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DMP 712 Bact Exam 1 The Microbial Cell Section 1 Robertson


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Age of Microorganisms
millions of years
size of microorganisms
0.3microm - 2.0microm
environment of microorganisms (temp, pH, oxygen, osmolarity)
-5 to 100C
pH 2 to 10
with or without oxygen
high osmotic pressure/salt concentration
environment of most microorganisms
mesophiles 37C, pH 7, osmotic of physiologic body
conditions of host
Survival of microorgansims due to:
design as single cells
Procaryotic vs Eucaryotic
membrane nucleus
P vs. E
membrane nucleus n y
nucleolus n y
mitochondria n y
ribosomes 70S(30+50) 80S (40+60)
chloroplasts n y
ER n y
Reproduction binary fis a/sexual
All bacteria are?
unicellular procaryotes
Eucaryotic size vs. procaryotic size
Eucaryotic 1000x that of procaryotic
Shape: coccus
shape: bacillus
shape: spirochete
spiral shaped
shape: spirillum
long wavy
covalent bonds location and examples:
C,H,N,P and S
Peptide: C-N, Disulfide S-S
proteins, ester bond in lipids and glycosidic bond in polysaccharides
ionic bonds/salt linkages defn
extreme example of polarity, e- has left one atom and jumped to another
Hydrogen bonds, properties and importance
weak bond - commonly formed and broken
important in secondary structures of proteins and nucleic acids
water and protein have ordered structures b/c of H-bonds
Hydrophobic bonds example
non-polar interactions
Van der Walls forces, properties and importance
weak but important in protein structure - electrostatic due to polarity
complex lipid picture
eg: phospholipid
hydrophobic and hydrophilic ends with phosphorus group attached
Primary structure
determined by sequence of specific amino acids (100-300)
secondary structure
first level of folding
due to H bonds and Van der Waals forces
Can form alpha helix or beta pleated sheets
tertiary structure
final 3D form of single polypeptide chain (subunit)
quaternary structure
3d structure of protein with multiple subunits - due to hydrophobic interactions and disulfide bonds
Complex lipid components
1) lipid = fatty acids + glycerol backbone
2) glycolipid: add sugar
also add to amino acids and amines
Formation of micelles
lipids, specifically fatty acids
Phospholipid bilayer
hydrophillic region on either side
hydrophobic region in middle
each strand composedof fatty acid (lipid with glycerol with phosphate on end)
-storage granules
chromosome - dsDNA
ribosomes - 3 sizes, workbenches for protein synthesis
storage granules - C (glycogen and poly-B-hydroxy butyrate) Phosphorus (polymerized phosphate groups)
proteins - (many are enzymes that carry out metabolic reactions within the cell
Cell membrane defn
molecular bilayer of phospholipids and proteins
cell membrane functions
cell permeability barrier
site of electron transport and generation of ATP
site of active transport - increases the concentration of nutrients within cells
proteins involved in communication - internal and external
cell wall (peptidoglycan) importance
composed of subunits (amino acids and sugars) not found elsewhere in nature
site of action for penicillins and cephlasporins
cell wall (peptidoglycan)
determines cell shape
determines Gram stain properties of baceteria
Provides structural rigidity/strangth to cell
protects cell membrane
Peptidoglycan layer of Gram +
abx and why functional
covered by?
thickness - 20 - 80nm
abx and why functional - site of action of penicillins and cephlasporins b/c cross links formed while cells grow
covered by - polysaccharid capsule or surface antigen e.g.
-Teichoic acids
-S layer (S for surface) - usu a glycoprotein
-Capsule/slime layer - confers resistance to phagocytosis and involved in formation of biofilms
3 major components of gram + peptidoglycan picture?
1. Backbone of NAG and NAMA
2. Tetrapeptide (L-Ala, D-GLU, L-Lys, and D-Ala
3 Glycine (5) bridge
Peptidoglycan of Gram - bacteria
covered by ____ and importance
-thickness: 2-3nm
-covered by a layer of lipopolysaccharide (LPS)
=provides structural rigidity
=toxic to animals-fever and circulatory changes in patient with gram-negative infection
=contains components not found elsewhere in nature (e.g. 2-keto-3-deoxy-octulosonic acid)
=may be covered by polysaccaride capsule or slime layer (not teichoic acids)
Outer membrane (OM) of Gm- bacteria
second lipid bilayer- not just phospholipids and proteins
-limited number of proteins (4-6)
-contains phospholipids and toxic lipopolysaccharide (endotoxin) - major component
-attachment to peptidoglycan - due to small lipopolyprotein
Outer membrane (OM) of Gm- bacteria
-molecular sieve (due to proteins called porins0
-adds structural stability - compensates for thin peptidoglycan
Comparison of Gram + and Gram - Bacterial Cell Envelopes
both have:
Gram+ has:
Gram- has:
both have: capsuel, cell wall, cytoplasmic membrane
Gram+ has: lipoteichoic acids, thick peptidoglycan
Gram- has: lipoprotein (glue for OM), LPS consisting of Lipid A and polysaccharide
Lipopolysaccharide components
1. Lipid A - responsible for toxicity of LPS
2. Core - polysaccharide needed for viability
3. O-Antigen- Antiphagocytic and major antigen
responsible for:
associated with:
-external structure
-protein appendages - attached inside cell membrane and free at other end
-responsible for motility
-complex in structure - filament is compoised of subunits of a protein called flagellin
-usually associated with rod-shaped bacteria
-antigenic (H-antigens associated with enteric bacilli)
Types of Flagella
Polar - one or both ends of cell
lopotrichous - tuft of flagella at one or both ends of the cell
peritrichous - all arouund
consists of:
defn: hair-like projections on bacterial surface
consists of: protein subunits
function: mediate adherence to host cells - especially epithelial cell surfaces
importance: virulence factor for many pathogens
vs fimbriae:
receptors for:
involved in:
structure: filamentous, composed of protein subunits that extend from outer surface
vs fimbriae: longer, 1-2/cell
receptors for: bacteriophage
involved in: conjugation (transfer of DNA)
facilitate: adhesion to host cells (not common)
Teichoic acid
associated with:
made of:
attached to:
associated with: only Gram+
made of: repeating units of ribitol phosphate or glycerol phosphate
attached to: peptidoglycan covalently
location: major surface antigen, negatively charged
binds: divalent cations (Mg++ and Ca++ facilitate transport into cells
S Layer
s =
made of:
Gram +/-:
s = surface
made of: 2d array of proteins
Gram +/-: both
function: major function unknown, probably acts as a selective sieve
Capsules/slime layers
made of:
made of: usually polysaccharide
funciton: facilitate attachment to surfaces of tissue cells and resistance to ingestion by phagocytic cells (surface is made more hydrophilic)
Bacterial endospores
form of:
formed by:
form of: heat resistant dormant form of bacteria
formed by: differentiation when a new type of cell is produced with in "mother cell"
properties: produced by bacillus and clostridia, heat resistant and impermeable to dyes, low H20 content
formation: induced under suboptimal growth condtions, mature spore not heat-stable until massive uptake of Ca++ and synthesis of dipicolinic acid

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