characterizing and classifying prokaryotes chapter 11
TRANSCRIPT
CHARACTERIZING AND CLASSIFYING PROKARYOTES
CHAPTER 11
Prokaryotes
Most diverse group of organismsHabitats
All possible habitats are exploited by some sort of prokaryote
Only a few capable of colonizing humans and causing disease
Morphology of Prokaryotic Cells
Figure 11.1
Arrangements of Prokaryotic Cells
Result from two aspects of division during binary fission Planes in which cells divide Separation of daughter cells
Arrangements of Cocci: Diplococci
Figure 11.6a
Arrangements of Cocci: Streptococci
Figure 11.6b
Arrangements of Cocci: Tetrads
Figure 11.6c
Arrangements of Cocci: Staphylococci
Figure 11.6e
Arrangements of Bacilli: Single Bacillus
Figure 11.7a
Arrangements of Bacilli: Diplobacilli
Figure 11.7b
Arrangements of Bacilli: Streptobacilli
Figure 11.7c
Arrangements of Bacilli: V-Shape and Palisade
Figure 11.7d
Endospores
Produced by Gram-positive bacteria Bacillus and Clostridium are examples
Each vegetative cell transforms into one endosporeEach endospore germinates to form one vegetative
cellConstitute a defensive strategy against hostile or
unfavorable conditionsEndospores are not reproductive structures
Modern Prokaryotic Classification
Three domains of Life Archaea (prokaryote) Bacteria (prokaryote) Eukarya (eukaryote)
Archaea
Features of Archaea
Prokaryotes (no membrane bound nucleus) Lack Peptidoglycan in their cell walls Genome is circular DNA Histone proteins are present Ribosomes are more similar to bacteria than
eukaryotes Many occupy "extreme' environments.
Extremophiles Not known to cause disease in humans or animals
Halophiles
Inhabit extremely saline habitatsDepend on greater than 9% NaCl to maintain integrity
of cell wallsMany contain red or orange pigments; protection from
visible and UV lightExtreme Halophiles… require very high salt (not just
tolerant) Most require at least 9 % NaCl Most require 12-23% NaCl for optimal growth Almost all can grow at 32% NaCl
Most studied – Halobacterium salinarium
Extreme Halophiles
Great salt lake
Seawater evaporation
ponds
SEM of halophiles
African “soda lake” high
alkalinity, high salinity
Methanogens
Convert carbon dioxide, hydrogen gas, and organic acids to methane gas
Largest group of archaeaConvert organic wastes in pond, lake, and ocean
sediments to methaneSome live in colons of animals; are one of primary
sources of environmental methane
Methanogens
CH4 (methane producers)Strict anaerobesExample genus: Methanococcus
Methanogens
Methanogen habitats
Hyperthermophiles
Most are obligate anaerobesMost require S as part of their metabolic schemeExample Genera:
Sulfolobus Thermococcus Pyrolobus
Hyperthermophiles – require temperatures over 80ºCHeat stable biomolecules
Hyperthermophile Habitats
Bacterial groups
Phototrophic Bacteria
PhotoautotrophsFive groups … (often grouped by color)
Blue-green bacteria (cyanobacteria) Chlorophyll a (oxygenic photosynthesis)
Green sulfur bacteria bacteriochlorophyll Green nonsulfur bacteria “ Purple sulfur bacteria “ Purple nonsulfur bacteria “
Phototrophic Bacteria
Table 11.1
Low G + C Gram-Positive Bacteria
ClostridiaMycoplasmaBacillusListeriaLactobacillus Streptococcus Staphylococcus
High G + C Gram-Positive Bacteria
Includes rod-shaped cells and filamentous bacteriaCorynebacteriumMycobacteriumActinomycetes
Actinomyces Nocardia Streptomyces
Actinomycetes
Figure 11.17
Gram-Negative Proteobacteria
Largest and most diverse group of bacteria More diseases are caused by this group than any other.
Five distinct classes Alphaproteobacteria Betaproteobacteria Gammaproteobacteria Deltaproteobacteria Epsilonproteobacteria
Alphaproteobacteria
Nitrogen fixers Azospirillum Rhizobium
Nitrifying bacteria Nitrobacter
Purple nonsulfur phototrophsPathogenic alphaproteobacteria
Rickettsia Brucella Ehrlichia
Caulobacter
Betaproteobacteria
Pathogenic betaproteobacteria Neisseria Bordetella
Nonpathogenic betaproteobacteria Thiobacillus Spirillum
Gammaproteobacteria
Purple sulfur bacteria Intracellular pathogens
Legionella Coxiella
Methane oxidizersFacultative anaerobes
Family Enterobacteriaceae
Pseudomonads Pseudomonas Azotobacter Azomonas
Deltaproteobacteria
Bdellovibrio
Myxobacteria
Epsilonproteobacteria
CampylobacterHelicobacter
Other Gram-Negative Bacteria
Chlamydias Chlamydia
Spirochetes Treponema Borrelia
Bacteroids Bacteroides