillus
- Chain = Streptobacillus
- Coccobacilli
1. Rods, sometimes called bacilli (singular, bacillus), differ considerably in
their length-to-width ratio
2. The coccobacilli being so short and wide that they resemble cocci.
3. The shape of the rod’s end often varies between species and may be flat,
rounded, cigar-shaped, or bifurcated.

16. Diplobacillus
Klebsiella rhinoscheloromatis

17. Streptobacillus
Streptobacillus moniliformis
Bacillus megaterium

18. Coccobacillus
Haemophilus influenzae
Bordetella pertussis
Haemophilus influenzae

19. Vibrio
1) Most closely resemble rods, as they are comma-shaped
2) Curve rod that resemble a comma
3) Eg. Vibrio cholerae

20. Spiral
1) Helical shape with a thick, rigid cell wall
2) Eg. Rhodospirillum rubrum

21. Spirochetes
• Helical but with thin flexible cell wall
• Have a unique, internal flagellar arrangement (endoflagella)
• Eg. Leptoospira

22. Actinomycetes
• Actinomycetes typically form long filaments called hyphae that may
branch to produce a network called a mycelium.
• In this sense, they are similar to filamentous fungi, a group of
eucaryotic microbes.

23. Budding bacteria
Hyphomicrobium cresentus

24. Stalked
Caulobacter cresentus

25. Flat, square to rectangular

27. Pleomorphic

28. Epulopicium fishelsoni
length~ 600 µm

29. Thiomargarita namibiensis

30. End

31. Endoflagella
Borrelia burgdorferi
1) Endoflagella run along length in the corkscrew shaped spirochetes.
2) Although these bacteria are gram negative (with a double membrane envelope
structure), they possess only 2, to 4 rings (the S, M and presumably the C rings
and sometimes an extra pair) in the basal complex - they lack the P and L
rings.
3) The result is that the basal complex does not cross the outer membrane and
the filaments lie between the peptidoglycan and outer membrane (in the
periplasm) wrapped around the cell (giving it a spiral appearance) as shown
above.
4) These internal flagella form a bundle or axial filament.