Facultative

Intracellular world

Facultative Extracellular

Free-living world

Obligate (Vertically

-transmitted)

Obligate(Horizontally-Transmitted)

Exposure to novel gene poolsHigh Low

Three Bacterial Lifestyles

Obligate(Horizontally-Transmitted)

Obligate Intracellular Bacteria That Host-Switch

Chlamydia Rickettsia

Maternal transmission of obligate intracellular bacteria

Bacterial symbionts Insect ovariole

Bacterial symbionts Insect nuclei

Mom knows best: Aphid maternal transmission of Buchnera

• Replicate in different hosts• Rickettsia, Chlamydia, Ehrlichia…

Horizontally-transmitted

• Replicate in only one host/individual

• Buchnera, Wolbachia, Blochmannia

Vertically- Transmitted

Does transmission of obligate intracellular bacteria affect mobile DNA content?

Horizontally-transmitted symbionts have more species with mobile DNA than vertically-transmitted species

Fisher’s exact test, P = 0.0005

Newton & Bordenstein 2011

31/32 SPECIES WITH MOBILE DNA

3/8 SPECIES WITH MOBILE DNA

Horizontally-transmitted Vertically-transmitted

How are Mobile DNAs Transmitted in Obligate Intracellular Bacteria ?

Chlamydia Rickettsia

Phylum Nematoda (mutualistic)

• 90% of filarial nematode species

Wolbachia = One of the great pandemics in the history of life

Phylum Arthropoda (parasitic)

• Up to 66% of arthropod species

(which comprise 85% of all animal spp.)

Homo sapiens (pathogenic)

• River Blindness

• Lymphatic filariasis

• The cause is Wolbachia, not the nematode

Wolbachia: Mutualist and Parasite

Parthenogenesis in wasps

Male-killing in insects

Feminization in isopods

Cytoplasmic incompatibility in arthropods

Reproductive parasitism

Mutualism

Required for nematode fertility and larval development

Required for insect oogenesis (Dedeine et al. 2001)

x

x

x

x

=

=

=

=

Wolbachia-infected offspring

Uninfected offspring

Wolbachia-infected offspring

X

CI

Late prophase Prometaphase

Metaphase Telophase

Courtesy of U. Tram

Testes

Embryo

Wolbachia Host

Cytoplasmic Incompatibility (CI)