Chapter 15 (2)

Bacteria:The Proteobacteria

15.12 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, and

Photobacterium

Most inhabit aquatic environments

The Vibrio Group (cont’d)

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)

* NADH + H+ + FMN → NAD+ + FMNH2

FMNH2 + O2 + RCHO → FMN + RCOOH + H2O + light

NAD+ + RCOOH → NADH + H+ + RCHO

Bioluminescent Bacteria

Blue light Green light

Aliivibrio fischeri MJ-1 Aliivibrio fischeri Y-1

Photobacterium phophoreum

Bioluminescent Bacteria as Light Organ Symbionts

Bioluminescent bacteria

15.13 Rickettsias

Rickettsias

Small, coccoid or rod-shaped cells

Most are obligate intracellular parasites

Causative agent of several human diseases

Rickettsias Growing Within Host Cells

Rickettsia rickettsii in tunica vaginalis cells of the vole.

Rickettsias Growing Within Host Cells

EM of cells of Rickettsiella popilliae within a blood cells of a beetle.

vacuole

Characteristics of Rickettsias

Wolbachia

Genus of rod-shaped Alphaproteobacteria

Intracellular parasites of arthropod insects Affect the reproductive fitness of hosts

- parthenogenesis

- killing of males

- feminization (the conversion of male insects into

females)

Wolbachia pipientis

Small genome: 1.5 Mbp

Does not cause disease in either vertebrates or its

invertebrates host Cause disease only in insects Passed from infected females to her offspring

through the egg infection

- colonize the insect egg (e.g. wasp)

Wolbachia

Wolbachia induced parthenogenesis

Occurs in a number of species of wasps Male normally arise from unfertilized eggs and

female arise from fertilized eggs Walbachia in unfertilized eggs triggers a doubling of

the chromosome number

- yields only females

Wolbachia induced killing of males

In lady beetles and butterflies Walbachia infection results in the death of male

offspring

Wolbachia induced feminization

In certain species of woodlice (= pillbugs) Walbachia causes male to develop as females due

to the damage in the male hormone-producing glands

Wolbachia is essential for survival

In the nematode worms causing the diseases

elephantiasis and river blindness Antibiotics kill the worms, apparantly by killing their

Walbachia symbionts

IV. Morphologically Unusual Proteobacteria

15.14 Spirilla

15.15 Sheathed Proteobacteria: Sphaerotilus and

Leptothrix

15.16 Budding and Prosthecate/Stalked Bacteria

15.14 Spirilla

Spirilla

Group of motile, spiral-shaped Proteobacteria

Key taxonomic features include

Cell shape and size

Number of polar flagella

Metabolism

Physiology

Ecology

Spirilla : Spirillum volutans

Spirillum volutans

Spirilla: An intestinal spirillum

Spirilla: Cells of Ancyclobacter aquaticus

Ancyclobacter aquaticus

Characteristics of the Genera of Spiral-Shaped Bacteria

Spirilla

A few are magnetotactic, demonstrating directed

movement in a magnetic field

A Magnetotactic Spirillium, M. magnetotacticum

Magnetosome(particles of Fe3O4)

Spirilla

Bdevellovibrio

Prey on other bacteria

Obligate aerobes

Members of Deltaproteobacteria

Widespread in soil and water, including marine

environments

Very thick flagellum

bdelloplast

Attachment and Penetration of a Prey Cell by Bdellevibrio

Developmental Cycle of Bdellevibrio bacteriovorus

15.15 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

Sheath: a complex of protein and polysaccharides

Common in freshwater habitats rich in organic matter

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

Sphaerotilus natans

Sphaerotilus natans

Sphaerotilus natans

Swarmer cells with polar flagellar tuft

Sphaerotilus and Leptothrix are able to precipitate

iron oxides on their sheath

Leptothrix also can oxidize Mn2+ to Mn4+

■ the protein responsible for the oxidation process

resides in the sheath

Leptothrix and Iron Precipitation

Protuberance of the cell envelope contacting the sheath

15.16 Budding and Prosthecate/Stalked Bacteria

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)

Features of Stalked, Appendaged and Budding Bacteria

Prosthecate Bacteria

Asticcacaulis biprosthecum

Ancalomicrobium adetum

Stella sp.

Cell Division

Budding Bacteria

Divide as a result of unequal cell growth

Two well-studied genera

Hyphomicrobium (chemoorganotrophic)

Rhodomicrobium (phototrophic)

Stages in the Hyphomicrobium Cell Cycle

Morphology of Hyphomicrobium

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

A Caulobcater rosettes

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

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+

Neutrophilic Ferrous Iron Oxidizer, Gallionella ferruginea

V. Delta- and Epsilonproteobacteria

15.17 Gliding Myxobacteria

15.18 Sulfate- and Sulfur-Reducing Proteobacteria

15.19 The Epsilonproteobacteria

15.17 Gliding Myxobacteria

Gliding

A form of motility exhibited by some bacteria

Gliding Bacteria

Are typically either long rods or filaments

Lack flagella, but can move when in contact with

surfaces

Classification of the Fruiting Myxobacteria

Myxobacteria Group of gliding bacteria that form multicellular

structures (fruiting bodies) and show complex

developmental life cycles

Deltaproteobacteria

Chemoorganotrophic soil bacteria

Lifestyle includes consumption of dead organic matter or

other bacterial cells

Most are obligate aerobes

- exception: a facultative aerobe Anaeromyxobacter

that can grow by anaerobic respiration

Fruiting myxobacteria exhibit complex behavioral patterns and life cycles

Vegetative cells are simple, nonflagellated rods that

glide across surfaces and obtain their nutrients

primarily by lysing other bacteria and utilizing released

nutrients

Under appropriate conditions, vegetative cells

aggregate, construct fruiting bodies, and undergo

differentiation into myxospores

Myxococcus xanthus

A vegetative cell

Myxospore with multilayered outer wall

Myxococcus xanthus

Stigmatella aurantiaca

Stigmatella aurantiaca

Fruiting Bodies of Myxococcus fulvus

Fruiting Body of Myxococcus stipitatus

Fruiting Body of Chondromyces crocatus

The life cycle of fruiting myxobacterium is complex

Life cycle of Myxococcus xanthus

(e.g.) glycerol

Swarming in Myxococcus

Fruiting Body Formation in Chondromyces crocatus

15.18 Sulfate- and Sulfur-Reducing Proteobacteria

Dissimilative sulfate- and sulfur-reducing bacteria

Over 40 genera of Deltaproteobacteria

Use SO42- and So as electron acceptors and organic

compounds or H2 as electron donors

H2S is an end product

Most obligate anaerobes

Widespread in aquatic and terrestrial environments

Characteristics of Sulfate- and Sulfur-Reducing Bacteria

Physiology of sulfate-reducing bacteria

Group I

Oxidize lactate, pyruvate, or ethanol to acetate and

excrete fatty acid as an end product

Group II

Oxidize fatty acids, lactate, succinate, and benzoate to

CO2

Sulfate- and Sulfur- Reducing Bacteria: Desulfovibrio desulfuricans

Sulfate- and Sulfur-Reducing Bacteria: Desulfonema limicola

Sulfate-and Sulfur-Reducing Bacteria: Desulfobulbus propionicus

Sulfate- and Sulfur-Reducing Bacteria: Desulfobacter postgatei

Sulfate- and Sulfur-Reducing Bacteria: Desulfosarcina variabilis

Sulfate- and Sulfur-Reducing Bacteria: Desulfuromonas acetoxidans

Enrichment Culture of Sulfate-Reducing Bacteria

Sterile medium Positive enrichment showing black FeS

Colonies of sulfate-reducing bacteria

15.19 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 (nitrite, oxygen, or elemental sulfur as electron

acceptor)

Pathogenic and non-pathogenic representatives

Campylobacter and Helicobacter

All Gram-negative, microaerophilic, motile spirilla

Most are pathogenic to humans or other animals

e.g., Campylobacter sp.

- acute enteritis leading to usually bloody diarrhea

e.g., Helicobacter pylori

- chronic and acute gastritis, leading to peptic ulcers

(Barry Marshall and Robin Warren: 2005 Nobel Prize in

Physiology and Medicine)

Helicobacter pylori

Arcrobacter

Unusually wide diversity of habitats

Some are pathogenic to humans and other animals,

infecting the reproductive and intestinal tract of

humans and other animals

Cause reproductive failures in animals, diarrhea-like

diseases in a wide range of animals, and gastroenteritis

and appendicitis in humans

Infection route: fecal-to-water-to-oral (?)

Sulfurospirillum and Thiovulvum

Sulfurospirillum

Non-pathogenic, free-living microaerophiles

Freshwater and marine habitats

Use elemental sulfur, selenate, or arsenate as an electron acceptor

Thiovulvum

Microaerophilic

Freshwater and marine habitats in which sulfide-rich muds interface

with oxygen-containing waters

Forms large internal sulfur granules

No pure culture is available yet

Secretes a slime stalk

Wolinella

Wolinella succinogenes

Anaerobic, isolated from the bovine rumen

Anaerobic respiration using fumarate or nitrate as

electron acceptors with hydrogen or formate as electron

donors

Contains genes for nitrogen fixation

Characteristics of Key Genera of Epsilonproteobacteria