Classification of microorganisms, On the basis of mode of nutrition,

1. General Classification and
Characterization of
Microorganisms
Dr. Sujeet Kumar Mrityunjay, PhD
Assistant Professor
Department of Life Science
School of Sciences
ITM University,Gwalior (Turari Campus)
Madhya Pradesh-474001 (India)
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2. Classification of living organisms is referred to as taxonomy and it aims to classify
living organisms by differentiating them and establishing relationships between groups
of organisms.
The kingdom of living organisms was termed as domain by Carl R. Woese in 1977.
Organisms are grouped in three domain systems namely eukarya, archaea and bacteria,
primarily on the basis of cell type. Other than the cell type, differences in rRNA, the
three domains differ in membrane lipid structure, transfer RNA molecules, and
sensitivity to antibiotics also account for classification of organisms.
2Classification of Microorganisms

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• Fungi are organisms that are grouped in a distinct kingdom within the eukaryotes. This
kingdom includes diverse organisms ranging from microorganisms such as yeasts or
moulds to large multicellular mushrooms.
• Fungi are ubiquitous and primarily found in the soil environment where they can adapt to
a variety of conditions and have a primary role as decomposers.
• As with bacteria, some fungi are pathogenic to both humans and plants (in fact
economically, fungi are the most important plant pathogens).
Fungi

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• Fungi are important in industrial processes involving fermentation and in biotechnology for the
production of antimicrobial compounds. (Penicillium spp. Antibiotic (penicillin) production).
• Metabolically, fungi are chemoheterotrophs. Most fungi are obligately aerobic but there are, of course,
exceptions.
• The zoosporic fungi found in ruminants are obligately anaerobic.
• The yeasts are facultative aerobes.
• These anaerobic fungi generally ferment sugars and in doing so produce a variety of useful by-
products, such as ethanol, acetic acid, and lactic acid, making them important commercially for
production of many staple foods (e.g., yogurt, cheese, bread, pickles) and alcoholic products such as
beer and wine.

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• In addition to their primary metabolism that supports biosynthesis and energy production, fungi are known
for producing secondary metabolites (compounds produced during the stationary phase of growth).
• These secondary metabolites have revolutionized medicine, biotechnology, and agriculture.
• For example, fungi are responsible for such antimicrobials as penicillin produced by Penicillium notatum ,
cephalosporin produced by Cephalosporium acremonium, and griseofulvin produced by Penicillium
griseofulvum .
• The fungal production of antimicrobials under in situ conditions is not well understood, it is hypothesized
that they help reduce competition from other microorganisms for nutrients.

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• Bacteria are organisms that consist of a single cell without a nucleus and with distinct structural,
physiological and evolutionary characteristics. Bacteria form one of the three domains of life; the others
are archaea and eukaryotes. Bacterial species and their habitats exhibit great diversity.
Bacteria

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ON THE BASIS OF
1. Mode Of Nutrition
2. Optimum Temperature Requirement For Growth
3. Optimal Ph For Growth
4. Salt Concentration
5. Gaseous Requirement
6. Morphology
7. Gram Staining
8. Flagella
9. Spore
CLASSIFICATION OF BACTERIA

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CLASSIFICATION OF BACTERIA ON THE BASIS OF MODE OF
NUTRITION
Those bacteria which gain energy from light.
Phototrops are further divided into two groups on the basis of source of electron.
a) Photolithotrops: these bacteria gain energy from light and uses reduced inorganic compounds such as H2S
as electron source. Eg. Chromatium okenii
b) Photoorganotrops: these bacteria gain energy from light and uses organic compounds such as succinate as
electron source.
Those bacteria gain energy from chemical compounds
They cannot carry out photosynthesis
Chemotrops are further divided into two groups on the basis of source of electron.
a) Chemolithotrops: they gain energy from oxidation of chemical compound and reduces inorganic
compounds such as NH3 as electron source. Eg. Nitrosomonas
b) Chemoorganotrops: they gain energy from chemical compounds and uses organic compound such as
glucose and amino acids as source of electron. eg. Pseudomonas pseudoflava
2. Chemotrops
1. Phototrops

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CLASSIFICATION OF BACTERIA ON THE BASIS OF MODE OF
NUTRITION
3. Autotrops
Those bacteria which uses carbondioxide as sole source of carbon to prepare its own food.
Autotrops are divide into two types on the basis of energy utilized to assimilate carbondioxide. i. e.
Photoautotrops and chemoautotrops
a) Photoautotrops: they utilized light to assimilate CO2. They are further divided into two group on the
basis of electron sources. i.e. Photolithotropic autotrops and Photoorganotropic autotrops
b) Chemoautotrops: they utilize chemical energy for assimilation of CO2
4. Heterotrops
• Those bacteria which uses organic compound as carbon source
• They lack the ability to fix CO2
• Most of the human pathogenic bacteria are heterotropic in nature
• Some heterotrops are simple, because they have simple nutritional requirement. However there are some
bacteria that require special nutrients for their growth; known as fastidious heterotrops.

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CLASSIFICATION OF BACTERIA ON THE BASIS OF OPTIMUM TEMPERATURE OF
GROWTH
1. 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
2. Psychrotrops (facultative psychrophiles)
• Those bacteria that can grow even at 0°C but optimum temperature for growth is (20-30)°C
3. Mesophiles
•Those bacteria that can grow best between (25-40) °C but optimum temperature for growth is 37°C
•Most of the human pathogens are mesophilic in nature. Examples: E. coli, Salmonella, Klebsiella,
Staphulococci

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4. Thermophiles
CLASSIFICATION OF BACTERIA ON THE BASIS OF OPTIMUM TEMPERATURE OF
GROWTH
• 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

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5. Hypethermophiles
CLASSIFICATION OF BACTERIA ON THE BASIS OF OPTIMUM TEMPERATURE OF
GROWTH
• Those bacteria that have optimum temperature of growth above 80°C.
• Mostly Archeobacteria are hyperthermophiles.
• Monolayer cell membrane of Archeobacteria is more resistant to heat and they
adopt to grow in higher remperature.
• Examples: Thermodesulfo bacterium, Aquifex, Pyrolobus fumari, Thermotoga

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CLASSIFICATION OF BACTERIA ON THE BASIS OF OPTIMUM PH OF GROWTH
1. Acidophiles
• Those bacteria that grow best at 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
2. Alkaliphiles
• Those bacteria that grow best at alkaline pH
• Example: vibrio cholerae: oprimum pH of growth is 8.2
3. Neutriphiles
• Those bacteria that grow best at neutral pH (6.5-7.5)
• Most of the bacteria grow at neutral pH
• Example: E. coli

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• Those bacteria that require high concentration of NaCl for growth.
• Cell membrane of halophilic bacteria is made up of glycoprotein with high content of negatively (-Ve)
charged glutamic acid and aspartic acids. So high concentration of Na+ ion concentration is required
to shield the –ve charge.
• Example: Archeobacteria, Halobacterium, Halococcus
1. Halophiles
• Most of the bacteria do not require NaCl but can tolerate low concentration of NaCl in growth media
are called halotolerant
2. Halotolerant

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• Those bacteria that require oxygen and cannot grow in the absence of O2.
• These bacteria carryout only oxidative type of metabolism.
• Examples; Mycobacterium, Bacillus
CLASSIFICATION OF BACTERIA ON THE BASIS OF GASEOUS REQUIREMENT
1. Obligate aerobes
• Those bacteria that do not require O2 but can use it if available.
• Growth of these bacteria become batter in presence of O2
• These bacteria carryout both oxidative and fermentative type of metabolism
• Examples: E. coli, Klebsiella, Salmonella
2. Facultative anaerobes

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• Those bacteria do not require O2 for growth but can tolerate the presence of O2.
• Growth of these bacteria is not affected by the presence of O2.
• These bacteria have only fermentative type of metabolism.
• Example: lactobacillus
3. Aerotolerant anaerobes
• Those bacteria that do not require O2 for growth but can tolerate low concentration of
O2.
• At atmospheric level of Oxygen growth of these bacteria is inhibited.
• These bacteria only have oxidative type of metabolism
• Example: Campylobacter
4. Microaerophiles
CLASSIFICATION OF BACTERIA ON THE BASIS OF GASEOUS REQUIREMENT

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• Those bacteria that can grow only in absence of Oxygen.
• Oxygen is harmful to obligate anaerobes
• These bacteria have only fermentative type of metabolism
• Examples: Peptococcus, Peptostreptococcus, Slostridium, methanococcus
5. Obligate anaerobes
6. Capnophiles
• Those bacteria that require carbondioxide for growth.
• They are CO2 loving organism
• Most of the microaerophiles are capnophilic in nature
• Example: Campylobacter, Helicobacter pylori, Brucella abortus
CLASSIFICATION OF BACTERIA ON THE BASIS OF GASEOUS REQUIREMENT

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i) Diplococcus:- coccus in pair. Eg, Neissseria gonorrhoae, Pneumococcus
ii) Streptococcus:- coccus in chain. Eg. Streptococcus salivarius
iii) Staphylococcus:- coccus in bunch. Eg. Staphylococcus aureus
iv) Tetrad:- coccus in group of four.
v) Sarcina:- cocus in cubical arrangement of cell. Eg. Sporosarcina
CLASSIFICATION OF BACTERIA ON THE BASIS OF MORPHOLOGY
1. Coccus:
• These bacteria are spherical or oval in shape
• On the basis of arrangement, cocci are further classified as-

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i) Coccobacilli: Eg. Brucella
ii) Streptobacilli: chain of rod shape bacteria: Eg. Bacillus subtilis
iii) Comma shaped: Eg. Vibrio cholarae
iv) Chinese letter shaped: Corynebacterium dephtherae
2. Bacilli
CLASSIFICATION OF BACTERIA ON THE BASIS OF MORPHOLOGY
• These are rod shaped bacteria
• On the basis of arrangement, bacilli are further classified as-

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They are spiral shaped bacteria
Spirochaetes
3. Mycoplasma
They are cell wall lacking bacteria
Also known as PPLO (Pleuropneumonia like organism)
Mycoplasma pneumoniae
4. Spirochaetes
CLASSIFICATION OF BACTERIA ON THE BASIS OF MORPHOLOGY

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They have filamentous or branching structure
They resemble more closely to Fungi than bacteria
Example: Streptomyces
5. Rickettsiae and Chlamydiae
They are obligate intracellular parasites resemble more closely to viruses than bacteria
6. Actinomycetes
CLASSIFICATION OF BACTERIA ON THE BASIS OF MORPHOLOGY

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Cell wall of these bacteria is composed of peptidoglycan layer only.
Eg. Staphylococcus, Streptococcus, micrococcus
CLASSIFICATION OF BACTERIA ON THE BASIS OF GRAN STAINING
1. Gram positive bacteria
Cell wall of these bacteria is composed of Peptidoglycan and outer membrane.
Eg. E. coli, Salmonella
2. Gram negative bacteria

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Bacteria having single flagella in one end of cell.
Eg. Vibrio cholera, Pseudomonas aerogenosa
CLASSIFICATION OF BACTERIA ON THE BASIS OF FLAGELLA
1. Monotrichous bacteria
Bacteria having bundle of flagella in one end of cell.
Eg. Pseudomanas fluroscence
2. Lophotrichous bacteria

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4. Peritrichous bacteria
CLASSIFICATION OF BACTERIA ON THE BASIS OF FLAGELLA
Bacteria having single or cluster of flagella at both end of cell.
Eg. Aquaspirillium
3. Amphitrichous bacteria
Bacteria without flagella
Eg. Shigella
Bacteria having flagella all over the cell surface.
Eg. E. coli, Salmonella, Klebsiella
5. Atrichous bacteria

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Those bacteria that produce spore during unfavorable condition.
These are further divided into two group
CLASSIFICATION OF BACTERIA ON THE BASIS OF SPORE FORMATION
1. Spore forming bacteria
ii) Exospore forming bacteria
Spore produced outside the cell
Methylosinus
i) Endospore forming bacteria
Spore produced within the bacterial cell.
Bacillus, Clostridium, Sporosarcina etc
Those bacteria which do not produce spore.
Eg. E. coli, Salmonella
2. Non spore forming bacteria

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Thank you