The Bacteria
Phylogenetic tree of the major lineages
of Bacteria based on 16S ribosomal RNA
Sequence comparisons
The Purple Bacteria, also called Proteobacteria is the
largest and most physiological diverse of all bacteria
Bacteria














Purple and Green (Anoxygenic Phototrophic Bacteria)
Cyanobacteria（藻青菌）
Prochlorophytes
Chemolithotrophs: Nitrifying Bacteria
Chemolithotrophs: Sulfur- and Iron-Oxidizing Bacteria
Chemolithotrophs: Hydrogen-Oxidizing Bacteria
Methanotrophs and Methylotrophs
Sulfate and Sulfur-Reducing Bacteria
Homoacetogenic Bacteria
Budding and Appendaged (Prosthecate) Bacteria
Spirilla
Spirochetes
Gliding Bacteria
Sheathed Bacteria
Purple and Green (Anoxygenic Phototrophic) Bacteria
 Purple Bacteria:
 Bacteriochlorophylls a, b （细菌叶绿素）
 Anoxygenic photosynthesis
 One photosystem
 Green Bacteria:
 Bacteriochlorophylls c, d or e
 Anoxygenic photosynthesis
 One photosystem
 Cyanobacteria:
 Bacteriochlorophyll a
 Oxygenic photosynthesis
 Two photosystems
Purple and Green (Anoxygenic Phototrophic) Bacteria
Bacteriochlorophylls
 Bacteriochlorophylls differ
in substituents on various
parts of the porphyrin ring;
 The various modifications
lead to changes in the
absorption spectra of the
bacteriochlorophylls;
 From the long-wavelength
maximum, the identification
of the bacteriochlorophyll
can be made.
Purple and Green (Anoxygenic Phototrophic) Bacteria
Classification
 Anoxygenic phototrophic bacteria are classified
based on their bacteriochlorophylls and
photosynthetic membrane systems into three major
groups:



Purple Bacteria (Nonsulfur purple, Purple sulfur bacteria)
Green Bacteria (Green sulfur, green nonfulfur bacteria)
Heliobacteria
 Anoxygenic phototrophic bacteria also produce
carotenoid （类胡罗卜素） pigments. Therefore, the
colors of the bacteria are the combination of
bacterio-chlorophylls and carotenoid pigments
Purple and Green (Anoxygenic Phototrophic) Bacteria
Classification
Purple and Green (Anoxygenic Phototrophic) Bacteria
Carotenoids
Carotenoid-less
mutant, the actual
Bchl a color
Carotenoid-less
mutant
Purple and Green (Anoxygenic Phototrophic) Bacteria
Photosynthetic Membrane Systems
Differences between green and purple bacteria in the Photosynthetic Membrane Systems
In purple bacteria: photosynthetic pigments are parts of the internal membane (lamellae
薄层).
In green bacteria: photosynthetic apparatus consists of a series of cylindrically shaped
structures called chloroforms underlaying and attached to the cytoplasmic membrane.
In heliobacteria: bacteriochlorophyll is associated with the cytoplasmic membrane
Purple bacteria
Heliobacteria
Green Bacteria
Purple and Green (Anoxygenic Phototrophic) Bacteria
Nonsulfur purple bacteria
 can only used sulfide at a low concentration;
 have great photoheterotrophic abilities;
 some have ability to utilize methanol as sole carbon
source for phototrophic growth;
Rhodospirilum fulvum
 most are active N2 fixers.
Rhodopseudomonas acidophila
Rhodopila globiformis
Rhodocyclus purpureus
Rhodomicrobium vannielii
Rhodobacter sphaeroides
Purple and Green (Anoxygenic Phototrophic) Bacteria
Purple sulfur bacteria
 deposit sulfur and oxidize it to sulfate,
 commonly found in anoxic zones of lakes as well as
in sulfur springs,
 Ectothiorhodospira deposits sulfur externally, grows
halophilically and at high pH, found in saline lakes,
saltern, and bodies of water high in salt,
 limited ability to utilize organic compounds as C
source for phototrophic growth
 Thiocapsa grows chemoorganotrophically on acetate
Purple and Green (Anoxygenic Phototrophic) Bacteria
Purple sulfur bacteria
Thiospirillum jenense
Chromatium okenii
Thiocapsa
Thiopedia rosea
Purple and Green (Anoxygenic Phototrophic) Bacteria
Green sulfur bacteria
 Morphologically diverse (nonmotile rods, spirals, spheres, motile
filamentous gliding, prosthecae);
 Some living planktonically in lakes possess gas vesicles;
 Strictly anaerobic;
 Obligate phototrophic;
 Most can assimilate simple organic substances (acetate, propionate,
pyruvate and lactate)for phototrophic growth provided that a
reduced sulfur compound is present as a sulfur source;
Chlorobium limicola
Pelodictyron clathratiforme
Purple and Green (Anoxygenic Phototrophic) Bacteria
Green nonsulfur bacteria
 Chloroflexus has been given the designation green nonsulfur
bacterium;
 able to grow chemoorganotrophically in the dark under aerobic
conditions;
 able to grow phototrophically on a wide variety of sugars, amino
acids, and organic acids;
 able to grow phototrophically with H2S or H2 and CO2;
 best grow photoheterotrophically;
Oscillochloris
Oscillochloris
Chloroflexus aurantiacus
Purple and Green (Anoxygenic Phototrophic) Bacteria
Heliobacteria
 Phylogenetically separate group of anoxygenic phototrophic
bacteria that contain bacteriochlorophyll g;
 Consisting of



Heliobacterium
Heliophilum
Heliobacillus
 Strictly anaerobic phototrophs;
 Unable to grow by respiratory means;
 Similarity between Bchl g and Chlorophyll a (modified form of
hydroxychlorophyll a);
Heliobacillus mobilis
Purple and Green (Anoxygenic Phototrophic) Bacteria
A Comparison of electron flow in green sulfur, heliobacteria and purple bacteria
Bchl a
Bchl g
Purple and Green (Anoxygenic Phototrophic) Bacteria
Ecology
Purple sulfur bacteria
from a stratified lake
Green sulfur bacteria
from a stratified lake
Purple and Green (Anoxygenic Phototrophic) Bacteria
Ecology
Membrane filters
through which
The phototrophic bacterium were passed water
forms a layer just at the top samples taken at
varying depth
of the anoxic zone
A syringe sampling
device that can collect
water at intervals
Vertical stratification
of purple sulfur
bacteria (Amoebabacter
purpureus in a
CanadianLake
Purple and Green (Anoxygenic Phototrophic) Bacteria
Ecology
Massive accumulation of purple sulfur
bacteria: Thiopedia roseopersicinia in a
spring in Madison. The green color is
from cells of alga Spirogyra
Cross-section through a bacterial mat:
top: cyanobacteria;
pink: phototrophic purple sulfur bacteria
black: sulfate-reducing bacteria
peach: Bchl b containing cells of Thiocapsa
Cyanobacteria: Diversity
 A large and heterogeneous group of phototrophic bacteria
 Oxygenic phototrophs, Bergey’s Manual has divided them into 5 major groups
 Contain unsaturated fatty acids with two or more double bonds instead of one in
other bacteria.
Unicellular Gloeothece
Filamentous, Oscillatoria Filamentous heterocystous Anabaena
Similar to gram-positive bacteria.
All cyanobacteria have chlorophyll a
All have biliprotein（胆蛋白质）
pigments:
Phycobilins（藻胆素）, or
Phycoerythrin（藻红蛋白）
Colonial Dermocarpa
Filamentous branching Fischerella
Cyanobacteria
Structural variations: gas vesicles and heterocysts
 Gas vesicles: provide flotation, so the cells
will remain where there is most light.
 Heterocysts: rounded, distributed regularly
along a filament or at one end of a filament,
are the sole sites of nitrogen fixation in
heterocystous cyanobacteria
Heterocysts in
cyanobacterium
Anabaena
Prochlorophytes
 Prokaryotic oxygenic phototrophs that contain
chlorophyll a and b but do not have phycobilins.
 Resemble both cyanobacteria and the plant chloroplast.
Filamentous prochlorophyte Prochlorothrix
The first prochlorophyte discovered
is Prochloron, has extensive thylakoid
membrane system similar to chloroplast
Prochlorophytes, cyanobacteria and
the plant chloroplasts share a common ancestor
Chemolithotrophs: Nitrifying Bacteria
 Bacteria able to grow chemolithotrophically at the
expense of reduced inorganic nitrogen compounds




(1) Nitrosifying bacteria:
NH3 + O2
NO2- + H+ + H2O
(2) Nitrifying bacteria:
NO2- + O2
NO3-
 No chemolithotroph is known that will carry out the
complete oxidation of ammonia to nitrate
 (1) Nitrosomonas, Nitrosococcus, Nitrosospira
 (2) Nitrobacter, Nitrospira, Nitrococcus
 They are members of the purple bacteria
Chemolithotrophs: Sulfur- and Iron-Oxidizing Bacteria
 Members of purple bacteria
 Have ability to grow chemolithotrophically on
reduced sulfur compounds
 Only six genera: Thiobacillus, Thiosphaera,
Thiomicrospira, Thermothrix, Beggiatoa and
Sulfolobus (Archaea) have been cultured.
 Two groups: neutrophilic and acidophilic
 The acidophilic group can grow
chemolithotrophically using ferrous iron as electron
donor
 Thiobacillus ferrooxidans has been used for leaching
Chemolithotrophs: Hydrogen-Oxidizing Bacteria
 Capable of growing with H2 as sole electron donor and
O2 as electron acceptor,
 Many of them can also grow autotrophically using
Calvin cycle to fix CO2,
 All contain hydrogenase for binding H2 and use it to
produce ATP,
 Can grow both chemoorganotrophs and
chemolithotrophs,
 Most are obligate aerobes, but prefer microaerobic
conditions when growing chemolithotrophically on H2,
 Some can grow on CO,
 Best studied Alcaligenes eutrophus, or Ralstonia
eutropha
Methanotrophs and Methylotrophs
 Methanotrophs:
 utilize methane, and/or a few other one-carbon
compounds as sole source of carbon
 aerobes (Purple Bacteria)
 widespread in nature in soil and water
 possess methane monooxygenase
 obligate C1 utilizers
 contain large amount of sterols in internal membrane
 Methylotrophs:
 utilize methane and other one-carbon compounds as
electron donors for energy generation and as sole
sources of carbon
 many can utilize organic acids, ethanols and sugars
Methanotrophs and Methylotrophs
Classification
 Based on internal cell structure and carbon
assimilation pathway:


Type I: ribulose monophosphate cycle, lack a
complete TCA cycle
Type II: Serine pathway
Methylosinus, Type II
Methylococcus capsulatus, Type I
Methanotrophic Symbionts of Animals
 Intact mussels as well as isolated mussel
gill tissue consume methane at high rates
in the presence of O2 due to symbiotic
methanotrophic bacteria presence.
Symbiotic methanotrophs in the gill tissue of a marine mussel living
near hydrocarbon seeps in the Gulf of Mexico