Edited_Proteobacteria_powerpoint - Copy.ppt

A major lineage (phyla) of Bacteria
Includes many of the most commonly encountered bacteria
Most metabolically diverse of all domain Bacteria
E.g., chemolithotrophy, chemoorganotrophy, phototrophy
Morphologically diverse
Divided into five classes
Alpha-, Beta-, Delta-, Gamma-, Epsilon-

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PROTEOBACTERIA
By Rikta Vekaria

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The Phylogeny of Bacteria
I. Phylum Proteobacteria
•Carl Woese proposed this group in 1987
•“Purple bacteria” and their relatives
•Due to red purple pigment
•With Various Shapes (spherical, rod-like,ringed,
spiral, filamentous or curved)
•Gram-negative

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The Phylogeny of Bacteria –Major phyla of domainBacteria
Phylogenetic Overview of Bacteria

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PHYLOGENIC TREE OF PROTEOBACTERIA

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Phylum Proteobacteria
A major lineage (phyla) of Bacteria
Includes many of the most commonly encountered bacteria
Most metabolically diverse of all domain Bacteria
E.g., chemolithotrophy, chemoorganotrophy, phototrophy
Morphologically diverse
Divided into five classes
Alpha-, Beta-, Delta-, Gamma-, Epsilon-

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Major Genera of Proteobacteria

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Major Genera of Proteobacteria

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DISTRIBUTION OF PROTEOBACTERIA

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S.N CLASS GENUS DISTRIBUTION
1. ALPHA
PROTEOBACTERIA
Rickettsiaand
Coxiella
PARASITICOR
MUTALSITIC :
Parasitic :Vertebrate
erythrocytes,macrophagesand vascular
endothelial cells
Invertebrates : Live in arthropods
Cauloobacterand
Hyphomicrobium
Hyphomicrobium:
Attach to solid objects in freshwater, marine
and terrestrial environments
Caulobacter: Freshwater and marine habitats
with low nutrient levels
AgrobacteriumInvade the crown ,roots and stems of plants
RhizobacteriumRootnodules

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S.NCLASS GENUS DISTRIBUTION
1. ALPHA
PROTEOBACTE
RIA
Nitrifyingbacteria:
Nitrosomonas
Nitrosopira
Soil, freshwater and
marine habitat

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S.NCLASS order DISTRIBUTION
2. Beta
PROTEOBACTE
RIA
Neisseriales Inhabitants of mucous
membranes of mammals
Burkholderiales Burkholderia:Organic
molecules
Sphaerotilus:slowly
running freshwater with
sewage or industrial waste
Leptothrix:High
concentration of soluble
iron compounds

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S.NCLASS order DISTRIBUTION
2. Beta
PROTEOBACTE
RIA
Nitrosomonadales Rootnodules
Hydrogenophilales
Thiobacillus:Soil,
aquatic habitat ,both
freshwater and marine

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S.NCLASS order DISTRIBUTION
3. GAMMA
PROTEOBACTE
RIA
Purplesulphurbacteria:
Thiotrichales
Grows in sulfide rich
habitats such as sulfur
springs,freshwater with
decaying plant material
Pseudomonadales Organic molecules
,Major animal and plant
pathogens, involved in
spoilage of refrigerated
milk, meat, egg, and
seafood

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S.NCLASS order DISTRIBUTION
3. GAMMA
PROTEOBACTE
RIA
Vibrionales Aquatic
microgorganisms,widespread
in freshwater and sea
Enterobacteriales Inhabitant of colon of humans
and other warm blooded
animals,Someare pathogens
of crop plants
Pasteurellales Disease causing in
humans and animals
4. DELTA
PROTEOBACTE
RIA
Desulfovibrionales,
Desulfobacterales,
Desulfomonadales
Aquatic and terrestrial
habitats

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CHARACTERISTICS OF PROTEOBACTERIA

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The characteristics of important genera of
Gammaproteobacteria.

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example Genus
Microscopic
Morphology
Unique Characteristics
Beggiatoa
Gram-negative
bacteria; disc-
shaped or cylindrical
Aquatic, live in water with high content of hydrogen
disulfide; can cause problems for sewage treatment
Enterobacter
Gram-negative
bacillus
Facultative anaerobe; cause urinary and
respiratory tract infections in hospitalized
patients; implicated in the pathogenesis of
obesity
Erwinia
Gram-negative
bacillus
Plant pathogen causing leaf spots and
discoloration; may digest cellulose; prefer
relatively low temperatures (25–30 °C)
Escherichia
Gram-negative
bacillus
Facultative anaerobe; inhabit the gastrointestinal tract
of warm-blooded animals; some strains are
mutualists, producing vitamin K; others, like
serotypeE. coliO157:H7, are pathogens;E. colihas
been a model organism for many studies in genetics
and molecular biology

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Example Genus
Microscopic
Morphology
Unique Characteristics
Klebsiella
Gram-negative
bacillus; appears
rounder and thicker
than other members
ofEnterobacteriaceae
Facultative anaerobe, encapsulated, nonmotile;
pathogenic species may cause
pneumonia, especially in people with
alcoholism
Legionella
Gram-negative
bacillus
Fastidious, grow on charcoal-buffered yeast
extract;L. pneumophilacauses
Legionnaires disease
Hemophilus
Gram-negative
bacillus
Pleomorphic, may appear as
coccobacillus, aerobe, or
facultative anaerobe; grow on blood
agar; pathogenic species can cause respiratory
infections, chancroid, and other diseases

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Example Genus
Microscopic
Morphology
Unique Characteristics
Proteus
Gram-negative
bacillus
(pleomorphic)
Common inhabitants of the human gastrointestinal
tract; motile; produce urease; opportunistic
pathogens; may cause urinary tract
infections and sepsis
Pseudomonas
Gram-negative
bacillus
Aerobic; versatile; produce yellow and blue pigments, making
them appear green in culture; opportunistic, antibiotic-resistant
pathogens may cause wound infections, hospital-acquired
infections, and secondary infections in patients with cystic fibrosis
Serratia
Gram-negative
bacillus
Motile; may produce red pigment; opportunistic pathogens
responsible for a large number of hospital-acquired infections

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Example Genus
Microscopic
Morphology
Unique Characteristics
Vibrio
Gram-negative,
comma-or
curved rod-
shaped bacteria
Inhabit seawater; flagellated, motile; may produce
toxin that causes hypersecretion of water and
electrolytes in the gastrointestinal tract; some
species may cause serious wound infections
Yersinia
Gram-negative
bacillus
Carried by rodents; human pathogens;Y.
pestiscauses bubonic plague and pneumonic
plague;Y. enterocoliticacan be a pathogen
causing

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The characteristics of important genera of
Alpha proteobacteria.

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AGROBACTERIUMINDUCED TUMORS

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CAULOBACTERIA

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RICKETTSIA

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ALIIVIBRIO FISCHERI
a)Aliivibrio fischeriis a bioluminescent bacterium.
(b)A. fischericolonizes and lives in a mutualistic relationship
with the Hawaiian bobtail squid

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a)Legionella pneumophila

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β-proteobacteria

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β-proteobacteria

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Class (delta) Proteobacteria
Genus Microscopic Morphology Unique characteristics
Bdellovibrio
Gram-negative, comma-shaped
rod
Obligate aerobes; motile;
parasitic (infecting other bacteria)
Desulfovibrio(formerlyDesufuro
monas)
Gram-negative, comma-shaped
rod
Reduce sulfur; can be used for
removal of toxic and radioactive
waste
Myxobacterium
Gram-negative, coccoid bacteria
forming colonies (swarms)
Live in soil; can move by gliding;
used as a model organism for
studies of intercellular
communication (signaling)

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Class (delta) Proteobacteria
Include some bacteria that have predators on other bacteria
Important contribution to sulfur cycle.
Genus Bdellovibrio
motile: single polar flagella
attacks other Gram negative bacteria
reproduces in periplasm
Genus Myxococcus
motile via slime trails
digest bacteria
low nutrients: aggregate to form a fruiting body ! myxospores

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Myxobacteria
Myxobacteria form fruiting bodies. (credit: modification of work by Michiel Vos)

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PREDATORYBDELLOVIBRIOBACTERIUM
LYSING A PREYE. COLICELL.

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Brock Biology of Microorganisms, Twelfth Edition
–Madigan / Martinko / Dunlap / Clark
Neisseria meningitidisgrowing in
colonies on a chocolate agar plate.

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Brock Biology of Microorganisms, Twelfth Edition
–Madigan / Martinko / Dunlap / Clark
The Epsilonproteobacteria
Epsilonproteobacteria
Abundant in oxic–anoxic interfaces in sulfur-rich
environments
e.g., hydrothermal vents
Many are autotrophs
Using H
2, formate, sulfide, or thiosulphate as electron
donor
Pathogenic and non-pathogenic representatives

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Characteristics of Key Genera of Epsilonproteobacteria

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Characteristics of Key Genera of Epsilonproteobacteria

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HELICOBACTERIA PYLORI
Helicobacter pylorian cause chronic gastritis,
which can lead to ulcers and stomach cancer.

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Sulfospirillum

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Acrobacter

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Zeta proteobacteria
•The classZetaproteobacteriais the sixth and most recently
described class of theProteobacteria. Zetaproteobacteria can also
refer to the group of organisms assigned to this class.
•The Zetaproteobacteria are represented by a single described
species,Mariprofundus ferroxidans ,which is aniron oxidizing
neutrophilic chemolithoautotroph originally isolated fromLoihi
seamount in 1996 (post-eruption).

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Zeta proteobacteria
•Molecular cloning techniques focusing on thesmall subunit
ribosomal RNA genehave also been used to identify a more
diverse majority of the Zetaproteobacteria that have as yet been
unculturable.

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GENERAL FEATURES OF
PROTEOBACTERIA:Grouping based on
common phenotype themes and metabolic
themes

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phenotype themes and metabolic themes
I .Phototrophic, Chemolithotrophic & Methanotrophic
Proteobacteria
II. Aerobic & Facultatively Aerobic Chemoorganotrophic
Proteobacteria
III. Morphologically Unusual Proteobacteria

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1. Purple Phototrophic Bacteria
2. The Nitrifying Bacteria
3. Sulfur-and Iron-Oxidizing Bacteria
4. Hydrogen-Oxidizing Bacteria
5. Methanotrophsand Methylotrophs
I Phototrophic, Chemolithotrophic & Methanotrophic
Proteobacteria

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1. Pseudomonadsincluding Pseudomonas
2. Acetic Acid Bacteria
3. Free-Living Aerobic Nitrogen-Fixing Bacteria
4. Neisseria, Chromobacterium, & Relatives
5. Enteric Bacteria
6. Vibrio, Alivibrio, and Photobacterium
7. Rickettsias
II Aerobic & Facultatively Aerobic Chemoorganotrophic
Proteobacteria

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III Morphologically Unusual Proteobacteria
1. Spirilla
2. SheathedProteobacteria: Sphaerotilus& Leptothrix
3. Budding and Prosthecate/Stalked Bacteria

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1.Phototrophic,
Chemolithotrophic
& Methanotrophic
Proteobacteria

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1. Purple Phototrophic Bacteria
2. The Nitrifying Bacteria
3. Sulfur-and Iron-Oxidizing Bacteria
4. Hydrogen-Oxidizing Bacteria
5. Methanotrophsand Methylotrophs
I Phototrophic, Chemolithotrophic & Methanotrophic
Proteobacteria

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1. Purple Phototrophic Bacteria
Purple Phototrophic Bacteria
Carry out anoxygenicphotosynthesis; no O
2evolved
Morphologically diverse group
Genera fall within the Alpha-, Beta-, or
Gammaproteobacteria
Contain bacteriochlorophyllsand carotenoidpigments
Produce intracytoplasmicphotosynthetic membranes
with varying morphologies

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Liquid Cultures of Phototrophic Purple Bacteria
Figure 15.2

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Membrane Systems of Phototrophic Purple Bacteria
Figure 15.3
a.Ectothiorhodospira
mobilis,showing the
photosynthetic
membranes in flat
sheet
b.Allochromatium
vinosum showing the
membranes as
individual spherical
shaped vesicles

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Purple Phototrophic Bacteria
Purple Sulfur Bacteria
Use hydrogen sulfide (H
2S) as an electron donor for
CO
2reduction in photosynthesis
Sulfide oxidized to elemental sulfur (S
o
) that is stored
as globules either inside or outside cells
Sulfur later disappears as it is oxidized to sulfate (SO
4
2-
)

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Purple Phototrophic Bacteria
Purple Sulfur Bacteria(cont’d)
Many can also use other reduced sulfur compounds,
such as thiosulfate(S
2O
3
2-
)
All are Gammaproteobacteria
Found in illuminated anoxic zones of lakes and other
aquatic habitats where H
2S accumulates, as well as
sulfur springs

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Photomicrographs of Purple Sulfur Bacteria
Figure 15.4

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Genera and Characteristics of Purple Sulfur Bacteria

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Genera and Characteristics of Purple Sulfur Bacteria

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Genera and Characteristics of Purple Sulfur Bacteria

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Blooms of Purple Sulfur Bacteria
Figure 15.5

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Purple Non-sulfur Bacteria
Purple NonsulfurBacteria
Originally thought organisms were unable to use sulfide as
an electron donor for CO
2reduction, now know most can
Most can grow aerobically in the dark as
chemoorganotrophs
Some can also grow anaerobicallyin the dark using
fermentative or anaerobic respiration
Most can grow photoheterotrophicallyusing light as an
energy source and organic compounds as a carbon source
All in Alpha-and Betaproteobacteria

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Representatives of Purple Nonsulfur Bacteria
Figure 15.6

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Genera and Characteristics of Purple Nonsulfur Bacteria

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Genera and Characteristics of Purple Nonsulfur Bacteria

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2. The Nitrifying Bacteria
Nitrifying Bacteria
Able to grow chemolithotrophically at the expense of
reduced inorganic nitrogen compounds
Found in Alpha-, Beta-, Gamma-, and Deltaproteobacteria
Nitrification(oxidation of ammonia to nitrate) occurs as two
separate reactions by different groups of bacteria
Ammonia oxidizers(nitrosifyers) (e.g., Nitrosococcus)
Nitrite oxidizer(nitrifyer) (e.g., Nitrobacter)
Many species have internal membrane systems that house key
enzymes in nitrification
Ammonia monooxygenase: oxidizes NH
3to NH
2OH
Nitrite oxidase: oxidizes NO
2
-
to NO
3
-

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Nitrifying Bacteria(cont’d)
Widespread in soil and water
Highest numbers in habitats with large amounts of
ammonia
i.e., sites with extensive protein decomposition and sewage
treatment facilities
Most are obligate chemolithotrophsand aerobes
One exception is annamoxorganisms, which oxidize ammonia
anaerobically

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Figure 15.7

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3. Sulfur-and Iron-Oxidizing Bacteria
Sulfur-Oxidizing Bacteria
Grow chemolithotrophically on reduced sulfur
compounds
Two broad classes
Neutrophiles
Acidophiles(some also use ferrous iron (Fe
2+
)
Thiobacillus(rods)
Sulfurcompounds most commonly used as electron
donors are H
2S, S
o
, S
2O
3
2-
; generates sulfuric acid
Achromatium(spherical cells)
Common in freshwater sediments
Some obligate chemolithotrophs possess special
structures that house Calvin cycle enyzmes
(carboxysomes)

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Beggiatoa
Filamentous, gliding bacteria
Found in habitats rich in H
2S
e.g., sulfur springs, decaying seaweed beds, mud layers
of lakes, sewage polluted waters, and hydrothermal vents
Most grow mixotrophically
with reduced sulfur compounds as electron donors
and organic compounds as carbon sources
Thioploca
Large, filamentous sulfur-oxidizing bacteria that form cell
bundles surrounded by a common sheath
Thick mats found on ocean floor off Chile and Peru
Couple anoxic oxidation of H
2S with reduction of NO
3
-
to NH
4
+

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Non-filamentous Sulfur Chemolithotrophs
Figure 15.9Filamentous Sulfur-Oxidizing
Bacteria

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3.Sulfur-and Iron-Oxidizing Bacteria
Sulfur-Oxidizing Bacteria(cont’d)
Thiothrix
Filamentous sulfur-oxidizing bacteria in
which filaments group together at their
ends by a holdfast to form cellular
arrangements called rosettes
Obligate aerobic mixotrophs

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Thiothrix
Figure 15.12

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4. Hydrogen-Oxidizing Bacteria
Hydrogen-Oxidizing Bacteria:
Most can grow autotrophically with H
2as sole electron
donor and O
2as electron acceptor (“knallgas” reaction)
Both gram-negative and gram-positive representatives
known
Contain one or more hydrogenaseenzymes that
function to bind H
2and use it to either produce ATP or
for reducing power for autotrophic growth
Most are facultative chemolithotrophs and can grow
chemoorganotrophically
Some can grow on carbon monoxide (CO) as electron
donor (carboxydotrophs)

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Hydrogen Bacteria
Figure 15.13

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Characteristics of Common Hydrogen-Oxidizing Bacteria

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5. Methanotrophs and Methylotrophs
Methanotrophs
Use CH
4and a few other one-carbon (C1) compounds
as electron donors and source of carbon
Widespread in soil and water
Obligate aerobes
Morphologically diverse
Methylotrophs
Organisms that can grow using carbon compounds
that lack C-C bonds [(CH3)2N (trimethylamine)HCOO-
(formate), CH3OCOO CH3 (Dimethyl carbonate),
(CH3)2SO (dimethyl sulfoxide), CH3OH (methanol),
CH3NH2 (methylamine), CH3)2NH (dimethylamine)]
Most are also methanotrophs –use CH
4

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5. Methanotrophs and Methylotrophs
Methanotrophs (cont'd)
Methanotrophs methane monooxygenase
Which incorporates an atom of oxygen from O
2into methane
to produce methanol
Methanotrophs contain large amounts of sterols
Classification of Methanotrophs
Two major groups:
Type I
Type II
Contain extensive internal membrane systems for methane
oxidation

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5. Methanotrophs and Methylotrophs
Type I Methanotrophs
Assimilate C1 compounds via the ribulose
monophosphate cycle
Gammaproteobacteria
Membranes arranged as bundles of disc-shaped vesicles
Lack complete citric acid cycle
Obligate methylotrophs
Type II Methanotrophs
Assimilate C1 compounds via the serine pathway
Alphaproteobacteria
Paired membranes that run along periphery of cell

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Electron Micrographs of Methanotrophs
Figure 15.14
Type II membrane system
Methylosinus(α Proteobacteria)
Carbon assimilation pathway: serine
Type I membrane system
Methylococcus capsulatans (β-Proteobacteria)
Carbon asimilation pathwy: ribulose
monophosphate pathway
Lookup the metabolic pathways for Methylomonas methanica(type II) and Methylococcus
capsulatans(type 1) in KEGG (http://www.genome.jp/kegg-
bin/show_pathway?scale=0.35&query=methylocystis&map=map01100&scale=0.35&auto_i
mage=&show_description=hide&multi_query=&show_module_list)

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Some Characteristics of Methanotrophic Bacteria

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5. Methanotrophs and Methylotrophs
Widespread in aquatic and
terrestrial environments
Methane monooxygenase
also oxidizes ammonia;
competitive interaction between
substrates
Certain marine mussels have
symbiotic relationships with
methanotrophs
Ecology and Isolation of
Methanotrophs

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1. Pseudomonadsincluding Pseudomonas
2. Acetic Acid Bacteria
3. Free-Living Aerobic Nitrogen-Fixing Bacteria
4. Neisseria, Chromobacterium, & Relatives
5. Enteric Bacteria
6. Vibrio, Alivibrio, and Photobacterium
7. Rickettsias
II Aerobic & Facultatively Aerobic Chemoorganotrophic
Proteobacteria

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•.
•Pseudomonads including Pseudomonas

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1. Pseudomonads including Pseudomonas
Members of the genus Pseudomonasand related
genera can be defined on the basis of phylogeny and
physiological characteristics
Nutritionally versatile
Ecologically important organisms in water and
soil
Some species are pathogenic
Includes human opportunistic pathogens
and plant pathogens

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1. Pseudomonads including Pseudomonas
Key Genera:
Pseudomonas
Burkholderia
Zymomonas
Xanthomonas
All genera are:
Straight or curved rods with polar flagella
Stain gram negative Chemoorganotrophs
Obligate aerobes
Posses polar flagella
Phylogenetically,thegroupisscatteredwithinthe
Proteobacteria

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Typical Pseudomonad Colonies –
eg Burkholderia cepacia
Figure 15.16a
Lophotrichous polar
flagella

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Subgroups and Characteristics of Pseudomonads

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Pathogenic Pseudomonads

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Genus Zymomonas
Genus of large, gram-negative rods that
carry out vigorous fermentation of
sugars to ethanol
Used in production of fermented
beverages

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• 2. Acetic Acid Bacteria

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2. Acetic Acid Bacteria
Organisms that carry out oxidation of alcohols & sugars
Leads to the accumulation of organic acids as end products
Motile rods
Aerobic
High tolerance to acidic conditions
Commonly found in alcoholic juices
Used in production of vinegar
Some can synthesize cellulose
Colonies can be identified on
CaCO
3agar plates containing ethanol

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•3. Free-Living Aerobic Nitrogen-Fixing Bacteria

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A variety of soil microbes are capable of fixing N
2
aerobically
Distributed in alpha, beta and gamma Proteobacteria
3. Free-Living Aerobic Nitrogen-Fixing Bacteria
The major genera of bacteria capable of fixing N
2
nonsymbiotically are Azotobacter, Azospirillium, and
Beijerinckia
Azotobacter are large, obligately aerobic rods; can form
resting structures (cysts)
All genera produce extensive capsules or slime layers;
believed to be important in protecting nitrogenase from
O
2 (nitrogenase is oxygen-sensitive)

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Azotobacter vinelandii
Figure 15.18
Cysts
(3 um)
Cells
(2 um)

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Figure 15.19a
Slime producing Nitrogen
2-fixing Bacteria
Cells of Derixia gummosaencased
in slime
Beijerinckiaspecies produce
colonies with abundant slime

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Acid-tolerant, free-living N
2fixing bacteria live in
acid soils
Derixia gummosa
Beijerinckia indica
(PHB is present)

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•4.Neisseria, Chromobacterium, and their relatives

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4. Neisseria, Chromobacterium, and Relatives
Neisseria, Chromobacterium, and their relatives can be
isolated from animals, and some species of this group are
pathogenic.
N. gonorrhoeae–gonorrhea
N. meningitidis–fatal inflammation of brain membrane

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Figure 15.21a
Chromobacterium violaceum –produces violacein,
a purple pigment
Colony showing purple colour
Structure of the aromatic compoun, violacein

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•
• 5. Enteric Bacteria (Fam. Enterobacteriaceae)

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5. Enteric Bacteria (Fam. Enterobacteriaceae)
Relatively homogeneous phylogenetic group within the
Gammaproteobacteria
Facultative aerobes
Motile or non-motile, nonsporulating rods
Possess relatively simple nutritional requirements
Ferment sugars to a variety of end products
Enteric bacteria can be separated into two broad groups by
the type and proportion of fermentation products generated
by anaerobic fermentation of glucose
Mixed-acid fermentators
2,3-butanediol fermentators

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Enteric Fermentations
Figure 15.23a

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Diagnostic tests and differential media are often
used to identify various genera of enteric bacteria

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Key Diagnostic Reactions Used to Separate Enteric Bacteria

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Key Diagnostic Reactions Used to Separate Enteric Bacteria

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Escherichia
Universal inhabitants of intestinal tract of humans and
warm-blooded animals
Synthesize vitamins for host
Some strains are pathogenic –cause health problems
Enteropathogenic(EPEC)–surface K antigens allows
attachment & colonisation
Enterhemorrhagic(EHEC) –food / water, O157:H7
(O = CW, somatic, LPS; H = flagella proteins)

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Salmonella and Shigella
Closely related to Escherichia (DDH > 50 & 70%
respectively)
Usually pathogenic
S. typhi-typhoid
Salmonellais characterized immunologically by 3
surface antigens: (used for tracking epidemics)
O antigens
H antigens
Vi antigens, outer polysaccharide layer; typing S.
typhi

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Proteus
Genus containing rapidly motile cells; capable of
swarming
Frequent cause of urinary tract infections in humans

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Butanediol fermentators –Enterobacter, Klebsiella&
Serratiaare a closely related group of organisms
Serratia
produces secondary metabolite, prodigiosin, a red
pigment
isolated from water, soil, insect / vertebrate guts,
human intestine.
S. marcescens:
human pathogen
infections from medical procedures
contaminant in intravenous fluids

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Reactions Used to Separate 2,3-Butanediol Producers

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•
•
• 6. Vibrio, Alivibrio, and Photobacterium

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6. Vibrio, Alivibrio, and Photobacterium
The Vibrio Group
Cells are motile, straight or curved rods
Facultative aerobes
Possess a fermentative metabolism
Best known genera are Vibrio, Alivibrio& Photobacterium
Most inhabit aquatic environments
Some are pathogenic
Some are capable of light production (bioluminescence)
Catalyzed by luciferase, an O
2-dependent enzyme
Regulation is mediated by population density (quorum
sensing)

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Bacterial Bioluminescence
Light emission
Most are marine isolates (Vibrio, Alivibrio, Photobacterium)
but some terrestrial
May colonise specialized light organs of some maring fish
& squids or on dead skin of crustacean / fish
V. cholera & V. vulnificus are pathogens; care when
handling luminous bacteria
Bioluminescence only when oxygen is present
LuxCDABE gene products, luciferase, oxygen and a
population density response (acyl homoserine [AHL],
quorum sensing) is required

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Bioluminescent Bacteriaas Light Organ Symbionts
Figure 15.27c

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7.Rickettsias

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7. Rickettsias
Rickettsias
Small, coccoid or rod-shaped cells
Mostly obligate intracellular parasites; small genome
size
Cannot grow outside a host cell; do not survive long
outside the host
Causative agent of several human diseases
Typical procaryotic cell structure

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Figure 15.28a
Figure
15.28b
Small 0.3um cells in tissue culture
(a). EM of R. popilliaegrowing in
a vacuole in the host beetle,
Melolontha melolontha (b)

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Characteristics of Rickettsias

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Wolbachia
Genus of rod-shaped Alphaproteobacteria
Intracellular parasites of arthropod insects
Affect the reproductive fitness of hosts

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•III Morphologically Unusual Proteobacteria

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III Morphologically Unusual Proteobacteria
1. Spirilla
2. SheathedProteobacteria: Sphaerotilus& Leptothrix
3. Budding and Prosthecate/Stalked Bacteria

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1. Spirilla
Group of motile, spiral-shaped Proteobacteria:
Spirillum & relatives
Magentospirillum
Bdellovibrio
Key taxonomic features include
Cell shape and size
Number of polar flagella
Metabolism
Physiology
Ecology

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Spirilla : Spirillum Volutans
Figure 15.30a

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Magnetotactic Spirilla
Highly motile
Isolated from freshwater habitats
Magnetotactic movement –directed by magnetic field
Fe
30
4magentosome & Fe
3S
4(greigite)

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Bdevellovibrio (leech)
Prey on other bacteria
Obligate aerobes
Members ofDeltaproteobacteria
Widespread in soil and water, including marine environments

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Developmental Cycle of Bdellevibrio Bacteriovorus
Figure 15.33b

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Attachment and Penetration of a Prey Cell by Bdellevibrio
Figure 15.32a

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2.Sheathed Proteobacteria: Sphaerotilus& Leptothrix
Sheathed Bacteria
Filamentous Betaproteobacteria
Unique life cycle in which flagellated swarmer cells
form within a long tube or sheath
Under unfavorable conditions, swarmer cells move out
to explore new environments
Common in freshwater habitats rich in organic matter

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Sheathed Proteobacteria: Sphaerotilus& Leptothrix
Sphaerotilus
Nutritionally versatile
Able to use simple organic compounds
Obligate aerobes
Cells within the sheath divide by binary fission
Eventually swarmer cells are liberated from sheaths

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Sphaerotilus Natans
Figure 15.34a

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Sphaerotilus Natans
Figure 15.34b

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Sphaerotilus Natans
Figure 15.34c

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Sheathed Proteobacteria: Sphaerotilus& Leptothrix
Sphaerotilusand Leptothrixare able to precipitate
iron oxides

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Leptothrixand Iron Precipitation
Figure 15.35

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Budding and Prosthecate/Stalked Bacteria
3. Budding and Prosthecate/Stalked Bacteria
Large and heterogeneous group
Primarily Alphaproteobacteria
Form various kinds of cytoplasmic extrusions bounded
by a cell wall (collectively called prosthecae)

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Budding and Prosthecate/Stalked Bacteria
Prosthecate and Stalked Bacteria
Appendaged bacteria that attach to particulate matter,
plant material, and other microbes in aquatic
environments
Appendages increase surface-to-volume ratio of the
cells

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Stalked Bacteria
Figure 15.40a

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Stalked Bacteria
Figure 15.40b

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Stalked Bacteria
Figure 15.40c

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Budding and Prosthecate/Stalked Bacteria
Caulobacter
Chemoorganotroph
Produces a cytoplasm-filled stalk
Often seen on surfaces in aquatic environments with
stalks of several cells attached to form rosettes
Holdfast structure present on the end of the stalk used
for attachment
Model system for cell division and development

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Growth of Caulobacter
Figure 15.41

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Budding and Prosthecate/Stalked Bacteria
Gallionella
Chemolithotrophic iron-oxidizing bacteria
Possess twisted stalk-like structure composed of ferric
hydroxide
Common in waters draining bogs, iron springs, and
other environments rich in Fe
2+

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The Neutrophilic Ferrous Iron Oxidizer, Gallione Ferruginea
Figure 15.42a

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The Neutrophilic Ferrous Iron Oxidizer, Gallione Ferruginea
Figure 15.42b

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Features of Stalked, Appendaged and Budding Bacteria

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Prosthecate Bacteria
Figure 15.36a

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Prosthecate Bacteria
Figure 15.36b

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Prosthecate Bacteria
Figure 15.36c

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Cell Division
Figure 15.37

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Budding and Prosthecate/Stalked Bacteria
Budding Bacteria
Divide as a result of unequal cell growth
Two well-studied genera
Hyphomicrobium(chemoorganotrophic)
Rhodomicrobium(phototrophic)

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Stages in the HyphomicrobiumCell Cycle
Figure 15.38

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Morphology of Hyphomicrobium
Figure 15.39a

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Morphology of Hyphomicrobium
Figure 15.39b