Transcript Tuesday, October 17, 2006 - Chicagoland Jewish High School

GOALS:
•Review characteristics of prokaryotic cells
•Describe how prokaryotic cells are classified
•Explain ecological roles & significance of prokaryotes
•Compare prokaryotic binary fission to eukaryotic mitosis
•Explain 4 mechanisms for how bacteria create new
genetic combinations
•Describe shape and cell wall structure of bacteria
Characteristics of Prokaryotic Cells
• Lack nucleus
-->have ‘nucleoid region’
• Have one, circular piece
of DNA with all genes
• Contain a cell wall made
of peptidoglycan
• Have ribosomes
• Lack membrane-bound
organelles
• May have a flagellum, but
it’s not made of
microtubules like those of
eukaryotes
• What else?
Classification of Prokaryotes-1 million
species(est)-4,000 named
• There are two domains of prokaryotic cells
• A domain is more inclusive than a kingdom
• Prokaryotic domains:
– BACTERIA- Kingdom Eubacteria (true bacteria)
– ARCHAEA- Archaea consists of Kingdom Archaea
Figure 27.2
QuickTime™ and a
mpeg4 decompressor
are needed to see this picture.
LIFE IN EXTREME ENVIRONMENTS
ARCHAEA
Most of us have the tendency to think of life a a rather cozy affair, taking place
at a pressure of one atmosphere, in an atmosphere of oxygen, at
approximately neutral pH and temperature near that of our own bodies (37 oC).
Indeed, most organisms have uniquely adapted to growth in this common
environment.
What is an extreme environment?
a. Environments that usually contain physical or chemical factors
that have traditionally used to kill microorganisms that spoil food
and clothing and cause disease of animals and plants.
b. An environment in which some organisms can \grow, whereas
others cannot. thus, an extreme environment has a low species
diversity with whole taxonomic groups missing.
Extremophiles are microorganisms that have been shown to exist(growth) in
more stringent conditions than do other organisms.
WHY STUDY THEM?
Anatomically related to bacteria but possess biochemical and genetic
properties similar
to those of Eukaryotes.
Extant hyperthermophiles live in environments that are thought to be
similar to those that existed on earth 3.9 billion years ago (when life
could have originated).
a. Hot
b. Reducing atmosphere (no oxygen)
c. High levels of hydrogen and sulfurous compounds
Paleobiological evidence that 400-million-year-old rocks contain
chemical, physical, and anatomical imprints of ancient hydrothermal
ecosystems (similar to todays hyperthermophiles).
Classification of Prokaryotes
• Domain Archaea consists of Kingdom Archaea
– Bacteria of Kingdom Archaea are called extremophiles
because they live in harsh environments
– ACIDOPHILES: live in highly acidic environments
– HALOPHILES: live in extremely salty environments
– THERMOPHILES: live in extremely hot
environments(65-113 C)(0-10 C)
• Thermus aquaticus lives in hot springs of
Yellowstone National Park
– METHANOGENS: derive energy by using CO2 to
oxidize H2 to make CH4 (methane)
MOST RESEARCH HAS BEEN CARRIED OUT WITH THERMOPHILIC
MICROORGANISMS
WHY HAS MOST OF THE RESEARCH FOCUSED ON THIS GROUP OF
MICROORGANISMS?
1. Identify the clever biochemical and genetic ways that these organisms have found to adapt to high
temperature environment.
. gene regulation
. unique protein structure
2. Direct utilization of these organisms and their products for industrial purposes.
. Enzymes used in research (molecular cloning)TAQ
. Enzymes used in medical diagnostic kits
. Enzymes used for production of ethanol
. Enzymes used for commercial purposes
3. Hyperthermophiles may be the oldest organisms still around. their natural habitats (associated with
volcanic activity) have existed throughout most of the time in which organisms have been evolving on earth
Domain Bacteria consists of
Kingdom Eubacteria
(true bacteria)
Ecology of Bacteria- Eubacteria
• Bacteria obtain energy in a variety of ways (table 27.1)
• Bacteria can be autotrophs
– Photoautotrophs
– Chemoautotrophs
• Bacteria can be heterotrophs
– Photoheterotrophs
– Chemoheterotrophs
• Chemo- = use inorganic chemicals as energy source
• CYANOBACTERIA:
– First photoautotrophic organisms on Earth which produced
oxygen as waste product and changed conditions of life on
Early Earth
Ecology of Bacteria
• Bacteria interact with other organisms within their
community
– SAPROBES: C, N element cycling
• Denitrifying:
• Nitrifying:
NO3- --> N2
Pseudomonas
NH4+ ---> NO2 or NO3 Nitrosomonas
– PARASITES
• Pathogens - cause disease / illness in plants, animal, fungi
– MUTUALISTIC
• Nitrogen fixing: N2 --> NH4+
Rhizobium
– BIOREMEDIATION
• Metabolize petroleum from oil spills
• Sewage treatment
– PHYTOPLANKTON & ZOOPLANKTON: base of food
chains & food webs
– BIOTECHNOLOGY & BIOCHEMICAL USES
• Copy human genes, make human proteins, make alcohol
QuickTime™ and a
mpeg4 decompressor
are needed to see this picture.
Bacteria Morphology
• There are three main
shapes of bacteria cells
(fig 27.3)
– Coccus = spherical
– Bacillus = rod-shaped
– Spirillum = helical
• Cells can be grouped:
– Staphylo = clusters
– Strepto = chains
Bacteria Morphology
• Prokaryotes have cell wall
made of peptidoglycan (27.5)
• Peptidoglycan is composed
of CHO & proteins
• There is >> variation in
structure & composition of
bacteria cell walls between
Eubacteria & Archaea
• Some bacteria also possess
a capsule & a pilus which
allow bacteria to bind to
substrates, swap genetic
info, or block immune
responses of hosts
• What is the function of the
cell wall?
Peptidoglycan
Molecular
Structure
Bacteria Reproduction
• Bacteria reproduce
asexually by BINARY
FISSION.
• In ideal environments,
bacteria can divide
every 20 minutes!
• What is the selective
advantage to such rapid
reproduction?
• How does prokaryotic
binary fission differ
from eukaryotic
mitosis?
Bacteria Reproduction
• Bacteria may swap genes
and therefore alter their
genetic make up
• What is selective
advantage for obtaining
new genes?
• CONJUGATION
– Obtain plasmid or swap
plasmid with another cell
thru sex pilus
• TRANSFORMATION
– Pick up naked DNA from
environment
• TRANSDUCTION
– Obtain new genes from
viruses
ROLE OF BACTERIA
1. Responsible for creating properties of atmosphere and soils
2. Are autotrophic, photosynthetic and chemosynthetic, contribute to world carbon
balance
3. Are heterotrophic and break down organic compounds
4. Few genera of bacteria are capable of fixing atmospheric nitrogen
5. Involved in industrial processes and chemical syntheses
a.
Produce acetic acid, vinegar, amino acids, enzymes
b.
Production of various milk products, bread and ethanol
c.
Antibiotics derived from bacterial sources
6. Genetic engineering applications
ROLE OF BACTERIA
1. Responsible for creating properties of atmosphere and soils
2. Are autotrophic, photosynthetic and chemosynthetic, contribute to world carbon
3. Are heterotrophic and break down organic compounds
4. Few genera of bacteria are capable of fixing atmospheric nitrogen
5. Involved in industrial processes and chemical syntheses
a.
Produce acetic acid, vinegar, amino acids, enzymes
b.
Production of various milk products, bread and ethanol
c.
Antibiotics derived from bacterial sources
6. Genetic engineering applications
III. PROKARYOTES("before nucleus") VERSUS EUKARYOTES
A. Structural Differences
1. Multicellularity: bacteria are fundamentally single-celled
a. May adhere within matrix, some form filaments
b.Few integrated activities between cells
2. Cell size: extremely small individual cell size
3. Chromosomes: non-membrane bound DNA is circular and lacks
proteins
4. Cell division and genetic recombination
a.
Simple division via binary fission
b.
True sexual reproduction absent, genetic recombination
irregular
5. Internal compartmentalization: Lack membrane-bound organelles
a.
Enzymes are bound to cell membrane
b.
Only organelles present are ribosome's
B.
Metabolic Diversity:
1. Eukaryotes exhibit only one form of photosynthesis
2. Bacteria exhibit several patterns of photosynthesis, aerobic and
anaerobic
3. Bacteria undergo chemosynthesis and fix atmospheric nitrogen
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TIFF ( Unc ompres s ed) dec ompres sor
are needed to s ee this pic tur e.