Microbiology Overview and Classification

Microbiology Overview

• Microbiology is the study of microscopic organisms, including bacteria, archaea, viruses, fungi, and protozoa.
• Microorganisms are too small to be seen with the naked eye and require a microscope.
• Defining microbiology is challenging as the field incorporates many sciences, and not all single-celled organisms are microscopic, and not all microscopic organisms are single-celled.

Three-Domain System of Life

• Carl Woese proposed a three-domain system of life: Bacteria, Archaea, and Eukarya.
• This system classifies organisms based on their shared characteristics.

Prokaryotes vs. Eukaryotes

• Prokaryotes lack a nucleus and membrane-bound organelles.
• Eukaryotes possess a nucleus and membrane-bound organelles.

Major Groups of Microorganisms

• Bacteria: Prokaryotic, single-celled organisms with peptidoglycan cell walls. Some are motile, and they can use organic or inorganic sources of nutrition.
• Archaea: Prokaryotic, single-celled organisms that do not have peptidoglycan cell walls. They can use organic or inorganic sources of nutrition.
• Eukarya: Includes protozoa, algae, fungi, and helminths (parasites). These are eukaryotic organisms and have more complex structures than prokaryotes.

Microorganism Characteristics

• Nutrition: Microorganisms can acquire nutrients from organic or inorganic sources.
• Cell Walls: Bacteria and archaea usually have cell walls, but of different chemical compositions.
• Motility: Some microorganisms can move using flagella or other structures.

Non-Cellular Microbes

• Viruses: DNA or RNA genome with a protein capsid, require a host cell for replication.
• Viroids: Infectious RNA molecules.
• Prions: Infectious proteins.

Microbiology Contributions

• Robert Hooke: Introduced the first compound microscope and observed "cells"
• Antonie van Leeuwenhoek: Observed single-celled microbes, which is credited as the "father of microbiology."
• Lazzaro Spallanzani: Demonstrated that spontaneous generation of microbes is not valid.
• Louis Pasteur: Contributed to germ theory, and pasteurization methods.
• Joseph Lister: Used phenol as an antiseptic for surgical instruments.
• Robert Koch: Developed Koch's Postulates for determining the cause of infectious diseases.
• Paul Ehrlich: Identified the first antimicrobial drug for syphilis.

Defining Features of Microorganisms

• Metabolic Diversity: Microbes can use various energy sources.

• Adaptation: Certain microorganisms thrive in extreme environments.

• Microbial Interactions: Microbes can influence each other, and other organisms.

• Importance: Organisms play a significant role in many environmental processes, including nutrient cycling.

Cell Structures

• Bacterial Cell Structures (e.g., capsules, cell walls, plasmids, pili, cytoplasm, etc.)
• Eukaryotic Cell Structures (e.g., Nucleus, mitochondria, ribosomes)

Microbes and Disease

• Pathogens can cause infectious diseases in humans.
• Microbiology is relevant in understanding disease mechanisms.

Evolutionary Relations and Endosymbiosis

• Organisms can evolve and have relationships among themselves.
• Endosymbiotic theory explains the evolutionary origins of eukaryotic organelles, such as mitochondria and chloroplasts, from prokaryotic cells.

Microbial Metabolism and Nutrition

• Microorganisms have different metabolic pathways and mechanisms to obtain nutrients from environment.
• Microbes have an important role in carbon and nitrogen cycles.

Microbial Growth and Reproduction

• Microbes reproduce and grow at rates determined by the environment and factors like temperature.

Classification

• Microbiology has a system for classifying and naming microorganism.
• Classification methods may be based on shared characteristics or genetics, etc.