Three Bacterial Lifestyles
Facultative
Extracellular
Obligate
(HorizontallyTransmitted)
Free-living world
Intracellular world
Facultative
High
Obligate
(HorizontallyTransmitted)
Exposure to novel gene pools
Obligate
(Vertically
-transmitted)
Low
Obligate Intracellular Bacteria That
Host-Switch
Maternal transmission of obligate intracellular bacteria
Bacterial symbionts
Bacterial symbionts
Insect nuclei
Insect ovariole
Mom knows best: Aphid maternal transmission of Buchnera
Does transmission of obligate intracellular
bacteria affect mobile DNA content?
Horizontallytransmitted
• Replicate in different hosts
• Rickettsia, Chlamydia, Ehrlichia…
VerticallyTransmitted
• Replicate in only one
host/individual
• Buchnera, Wolbachia, Blochmannia
Horizontally-transmitted symbionts have more species
with mobile DNA than vertically-transmitted species
Horizontally-transmitted
Vertically-transmitted
Fisher’s exact test, P = 0.0005
Newton & Bordenstein 2011
How are Mobile DNAs Transmitted in
Obligate Intracellular Bacteria ?
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.)
Phylum Nematoda (mutualistic)
• 90% of filarial nematode species
Homo sapiens (pathogenic)
• River Blindness
• Lymphatic filariasis
• The cause is Wolbachia, not the nematode
Wolbachia:
Mutualist and Parasite
Required for insect
oogenesis (Dedeine et al. 2001)
Parthenogenesis in
wasps
Mutualism
Reproductive
parasitism
Required for nematode
fertility and larval
development
Male-killing in insects
Feminization in isopods
Cytoplasmic incompatibility in
arthropods
Cytoplasmic Incompatibility (CI)
CI
Late prophase
x
x
x
x
=
X
=
Wolbachiainfected
offspring
=
Uninfected
offspring
=
Wolbachiainfected
offspring
Metaphase
Testes
Prometaphase
Telophase
Embryo
Courtesy of U. Tram
Wolbachia
Host