Microbiology Quiz

Introduction to Microbiology

• Microbiology is the study of living organisms of microscopic size, including:
  • Bacteria
  • Fungi
  • Algae
  • Protozoa
  • Viruses (infectious agents at the borderline of life)
• The field of microbiology encompasses the study of:
  • Form and structure of microorganisms
  • Reproduction
  • Physiology
  • Metabolism
  • Classification
• Microbiology also explores:
  • Distribution of microorganisms in nature
  • Relationships between microorganisms and other living organisms
  • Effects of microorganisms on human beings, animals, and plants
  • Ability of microorganisms to make physical and chemical changes in the environment
  • Reactions to physical and chemical agents

Importance of Microbiology

• Microorganisms are closely associated with human health and welfare

• Beneficial microorganisms:

  • Involved in the production of yogurt, cheese, and wine
  • Used in the production of penicillin, interferon, and alcohol
  • Play a role in processing domestic and industrial wastes

• Detrimental microorganisms:

  • Cause diseases and spoilage### Introduction to Microbiology

• Microorganisms can cause disease, spoil food, and deteriorate materials like iron pipes, glass lenses, and wood pilings.

• Most microorganisms are unicellular, meaning all life processes are performed by a single cell.

• The cell is the basic structural unit of life, and all living cells are fundamentally similar.

The Discovery of Cells

• The word "cell" was first used by Robert Hooke in 1665 to describe the honeycomb-like structure he observed in a thin slice of cork.
• Matthias Schleiden and Theodor Schwann, two Germans, are credited with developing the cell theory in 1838-1839, which states that cells are the basic structural and functional units of all organisms.

Cell Structure and Function

• Protoplasm is a colloidal organic complex consisting largely of protein, lipids, and nucleic acids, enclosed by membranes or cell walls.
• All cells have a nucleus or an equivalent nuclear substance, and protoplasm always contains nuclei.
• Electron-microscope techniques have revealed the complex intricacies of intracellular organization.

Characteristics of Biological Systems

• All biological systems have the following characteristics in common: the ability to reproduce, ingest or assimilate food substances, metabolize, excrete waste products, react to changes in their environment, and susceptibility to mutation.

Microbiology as a Field of Biology

• Microbiology is the study of microorganisms, which are ideal specimens for studying fundamental life processes.
• Microorganisms have characteristics that make them ideal models for studying life processes, such as rapid growth, high reproduction rates, and simplicity of nutritional requirements.

The Scope of Microbiology

• Microorganisms have a wide range of physiological and biochemical potentialities, including the ability to utilize atmospheric nitrogen, synthesize vitamins, and require varying degrees of nutritional complexity.
• The study of microorganisms has led to the discovery of antibiotics, such as streptomycin, and has provided insights into biological phenomena, including genetics.

Classification of Microorganisms

• Classification in microbiology is based on the principles established for the plant and animal kingdoms.
• The classification of microorganisms placed them into one of two kingdoms, plant and animal, until the proposal of new kingdoms to include organisms that are neither plants nor animals.
• Haeckel's kingdom Protista was established in 1866 to include unicellular microorganisms that are typically neither plants nor animals.
• Procaryotic cells, such as bacteria, lack membrane-bound internal structures, while eucaryotic cells, such as algae, fungi, and protozoa, have membrane-bound structures.

The Importance of Microorganisms

• Microorganisms play an important and often dominant role in various fields, including industry, agriculture, food preparation, and human and animal health.### Cellular Structure of Microorganisms
• Eucaryotic cells have a nucleus bounded by a nuclear membrane, containing more than one chromosome, and have histones.
• Procaryotic cells lack a nucleus and have a single circular chromosome without histones.
• Eucaryotic cells have mitochondria, chloroplasts, and a true nucleus, while procaryotic cells lack these organelles.

Characteristics of Procaryotic and Eucaryotic Cells

• Procaryotic cells:
  • Have a peptidoglycan (murein or mucopeptide) cell wall.
  • Lack a true nucleus.
  • Have 70S ribosomes distributed in the cytoplasm.
  • May have gas vacuoles.
  • Have a mesosome.
  • Lack mitochondria, chloroplasts, and Golgi structures.
• Eucaryotic cells:
  • Have a sterol-containing cell membrane.
  • Have a true nucleus.
  • Have 80S ribosomes arrayed on membranes.
  • Have mitochondria and chloroplasts.
  • Have Golgi structures and endoplasmic reticulum.

Metabolic Mechanisms

• Procaryotic cells:
  • Have a wide variety of metabolic mechanisms, including anaerobic energy-yielding reactions.
  • Some fix nitrogen gas.
  • Some accumulate poly-hydroxybutyrate as a reserve material.
• Eucaryotic cells:
  • Have glycolysis as a pathway for anaerobic energy-yielding mechanisms.

DNA Base Ratios

• Procaryotic cells: 28-73% GC (guanine + cytosine) content.
• Eucaryotic cells: approximately 40% GC content.

Whittaker's Five-Kingdom System

• Kingdom Monera: procaryotic cells, including bacteria and cyanobacteria.
• Kingdom Protista: unicellular eucaryotic microorganisms, including microalgae, protozoa, and fungi.
• Kingdom Plantae: multicellular green plants and higher algae.
• Kingdom Animalia: multicellular animals.
• Kingdom Fungi: multicellular higher fungi.

Classification of Microorganisms

• Bergey's Manual of Systematic Bacteriology: places all bacteria in the kingdom Procaryotae, divided into four divisions.
• Major groups of microorganisms: algae, viruses, bacteria, fungi, and protozoa.
• Microorganisms are found in three of the five kingdoms: Monera, Protista, and Fungi.