Prokaryotes, and Archea 2020
Page 1: Introduction to Microbial World
Focus: Prokaryotes (Bacteria & Archaea), Eukaryotes, and Viruses
Course: MICR1010: Introductory Microbiology & Molecular Biology
Page 2: Classifying Living Things
Biological Classification: Organisms grouped based on evolutionary relationships.
Evidence includes:
Fossil record
Comparative homologies (similarity in anatomy/physiology due to shared ancestry)
Comparative sequencing of Genetic Material (DNA & RNA)
Page 3: Gene Encoding and Phylogenetic Analysis
Steps for analyzing rRNA genes:
Isolate DNA from each organism.
Make copies of rRNA gene by PCR.
Sequence DNA.
Analyze sequences and produce aligned rRNA gene sequences.
Generate phylogenetic tree to show relationships between:
Archaea
Bacteria
Eukarya
Examples of organisms include:
Green nonsulfur bacteria
Cyanobacteria
Various extremophiles (e.g., Methanogen)
Page 4: Three Domains of Life
Bacteria: True bacteria, prokaryotic (e.g., Streptococcus pneumoniae, Lactobacillus).
Archaea: Initially thought to be the same as bacteria, now identified as distinct prokaryotes (e.g., extremophiles).
Eukarya: All eukaryotic organisms classified into four kingdoms:
Protista: Algae
Fungi: Mushrooms
Plantae: Ackee tree
Animalia: Humans
Page 5: Binomial Nomenclature
System for Naming Organisms: Proposed by Carolus Linnaeus in 1700s.
Universal language: Latin
Each organism has:
Genus (capitalized)
Species (lower case)
Format: Names italicized or underlined
Examples:
Vibrio cholerae
Homo sapiens
Page 6: Characteristics of Prokaryotes
General Features:
Very small, single-celled, and relatively simple.
Genetic material not enclosed in a nuclear membrane.
Main shapes include bacillus (rod), coccus (sphere), and spiral (corkscrew).
Page 7: Bacterial Sizes
Size range from 0.1 μm to 600 μm (visible).
Examples:
Mycoplasma: 100-200 nm diameter
Escherichia coli: 1.1-1.5 μm x 2-6 μm
Epulopiscium fishelsoni: up to 600 μm x 80 μm
Page 8: Surface-to-Volume Ratio
Large surface-to-volume ratio enables efficiency.
Microorganisms thrive despite simple morphologies due to minimal distance to surface.
Page 9: Bacterial Cell Morphology
Cell shapes include:
Spherical (coccus)
Rod-shaped (bacillus)
Spiral-shaped
Comma-like, coiled forms
Page 10: Arrangement of Bacterial Cells
Different planes of division result in:
Diplococci: in pairs
Streptococci: in chains
Tetrad: in groups of four
Sarcinae: cubical packets
Staphylococci: in clusters
Page 11: Arrangement of Bacilli
Types include:
Diplobacilli: in pairs
Streptobacilli: in chains
Coccobacillus: short rod shape
Page 12: Spiral Bacteria Shapes
Types include:
Vibrio: curved rod
Spirillum: spiral-shaped, rigid
Spirochete: flexible spiral
Page 13: Bacterial Shapes Summary
Various patterns of cell arrangement and shape:
Diplo-, strepto-, staphylo- (e.g., cocci, bacilli, spirochetes)
Page 14: Prokaryotic Cell Structures
External Structures:
Flagella, pili, fimbriae, glycocalyx (capsule/slime layer)
Internal Structures:
Cytoplasmic matrix, ribosomes, nucleoid, inclusions, endospore
Page 15: Function of Prokaryotic Structures
Plasma Membrane: Selectively permeable, boundary, transport, metabolism, environmental cue detection.
Gas Vacuoles: Buoyancy in aquatic habitats.
Ribosomes: Sites for protein synthesis.
Nucleoid: Localization of genetic material.
Page 16: Overview of Prokaryotic Cells
Basic structures include: Cell wall, plasma membrane, cytoplasm, nucleoid, and ribosomes.
Variability in structures contributes to antibiotic targets and pathogenicity.
Page 17: Bacterial Cell Internal Composition
Structures vary by species:
Capsule, cell wall, cytoplasmic membrane, nucleoid, ribosomes.
Key roles in bacterial identification and antibiotic susceptibility.
Page 18: Gram-Positive vs. Gram-Negative Bacteria
Gram-Positive Envelope:
Thick peptidoglycan layer with teichoic acids.
Gram-Negative Envelope:
Thin peptidoglycan layer between inner and outer membranes.
Contains lipopolysaccharides (LPS).
Page 19: Structure of Bacterial Cell Walls
Comparison of Gram-positive and Gram-negative cell envelopes, highlighting peptidoglycan and membrane structure.
Page 20: Characteristics of the Cell Wall
Function:
Provides shape, protects from osmotic lysis, consists of peptidoglycan.
Teichoic acids present in Gram-positive bacteria; some bacteria lack a cell wall.
Page 21: Gram Staining Properties
Gram-positive Example: Staphylococcus aureus
Staining process: crystal violet → Gram's iodine → decolorizer → safranin red.
Gram-negative Example: Escherichia coli
Page 22: Features of Gram-Positive Cell Wall
Peptidoglycan:
Thick layer making up most of the cell wall weight; contains teichoic and lipoteichoic acids.
Page 23: Components of Gram-Positive Cell Wall
Structural features of Gram-positive bacteria include peptidoglycan and teichoic acid components.
Page 24: Peptidoglycan Structure
Characteristics:
Mesh-like, thick structure composed of NAG and NAM repeating units with tetrapeptide chains regulating rigidity and support.
Page 25: Peptidoglycan Overview
Description:
Three-dimensional latticework that surrounds and supports bacterium; critical for shape and protection.
Page 26: Gram-Negative Cell Wall Features
Composition:
Outer membrane, thin peptidoglycan, and gel-like periplasmic space containing numerous proteins.
Page 27: Lipopolysaccharides in Gram-Negative Bacteria
LPS Components:
Lipid A (toxic component), core, and O antigen (important for immune recognition).
Page 28: Importance of Gram-Negative LPS
Functions include providing a permeability barrier, stabilizing the membrane, and eliciting immune responses.
Page 29: External Prokaryotic Structures
Focus on flagella, fimbriae, and capsules as external features facilitating movement and adherence.
Page 30: Flagella Overview
Structure: Thin (about 20 nm) and long, associated with motility.
Types: Monotrichous, lophotrichous, amphitrichous, peritrichous.
Page 31: Arrangement of Flagella
Visual representations of flagellar arrangements in bacteria:
Monotrichous, amphitrichous, lophotrichous, and peritrichous configurations.
Page 32: Bacterial Motility
Types of movement initiated by:
Chemotaxis (chemical stimulus)
Phototaxis (light)
Aerotaxis (oxygen)
Magnetotaxis (magnetic field orientation)
Page 33: Bacterial Movement Patterns
Behavior in response to attractants:
Random movement without attractants.
Directed movement toward attractants.
Page 34: Fimbriae and Pili Overview
Fimbriae: Short, hair-like appendages aiding in attachment and biofilm formation.
Pili: Longer structures facilitating adhesion, genetic exchange, and twitching motility.
Page 35: Fimbriae and Pili Functions
Illustrate the roles of fimbriae and pili in bacterial adhesion and genetic transfer during conjugation.
Page 36: Glycocalyx Overview
A sticky, gelatinous polymer external to the cell wall, composed of polysaccharides and/or polypeptides.
Two main types:
Slime layer: loosely attached
Capsule: firmly attached, highly organized.
Page 37: Capsule Features
Composed of varying polysaccharides, aiding in evasion of phagocytosis, adherence, virulence, and dehydration prevention.
Page 38: Internal Components of Prokaryotic Cells
Structures include:
Cytoplasmic membrane, cytoplasm, ribosomes, nucleoid, inclusions, and endospores.
Page 39: Cytoplasmic Membrane Functions
Apart from serving as a permeability barrier, plays roles in energy production and transport protein function.
Page 40: Cytoplasm as Antibiotic Target
Key components include nucleoid, ribosomal subunits, plasmids.
Targeted by different antibiotics to inhibit bacterial growth.
Page 41: Endospores in Bacteria
Overview:
Dormant structures formed by certain Gram-positive bacteria to withstand harsh environmental conditions.
Subject to quick germination under favorable conditions.
Page 42: Endospore Formation Cycle
Detailed stages of sporulation leading to endospore formation and subsequent germination under suitable conditions.
Page 43: Types of Endospores
Classifications of endospores based on their terminal, subterminal, or central positioning within the bacterial cell.
Page 44: Gram-Negative vs. Gram-Positive Cell Walls
Differences in peptidoglycan content, outer membrane presence, and susceptibility to antibiotics.
Page 45: Domain Archaea Overview
Distinct from bacteria; found in extreme environments, lacking peptidoglycan but may contain pseudomurein.
Page 46: Archaea Characteristics
Identified in late 1970s as unique domain; often live in extreme conditions and do not cause diseases in humans.
Page 47: Extremophiles Characteristics
Require extreme environmental conditions including temperature, salinity, or pH.
Subcategories include thermophiles, halophiles, and acidophiles.
Page 48: Halophiles and Thermophiles
Definition:
Halophiles: thrive in saline environments.
Thermophiles: survive at elevated temperatures, such as those found in geothermal areas.
Page 49: Methanogens Overview
Largest group of Archaea; produce methane as a metabolic byproduct found commonly in wetlands and guts of animals.
Page 50: Methane Cycle
Details the ecological cycle involving methane production and oxidation, highlighting interactions between anaerobic environments and organism activity.
Page 51: Major Physiological Classes of Archaea
Classes include extreme halophiles, thermoacidophiles, hyperthermophiles, and methanogens with examples provided.
Page 52: Unique Cellular Characteristics of Archaea
Membrane lipids with ether-linked bonds and absence of peptidoglycan in cell walls.
Page 53: Archaeal Membranes
Differences in membrane structure compared to bacteria and eukarya with ether bonds and lipid layers.
Page 54: Comparative Membrane Structure
Contrast between membrane structures of Archaea, Bacteria, and Eukarya focusing on bonding types (ester vs ether).
Page 55: Habitats of Extreme Halophiles
Various extreme environments showcasing organisms' adaptability to high salinity.
Page 56: Growth Conditions for Thermoplasma
Thermoplasma habitat showing the importance of acidic, hot spring conditions for specific archaeal growth.
Page 57: Methanogen Overview
Methanogens as strictly anaerobic organotrophs or chemoautotrophs prevalent in diverse environments.
Page 58: Comparative Summary of Cell Types
Overview comparing Bacteria, Archaea, and Eukarya regarding structure, size, cell wall composition, and environmental habitats.