Chapter 5.1

Unit 4: Microbial Biotechnology

Chapter 5.1: The Structure of Microbes

Introduction to Microbes

• Microbes are microscopic organisms that cannot be seen without a microscope.

• Types of microbes include bacteria, fungi, algae, viruses, and protozoa.

• Bacteria are the most abundant type of microbe and have existed for over 3.5 billion years.

• Less than 1% of bacteria have been cultured or identified.

Bacterial Population in Humans

• Estimated amount of bacteria in/on humans: 100 trillion (100,000,000,000,000)

• Total number of human cells: approximately 35 trillion (35,000,000,000,000)

Classifications of Microorganisms

• Prokaryotic Microbes: Include bacteria and archaea, lack nucleus.

• Eukaryotic Microbes: Include protista, plants, animals, and fungi, contain a nucleus.

Microbial Structure

Eukaryotic Microbes

• Include plant and animal cells, fungi (such as yeast), algae, and protozoans.

Prokaryotic Microbes

• Comprise bacteria and archaea.

General Bacteria Facts

• Bacterial Characteristics:

  • Prokaryotic: lack a nucleus, have a simple DNA structure typically in a circular shape without histones.

  • May contain plasmids (small DNA circles).

  • Lack membrane-bound organelles.

  • Cell wall is rich in peptidoglycan.

  • Some bacteria possess an outer capsule made of carbohydrates.

  • Classified using Gram staining method.

  • Chromosomes range from 2-4 Mb (mega bases).

  • Use pili for DNA transfer.

  • Reproduce typically every 20 minutes.

Types of Pili

• Thick Pili: Function like a fishing net for DNA.

• Thin Pili: Used for adhesion and movement on solid surfaces.

Gram Staining Process

1. Application of crystal violet.

2. Application of iodine.

3. Alcohol wash.

4. Application of safranin.

Peptidoglycan and Gram Staining

• Gram-Positive: Thick peptidoglycan layer; no outer membrane.

• Gram-Negative: Thin peptidoglycan layer; has an outer membrane.

Bacterial Shapes

• The three common shapes of bacteria:

  • Cocci: Spherical.

  • Bacilli: Rod-shaped.

  • Spirilli: Spiral-shaped.

Kingdom Fungi: Yeast

• Historically significant: Used in beer recipes from ancient Babylonians (~4300 B.C.)

• Biological applications: Used to produce medicine (antibiotics, cholesterol-lowering drugs).

• Can grow in both anaerobic and aerobic conditions.

• S. cerevisiae: First eukaryote to have its genome sequenced.

• Pichia pastoris: Utilized in batch processes due to its many promoters.

Use of Microbes as Model Organisms

Bacteria

• Applications include studying molecular biology, genetics, biochemistry, and biotechnology.

Yeast

• Key areas of research include chromosome structure, gene regulation, cell division, and cell cycle control.