Edited_Proteobacteria_powerpoint - Copy.ppt

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
PROTEOBACTERIA
By Rikta Vekaria

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

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

PHYLOGENIC TREE OF PROTEOBACTERIA

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-

Major Genera of Proteobacteria

DISTRIBUTION OF PROTEOBACTERIA

S.N CLASS GENUS DISTRIBUTION
1. ALPHA
PROTEOBACTERIA
Rickettsia and
Coxiella
PARASITIC OR
MUTALSITIC :
Parasitic :Vertebrate
erythrocytes,macrophages and vascular
endothelial cells
Invertebrates : Live in arthropods
Cauloobacter and
Hyphomicrobium
Hyphomicrobium:
Attach to solid objects in freshwater, marine
and terrestrial environments
Caulobacter: Freshwater and marine habitats
with low nutrient levels
Agrobacterium Invade the crown ,roots and stems of plants
Rhizobacterium Root nodules

S.N CLASS GENUS DISTRIBUTION
1. ALPHA
PROTEOBACTE
RIA
Nitrifying bacteria:
Nitrosomonas
Nitrosopira
Soil, freshwater and
marine habitat

S.N CLASS 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

2. Beta
PROTEOBACTE
RIA
Nitrosomonadales Root nodules
Hydrogenophilales Thiobacillus:Soil,
aquatic habitat ,both
freshwater and marine

3. GAMMA
PROTEOBACTE
RIA
Purple sulphur bacteria:
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

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

CHARACTERISTICS OF PROTEOBACTERIA

The characteristics of important genera of
Gammaproteobacteria.

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
serotype E. coli O157:H7, are pathogens; E. coli has
been a model organism for many studies in genetics
and molecular biology

Example Genus
Microscopic
Morphology
Klebsiella
Gram-negative
bacillus; appears
rounder and thicker
than other members
of Enterobacteriaceae
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. pneumophila causes
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

Example Genus
Microscopic
Morphology
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

Example Genus
Microscopic
Morphology
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.
pestis causes bubonic plague and pneumonic
plague; Y. enterocolitica can be a pathogen
causing

The characteristics of important genera of
Alpha proteobacteria.

AGROBACTERIUM INDUCED TUMORS

CAULOBACTERIA

RICKETTSIA

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

a) Legionella pneumophila

β-
proteobacteria

β- proteobacteria

Class  (delta) Proteobacteria
Genus Microscopic Morphology Unique characteristics
Bdellovibrio
Gram-negative, comma-shaped
rod
Obligate aerobes; motile;
parasitic (infecting other bacteria)
Desulfovibrio(formerly Desufuro
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)

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

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

PREDATORY BDELLOVIBRIO BACTERIUM
LYSING A PREY E. COLI CELL.

Click to add Text
Brock Biology of Microorganisms, Twelfth Edition
– Madigan / Martinko / Dunlap / Clark
Neisseria meningitidis growing in
colonies on a chocolate agar plate.

Click to add Text
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 H2, formate, sulfide, or thiosulphate as electron
donor
 Pathogenic and non-pathogenic representatives

Characteristics of Key Genera of Epsilonproteobacteria

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

Sulfospirillum

Acrobacter

Zeta proteobacteria
• The class Zetaproteobacteria is the sixth and most recently
described class of the Proteobacteria. 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 an iron oxidizing
neutrophilic chemolithoautotroph originally isolated from Loihi
seamount in 1996 (post-eruption).

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

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

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

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

1. Pseudomonads including 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

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

1.Phototrophic,
Chemolithotrophic
& Methanotrophic
Proteobacteria

1. Purple Phototrophic Bacteria
 Purple Phototrophic Bacteria
 Carry out anoxygenic photosynthesis; no O2 evolved
 Morphologically diverse group
 Genera fall within the Alpha-, Beta-, or
Gammaproteobacteria
 Contain bacteriochlorophylls and carotenoid pigments
 Produce intracytoplasmic photosynthetic membranes
with varying morphologies

Liquid Cultures of Phototrophic Purple Bacteria
Figure 15.2

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

Purple Phototrophic Bacteria
 Purple Sulfur Bacteria
 Use hydrogen sulfide (H2S) as an electron donor for
CO2 reduction in photosynthesis
 Sulfide oxidized to elemental sulfur (So) that is stored
as globules either inside or outside cells
 Sulfur later disappears as it is oxidized to sulfate (SO4
2-)

Purple Phototrophic Bacteria
 Purple Sulfur Bacteria (cont’d)
 Many can also use other reduced sulfur compounds,
such as thiosulfate (S2O3
2-)
 All are Gammaproteobacteria
 Found in illuminated anoxic zones of lakes and other
aquatic habitats where H2S accumulates, as well as
sulfur springs

Photomicrographs of Purple Sulfur Bacteria
Figure 15.4

Genera and Characteristics of Purple Sulfur Bacteria

Blooms of Purple Sulfur Bacteria
Figure 15.5

Purple Non-sulfur Bacteria
 Purple Nonsulfur Bacteria
 Originally thought organisms were unable to use sulfide as
an electron donor for CO2 reduction, now know most can
 Most can grow aerobically in the dark as
chemoorganotrophs
 Some can also grow anaerobically in the dark using
fermentative or anaerobic respiration
 Most can grow photoheterotrophically using light as an
energy source and organic compounds as a carbon source
 All in Alpha- and Betaproteobacteria

Representatives of Purple Nonsulfur Bacteria
Figure 15.6

Genera and Characteristics of Purple Nonsulfur Bacteria

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 NH3 to NH2OH
 Nitrite oxidase: oxidizes NO2
- to NO3
-

 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 chemolithotrophs and aerobes
 One exception is annamox organisms, which oxidize ammonia
anaerobically

Figure 15.7

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 (Fe2+)
 Thiobacillus (rods)
 Sulfur compounds most commonly used as electron
donors are H2S, So, S2O3
2-; generates sulfuric acid
 Achromatium (spherical cells)
Common in freshwater sediments
 Some obligate chemolithotrophs possess special
structures that house Calvin cycle enyzmes
(carboxysomes)

 Beggiatoa
 Filamentous, gliding bacteria
 Found in habitats rich in H2S
 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 H2S with reduction of NO3
- to NH4
+

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

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

Thiothrix
Figure 15.12

4. Hydrogen-Oxidizing Bacteria
 Hydrogen-Oxidizing Bacteria:
 Most can grow autotrophically with H2 as sole electron
donor and O2 as electron acceptor (“knallgas” reaction)
 Both gram-negative and gram-positive representatives
known
 Contain one or more hydrogenase enzymes that
function to bind H2 and 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)

Hydrogen Bacteria
Figure 15.13

Characteristics of Common Hydrogen-Oxidizing Bacteria

 Methanotrophs
 Use CH4and 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 CH4

Methanotrophs (cont'd)
 Methanotrophs methane monooxygenase
 Which incorporates an atom of oxygen from O2 into 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

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

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)

Some Characteristics of Methanotrophic Bacteria

 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

• .
• Pseudomonads including Pseudomonas

 Members of the genus Pseudomonas and 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

 Key Genera:
 Pseudomonas
 Burkholderia
 Zymomonas
 Xanthomonas
 All genera are:
 Straight or curved rods with polar flagella
 Stain gram negative Chemoorganotrophs
 Posses polar flagella
 Phylogenetically, the group is scattered within the
Proteobacteria

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

Subgroups and Characteristics of Pseudomonads

Pathogenic Pseudomonads

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

• 2. Acetic Acid Bacteria

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
CaCO3 agar plates containing ethanol

• 3. Free-Living Aerobic Nitrogen-Fixing Bacteria

 A variety of soil microbes are capable of fixing N2
aerobically
 Distributed in alpha, beta and gamma Proteobacteria
3. Free-Living Aerobic Nitrogen-Fixing Bacteria
 The major genera of bacteria capable of fixing N2
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
O2 (nitrogenase is oxygen-sensitive)

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

Figure 15.19a
Slime producing Nitrogen2-fixing Bacteria
Cells of Derixia gummosa encased
in slime
Beijerinckia species produce
colonies with abundant slime

Acid-tolerant, free-living N2 fixing bacteria live in
acid soils
Derixia gummosa
Beijerinckia indica
(PHB is present)

• 4.Neisseria, Chromobacterium, and their relatives

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

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

•
• 5. Enteric Bacteria (Fam. Enterobacteriaceae)

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

Enteric Fermentations
Figure 15.23a

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

Key Diagnostic Reactions Used to Separate Enteric Bacteria

 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)

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

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

 Butanediol fermentators – Enterobacter, Klebsiella &
Serratia are 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

Reactions Used to Separate 2,3-Butanediol Producers

•
•
• 6. Vibrio, Alivibrio, and Photobacterium

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 O2-dependent enzyme
 Regulation is mediated by population density (quorum
sensing)

 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

Bioluminescent Bacteria as Light Organ Symbionts
Figure 15.27c

7.Rickettsias

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

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

Characteristics of Rickettsias

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

• III Morphologically Unusual Proteobacteria

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

Spirilla : Spirillum Volutans
Figure 15.30a

 Magnetotactic Spirilla
 Highly motile
 Isolated from freshwater habitats
 Magnetotactic movement – directed by magnetic field
 Fe304 magentosome & Fe3S4 (greigite)

 Bdevellovibrio (leech)
 Prey on other bacteria
 Members of Deltaproteobacteria
 Widespread in soil and water, including marine environments

Developmental Cycle of Bdellevibrio Bacteriovorus
Figure 15.33b

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

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

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

Sphaerotilus Natans
Figure 15.34a

Sphaerotilus Natans
Figure 15.34b

Sphaerotilus Natans
Figure 15.34c

Sheathed Proteobacteria: Sphaerotilus & Leptothrix
 Sphaerotilus and Leptothrix are able to precipitate
iron oxides

Leptothrix and Iron Precipitation
Figure 15.35

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)

 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

Stalked Bacteria
Figure 15.40a

Stalked Bacteria
Figure 15.40b

Stalked Bacteria
Figure 15.40c

 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

Growth of Caulobacter
Figure 15.41

 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 Fe2+

The Neutrophilic Ferrous Iron Oxidizer, Gallione Ferruginea
Figure 15.42a

The Neutrophilic Ferrous Iron Oxidizer, Gallione Ferruginea
Figure 15.42b

Features of Stalked, Appendaged and Budding Bacteria

Prosthecate Bacteria
Figure 15.36a

Figure 15.36b

Figure 15.36c

Cell Division
Figure 15.37

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

Stages in the Hyphomicrobium Cell Cycle
Figure 15.38

Morphology of Hyphomicrobium
Figure 15.39a

Morphology of Hyphomicrobium
Figure 15.39b

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