Chemotaxonomy: Microbial Cell Classification

Study Notes

Chemotaxonomy

Chemotaxonomy is the study of chemical variation in microbial cells and the use of chemical characteristics in the classification and identification of bacteria.
It examines the distribution of chemical macromolecules containing amino acids, peptides, lipids, polysaccharides, and other related polymers, proteins, enzymes, and complex polymeric molecules.

Characters Used in Bacterial Chemotaxonomy

Peptidoglycan
Diamino acids
Polysaccharides
Teichoic acids
Mycolic acids
Fatty acids
Polar acids
Isoprenoid quinones
Polyamines
Prokaryotic pigments
LPS (Lipopolysaccharides)

Amino Acids of the Cell Wall

Differences in amino acid sequence of peptide chains, mode of cross-links between chains, and diaminoacids present give important information for classification of bacteria.
Used for description of peptidoglycan type.

Sugars of Whole Cell

Certain sugars are characteristic for certain taxa (family, genus, species).
Separation of whole cell sugars from whole cell hydrolysate by thin-layer chromatography:
- Rha (rhamnose)
- Xyl (xylose)
- Man (mannose)
- Rib (ribose)
- Mad (madurose)
- Ara (arabinose)
- Glu (glucose)

Polar Lipids

Important components of bacterial plasma membranes.
Amphipathic polar lipids consist of hydrophilic head groups linked to two hydrophobic fatty acid chains.
Phospholipids are the most common polar lipids, including:
- Phosphatidyglycerol
- Diphosphatidyglycerol
- Phosphatidylcholine
- Other phosphatidylglycolipids

Respiratory Quinones

Constituents of bacterial cytoplasmic membrane and mitochondrial membrane.
Play an important role in the electron transport chain.
Chemotaxonomic value based on:
- Different types of quinones (e.g., ubiquinones, menaquinones, and their derivatives)
- Length of isoprenoid side chain
- Number of saturated isoprenoid units

Fatty Acids

Fatty acid profiles analysis is used for chemotaxonomy of bacteria.
Fatty acids are found in:
- Cytoplasmic membrane
- Lipopolysaccharides of outer membrane of Gram-negative bacteria
- Lipoteichoic acids in Gram-positive bacteria
Characteristics of fatty acids:
- Carbon chain length (8-20 carbon atoms)
- Presence of saturated and unsaturated
- Occurrence of methyl groups (iso-, anteiso-, and methylated)
- Occurrence of cyclopropane fatty acid (cyclo 17:0, cyclo 19:0)
- Occurrence of hydroxyl-fatty acid with an OH-group at position 2 or 3 of the molecule

Description

Learn about chemotaxonomy, the study of chemical variations in microbial cells, and how it's used to classify and identify bacteria. Explore the distribution of chemical macromolecules and their role in identification.

Chemotaxonomy: Microbial Cell Classification

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Questions and Answers

Where are respiratory quinones typically found in bacterial cells?

What is the primary characteristic of respiratory quinones that makes them useful for chemotaxonomy?

What type of fatty acids are commonly found in Gram-negative bacteria?

What is the characteristic of fatty acids that makes them useful for chemotaxonomy?

Which of the following is NOT a type of respiratory quinone?

In which type of bacteria are lipoteichoic acids typically found?

What is the main focus of chemotaxonomy?

Which of the following is NOT a character used in bacterial chemotaxonomy?

What is the significance of amino acid sequence in peptidoglycan?

What is the purpose of thin-layer chromatography in bacterial chemotaxonomy?

What are the hydrophilic head groups of amphipathic polar lipids usually linked to?

What is the most common type of polar lipids in bacterial plasma membranes?

What is the significance of sugar composition in bacterial chemotaxonomy?

What is the main component of bacterial plasma membranes?