Microbio 1

microorganisms

• populous/diverse group

• recycle essential elements

• nutrient source/carry out photosynthesis

Three Domain Classification System

• classification system based on rRNA analysis

• separated bacteria into 2 distinct domains

domain bacteria

common prokaryotes

domain archaea

unique, extreme prrokaryotes

domain eukarya

eukaryotic microbes, fungi, protists

Acellular Infectious Agents

• viruses: smallest, req host cell (replicate), cause diseases/cancer

• viroids: infectious RNA agents, prions (infectious proteins)

microbiology

• study of microorganisms

• microscopes, culture techniques, molecular genetics, genomics

microbial structure

• all cells: metabolism, growth, evolution

• some cells: differentiation, communication, genetic exchange, motility

RNA

• fulfilled protein and hereditary function

• protein synthesis catalytic

• regulate gene expression

• precursor to double stranded DNA

ribozymes

• RNA molecules forming peptide bonds

• perform cell work/ replication

Last Universal Common Ancestor (LUCA)

• root/origin of modern life on bacterial branch

• Archaea/Eukarya evolved independently of Bacteria (common ancestry)

Endosymbiotic Hypothesis

mitochondria, chloroplasts, and hydrogenosome origin from endosymbiont

Endosymbiotic Hypothesis steps

1. Ancestral eukaryotic cell lost cell wall

2. Endosymbiote engulfment

3. Produced needed product (ATP)

4. Genome reduction

5. Organelle evolution (mitochondria, hydrogenosome, chloroplast)

Cellular Microbe evolution

1. genetic material mutation > selected traits

2. new genes/genotypes evolved > genetic info mosaic

3. Bacteria/Archaea increase genetic pool (same gen horizontal gene transfer)

microbial species

• eukaryotic microbes reproduce isolated populations

• bacteria/archaea don’t reproduce sexually (strains)

• binomial nomenclature: genus/species epithet

strains

descendants of a single, pure microbial culture

Bergey’s Manual

• bacterial taxonomy system

• currently identified bacterial species descriptions

cocci (s., coccus)

spheres

streptococci

chains/strip

straphylococci

grape-like clusters

tetras, micrrococcus

4 cocci in a square

sarcinae, saraina

cubic configuration of 8 cocci

bacilli

rods

coccobacilli

very short rods

vibrios

resemble rods, comma shaped

spirilla

rigid helices

spirochetes

flexible helices

mycelium

long, multinucleate filament network

pleomorphic

variable shape organisms

size-shape relationship

• nutrient uptake

• surface to volume ratio (S/V), decrease as cells increase

• large size/odd shape > predation protective mechanism

plasma membrane functions

• encompasses cytoplasm, all living organisms req

• selectively permeable barrier (fluid)

• interacts w external environment

• surrounding chemical detection receptors/responses

• transport systems

• metabolic processes

bacterial cell wall

• maintain bacterium shape

• protect from osmotic lysis/toxic materials

• pathogenicity contribution

• peptidoglycan (murein)

• gram-positive/negative

Peptidoglycan (murein)

• rigid structure outside cell PM

• structure: identical subunit polymers forming long strands, alternating 2 sugars (NAG/NAM), alternating D- and L- AAs

gram-positive stain

• purple, thick peptidoglycan

• cell wall 90% PG

• 10% techoic acids

gram negative stain

• pink/red, thin peptidoglycan/outer membrane

• cell wall 10% PG

lipopolysaccharide

• lipid A (buried in outer membrane)

• core polysaccharide (O antigen/side chain extend out from cell)

archaeal cell walls

• no peptidogylcan (pseudopeptidoglycan)

• S-Layers: most common cell wall type, (glyco) protein,

• paracrystalline structure

• in many organisms, S-layers present in addition to

other cell wall components, usually polysaccharides

• outermost layer

Capsules + shine layer

• well organized, not easily removed

• polysaccharides

• phagocytosis resistant

• desiccation protection

• exclude viruses/detergents

pili

• longer, thicker, less numerous

• formation genes on plasmids

• req for conjugation

fibriae

• short, thin, hairlike, protein appendages

• mediate surface attachment, motility, DNA uptake

slime layers

• diffuse, unorganized, easily removed

• facilitate motility

Archaeal External Structures

• pili: archaeal adhesion mechanisms

• cannulae: hollow, tubelike structures on surface of thermophilic archae

• hami: ‘grappling hook’ appearance, cell adhesion

flagella

• threadlike, locomotor appendages extending outward from PM/cell wall

• motility/swarming behavior, surface attachment

chemotaxis

• move towards chemical attractants (nutrients)

• stay away from harmful substances

• move in response to temp, light, O2, osmotic pressure, gravity

inclusions

• granules, crystals, globules of (in)organic material stockpiled by cell for future use

• enclosed by single-layered membrane (composition varies, proteins or lipids)

ribosomes

• complex protein/RNA structures

• protein synthesis site