Bacteria classification and nutrition

Unit I
Pharmaceutical Microbiology
B. Pharm III Sem.

Bacteria: Classification
 Bacteria are classified on various basis those are:
 Classification on the basis of
 Bergey's 4 Divisions (Gram Stainning and
Bacterial Cell Wall)
 Shape
 Mode of Nutrition
 Temperature Requirement
 Oxygen Requirement
 pH of Growth
 Osmotic Pressure Requirement
 Number of Flagella
 Spore Formation
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Gurunanak College of Pharmacy, Nagpur

 Bergey's 4 Divisions of Bacteria
 Division: Gracilicutes
 Gracilicutes (gracilis=slender, and cutis=skin) have a cell wall that is
consistent with being gram negative even though they do not necessarily
stain gram negative.
 Examples of gracilicutes include E. coli, Klebsiella pneumoniae, Neisseria,
Rickettsia, Trepanoma pallidum.
 Division: Firmicutes
 Firmicutes (firmus=strong, and cutis=skin) have mostly a gram
positive cell wall structure.
 Examples include Bacillus, Staphylococcus, Streptococcus, Clostridium,
Mycobacterium, Corynebacterium diphteriae.
 Division: Tenericutes
 Tenericutes (soft skin) have no cell wall. A notable example is mycoplasma.
 Division: Mendosicutes
 Mendosicutes (faulty skin) have no murein in cell walls, and are also known
as archaea. These can stain both gram positive or negative, since archaea
have a lot of variety. Defective cell wall with unusual cell wall composition.
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Difference Between Gram Positive and Gram
Negative Bacteria
Characteristic Gram Positive Gram Negative
Gram Staining Retain crystal violet
Appear violet colored
Decolorized and stained
by counter stain
Appear red coloured
Layers One Two
Peptidoglycan Layer Thick (Multilayered) Thin (Single layered)
Teichoic acid Present Absent
Perplasmic space Absent Present
Lipopolysaccharide
Content
Almost absent High
Lipid and lipoprotein Low High
Flagellar Rings Two Four
Toxins produced Exotoxin Endotoxin
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Characteristic Gram Positive Gram Negative
Resistance to physical
disruption
High Low
Cell wall disruption by
lysozyme
High Low
Resistance to drying High Low
Inhibition by basic dyes High Low
Susceptibility to anionic
detergents
High Low
Resistance to antibiotics Low High
Difference Between Gram Positive and Gram
Negative Bacteria (Contd…..)
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Shapes of Bacteria
There are three basic shapes of bacteria
 Spherical shaped: cocci (Singular: Coccus)
 Rod or cylindrical shaped: bacilli (Singular: Bacillus),
and
 Spiral shaped: Spirilla (Singular: spirillum)
Other Shapes:
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Spatial Arrangements and Shapes of bacterial
Cells
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 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.
 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.
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Autotrophs and Heterotrophs
 These bacteria synthesize all their food from inorganic
substances (H2O, C02, H2S salts).
 The autotrophic bacteria are of two types:
(i) Photoautotrophsand (ii) Chemoautotrophs
 (i) Photoautotrophs
 These bacteria capture the energy of sunlight and transform it
into the chemical energy.
 In this process, CO2 is reduced to carbohydrates.
 The hydrogen donor is water and the process produce free
oxygen.
 Photoautotroph has Chlorophyll pigment in the cell and its
main function is to capture sunlight e.g., Cyanobacteria.
 Some photoautotrophic bacteria are anaerobes and have
bacteriochlorophyll and bacteriovirdin pigments respectively.
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Autotrophs and Heterotrophs (Contd…..)
 Purple Sulphur Bacteria:
 These bacteria have the pigment bacteriochlorophyll located
on the intracytoplasmic membrane i.e., thylakoids. These
bacteria obtain energy from sulfur compounds
e.g., Chromatiiun. Theopedia rosea, Thiospirilium.
 Green Sulphur Bacteria:
 These bacteria use hydrogen sulfide (H2S) as hydrogen donor.
The reaction takes place in the presence of light and pigment
termed as bacteriovirdin or bacteriopheophytin
or chlorobium chlorophyll e.g., Chlorobium limicola,
Chlorobacterium etc.
 These bacteria take hydrogen from inorganic sources
like sulphides and thiosulphates. Therefore, these bacteria are
also known as photolithographs.
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Autotrophs and Heterotrophs (Contd…..)
 (ii) Chemoautotrophs
 These bacteria do not require light (lack the light phase but
have the dark phase of photosynthesis) and pigment for their
nutrition.
 These bacteria oxidize certain inorganic substances with the
help of atmospheric oxygen.
 This reaction releases the energy (exothermic) which is used
to drive the synthetic processes of the cell.
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Bacterial Classification as per Gaseous
Requirement
Depending on the gaseous requirement, Bacteria are
classified in four types as follows…..
Aerobic Microorganisms
Anaerobic Microorganisms
Facultative Microorganisms
Microaerophilic Microorganisms
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 Require oxygen to live.
 Example: Pseudomonas, common nosocomial
pathogen
Aerobic Bacteria
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Anaerobic Bacteria
 Cannot use oxygen and are harmed by the presence of
toxic forms of oxygen.
 Examples: Clostridium bacteria that cause tetanus and
botulism.
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Facultative Anaerobic Bacteria
 Can use oxygen, but can grow in its absence.
 They have complex set of enzymes.
 Examples: E. coli, Staphylococcus, yeasts, and many
intestinal bacteria.
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Microaerophilic Bacteria
 Require oxygen, but at low concentrations.
 Sensitive to toxic forms of oxygen.
 Example: Campylobacter.
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Bacterial Classification as per Temperature
Requirement
Depending on the temperature requirement for optimum
growth, Bacteria are classified in three types as follows…..
Thermophiles
Mesophiles
Psycchrophiles
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Requirement
 Thermophiles:
Those bacteria that can best grow above 45˚C.
Thermophiles capable of growing in mesophilic range are called
facultative thermophiles.
True thermophiles are called as Stenothermophiles, they are obligate
thermophiles,
Thermophils contains saturated fattyacids in their cell membrane so
their cell membrane does not become too fluid even at higher
temperature.
Examples: Streptococcus thermophiles, Bacillus stearothermophilus,
Thermus aquaticus.
 Hypethermophiles:
Those bacteria that have optimum temperature of growth above 80C.
Mostly Archeobacteria are hyperthermophiles.
Monolayer cell membrane of Archeobacteria is more resistant to heat
and they adopt to grow in higher remperature.
Examples: Thermodesulfobacterium, Aquifex, Pyrolobus fumari,
Thermotoga.
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 . Mesophiles:
Those bacteria that can grow best between (25-40)o C but optimum
temperature for growth is 37˚̊C
Most of the human pathogens are mesophilic in nature.
Examples: E. coli, Salmonella, Klebsiella, Staphylococci.
Requirement
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 Psychrophiles:
 Bacteria that can grow at 0°C or below but the optimum temperature of
growth is 15 °C or below and maximum temperature is 20°C are called
psychrophiles
 Psychrophiles have polyunsaturated fatty acids in their cell membrane
which gives fluid nature to the cell membrane even at lower
temperature.
 Examples: Vibrio psychroerythrus, vibrio marinus, Polaromonas
vaculata, Psychroflexus.
 Psychrotrops (facultative psychrophiles):
 Those bacteria that can grow even at 0°C but optimum temperature for
growth is (20-30)°C
Requirement
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 Acidophiles:
 These bacteria grow best at an acidic pH.
 The cytoplasm of these bacteria are acidic in nature.
 Some acidopiles are thermophilic in nature, such bacteria are called
Thermoacidophiles.
 Examples: Thiobacillus thioxidans, Thiobacillus, ferroxidans,
Thermoplasma, Sulfolobus
 Alkaliphiles:
 These bacteria grow best at an alkaline pH.
 Example: Vibrio cholerae optimum ph of growth is 8.2.
 Neutrophiles:
 These bacteria grow best at neutral pH (6.5-7.5).
 Most of the bacteria grow at neutral pH.
 Example: E. coli
Bacterial Classification as per pH Requirement
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 Halophiles:
 Require moderate to large salt concentrations.
 Cell membrane of halophilic bacteria is made up of glycoprotein with
high content of negatively charged glutamic acid and aspartic acids. So
high concentration of Na+ ion concentration is required to shield the –
ve charge.
 Ocean water contains 3.5% salt. Most such bacteria are present in the
oceans.
 Archeobacteria, Halobacterium, Halococcus.
Bacterial Classification as per Requirement of
osmotic pressure
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 On the basis of flagella the bacteria can be classified as:
 Atrichos: – These bacteria has no flagella.
Example: Corynebacterium diptherae.
 Monotrichous: – One flagellum is attached to one end of the
bacteria cell. Example: – Vibro cholerae.
 Lophotrichous: – Bunch of flagella is attached to one end of
the bacteria cell. Example: Pseudomonas.
 Amphitrichous: – Bunch of flagella arising from both end of
the bacteria cell. Example: Rhodospirillum rubrum.
 Peritrichous : – The flagella are evenly distributed surrounding the
entire bacterial cell. Example: Bacillus
Bacterial Classification as per Presence and
Number of Flagella
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Bacterial Classification as per Presence and
Number of Flagella
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 Spore forming bacteria:
 Those bacteria that produce spore during unfavorable condition.
 These are further divided into two groups:
 i) Endospore forming bacteria:
 Spore is produced within the bacterial cell.
 Examples. Bacillus, Clostridium, Sporosarcina etc
 ii) Exospore forming bacteria:
 Spore is produced outside the cell.
 Example. Methylosinus
 Non sporing bacteria:
 Those bacteria which do not produce spores.
 Eg. E. coli, Salmonella.
Bacterial Classification as per Formation of spores
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Bacterial Nutrition
Type of Nutrient Function Examples
Carbon Source Provide energy through
oxidation and provides various
structural components of
bacterial cell
Carbon di oxide and any
other carbon containing
organic or inorganic
substances
Nitrogen Source Necessary for synthesis of
amino acids, nucleic acids and
coenzymes
Atmospheric nitrogen and
other inorganic nitrogen
compounds like NO or NH4
+
and organic compounds such
as aspargine or glutamine
Inorganic Ions Works as cofactors for enzymes
in various biochemical
reactions, in storage of energy
and electron transport system
Mg2
+, Mn2
+, Fe2
+, PO4
2-, Na+,
K+ and Mo
Vitmines and
Other Essential
metabolites
Provide complex organic
compounds which an organism
is unable to synthesize
Vitamines, amino acids,
purines, pyrimidines,
coenzymes and heme
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Some Terminologies
 Media or Medium (Bacteriological)
 Bacterial Culture
 Fastidious organism
Bacterial Nutrition
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 Liquid Media:
Bacteriological media in liquid physical state is called as broth
medium. It is meant for growth of pure batch cultures. In broth
medium bacterial cells are present in suspended form.
 Semisolid Media
Semisolid media are used widely for the isolation of pure
cultures, for estimating viable bacterial populations, and a variety of
other purposes. e.g. Nutrient Agar, EMB Agar
The usual gelling agent for solid or semisolid medium is Agar,
a hydrocolloid derived from red algae. Agar is used because of its
unique physical properties (it melts at 100oC and remains liquid until
cooled to 40oC, the temperature at which it gels) and because it cannot
be metabolized by most bacteria. Hence as a medium component it is
relatively inert
Bacterial Nutrition (Types of Bacterial Media)
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Natural or Complex Media Synthetic Media
(Chemically Defined Media)
Chemical composition may not be
so clearly known
The exact chemical composition is
known
Usually contains materials of
biological origin such as blood or
milk, peptone yeast extract and beef
extract.
Synthetic media usually contains
peptone water medium
complex media provides a full range
of growth factors
Synthetic media provides only
limited growth factors.
Used for the cultivation of
heterotrophic microorganisms
Used for the cultivation of
autotrophs
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1. Basal Media.
Basal media are those that may be used for growth (culture) of
bacteria that do not need enrichment of the media.
Examples: Nutrient broth, nutrient agar and peptone water.
2. Enriched Media.
Enriched media contain the nutrients required to support the
growth of a wide variety of organisms, including some fastidious ones.
The media are enriched usually by adding blood, serum or egg.
Examples: Blood agar
3. Enrichment Media
Enrichment media promotes the growth of a particular organism
by providing it with the essential nutrients and rarely contains certain
inhibitory substance to prevent the growth of normal competitors.
Example: Selenite F broth favors the growth of Salmonella
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4. Selective Media.
These media favour the growth of a particular bacterium by
inhibiting the growth of undesired bacteria and allowing growth of
desirable bacteria.
Examples: MacConkey agar, Lowenstein-Jensen media, tellurite
media
(Tellurite inhibits the growth of most of the throat organisms
except diphtheria bacilli).
(Antibiotic may be added to a medium for inhibition.)
5. Differential (Indicator) Media.
An indicator is included in the medium. A particular organism
causes change in the indicator, e.g. blood, neutral red, tellurite.
Examples: Blood agar and MacConkey agar are indicator media.
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6. Transport Media. (Media For Transportation)
These media are used when specie-men cannot be cultured soon
after collection.
Examples: Cary-Blair medium, Amies medium, Stuart medium.
7. STORAGE MEDIA (Media for Preservation).
Media used for storing the bacteria for a long period of time.
Examples: Egg saline medium, chalk cooked meat broth
 8. Assey Media
These media are used for the assay of vitamins, amino acids, and
antibiotics. E.g. antibiotic assay media are used for determining
antibiotic potency by the microbiological assay technique.
Other types of medium include;
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9. Media for enumeration of bacteria
Specific kinds of media are used for determining the bacterial
content of such materials as milk and water. Their composition must
adhere to prescribed specifications. e.g., Nutrient agar
10. Media for characterization of bacteria
A wide variety of media are conventionally used to determine the
types of growth produced by bacteria, as well as to determine their
ability to produce certain chemical changes.
11. Maintenance media
Satisfactory maintenance of the viability and physiological
characteristics of a culture over time may require a medium different
from that which is optimum for growth. Prolific, rapid growth may also
be associated with rapid death of the cells at the end of the growth
phase. For example, glucose in a medium frequently enhances growth,
but acid harmful to the cells is likely to be produced. Therefore,
omission of the glucose is preferable in a maintenance medium.
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Thank You…..
Gurunanak College of Pharmacy, Nagpur 35

Bacteria classification and nutrition

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