U 1, 7 of 7 classification of bacteria

Date:4/26/2021 www. qadricohs.edu.pk FB Page: Qadri College of Health Sciences, Karachi, Sindh, Pakistan. 1
QADRI COLLEGE OF HEALTH SCIENCES, KARACHI
U-1, 7 OF 7
CLASSIFICATION OF BACTERIA ON
THE BASIS OF THEIR NUTRITONAL
REQUIREMENT AND MORPHOLOGY
Faculty: Aftab H. Abbasi
RN, DCHN, BSN, MA, LL.B
Lecturer Nursing
Qadri College of Health Sciences Karachi

DIFFERENT NUTRITONAL TYPES OF BACTERIA
• Nutrition is substances used in biosynthesis and energy
production and therefore are required for all living things.
• Bacteria, like all living cells, require energy and nutrients to build
proteins and structural membranes and drive biochemical
processes.
• Bacteria require sources of carbon, nitrogen, phosphorous, iron
and a large number of other molecules.
• Carbon, nitrogen, and water are used in the highest quantities.
• The nutritional requirements for bacteria can be grouped
according to the carbon source and the energy source.
• Some types of bacteria must consume pre-formed organic
molecules to obtain energy, while other bacteria can generate their
own energy from inorganic sources.

On the basis of energy source organisms are
designated as:
Phototrophs:
The organisms which can utilize light as an
energy source are known as phototrophs.
These bacteria gain energy from light.
Chemotrophs:
These bacteria gain energy from chemical
compounds. They cannot carry out
photosynthesis.

DIFFERENT NUTRITONAL REQUIREMENTS OF BACTERIA
On the basis of electron source organisms are
designated as:
Lithotrophs:
-Some organisms can use reduced organic compounds
as electron donors and are termed as Lithotrophs.
-They can be Chemolithotrophs and Photolithotrophs
Organotrophs:
-Some organisms can use organic compounds as
electron donors and are termed as organotrophs.
-Some can be Chemoorganotrophs and
Photoorganotrophs.

On the basis of carbon source bacteria may be:
- All organisms require carbon in some form for use in
synthesizing cell components.
- All organisms require at least a small amount of CO2.
- However, some can use CO2 as their major or even sole
source of carbon; such organisms are termed as
Autotrophs (Autotrophic bacteria).
- Others require organic compounds as their carbon source
and are known as Heterotrophs (Heterotrophic bacteria).

Thus, bacteria may be either:
Photo-lithotrops:
These bacteria gain energy from light and use reduced inorganic compounds such as (H2S)
Hydrogen Sulfide as a source of electrons.
eg: Chromatium okeinii. (a Gram-negative bacterium found in water)
Photo-organotrophs:
These bacteria gain energy from light and use organic compounds such as Succinate
(Succinate or succinic acid is involved in several chemical processes in the body.) as a source of
electrons.
eg; Rhodospirillum. (genus of photosynthetic bacteria)
Chemo-lithotrophs:
These bacteria gain energy from reduced inorganic compounds such as NH3 (Ammonia is a
colorless gas consists of hydrogen and nitrogen) as a source of electron. eg; Nitrosomonas. (genus
of Gram-negative bacteria)
Chemo-organotrophs:
These bacteria gain energy from organic compounds such as glucose and ammino acids as a
source of electrons.
eg; Pseudomonas (The bacteria are found widely in the environment, such as in soil, water, and
plants) pseudoflora.

Morphology:
The study of the size, shape, and structure of
animals, plants, and microorganisms and of the
relationships of their constituent parts.

Size of bacteria:
- Unit of measurement used in bacteriology is
micron or micrometre (µm).
- One micron is equal to one thousandth of
millimetre.
- One nanometre (nm) or millimicron (mµ) is equal
to one thousandth of a micron or one millionth of
a millimetre.
- One Angstrom unit (Å) is equal to one tenth of a
nanometre.

Limit of resolution:
- Limit of resolution with the unaided
human eye is 200 microns (0.2mm)
- Bacteria are even much smaller and can
be visualized only under magnification.
- Bacteria of medical importance generally
measure 0.2- 1.5µm in diameter and
about 3-5µm in length

Shape of Bacteria:
- Cocci – spherical/ oval shaped major groups
- Bacilli – rod shaped
- Vibrios – comma shaped
- Spirilla – rigid spiral forms
- Spirochetes – flexible spiral forms
- Actinomycetes – branching filamentous bacteria
- Mycoplasmas – lack cell wall
Other shapes of bacteria
• Comma shaped
• Spirochetes
• Spirilla

Anatomy of A Bacterial Cell
- Outer layer – two components:
1. Rigid cell wall
2. Cytoplasmic (Cell/ Plasma) membrane –
present beneath cell wall.
- Cytoplasm – cytoplasmic inclusions,
ribosomes, mesosomes and nucleus.
- Additional structures – plasmid, slime layer,
capsule, flagella, fimbriae (pili), spores.

Structure & Function of Cell Components:
CELL WALL :
Outermost layer, encloses cytoplasm
1. Confers shape and rigidity
2. 10 - 25 Nm (Nanometer) thick
3. Composed of complex polysaccharides
(peptidoglycan/ mucopeptide) - formed
by N acetyl glucosamine (NAG) & N
acetyl muramic acid (NAM) alternating in
chains, held by peptide chains.

4. Carries bacterial antigens – important in
virulence & immunity.
5. Chemical nature of the cell wall helps to
divide bacteria into two broad groups –
Gram positive & Gram negative.
6. Gram +ve bacteria have simpler chemical
nature than Gram –ve bacteria.
7. Several antibiotics may interfere with cell
wall synthesis e.g. Penicillin,
Cephalosporins

Cytoplasmic (Plasma) membrane:
- Thin layer 5-10 nm, separates cell wall from
cytoplasm
- Acts as a semipermeable membrane:
controls the inflow and outflow of
metabolites
- Composed of lipoproteins with small
amounts of carbohydrates

Other Cytoplasmic Components:
- Ribosomes – protein synthesis
- Mesosomes –
1. Multilaminated structures formed as invaginations of plasma
membrane.
2. Principal sites of respiratory enzymes
3. Coordinate nuclear & cytoplasmic division during binary fission
4. More prominent in Gram +ve bacteria.
- Intracytoplasmic inclusions –
Reserve of energy & phosphate for cell metabolism.
e.g. Metachromatic granules in diphtheria bacilli

Nucleus:
The nucleus is a membrane-bound
organelle that contains genetic material
(DNA) of eukaryotic organisms. As such,
it serves to maintain the integrity of the
cell by facilitating transcription and
replication processes. It's the largest
organelle inside the cell taking up about
a tenth of the entire cell volume.

Additional Organelles:
1. Plasmid:
- Extranuclear genetic elements consisting of
DNA
- Transmitted to daughter cells during binary
fission
- May be transferred from one bacterium to
another
- Not essential for life of the cell
- Confer certain properties
e.g. drug resistance, toxicity

2. Capsule & Slime layer –
• Viscous layer secreted around the cell wall.
• Polysaccharide / polypeptide in nature.
a) Capsule – sharply defined structure, antigenic in
nature
• Protects bacteria from lytic (lysis refers to the disintegration of a cell by disruption of its plasma
membrane) enzymes.
• Inhibits phagocytosis
• Stained by negative staining using India Ink
• Can be demonstrated by Quellung reaction (capsule
swelling reaction)
b) Slime layer – loose undemarcated secretion.

3. Flagella –
• Long (3 to 12 µm), filamentous surface
appendages
• Organs of locomotion.
• Chemically, composed of proteins called
flagellins.
• The number and distribution of flagella on the
bacterial surface are characteristic for a given
species - hence are useful in identifying and
classifying bacteria.
• Flagella may serve as antigenic determinants
(e.g. the H antigens of Gram-negative enteric
bacteria).
• Presence shown by motility e.g. hanging drop
preparation.

Aftab H. Abbasi
RN, DCHN, BSN, MA, LL.B
Lecturer Nursing

U 1, 7 of 7 classification of bacteria

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