This document discusses the nutritional classification of microbes. It explains that microbes are classified based on their carbon, energy, and electron sources into categories such as autotrophs and heterotrophs. Some key points: - Autotrophs use inorganic carbon sources while heterotrophs use organic carbon sources. - Phototrophs use light as an energy source while chemotrophs use chemical oxidation. - Lithotrophs use inorganic electron sources while organotrophs use organic electron sources. - Combining these yields classifications like photolithoautotrophs, photoorganoheterotrophs, and chemoorganoheterotrophs. - Growth factors like

1. NUTRITIONAL CLASSIFICATION OF MICROBES
Lecture by:
Dr. Aswartha Harinath Reddy M.Sc, Ph.D
Department of Life Sciences
Srikrishnadevaraya University
Anantapur –A.P. India
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2. The microbial cell composition shows that over 95% of cell dry
weight is made up carbon, oxygen, hydrogen, nitrogen, sulfur,
phosphorus (C, O, H, N, S, P), potassium, calcium, magnesium,
and iron (K, Ca, Mg, and Fe).
These are called macroelements or macronutrients because
they are required by microorganisms in relatively large
amounts.
The first six (C, O, H, N, S, and P) are components of
carbohydrates, lipids, proteins, and nucleic acids.

3. The remaining four macroelements exist in the cell as cations and
play a variety of roles.
For example, potassium (K+) is required for activity by a number of
enzymes (Co-factor enzymes).
Ex: Aminoacyl tRNA synthetase, Pyruvate kinase.
Calcium (Ca2+), contributes to the heat resistance of bacterial
endospores.
Magnesium (Mg2+) serves as a cofactor for many enzymes, like
ATPase, Kinases and stabilizes ribosomes and cell membranes.
 Iron (Fe2+ and Fe3+) is a part of cytochromes and a cofactor for
enzymes like catalase, peroxidase and electron-carrying proteins.

4. All organisms, including microorganisms, require several
micronutrients or trace elements besides macroelements.
The micronutrients manganese, zinc, cobalt, nickel, molybdenum, and
copper are needed by most cells.
 For example, zinc (Zn2+) is a co-factor for DNA Polymerase and
Alcoholic dehydrogenase.
Manganese (Mn2+) is a co-factor for Superoxide dismutase (SOD).
Molybdenum (Mo2+) is required for nitrogen fixation and cofactor
Nitrogenase and Nitrate reductase.
Cobalt (Co2+) is a major component of vitamin B12.

5. Nutritional Types of Microorganisms
Microorganisms can be classified as Autotrophs and Heterotrophs
based on their sources of carbon.
• Autotrophs: can use CO2 as a source of carbon or Organisms
obtain carbon form inorganic source.
• Many microorganisms are autotrophic, and most of these carry out
photosynthesis and use light as their energy source.
• Example: Cyanobacteria bacteria and Algae.

6. Heterotrophs:
• Organisms which obtain carbon from organic source is called
Heterotrophs.
• The reduction of CO2 is a very energy-expensive process. Thus
many microorganisms cannot use CO2 as their carbon source.
• Organisms that use reduced, organic molecules as carbon sources
are heterotrophs.

7. Energy sources:
• There are only two sources of energy available to organisms:
• (1) light energy, and (2) the energy derived from oxidizing organic
or inorganic molecules.
• Phototrophs: use light as their energy source.
Ex: Algae, Cyanobacteria.
• Chemotrophs: obtain energy from the oxidation of chemical
compounds (either organic or inorganic).
• Ex: Fungi, Non photosynthetic bacteria, Protozoa.

8. Electron source:
• Lithotrophs: Organisms which use inorganic molecules
as their electron source, (H2O, H2, N2) is called
Lithotrophs.
• Organotrophs: Organisms which us organic molecules
(malate, fumarate, succinate etc) as a source of electrons
are called Organotrophs.

9. Based on energy, carbon and electron source
1. Photolithoautotrophs
2. Photoorganoheterotrophs
3. Chemolithoautotrophs
4. Chemoorganoheterotrophs

10. Photolithoautotrophs
Organisms obtain energy form sun light and carbon,
electrons form inorganic source are called
Photolithoautotrophs.
Example: Purple and green sulfur bacteria, cyanobacteria
and algae.

11. Photoorganoheterotrophs:
• Also know as photoorganotrophs or photoheterotrophs.
• Organisms which obtain energy form sun light and carbon,
electrons form organic molecules.
Ex: Purple nonsulfur bacteria and Green nonsulfur bacteria.

12. Chemolithoautotrophs:
• Also know as chemoautotrophs or chemolithotrophs.
• Organisms which use inorganic substance as source of
energy, carbon and electrons are called
Chemolithotrophs.
Example: Sulfur-oxidizing bacteria, Nitrifying bacteria and
Iron-oxidizing bacteria.

13. Chemoorganoheterotrophs
• Also known as Chemoorganotrophs or Chemoheterotrophs.
• Organisms which obtain energy, carbon and electrons form
organic sources are called Chemoorganoheterotrophs.
Examples are: E. coli, Salmonella, Fungi, Protozoa.
The dominant group of organisms present in nature are
Chemoheterotrophs.

14. Mixotrophs:
• Organisms which survive both as Autotrophs and
heterotrophs.
• These microorganisms use both organic and inorganic
substances as a source of carbon.
• Examples are: Bacillus licheniformis

15. Methylotrophs:
• Methylotrophs are a diverse group of microorganisms that
can use reduced one-carbon compounds, such as methanol
or methane, as the carbon source for their growth.
• Some methylotrophs can degrade the greenhouse gas
methane, and in this case they are called Methanotrophs.
• Examples are: Metylococcus, Methylomonas.

16. • Auxotroph: Organisms which cannot synthesize essential
components form raw material available in the medium is
called Auxotrophs.
• Medium with out growth factors is called Minimal medium.
• Prototroph: An organism or cell capable of synthesizing all
its metabolites from inorganic material, requiring no organic
nutrients.

17. Halophiles:
• Halophiles have adapted so completely to hypertonic, saline
conditions.
• That they require high levels of sodium chloride to grow,
concentrations between about 2.8 M for Halophiles and about
6.2 M for extreme halophilic bacteria.

18. • Example: Halobacterium salinarum and Halomonas
titanicae.
• Halomonas titanicae is a gram-negative, halophilic species
which was discovered on wreck of the RMS Titanic in 2010.
• The researchers, estimated that the action of microbes like
Halomonas titanicae may bring about the total decompose of
the Titanic by 2030.

21. Growth Factors:
Microorganisms often grow and reproduce when minerals and
sources of energy, carbon, nitrogen, phosphorus, and sulfur are
supplied. These organisms have the enzymes and pathways
necessary to synthesize all cell components.
Organic compounds required because they are essential cell
components such components and cannot be synthesized by the
organism are called growth factors.
There are three major classes of growth factors: (1) amino acids,
(2) purines and pyrimidines, and (3) vitamins.
Amino acids are needed for protein synthesis, purines and
pyrimidines for nucleic acid synthesis. Vitamins are small organic
molecules that usually make up all or part of enzyme cofactors.
Some microorganisms require many vitamins; for example,
Enterococcus faecalis needs eight different vitamins for growth.

22. • Many microorganisms can synthesize large quantities of
vitamins has led to their use in industry.
• Good examples of such vitamins and the microorganisms that
synthesize them are riboflavin (Clostridium, Candida,),
coenzyme A (Brevibacterium), vitamin B12 (Streptomyces,
Propionibacterium Pseudomonas), vitamin C (Gluconobacter,
Corynebacterium), and vitamin D (Saccharomyces).