3. Morphological classification
S.N Type of Bacteria Shape
1 True Bacteria
I) -Coccus Round
II) -Bacillus Rod
2 Spirillum Small, spiral
3 Spirochete Longer,
slender-spiral
4 Vibro Coma (,)
5 Mycoplasm Irregular
6 Actinomycine Sun Light ray
Bacteria canbe classified into sixmajor groups on morphological basis.
4. • Cocci – These are spherical or oval cells. On the
basis of arrangement of individual organisms
they can be described as
– Monococci (Cocci in singles)
Ex.- Monococcus spp.
– Diplococci (Cocci in pairs)
Ex.- Streptococcus pneumoniae
– Staphylococci (Cocci in grape-like clusters)
Ex.- Staphylococcus aureus
– Streptococci (Cocci in chains)
Ex.- Streptococcus pyogenes
– Tetrad (Cocci in group of four)
Ex.- Micrococcus spp.
– Sarcina(Cocci in group of eight) 3
1. TRUE BACTERIA
6. •
6
Bacilli – These are rod-shaped bacteria. On the basis of
arrangement of organisms, they can be described as
– Monobacilli
– Diplobacilli
– Streptobacilli
– Palisades
– Coccobacilli
7. 2. Spirillum
These are small, regularly coiled, rigid organisms
measuring about 3–4 um in length.
Each coil measures about 1 um.
Spirilla are motile with groups of flagella at both ends.
example - Spirillum minus.
8. 8
3. Spirochaetes
These are relatively longer, slender, non-branched
microorganisms of spiral shape having several coils.
9. 9
4. vibrios
These are small slightly curved rods measuring 3–4
um in length by 0.5 um in width.
Most vibrios are motile with a single flagellum at
one end.
e.g. Vibrio cholerae.
10. 5. Mycoplasmas
• These bacteria lack in rigid cell wall (cell
wall lacking) and are highly pleomorphic
and of indefinite shape.
• They occur in round or oval bodies and in
interlacing filaments.
10
11. 11
6. ACTINOMYCETES (actin- ray, mykes-fungus)
These are rigid organisms like true bacteria but they resemble
fungi in that they exhibit branching and tend to form filaments.
They are termed such because of their resemblance to sun
rays when seen in tissue sections.
18. Oxygendependence
18
• Aerobe (grow in ambient temperature,which
contains 21%O2and asmall amount of CO2,
0.03%)
• Obligateaerobes– Strictly require O2for their
growth (Pseudomonasaeruginosa)
• Microaerophilic (grow under reduced O2,5-
10%and increased CO2,8-10%)-Campylobacter
jejuni,Helicobacter pylori
19. Oxygendependence
19
• Facultativeanaerobe(capable of growing
either in presence or absenceof O2)-E.coli
• Obligateanaerobe– Clostridium spp.
• Capnophilic(require increased concentration
of CO2,i.e., 5-10%) –
H. influenzae,
N. gonorrhoeae
• Aerotolerant 19
•
•
•
•
20. pH
20
• Acidophiles(Lactobacillus acidophilus)
• Alkaliphiles (Vibrio)
• Neutralophiles(pH 6-8)
Majority of the medically important bacteria grow
best at neutral or slightly alkaline reaction (pH
7.2-7.6)
