Chapter 11, part A
Characterizing and Classifying Prokaryotes
Prokaryotes
" Most diverse group
of organisms
" Habitats
" From
Antarctic glaciers to thermal hot springs
" From colons
of animals to cytoplasm of other prokaryotes
" From
distilled water to supersaturated brine
" From
disinfectant solutions to basalt rocks
" Only a few capable
of colonizing humans and causing disease
Reproduction of Prokaryotic Cells
" All reproduce
asexually
" Three methods
" Binary
fission (most common)
" Snapping
division
" Reproductive
structure formation
Arrangements of Prokaryotic Cells
" Result from two
aspects of division during binary fission
" Planes in
which cells divide
" Separation
of daughter cells
Endospores
" Produced by
Gram-positive Bacillus and Clostridium
" Each vegetative
cell transforms into one endospore
" Each endospore
germinates to form one vegetative cell
" Constitute a
defensive strategy against hostile or unfavorable conditions
Endospores
" Extremely
resistant to drying, heat, radiation, and lethal chemicals
" Stable resting
stages
" Can remain viable
for tens to thousands of years
" Serious concern to
food processors, health care professionals, and governments
Modern Prokaryotic Classification
" Currently based on
genetic relatedness of rRNA sequences
" Three domains
" Archaea
" Bacteria
" Eukarya
Survey of Archaea
" Common features
" Lack
peptidoglycan
" Cell
membrane lipids have branched hydrocarbon chains
" Lack tRNA
specific for thymine
" AUG codon
codes for methionine (prokaryotes N-formylmethionine)
" Reproduce by
binary fission, budding, or fragmentation
" Most are cocci,
bacilli, or spiral forms; unusual shapes exist
" Not known to cause
disease in humans or animals
Extremophiles
" Require extreme
conditions of temperature, pH and/or salinity to survive
" Prominent members
are thermophiles and halophiles
Thermophiles
" DNA, RNA,
cytoplasmic membranes, and proteins do not function properly below 45ēC
" Hyperthermophiles
require temperatures over 80ēC
" Three
representative genera
" Acidanus
" Pyrodictium
" Sulfolobus
Halophiles
" Inhabit extremely
saline habitats
" Depend on greater
than 9% NaCl to maintain integrity of cell walls
" Contain red or
orange pigments; protection from visible and UV light
"
Most studied Halobacterium salinarium
Methanogens
" Convert carbon
dioxide, hydrogen gas, and organic acids to methane gas
" Largest group of
archaea
" Convert organic
wastes in pond, lake, and ocean sediments to methane
" Some live in
colons of animals; are one of primary sources of environmental methane
" Have produced ~10
trillion tons of methane that is buried in mud on ocean floor
Non-Archaea Prokaryotes:
Deeply Branching Bacteria
" Scientists believe
these organisms are similar to earliest bacteria
" Autotrophic
" Live in habitats
similar to those scientists think existed on early Earth
" Aquifex
considered to represent earliest branch of bacteria
" Deinococcus
has outer membrane similar to Gram-negatives, but stains Gram-positive
Phototrophic Bacteria
" Phototrophs that
contain photosynthetic lamellae; autotrophic
" Five groups
" Blue-green
bacteria (cyanobacteria)
" Green sulfur
bacteria
" Green
nonsulfur bacteria
" Purple
sulfur bacteria
" Purple
nonsulfur bacteria
Low G + C Gram-Positive Bacteria
" Clostridia
" Mycoplasma
" Low C + C
Gram-positive bacilli and cocci
" Bacillus
" Listeria
" Lactobacillus
" Streptococcus
and Enterococcus
"
Staphylococcus
High G + C Gram-Positive Bacteria
" Includes
rod-shaped cells and filamentous bacteria
" Corynebacterium
" Mycobacterium
" Actinomycetes
" Actinomyces
" Nocardia
"
Streptomyces
Gram-Negative Proteobacteria
"
Largest and most diverse group of bacteria
"
Five distinct classes
"
Alphaproteobacteria
"
Betaproteobacteria
"
Gammaproteobacteria
"
Deltaproteobacteria
" Epsilonproteobacteria
Alphaproteobacteria
" Nitrogen Fixers
" Azospirillum
" Rhizobium
" Nitrifying
Bacteria
" Nitrobacter
" Purple Nonsulfur
Phototrophs
Alphaproteobacteria (continued)
" Pathogenic
Alphaproteobacteria
" Rickettsia
" Brucella
" Ehrlichia
" Other
Alphaproteobacteria
" Acetobacter
" Gluconobacter
"
Caulobacter
Betaproteobacteria
" Pathogenic
Betaproteobacteria
" Neisseria
" Bordetella
" Burkholderia
" Nonpathogenic
Betaproteobacteria
" Thiobacillus
" Zoogloea
" Sphaerotilus
"
Spirillum
Gammaproteobacteria
" Purple Sulfur
Bacteria
" Intracellular
Pathogens
"
Legionella
" Coxiella
" Methane Oxidizers
" Glycolytic
Facultative Anaerobes
"
Family Enterobacteriaceae
Gammaproteobacteria
" Pseudomonads
" Pseudomonas
" Azotobacter
"
Azomonas
Deltaproteobacteria
" Desulfovibrio
" Bdellovibrio
" Myxobacteria
Bdellovibrio
Epsilonproteobacteria
"
Campylobacter
"
Helicobacter
Other Gram-Negative Bacteria
" Chlamydias
" Chlamydia
" Spirochetes
" Treponema
" Borrelia
" Bacteroids
" Bacteroides
"
Cytophaga