Transcript Intimate Strangers - Kent City School District

Intimate Strangers
The Infectious Agents of Disease
Infectious Agents
•Viruses
•Bacteria
•Protozoa
Bacteria (19-1)
Kingdom Eubacteria/Kingdom Archeabacteria
• Microscopic unicellular organisms
• Free living/ Prokaryotic
• Self replicating
• Usually sensitive to antibiotics
• Responsible for the majority of human
infectious diseases
Review of Kingdoms
Archaebacteria
• earliest monerans
• found in extreme
habitats
• oxygen free, salty, and
acidic environments
• Chemosynthetic
metabolisms
• Diff. Membrane
structures (p.472)
Eubacteria
• modern bacteria
• found in diverse
number of habitats
• Heterotrophic
(chemo and photo-)
& Autotrophic
(chemo and photo-)
• Cyanobacteria
group
Structure of Bacteria
Classification by shape (morphology)
Sphere
Rod
Spiral
Prefixes are added to the three basic shapes to further
classify the bacteria according to their arrangement.
The three basic arrangements are:
1) Diplo-paired arrangement
2) Staphylo- clustered arrangement
3) Strepto- chained arrangement
1
2
3
More Ways to Identify
• Movement
•
•
•
•
Flagella
Slime Movement
Cilia
None
• Cell Walls
• Gram Positive gives
a purple color after
staining
• Gram Negative gives
a pink color after
staining
Pilus
These are hollow, hair like structures made of
protein allow bacteria to attach to other cells. A
specialized pilus, the sex pilus, allows the transfer of
DNA from one bacterial cell to another
Flagella
The purpose of flagella (sing., flagellum) is
motility. Flagella are long appendages which
rotate. Bacteria may have one, a few, or many
flagella in different positions on the cell.
Other specialized structural adaptations:
Capsule
gelatinous like coating that protects
bacteria from white blood cells and
chemical agents.
Endospore
hard coating that is resistant to drying out
boiling, and many chemical agents
Clostridium botulinium and Clostridium tetani
forms endospores and toxic poisons
Structure of a Bacterial Cell
Metabolic Diversity
• Heterotrophs
• Autotrophs
1. Chemoheterotroph: 1. Photoautotroph:
taking in of organic
require light to
molecules
perform
photosynthesis
2. Photoheterotroph:
use photosynthesis 2. Chemoautotroph:
AND take in
no light needed,
chemicals
undergo
chemosynthesis
Releasing Energy
Aerobic
Anaerobic
• require oxygen for cellular
respiration
• “obligate aerobes”without oxygen they will
die
• do not require oxygen for
cellular respiration
• “obligate anaerobes”-will
die in the presence of
oxygen
“Faculties Aerobes/Anaerobes”
•Can live with or without oxygen
•Capable of switching metabolism
•Fermentation vs. Cellular respiration
Reproduction
• Binary fission
-Asexual form of
reproduction
-Produces identical
clones
-Rapid (20 min)
• Conjugation
-Sexual form of
reproduction
-Pilus is used to exchange
genetic material
-Produces a variant,
making them hard to
treat with antibiotics
http://www.hhmi.org/biointeractive/animations/conjugation/conj_f
rames.htm
Economic Importance of
Bacteria
• Nitrogen fixation- bacteria convert
atmospheric nitrogen (N2) to ammonia
(NH3) a fertilizer for plants
• Recycle organic material and oxygen
• Food and beverages
• Medicines (antibiotics)
• Industrial uses
Identifying Bacteria- What is
gram staining?
• Gram reaction is based on the structure of the
bacterial cell wall.
1. In Gram-positive bacteria, the purple crystal
violet stain is trapped by the layer of peptidoglycan
which forms the outer layer of the cell.
2. In Gram-negative bacteria, the outer membrane
prevents the stain from reaching the peptidoglycan
layer in the periplasm. The outer membrane is then
permeabilized by acetone treatment, and the pink
safranin counterstain is trapped by the
peptidoglycan layer.
Check It Out
Results
Why is the cell wall and gram
staining important?
Acquired resistance
Many bacteria acquire resistance to one or more of the antibiotics to
which they were formerly susceptible. Example: In the U.S. in
the decade from 1985–1995, resistance of Shigella (which causes
gastrointestinal illness) to ampicillin grew from 32% to 67%.
And, while only 7% of these isolates were resistant to the
combination of sulfamethoxazole and trimethoprim at the start
of the decade, that figure had grown to 35% by the end of the
decade.
Bacteria develop resistance by acquiring genes encoding proteins
that protect them from the effects of the antibiotic. In some cases
the genes arise by mutation; in others, they are acquired from
other bacteria that are already resistant to the antibiotic. The
genes are often found on plasmids which spread easily from
one bacterium to another — even from one species of bacterium
to another.
Antibiotics
• An antibiotic will attack a cell wall of a
bacteria
• Different antibiotics are engineered to attack
different cell walls based on the
peptidoglycan they contain.
• “The walls of bacteria are made of a complex
polymeric material called peptidoglycan. It
contains both amino acids and amino sugars”
Infectious Animation
• http://www.sp.uconn.edu/~terry/Co
mmon/phago053.html