Microbiology (Unit 2)

4 Fundamental Components of Cells

• Cytoplasm: gel like substance (water/dissolved chems)

• Chromosomes (nucleic acid): stores genetic material

• Plasma Membrane: boundary of cell

• Ribosomes: organelle used for protein synthesis

DNA, RNA & Proteins

DNA: stores genetic info

• deoxyribose (sugar), phosphate group, nitrogen (adenine, cytosine, guanine, thymine)

RNA: transfers genetic info for proteins to be made

• ribose (sugar), phosphate group, nitrogen (a,c,g, uracil)

Proteins: performs func of cells (ex. structure, antibodies, transport)

• amino acids w peptide bonds

Central Dogma Process

= flow of genetic info in cells:

1. Replication of DNA (copy before cell division) → enzyme: DNA polymerase

2. Transcription (mRNA synthesized using DNA as template) → enzyme: DNA dependent RNA polymerase

3. Translation (proteins synthesized using mRNA as template) → needs ribosomes

Eukaryotes v. Prokaryotes: Size

E: larger microbes (5-20 um)

P: small (0.5-1 um)

Eukaryotes v. Prokaryotes: DNA Characteristics

E:

• DNA in nucleus, packaged w histones (proteins)

• microbes have multiple linear diploid chromosomes

P:

• DNA in nucleoid (DNA is concentrated, not surrounded by mem)

• single circular haploid chromosome

• plasmids → circular extrachromosomal DNA (no essential genes → antibiotic resistance), in cytoplasm

Eukaryotes v. Prokaryotes: Cell Division

E:

• mitosis

P:

• binary fission (DNA rep → cell elongation → formation of divison septum → cells seperate)

Eukaryotes v. Prokaryotes: Genetic Variation

E:

• meiosis (gametes)

P:

• horizontal gene transfer

• 3 types: transformation, transduction, conjunction

Horizontal Gene Transfer: Transformation

• prokaryotes take up DNA from enviornment (from dead cells)

• ex. picking up chair on sidewalk

Horizontal Gene Transfer: Transduction

• bacteriophage (virus that attacks bacteria) transfers DNA from 1 bacterium to another

• ex. new chair delivered

Horizontal Gene Transfer: Conjugation

• one bacterium directly transfers DNA to another using pilus

• direct contact b/w donor & receptor

• ex. family/friends gives you chair

Eukaryotes v. Prokaryotes: Organelles

E: many, contain

• mitochondria: ATP synthesis

• lyosomes: contain degradative enzymes (phagocytosis)

• ribosomes: free in cytoplasm/bound to endoplasmic reticulum

P: no mem bound

• ribosomes: only free (smaller/less dense)

Eukaryotes v. Prokaryotes: Cytoplasm

E:

• complex cytoskeleton (protein network, provides internal structural support)

P:

• simple cytoskeleton

Eukaryotes v. Prokaryotes: Plasma Membrane

E:

• composed of phospholipid bilayer (w proteins/sterols)

P:

• phospholipid bilayer, no sterols in mem

Eukaryotes v. Prokaryotes: Cell Wall

= protect cell from harsh conditions in outside enviornment

E:

• algae: cellulose/silica

• fungi: chitin

• protozoa/helminths: no cell wall

P:

• bacteria: peptiodglycan

• archaea: pseudopeptidoglycan

Peptiodglycan Components & Structure

contains:

• monosaccharides (NAG & NAM)

• peptide chains

structure:

• alternating NAG & NAM linked together → forms polysaccharides

• polysac chains cross linked w peptide chains

Gram Positive Cell Walls

• purple

• thick petidoglycan

• teichoic acids embedded in peptido (stabilizes)

• no outer mem

• no periplasm (tech no, not b/w peptido + outer mem)

Gram Negative Cell Walls

• pink

• thin peptidoglycan

• no teichoic acifs

• outer mem (outside peptido layer) made of LPS

• periplasm (gel like) → b/w outer mem + peptido

Eukaryotes v. Prokaryotes: Extracellular Layer

E:

• external layer outside cell wall / plasma (if no cell wall) = extracellular matrix (carbs/proteins)

P: external layer either

• capsule: rigid organized layer (↑ virulence) (polysac/protiens)

• slime layer: loosely attached, less organized (polysac/glycoproteins/glycolipids)

Eukaryotes v. Prokaryotes: Movement

• term for movement: taxis

• direction: pos = towards, neg = away

stimuli

• chem: chemotaxis

• light: phototaxis

• temp: thermotaxis

ex. towards light → positive phototaxis

Eukaryotes v. Prokaryotes: Structures for Movement

E:

• algae: flagella

• protozoa: cillia, flagella, pseudopods

• fungi/helminths: none

• flagella → more complicated structure, undulating movement, 1-2

P:

• only flagella → simple, rotating, more than 1

Prokaryote Flagella Types

• none: atrichous

• 1: monotrichous

• tuft of: lophotrichous

• @ both ends: amphitrichous

• over entire surface: peritrichous

coordination of movement:

run: flagella rotate counterclockwise, spec direction

tumble: rotate clockwise, change direction

(attractant exists: longer runs, shorter tumbles)