Download Lecture VII – Prokaryotes – Dr

Lecture VII – Prokaryotes – Dr. Kopeny
Delivered 2/6
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Bacteria and Archaea:
The Prokaryotic Domains
TER 26
Nitrogen cycle
Mycobacterium tuberculosis
Color-enhanced images shows
rod-shaped bacterium
responsible for tuberculosis (Raven
et al 2002)
Endosymbiotic Theory
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Structure of a Eukaryotic Animal Cell
Structure of a Prokaryotic Cell
Prokaryotic cells have a simple interior
organization compared to Eukaryotes.
•Membrane-enclosed nucleus lacking
•Membrane-enclosed cytoplasmic organelles
lacking
•Cytoskeleton lacking-support from rigid cell
wall
Structure of a Eukaryotic Plant Cell
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Lecture Themes
•origins, evolution and diversity
•structure and function
•ecological function and relationships
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
1. Prokaryote Phylogeny
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Genome of the Archaeon
Methanococcus jannaschii was
sequenced in 1996. Sequencing of M.
jannashcii confirmed Carl Woese’s longstanding hypothesis that life traces back to
three main lineages, one of which
(Archaea) includes prokaryotes that share
a more recent common ancestry with
eukaryotes than with the prokaryotic “true
bacteria”
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Prokaryotic Structure and Function
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
(Keaton 1993)
Cyanobacteria 10 um dia.
E. coli 1X2 um
Mycoplasma 0.3-0.8 um dia.
Bacteriophage 0.07X 0.2 um
Viroid 0.01 X 0.3 um
Lymphocycte 10 um dia.
Largest known prokaryote is
the marine bacterium
Thiomargarita namibiensis;
bright white cell in upper left,
about .75 mm dia., attached to
two dead ones. Fruitfly in
picture for size comparison.
Paramecium 30X 75 um
Sizes of viruses, bacteria and eukaryotes
compared Most bacteria are 1-5 um diameter
(most Eukaryotic cells are 10-100 um)
Bacillus on the head of a pin
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Raven et al 2002
Spherical coccus
(Enterococcus)
Pseudomonas
aeruginosa
Streptococcus
Spirillum
volutans
Bacterial Form
Rod-shaped bacillus
(E. coli)
Three shapes are especially common among bacteria –
spheres, rods and spirals
Most are unicellular, some aggregate transiently, some
form permanent aggregations of identical cells;some
show division of labor between two or more specialized
cell times
Helical spirilla
(|Aquaspirillum spirosa)
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Scanning electron micrograph of a colony of streptomyces, one of the
actinomycetes. The actinomycetes have a much more complicated
morphology than most other bacteria. (Keaton and Gould 1993)
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
•Most bacterial cell walls
contain peptidoglycan (lacking
in Archaea)
•Gram staining is an important
technique for identifying
bacterial; cells stain
differentially based on
structure and composition of
walls
•Pathogenesis is related to
cell wall structure and
composition
•Many antibiotics act by
preventing formation of cell
walls, by inhibiting synthesis
of cross-links in peptidoglycan
•Many prokaryotes produce
capsules that function in
adherance and protection
Penicillium
chrysogenum
Neisseria
gonorrhoeae
•Many prokaryotes have
surface appendages called pili
that are function in adherance
E. coli
The exterior surfaces of Prokaryotes. Almost all prokaryotes have a cell wall, and in
most that wall contains peptidoglycan – polymers of modified sugars that are crosslinked by short polypeptides
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Aquaspirillum sinosum
Mechanisms of Motility Many bacteria
are motile. Fllagellar action is the most
common,but not the only mechanism,
for generating movement.
Spirillum volutans
Borrelia burgdorferi
•Prokaryotic flagella
•Flagella-like helical filaments
•Growing gelatinous threads
Motility Behavior
Lyme disease
symptoms, and the
disease vector – a
tick
•Kinesis
•Taxis
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
0.05 um
1 um
Electron micrograph of E. coli
shoing long helical flagella.
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Vibrio cholerae (pathogen responsbible for cholera); the
unsheathed core visible at top of photo is composed of a single
crystal of the protein flagellin.
In intact flagella, core is surrounded by a flexible
sheath. Rotary motion of the motor creates a kind
of rotary motion when organism swims.
Bacteria swim by rotating their flagella.
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
mesosome
•various specialized
membranes, but lacking
extensive
compartmentalization by
internal membranes
plasma
membrane
DNA
The mesosome is an infolding
of the plasma membrane
serves as a point of
attachment for DNA in some
bacterial cells
Infoldings of plasma
membrane, similar in
ways to cristae of
mitochondria, function
in cellular respiration
in aerobic bacteria
•ribosomes present but
differ from eukaryotic ones
in size and composition
Exensive folded photosynthetic
membranes are visisble in Prochloron
cell. The single, circular DNA
molecule is located in the clear area
in the central region of the cell.
•genomes are smaller and
simpler than in eukaryotes;
one major chromosome
and, in some species,
plasmids
•Processes of DNA
replicatin and protein
translation are generally
similar to eukaryotes
Thylakoid
membranes of
photosynthetic
cyanobacteria
Cellular and Genomic Organization The organization of cellular components, including
the genome, differs substantially between prokaryotes and eukaryotes
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Cell division
Asexual reproduction
by cell division via
binary fission
Mechanisms of gene
transfer
-transformation; genes
from environment
-conjugation; genes
from another
prokaryote
-transduction genes
via a virus
Adaptation
short generation time
allows favorable
mutations and novel
genomes arising from
gene transfer to
spread quickly in
rapidly reprducing
Growth virtual
geometric growth while
in environments with
unlimited resources
Prokaryote Reproduction and Population Growth Prokaryote populations grow and adapt rapidly,
through asexual reproduction as well as mechanisms involving gene transfer
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Dormancy and
Endosporulation Some
bacteria form highly
resistant spores under
harsh environmental
conditions
Sporulating Bacillus cell
Antibiotic synthesis
Some prokaryotes (and
protists and fungi)
synthesize and release
antibiotic chemicals that
inhibit growth of other
microbes
Bacillus anthracus
Adaptations to Harsh Environmental Conditions: Some bacteria are capable of
dormancy, endosporulation and antibiotic synthesis
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Nutritional and Metabolic Diversity
Sources: Campbell et al (2002), Freeman (2002), Purves et al (2001)
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Nutrition; how an organism obtains two
resources from the environment;
-energy
-carbon source to build the organic
molecules of cells
•Phototrophs; use light energy
•Chemotrophs; obtain energy from
chemicals taken from the environment
•Autotroph; needs only the inorganic
compound CO2 as a carbon source
Hetertroph: requires at least one organic
nutrient for making other organic compounds
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Sources: Freeman 2002, Campbell 2002
The basic themes of metabolism, among all domains
are
-extracting usable energy from reduced compounds
-using light to produce high-energy electrons
-fixing carbon.
All organisms have mechanisms for trapping usable
energy in ATP; ATP allows cells to do work; there is
no life without ATP
At one point or another, you have studied these
metabolic themes as they occur Eukaryotes and
perhaps Prokaryotes; photosynthesis(eg,in green
plants and respiration (eg in all Eukaryotes)
Prokaryotes show tremendous diversity in
metabolic process.in that they have evolved
dozens of variations on these most basic themes of
metabolism
This Prokarotic metabolic diversity is important for
two reasons:
1.It explains their ecological diversity; they are found
almost everywhere because they exploit such a
tremendous variety of molecules as food
2.Global nutrient cycling of (eg nitrogen,
phosphorous, sulfur, carbon) is mediated by, exists
because, prokaryotes can use them in almost any
molecular form
Overview of photosynthesis and respiration
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Sources: Freeman 2002, Campbell 2002
Overview of cellular respiration One (very
important!!) example of metabolic pathways by
which many species obtain energy for generating
ATP by oxidizing reduced organic compounds
Highly reduced molecule, glucose, serves as
original electron donor (ie, molecule is oxidized)
and highly oxidized molecule, oxygen, serves as
final electron acceptor
Overview of Photosynthesis
Many prokaryotes generate ATP by employing electron donors and acceptors other than sugars
and oxygen, and produce by-products other than water
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Source: Freeman (2002), Purves et al (2001)
Some Electron Donors and Acceptors Used by Bacteria and Archaea
Electron Donor
Electron Acceptor Product
Metabolic Strategy *
H2 or organic compounds
SO42-
H 2S
sulfate-reducers
H2
CO2
CH4
methanogens
CH4
O2
CO2
methanotrophs
2-
S or H2S
O2
SO4
organic compounds
Fe3+
Fe2+
NH3
O2
organic compounds
NO3
NO2-
O2
NO2
-
-
sulfur bacteria
iron-reducers
nitrifiers
N2O, NO or N2 denitrifiers (or nitrate reducers)
NO3-
nitrosifiers
* This column gives the name biologists use to identify species that use a particular metabolic
strategy
nitrification: oxidation of
ammonia to nitrite and
nitrate ions
denitrification:
reduction of nitrogencontaining ions to form
nitrogen gas and other
products
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Source: Freeman (2002)
•lateral gene transfer has
taken place repeatedly
through transformation and
viral infection
•in transfers among bactera
and archaea the primary
mechanism probably
involves loops of mobile
DNA (plasmids)
•swapped genes tend to be
those involved in energy
and carbon metabolism
(not information processing
, eg DNA replication,
transcription, protein
synthesis) – interesting…as
metabolic diversity is a
hallmark of the Bacteria
and Archaea!!
Lateral Gene Transfer. Gray branches show
diversification of the three domains. Red branches
show movement of genes from species in one part of
the tree to species in other parts
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Nutritional Diversity among Chemoheterotrophs
(most known Prokaryotes)
•Saprobes; decomposers that absorb nutrients from
dead organic matter
•Parasites; absorb nutrients from body fluids of living
hosts
Relevance of Oxygen to Metabolism among Bacteria
and Archaea
•Obligate aerobes
•Facultative anaerobes
•Obligate anaerobes