Microorganisms

Biodiversity and Classification of Micro-organisms

• Definition of Biodiversity: The variety of life forms in a given habitat or on Earth as a whole, encompassing different species of animals, plants, fungi, and microorganisms.

Five-Kingdom System

Overview

• Introduced to classify living organisms based on their cellular structure, mode of nutrition, reproduction, and other factors.

Kingdoms

1. Monera

   • Prokaryotic, unicellular.

   • Nutritional methods: absorb or photosynthesize.

   • May be motile or non-motile; reproduce asexually.

2. Protista

   • Eukaryotic, unicellular or multicellular.

   • Modes of nutrition: absorb, ingest, or photosynthesize; reproduce sexually and asexually.

3. Fungi

   • Eukaryotic, multicellular.

   • Mode of nutrition: absorb.

   • Reproduction is sexual.

4. Plants

   • Eukaryotic, multicellular.

   • Photosynthesize.

   • Non-motile and sexual.

5. Animals

   • Eukaryotic, multicellular.

   • Ingest nutrients and reproduce sexually.

Prokaryotes vs. Eukaryotes

Differences

• Prokaryotes:

  • Cells without true nuclei.

  • DNA is free in the cytoplasm (not surrounded by a nuclear membrane).

  • Lack membrane-enveloped organelles.

• Eukaryotes:

  • Cells with true nuclei.

  • DNA is surrounded by a nuclear membrane.

  • Contain membrane-enveloped organelles (e.g., mitochondria, chloroplasts).

Types of Micro-organisms

• Viruses: Non-cellular entities that can cause diseases.

• Bacteria: Unicellular organisms under the kingdom Monera that can be beneficial or pathogenic.

• Protista: Diverse group including unicellular and multicellular organisms.

• Fungi: Organisms that absorb nutrients through external digestion, including both unicellular and multicellular forms.

Characteristics of Micro-organisms

• General Properties:

  • Invisible to the naked eye; majority are beneficial to ecosystems.

  • Require favorable conditions for growth: food, moisture, optimal temperature.

Pathogenic Micro-organisms

• Can cause diseases; examples include viruses and some bacteria.

• Infectious diseases result from microbial pathogens.

Size of Micro-organisms

• Range from 0.1 nm (viruses) to over 1 mm (large protozoa).

• Detection methods include transmission electron microscopy, scanning electron microscopy, and compound light microscopy.

Virus Characteristics

• Difficult to classify: considered neither living nor non-living.

• They reproduce only inside host cells and are composed of genetic material (DNA or RNA) surrounded by a protein coat (capsid).

Virus Structure

• Capsid: Protective protein coat made of capsomeres.

• Viral Envelope: Fatty lipid molecules from the host cell.

• Surface Proteins: Assist in binding to host cells.

Bacteria Characteristics

General

• Unicellular prokaryotes with rigid cell walls composed of peptidoglycan.

• Can be autotropic or heterotropic, including parasitic forms.

Structure

1. Cell Wall: Provides protection and structure.

2. Plasma Membrane: Surrounds the cytoplasm.

3. Genetic Material: Single DNA strand (nucleoid).

Movement Structures

• Flagella: Aid in motility.

• Fimbrae: Help with adherence.

• Pilli: Aid in DNA transfer between bacteria.

Protista Characteristics

• Eukaryotes with simple structures, can be unicellular or multicellular.

• Plant-like Protists: E.g., algae which contain chlorophyll for photosynthesis.

• Animal-like Protists: Unicellular, feed like animals, some are parasitic (e.g., amoeba).

Fungi Characteristics

• Include both macroscopic (e.g., mushrooms) and microscopic fungi (yeasts).

• Structure includes hyphae forming mycelium and used for nutrient absorption.

Role of Micro-organisms in the Environment

• Producers: Serve as primary producers in food chains (e.g., autotrophic protists).

• Decomposers: Break down dead organic material, recycling nutrients, maintaining ecological balance.

Infection and Disease by Micro-organisms

Pathogens

• Micro-organisms that cause disease (e.g., HIV, TB, malaria).

• Prevention and Treatment: Importance of sanitation, health education, and vaccinations.

Specific Diseases

• HIV: Damages the immune system leading to AIDS; treatment involves antiretroviral drugs.

• TB: Caused by Mycobacterium tuberculosis with treatments via long-term antibiotics.

• Malaria: Caused by Plasmodium species, transmitted by mosquitoes; prevention involves insecticides and nets.

Fungal Infections

• Candidiasis: Can occur due to an overgrowth of Candida; treated with antifungal medications.

Conclusion

• Micro-organisms play crucial roles in ecosystems as well as in human health, both positively and negatively.