Download Bacteria and Viruses

Chapters 23 and 24
2013
The most numerous organisms on earth
Earliest fossils 3.5 Billion years old
Lived before other life evolved.
Two major domains: Archaea and Bacteria
1.
2.
Living organisms have been categorized into
three main groups based on ribosomal RNA
analysis.
Different from bacteria
Makeup of cell walls different– no peptidoglycan
Different lipids in cell membranes
DNA has introns
Three groups
Methanogens: convert hydrogen gas and carbon
dioxide to methane. Anaerobic, many live in
intestinal tract of cows and termites.
Halophiles: salt loving
Thermoacidophiles: acidic environments that are
high in temperature.
Most prokaryotes are bacteria
Three common shapes
Bacilli
Cocci
Spirilla
They may occur in chains (streptococci) or clusters
(staphylococci)
Work with your shoulder partner to complete the
“Classifying Bacteria : Shapes of Bacteria” worksheet.
Proteobacteria: live symbiotically with other
organisms Example: nitrogen-fixing Rhizobium
Gram-Positive Bacteria: many cause disease
such as streptocaccus, others are helpful such as
Lactobacilli which makes yogurt
Cyanobacteria: use photosynthesis but lack
membrane-bound nucleus and chloroplasts.
Spirochetes: move by a corkscrew-like motion.
Chlamydia: gram-negative, coccoid pathogens
live only inside animal cells.
Cell Wall: protective, different composition in
Bacteria compared to Archaea
Cell Membrane and Cytoplasm: lipid bilayer but
different between Archaea and Bacteria
Important metabolic functions occur on the
membrane such as respiration.
In photosynthetic bacteria, the membrane folds like
a thylakoid
DNA: a single closed loop of double-stranded
DNA. Additional DNA maybe found in plasmids
which are small, circular and self-replicating.
Capsules and Pili
Capsule is made of polysaccharides and protects
the cell against drying or harsh chemicals, or in the
case of pathogens, the hosts white blood cells.
Pili: short, hair-like protein structures on the
surface. Help bacteria connect to each other and
to surfaces such as the host cell.
Endospores: a thick-coated, resistant structure
formed by some bacteria when environmental
conditions aren’t favorable.
Can resist high temp., chemicals, radiation,
drying and other environmental extremes.
This allows the bacteria’s DNA to survive for a
long time.
Prokaryotes obtain nutrients either from
nonliving environment or by utilizing the
products or bodies of living organisms.
Heterotrophs obtain carbon from other
organisms
Autotrophs obtain their carbon from CO2
Live in habitats based on their biochemical
abilities
Obligate anaerobes: ?
Facultative anaerobes:?
Obligate aerobes:?
Prokaryotes have various temperature
requirements for growth
Most bacterial species grow best at a pH of 6.5
to 7.5
Prokaryotes usually
reproduce by binary
fission which is a form
of asexual reproduction.
Three ways:
Transformation: takes in NDA from its outside
environment.
Conjugation: two prokaryotes bind together and
one transfers DNA to the other.
Transduction: a virus obtains a small part of DNA
from a host prokaryote which gets copied with the
viral DNA
How can bacteria cause disease in humans?
Exotoxins: toxic substances that bacteria secrete
into their environment.
Clostridium tetani = tetanus
Endotoxins: not released until the bacteria dies.
E. coli = fever, body aches, diarrhea, hemorrhage and
weakness
By destroying body tissues by releasing enzymes.
Complete the activity with both the helpful and
harmful bacteria and the microviewers.