Bacteria and Archaea - Wilmington College

12 Pages·2014·0.53 MB·English

by  Kendra Cipollini

9/14/2014
Three domain system: The present
tree of life
Bacteria and Archaea

Chapter 27
Structural and functional adaptations
Cell-surface structures
contribute to prokaryotic success
Cell wall
Unicellular Eukaryote cell walls are made of cellulose or chitin
Small Bacteria have peptidoglycan
Variety of shapes Archaea have polysaccharides and proteins but lack peptidoglycan
Cocci
Bacilli
Spiral
Well organized

Gram-positive bacteria include
Scientists use the Gram stain to classify bacteria by cell
–Actinomycetes, which decompose soil
wall composition
–Bacillus anthracis, the cause of anthrax
Gram-positive bacteria have simpler walls with a large
–Clostridium botulinum, the cause of botulism
amount of peptidoglycan
–Some Staphylococcus and Streptococcus, which can be
Gram-negative bacteria have less peptidoglycan and an pathogenic
outer membrane that can be toxic
–Mycoplasms, the smallest known cells
More likely to be antibiotic resistant Gram-Positive Bacteria
Gram-Positive Bacteria
m m
 5  2
Streptomyces, the source of many Hundreds of mycoplasmas covering
antibiotics (SEM) a human fibroblast cell (colorized SEM)
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Cell surface structures
Motility
Many bacteria exhibit taxis, the ability to move toward or
Capsule away from a stimulus
Slime layer Chemotaxis
Fimbriae
Pili Flagella –Formed from from secretory protein system

Most motile bacteria propel themselves by flagella scattered Internal Organization and DNA
about the surface or concentrated at one or both ends
Flagella of bacteria, archaea, and eukaryotes are composed of Lack compartmentalization
different proteins and likely evolved independently Specialized membranes perform metabolic functions
DNA packaged in a circular chromosome in the nucleoid
region
Additional rings of DNA called plasmids
Chromosome Plasmids
0.2 m 1 m
Respiratory
membrane
Thylakoid
membranes 1 m
Reproduction and Adaptation Prokaryotes have considerable genetic
variation: why?
Key features:

They are small, reproduce by binary fission, and have short
generation times Three factors contribute to genetic diversity:
Many prokaryotes form metabolically inactive endospores, –Rapid reproduction
which can remain viable in harsh conditions for centuries –Mutation
–Genetic recombination
Endospore
Coat
0.3 m
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Transformation and Transduction Conjugation
Transformation: Phage Conjugation: process where genetic material is transferred
incorporating foreign DNA A B Donor cell between prokaryotic cells
from the surrounding
environment A B
Transduction: movement of
genes between bacteria by Sex pilus
bacteriophages (viruses that
infect bacteria) A
Recombination
A
A B Recipient
cell
A B Recombinant cell
The role of oxygen in metabolism
Diverse nutritional and metabolic
adaptations have evolved in prokaryotes
–Obligate aerobes require O for cellular respiration
2
–Obligate anaerobes are poisoned by O and use
2
Phototrophs obtain energy from light fermentation or anaerobic respiration
Chemotrophs obtain energy from chemicals –Facultative anaerobes can survive with or without O
2
Autotrophs require CO as a carbon source
2
Heterotrophs require an organic nutrient to make
organic compounds
Nitrogen metabolism
Nitrogen is essential for the production of amino acids and
nucleic acids
Prokaryotes can metabolize nitrogen in a variety of ways
In nitrogen fixation, some prokaryotes convert
atmospheric nitrogen (N) to ammonia (NH)
2 3
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Archaea
Extremophiles
Extreme halophiles
Halobacterium
Extreme thermophiles
Thermophilus aquaticus
Methanogens

Prokaryotes play crucial roles in the Ecological Interactions
biosphere
Symbiosis
Chemical Recycling
larger host and smaller symbiont
Chemoheterotrophic
Mutualism
prokaryotes function
as decomposers Commensalism
Parasitism
Availability of
nitrogen,
phosphorus, and
potassium for plant
growth

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Prokaryotes have both beneficial and
harmful impacts on humans Pathogenic prokaryotes typically cause
disease by releasing toxins
Mutualistic Bacteria
Human intestines are home to about 500–1,000 species of bacteria
Pathogenic Bacteria  Exotoxins are secreted and cause disease even if the
Lyme disease is caused by a bacterium and carried by ticks prokaryotes that produce them are not present
 Endotoxins are released only when bacteria die
5 m
Toxic protein crystals from
Bacillus thuringiensis “Bt”
Most eukaryotes are single-celled
organisms
Protists are eukaryotes
Protists Eukaryotic cells have organelles and are more complex than
prokaryotic cells
Most protists are unicellular, but there are some colonial and
Chapter 28 multicellular species

Structural and functional diversity in Protists, the most nutritionally diverse
Protists of all eukaryotes, include:
Protists exhibit more structural and functional diversity than Photoautotrophs
any other group of eukaryotes which contain chloroplasts
Single-celled protists can be very complex, as all biological Heterotrophs
functions are carried out by organelles in each individual cell absorb organic molecules or ingest larger food particles
Mixotrophs
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Endosymbiosis
Endosymbiosis is the process in which a unicellular organism
engulfs another cell
Mitochondria
Aerobic prokaryote
Plastids
Photosynthetic cyanobacterium
The plastid-bearing lineage of protists evolved into red and
green algae

Five Supergroups of Eukaryotes Polyphyletic
Group
Excavata
Chromalveolata
Rhizaria
Archaeplastida
Unikonta
Excavates
Diplomonads
modified mitochondria
Lack plastids and most live in anaerobic environments
unique flagella
Diplomonads
Giardia intestinalis, a diplomonad
parasite
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Parabasalids Euglenozoans
Trichomonas vaginalis, a sexually transmitted disease Includes predatory heterotrophs, photosynthetic autotrophs,
and parasites
A spiral or crystalline rod of unknown function inside their
Flagella flagella
m
5 Flagella
0.2 m
8 m Crystalline rod
(cross section)
Undulating Ring of microtubules
membrane (cross section)
Chromalveolates may have originated
by secondary endosymbiosis Alveolates
The proposed endosymbiont is a red alga Members of the clade Alveolata have membrane-bounded
Includes the alveolates and the stramenopiles sacs (alveoli) just under the plasma membrane
The alveolates include
Dinoflagellates
Apicomplexans
Ciliates
Flagellum Alveoli
m

2
.0
Dinoflagellates
Have two flagella and each cell is reinforced by cellulose
plates
They are a diverse group of aquatic phototrophs, mixotrophs,
and heterotrophs
Toxic “red tides” are caused by dinoflagellate blooms
Flagella
m

3
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Apicomplexans Ciliates
Parasites of animals Use of cilia to move and feed
Most have sexual and asexual stages that require two or more Large macronuclei and small micronuclei
different host species for completion Genetic variation results from conjugation, in which two
Plasmodium requires both mosquitoes and humans to individuals exchange haploid micronuclei
complete its life cycle Paramecium
50 m

Stramenopiles Diatoms
Important phototrophs as well as several clades of  Unicellular algae with a
unique two-part, glass-like
heterotrophs wall of hydrated silica
Most have a “hairy” flagellum paired with a “smooth”  Major component of
flagellum phytoplankton and are
highly diverse
Stramenopiles include diatoms, golden algae, brown algae,  Fossilized diatom walls
and oomycetes compose much of the
sediments known as
diatomaceous earth
This removes carbon
Hairy dioxide from the m
Smooth flagellum atotm thoesp ohceeraen afnlodo “rp umps” it 04
flagellum

5 m
Golden Algae
Golden algae are named for
their color, which results
from their yellow and
brown carotenoids
The cells of golden algae are
typically biflagellated, with
both flagella near one end
Most are unicellular, but
some are colonial
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Alternation of Generations
Brown Algae
A variety of life cycles have evolved among the multicellular
Largest and most
complex algae algae
All are multicellular, and The most complex life cycles include an alternation of
most are marine generations, the alternation of multicellular haploid and
Brown algae include diploid forms
many species commonly Heteromorphic generations are structurally different, while
called “seaweeds” isomorphic generations look similar
Alternation of generations Oomycetes
Water molds, white rusts, and downy mildews
Once considered fungi based on morphological studies
Most are decomposers or parasites
They have filaments (hyphae) that facilitate nutrient uptake
Their ecological impact can be great, as in potato blight
caused by Phytophthora infestans
Rhizarians are a diverse group of
protists defined by DNA similarities Radiolarians
DNA evidence supports Rhizaria as a monophyletic clade Marine protists called radiolarians have tests fused into one
Rhizarians include Radiolarians, Forams, and Cercozoans delicate piece, usually made of silica
Radiolarians use their pseudopodia to engulf microorganisms
through phagocytosis
The pseudopodia of radiolarians radiate from the central
body
Pseudopodia
200 m
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Foraminiferans or Forams Cercozoans
Porous, generally multichambered shells, called tests Include most amoeboid and flagellated protists with
Pseudopodia extend through the pores in the test threadlike pseudopodia
Foram tests in marine sediments form an extensive fossil They are common in marine, freshwater, and soil ecosystems
record Most are heterotrophs, including parasites and predators
Many forams have endosymbiotic algae
Chromatophore
5 m
Bonnemaisonia
Red algae and green algae are the hamifera
20 cm
closest relatives of land plants Red Algae
Over a billion years ago, a heterotrophic protist acquired a Reddish in color due to an
cyanobacterial endosymbiont accessory pigment called
phycoerythrin 8 mm
Red algae are usually Dulse (Palmaria palmata)
multicellular; the largest are
Nori
seaweeds
Red algae are the most abundant
large algae in coastal waters of
the tropics
Unikonts include protists that are
Green Algae closely related to fungi and animals
Green algae are a paraphyletic group Includes animals, fungi, and some protists
The two main groups are chlorophytes and charophyceans This group includes amoebozoans and the opisthokonts
Charophytes are most closely related to land plants (animals, fungi, and related protists)
Most chlorophytes live in fresh water, although many are
marine
Other chlorophytes live in damp soil, as symbionts in lichens,
or in snow

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