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 = 0.0005Newton & 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
CILate prophase Prometaphase
Metaphase Telophase
Courtesy of U. Tram
Testes
Embryo
Wolbachia Host
Cytoplasmic Incompatibility (CI)
