Microbiology Lecture 2, Taxonomy and Types of Microbes

Introduction to Microbiology

• Purpose: Support students enrolled in Microbiology for Health Science course or Biology 2420 at Del Mar College

• Encouragement for feedback and interaction with the content.

Overview of Taxonomy

Definition

• Taxonomy: Classification system for living organisms.

• Importance of classification for understanding biological diversity.

Examples of Classification

• Insects: Three body parts, pairs of legs, sometimes antennae.

• Arachnids: Two body parts, eight legs, multiple eyes.

• Understanding traits leads to knowledge about anatomy and behavior.

Carolus Linnaeus

• Father of Taxonomy, began classification around 1735.

• Developed a system to name organisms using genus and species.

• Example: Humans are Homo sapiens; Escherichia coli describes bacteria from the colon.

Naming Convention

• Genus and species are italicized or underlined.

• Genus is capitalized; species is not.

• Example names: Homo sapiens, Escherichia coli, Staphylococcus aureus.

Levels of Classification

Taxonomic Hierarchy

• King Philip Came Over For Good Soup (mnemonic for remembering categories):

  • Domain

  • Kingdom

  • Phylum (plural: phyla)

  • Class

  • Order

  • Family

  • Genus

  • Species

Three Major Domains

• Archaea: Ancient prokaryotic cells.

• Bacteria: Prokaryotic organisms.

• Eukarya: Eukaryotic cells with organelles.

Six Kingdoms

• Archaea (kingdom), Bacteria (kingdom).

• Eukarya divides into:

  • Protista (single-celled organisms)

  • Fungi (multicellular, includes molds and yeast)

  • Plantae (plants)

  • Animalia (animals)

Overview of Microbes

Archaea

• Characteristics:

  • Prokaryotic, lack membrane-bound organelles.

  • Unique features: flagella, no peptidoglycans in cell wall.

  • Often extremophiles: survive in extreme environments.

• Categories of extremophiles:

  • Thermophiles: Thrive in extreme temperatures.

  • Halophiles: Survive in very salty conditions.

  • Methanogens: Generate methane, live in gassy environments (some are anaerobic).

  • Acidophiles: Love acidic environments (e.g., Helicobacter pylori).

  • Alkaliphiles: Thrive in basic/alkaline conditions.

Bacteria

• Characteristics:

  • Unicellular, prokaryotic, small in size.

  • Contains a cell wall with peptidoglycans (distinction for types).

• Energy sources:

  • Photosynthetic Autotrophs: Create energy from sunlight.

  • Chemosynthetic Autotrophs: Use inorganic compounds for energy.

  • Heterotrophs: Depend on organic compounds for energy.

Algae

• Characteristics:

  • Photosynthetic eukaryotes with cell walls made of cellulose.

  • Reproduce sexually and asexually, producing oxygen in the process.

Fungi

• Characteristics:

  • Eukaryotes, usually multicellular;

  • Cannot produce their own food, absorb nutrients from the environment.

  • Cell walls made of chitin.

  • Reproduce asexually or sexually through spores.

Protozoa

• Characteristics:

  • Single-celled eukaryotes, motile (using pseudopods, flagella, or cilia).

  • Mostly heterotrophic; some can photosynthesize.

Viruses

• Characteristics:

  • Acellular, obligate intracellular parasites.

  • Composed of a protein coat (capsid) and genetic material (DNA or RNA).

  • Require host cells to reproduce.

Multicellular Animal Parasites

• Not true microbes; often visible to the naked eye (e.g., helminths).

• Studied through microbiological techniques due to their disease-causing nature.

Conclusion

• Students should understand taxonomy levels, major domains, and key characteristics of microbes discussed.

• Aim: Prepare for exams and future studies in microbiology.

Introduction to Microbiology

Purpose

• Support students enrolled in the Microbiology for Health Science course or Biology 2420 at Del Mar College.

• Encourage feedback and interaction with the content to enhance the learning experience.

Overview of Taxonomy

Definition

• Taxonomy: A systematic classification framework for living organisms, allowing scientists to organize and identify species based on shared characteristics and evolutionary history.

• Understanding biological diversity through classification is crucial for biology, ecology, and environmental science, as it helps in identifying relationships among species.

Examples of Classification

• Insects: Have three distinct body parts (head, thorax, abdomen), six jointed legs, and often one or two pairs of wings. Some have antennae for sensory perception.

• Arachnids: Feature two main body segments (cephalothorax and abdomen), eight legs, and typically multiple eyes, aiding in their predatory behaviors.

• Understanding traits leads to knowledge about anatomy, behavior, ecological roles, and interactions within ecosystems.

Carolus Linnaeus

• The Father of Taxonomy, Linnaeus pioneered the classification system in the 18th century, first publishing his work "Systema Naturae" in 1735. His innovative approach distinguished between organisms by assigning them specific names and categories.

• He developed the binomial nomenclature system, where each species is designated by a two-part Latin name representing its genus and species. This naming convention standardizes the way species are identified worldwide.

• Examples:

  • Humans are referred to as Homo sapiens.

  • The bacterium commonly found in the colon is identified as Escherichia coli.

Naming Convention

• Genus and species names must always be italicized or underlined to denote their Latin origin.

• The genus name is capitalized while the species name is written in lowercase.

• Example names:

  • Homo sapiens (humans)

  • Escherichia coli (bacterium)

  • Staphylococcus aureus (a bacterial pathogen responsible for various infections).

Levels of Classification

Taxonomic Hierarchy

• A mnemonic to help remember the categories of classification is "King Philip Came Over For Good Soup":

  1. Domain

  2. Kingdom

  3. Phylum (plural: phyla)

  4. Class

  5. Order

  6. Family

  7. Genus

  8. Species

Three Major Domains of Life

• Archaea: Consists of ancient prokaryotic cells with unique molecular characteristics. These organisms are often extremophilic, thriving in conditions that are inhospitable to most life forms.

• Bacteria: Includes prokaryotic organisms known for their diversity in structure, metabolism, and ecological niches.

• Eukarya: Encompasses complex cells with membrane-bound organelles, incorporating kingdoms such as plants, animals, fungi, and protists.

Six Kingdoms of Organisms

• Archaea (Kingdom): Comprising various extremophiles, including halophiles and thermophiles.

• Bacteria (Kingdom): Includes all prokaryotic organisms that exhibit enormous metabolic diversity.

• Eukarya is divided into:

  • Protista: Diverse group mostly consisting of single-celled organisms, some of which are photosynthetic.

  • Fungi: Composed of mostly multicellular organisms that absorb nutrients, such as molds and mushrooms.

  • Plantae: Multicellular organisms that perform photosynthesis and contribute to the planet's oxygen supply.

  • Animalia: Multicellular organisms with diverse dietary habits.

Overview of Microbes

Archaea

• Characteristics: Prokaryotic, lacking membrane-bound organelles, with distinct biochemistry from bacteria; they often possess enzymes that function under extreme conditions.

• Unique Features: Some have flagella, and their cell wall does not contain peptidoglycans.

• Categories of Extremophiles:

  • Thermophiles: Thrive in high-temperature environments, such as hot springs.

  • Halophiles: Adapted to extremely salty conditions, often found in salt lakes.

  • Methanogens: Produce methane and are often found in anaerobic environments, such as in marshes or within the digestive systems of ruminants.

  • Acidophiles: Favor acidic habitats, such as sulfuric hot springs (e.g., Helicobacter pylori contributes to gastric ulcers).

  • Alkaliphiles: Preferring alkaline environments such as soda lakes.

Bacteria

• Characteristics: Unicellular, prokaryotic, typically ranging from 0.5 to 5.0 micrometers in size.

• Bacterial cell walls are primarily composed of peptidoglycan, which is essential for structural integrity.

• Energy Sources:

  • Photosynthetic Autotrophs: Convert sunlight into chemical energy (e.g., cyanobacteria).

  • Chemosynthetic Autotrophs: Utilize inorganic compounds as energy sources (e.g., nitrifying bacteria).

  • Heterotrophs: Rely on consumption of organic compounds (e.g., decomposers such as Bacillus cereus).

Algae

• Characteristics: Photosynthetic eukaryotes that exhibit a wide variety of forms, often with cell walls made of cellulose. Algae play a pivotal role in oxygen production.

• They can reproduce both sexually (via gametes) and asexually (via spores or fragmentation).

Fungi

• Characteristics: Eukaryotic organisms, typically multicellular, with chitin-based cell walls that differentiate them from plants.

• Fungi are heterotrophic and absorb nutrients from their surroundings, playing a crucial role in decomposition and nutrient cycling.

• Reproduction occurs through spores which can be dispersed by wind or water.

Protozoa

• Characteristics: Unicellular eukaryotes with the ability to move independently (using structures like pseudopodia, flagella, or cilia).

• They are mostly heterotrophic but encompass some photosynthetic species, contributing to food webs in aquatic environments.

Viruses

• Characteristics: Acellular entities that cannot carry out metabolic processes independently; classified as obligate intracellular parasites.

• Viruses consist of a protein coat (capsid) surrounding genetic material (either DNA or RNA) and depend on living host cells to replicate.

Multicellular Animal Parasites

• Not classified as true microbes due to their size; often visible to the naked eye (e.g., helminths).

• Despite being larger, their study is essential in microbiology due to their impact on human health and disease, requiring microbiological techniques for identification and treatment.

Conclusion

• Students should possess a clear understanding of the levels of taxonomy, the major domains of life, and the distinctive characteristics of various microbial groups as discussed.

• The aim is to equip students with the knowledge necessary for exams and future studies in the expansive field of microbiology.