Microbiology: Chemistry of Life, Carbohydrates & Lipids

Basic microbiology encompasses the chemistry of life, chemical reactions, and microbiological laboratory techniques.

Chemistry of Life

Life's chemistry is based on carbon compounds.
Carbon's versatility stems from its ability to form stable covalent bonds with itself and other elements.
Biomolecules include carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

Carbohydrates serve as primary energy sources and structural components.
Monosaccharides are simple sugars (e.g., glucose, fructose).
Disaccharides consist of two monosaccharides joined by a glycosidic bond (e.g., sucrose, lactose).
Polysaccharides are complex carbohydrates composed of many monosaccharides (e.g., starch, cellulose, glycogen).

Lipids

Lipids are hydrophobic molecules crucial for energy storage, cell membrane structure, and insulation.
Triglycerides (fats and oils) are composed of glycerol and three fatty acids.
Saturated fatty acids have no double bonds, while unsaturated fatty acids contain one or more double bonds.
Phospholipids are major components of cell membranes, containing a phosphate group, glycerol, and two fatty acids.
Steroids, such as cholesterol, have a ring structure and serve various functions, including membrane stabilization and hormone synthesis.

Proteins

Proteins are made up of amino acids and perform a wide array of functions, including catalysis, transport, and structural support.
Amino acids are linked by peptide bonds to form polypeptide chains.
Protein structure is organized into four levels: primary (amino acid sequence), secondary (alpha-helices and beta-sheets), tertiary (3D folding), and quaternary (arrangement of multiple polypeptide chains).
Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.
Enzymes exhibit specificity, binding to specific substrates at their active site.
Environmental factors like temperature and pH can significantly affect enzyme activity.

Nucleic Acids

Nucleic acids (DNA and RNA) store and transmit genetic information.
DNA contains the genetic instructions for all cellular activities.
RNA helps carry out these instructions.
Nucleotides are the building blocks of nucleic acids, consisting of a sugar, a phosphate group, and a nitrogenous base.
DNA contains the bases adenine (A), guanine (G), cytosine (C), and thymine (T), while RNA contains uracil (U) instead of thymine.
DNA is a double-stranded helix, with A pairing with T and G pairing with C.
RNA is typically single-stranded and comes in various forms (mRNA, tRNA, rRNA) involved in protein synthesis.

Chemical Reactions

Chemical reactions involve the making and breaking of chemical bonds.
Reactants are the substances that enter a reaction, while products are the substances formed.
Energy is either absorbed or released during chemical reactions.
Catabolism: Breakdown of complex molecules into simpler ones, releasing energy (exergonic).
Anabolism: Synthesis of complex molecules from simpler ones, requiring energy (endergonic).
Redox reactions (oxidation-reduction) involve the transfer of electrons.
Oxidation is the loss of electrons, while reduction is the gain of electrons.
These reactions are crucial for energy transfer in cells.
pH measures the acidity or alkalinity of a solution.
Acids donate protons (H+), while bases accept protons.
The pH scale ranges from 0 to 14, with 7 being neutral.
Buffers help maintain a stable pH by resisting changes in hydrogen ion concentration.

Microbiological Laboratory Techniques

Microbiological laboratory techniques are essential for studying microorganisms.
Sterilization eliminates all forms of microbial life.
Autoclaving uses high pressure and temperature to sterilize equipment and media.
Filtration removes microbes from liquids using filters with small pore sizes.
Chemical sterilization involves using chemicals to kill microbes.
Disinfection reduces the number of microbes on surfaces or tissues.
Antiseptics are disinfectants used on living tissues.
Culture media provide nutrients for microbial growth.
Agar is a solidifying agent used in culture media.
Different types of media include:
- Complex media: Exact chemical composition is unknown.
- Defined media: Exact chemical composition is known.
- Selective media: Allow the growth of specific microbes while inhibiting others.
- Differential media: Distinguish between different types of microbes based on observable traits.
Pure cultures contain only one species of microorganism.
Streak plate method: Used to isolate pure cultures by diluting microbes on an agar surface.
Pour plate method: Serial dilutions of the inoculum are added to molten agar.
Spread plate method: Serial dilutions of the inoculum are spread over the surface of an agar plate.
Microscopy is used to visualize microorganisms.
Light microscopy uses visible light to magnify specimens.
Types of light microscopy:
- Brightfield microscopy: Provides a clear image against a bright background.
- Darkfield microscopy: Provides a bright image against a dark background, useful for observing live microbes.
- Phase contrast microscopy: Enhances contrast in transparent specimens.
- Fluorescence microscopy: Uses fluorescent dyes to visualize specific structures.
Electron microscopy uses beams of electrons to magnify specimens.
Types of electron microscopy:
- Transmission electron microscopy (TEM): Provides high-resolution images of internal structures.
- Scanning electron microscopy (SEM): Provides high-resolution images of surface structures.
Staining techniques are used to enhance contrast and differentiate between microbes.
Simple stains use a single dye to color microbes.
Differential stains use multiple dyes to distinguish between different types of microbes.
- Gram stain: Differentiates bacteria based on cell wall structure (Gram-positive and Gram-negative).
- Acid-fast stain: Differentiates bacteria with mycolic acid in their cell walls (e.g., Mycobacterium).
- Endospore stain: Stains endospores, which are resistant structures formed by some bacteria.