lecture 3 & 4 - Microbial Life I & ll

Earth’s Timeline

• Earth formed ~4.5 bya

• Liquid water ~4.3 bya

• Life ~4 bya

What is needed to make a primitive cell?

• Container

• Mechanism of self replication/catalysis

What are the requirements for life?

• Heredity

• Reproduction

• Growth

• Development

• Metabolism

• Responsiveness

• Metabolism

• Transport

Archean Era

• 4.25 bya

• 3.8 bya Bacteria & Archaea diverge

• 3.4 bya Orgin of photosynthesis

• 2.5 bya Ends with Great Oxygenation Event

Proterozoic Era

• 2.5 bya Great oxygenation event

• 1.7 bya Eukaryotes emerge

• 0.6 bya Cambrian Explosion

Macromolecules

• Carbohydrates

• Lipids

• Protein

• Nucleic Acids

Carbohydrates

• Organic compounds that contain carbon and hydrogen atoms

• (CH2O)n

→ Resembles carbon + water

→ N=Number of units that combine to make the finished carbohydrate

Saccharide

Simple carbohydrate

Monosaccharide

Simple polyhydroxy aldehyde/ketone containing 3-7 carbons

Disaccharide

Combination of two monosaccharides

Polysaccharide

Polymer of 5 or more monosaccharides, can be branced or linear

Role of Carbohydrates

Provide structural support, nutrient and energy storage, adhesion

Celluose

• Carbohydrate

• Rigid polymer that provides cell wall support in plants and algae

  • Only a few bacteria can break down cellose

Peptidoglycen

Structural support in bacterial cell walls

Form of carbs in plants and

• Starch ( plants, algae, fungi )

• Glycogen ( animals, bacteria, protozoa)

Hydrolysis

breaking down large molecules

Lipids

• Not soluble

  • Long hydrocarbon chains that are hydrophobic

Function of Lipids

Storage and structue

Storage: Triglycerides

Cell membrane structure: Phospholipids

Cell membrane components: Sterols and steroids

Waterproofing: Wax

Triglycerides

Saturated and unsaturated fatty acids

Building blocks of proteins

Amino acids

Peptide bonds

Bonds between amino acidsP

Peptide

Short amino acids

Polypeptide

Long amino acid chain (20+)

Primary Protein Structure

Amino acid sequence

Secondary protein structure

• Hydrogen bonds between amino acids located near each other

  • a helix or B sheet

Tertiary

Complex 3D structure of a protein

Quartnary

2 or more polypeptides form a protein complex

DNA

Genetic info

RNA

Carries the instructions stored in DNA

Components of nucleotides

• Nitrogenous Base

• Pentose

• Phosphate

Purine

A and G{

Pyrimideine

T C and U

Phylogeny

Evolutionary history and relationships between organisms

Taxonomy

Organization and classification of organism

3 domains of life

• Bacteria

• Eukarya

• Archaea

What is the classification naming system for organisms?

Kingdom

Phylum

Class

Order

Family

Genus

Species

External Bacterial Cell Structure

• Locomotor Appendages

• Attachment Appendages

• Glycocalyx

  • Capsules

  • Slimes

Appendages of a bacterial cell

• Locomotor Appendages

• Attachment Appendages

Locomotor / Motility appendages

• Flagella

  • Propellor like action

  • Gives cells the ability to move in aq. environments

Attachment appendages

• Fimbriae

  • Short bristles

  • Gives the cell the ability to attach to surfaces and host cells

• Pilli

  • Longer

  • Gives the cell the ability to attach to surfaces and cells

  • Can have a specific function like transferring DNA between cells

3 types of bacterial motility

• Phototaxis

• Magnetotaxis

• Chemotaxis

Phototaxis

Movement response to a light signal

Magnetotaxis

Movement response to a magnetic field

Chemotaxis

Movement in response to a chemical signal

How does a flagella move

• Run: counterclockwise

• Tumble: Flagella move clockwise

Bacterial glycocalyx

• Coating of macromolecules that provides protection for the cell

• Slime layer: Loose shield protects from dehydration and allows adhesion

• Capsule: Tightly bounded

Encapsulated cells have an increased pathogenicity. Why?

Cell Wall

Provides cell shape and structural support

Composed of Peptidoglycan

Peptidoglycan

• Composed of glycan chains crosslinked by peptide fragments

• Peptidoglycan amount varies among different bacteria

• Peptidoglycan is needed to prevent cell lysis

Lysozyme

• Breaks bonds in glycan chains resulting into bacterial cell walls down

• Located in tear, saliva, sinus and nasal fluids

Gram positive cell walls

• Thick peptidoglycan layer

• Teichoic acids

• Loosely bounded to cell membrae

• Periplasmic space

Gram Negative Cell wall

•Comprised of a thinner layer of peptidoglycan + an outer membrane

•Lipopolysaccharides (LPS)

•Outer membrane proteins

•Porins- Control transport in/out of cell

•Structural proteins

•Thinner layer of peptidoglycan makes Gram – cells much more flexible than Gram + cells

Cell membrane components

• Phospholipid bilayer

• Selective permeability

• Fluid mosaic model

Simple diffusion

Molecules move down a concentration gradient down the phospholipid bilayer

Active transport

Energy dependent movement against a concentration gradient through a pump

Facilitated Transport

Movement down a concentration gradient through a membrane protein

Nucleoid & DNA

• Chromosome location

• Prokaryotic cells have a circular chromosomes and there is one

Plasmids

•small, extrachromosomal, circular pieces of DNA

•Not all cells of a species (or a population) will have these plasmids

•Contain genes that are NOT necessary for cellular function

Ribosomes

• Protein synthesis

• Composed of individual subunits: proteins and subunits

• Smaller than eukaryotic ribosomes

Gram stain steps