A1260909914PbSUj

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Pathogens are impacted on many levels by host
responses
-communication between host and pathogen
in compatible response results in
development -pathogen detection of host immune
response antigen masking active suppression of
defenses alternative development survival
stages sporulation These are both infective
agents for dispersal!
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Pathogens must defend themselves against numerous
factors
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Rhizosphere bacteria secrete antimicrobials
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The malaria pathogen alters its antigenic
profile during development and infection
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The available evidence suggests that nematodes
both actively suppress defense responses and mask
their surface profiles to avoid host
detection! How? -secretion of
enzymes -binding of host proteins -molting
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The nematode cuticle offers an antigenic profile
that is stage- specific and changes with each molt
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Life cycle
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Diapause
Hatch
Host Location
Reproduction
Penetration and Migration
Feeding Site Establishment
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ENVIRONMENTAL FACTORS
CROWDING OF LARVAE TEMPERATURE ? INCUBATION
OF GALLS NUTRITION ? RESISTANT VARIETIES ?
OTHERS ? MH-30
Adult female
Female intersex
Second stage (late)
Second stage (early)
Adult male (sex reversed)
Second stage (middle)
Second stage (undif. larva)
Adult male
Third to fourth stage
Second stage
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Life cycle
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Environmental Cues
Sensory Processing
Action
DAF pathway
INTER- NEURONS
DAUER
AMPHIDS
SURFACE
SEX
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Infective second-stage larva of RKN arrested in
development
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Dauer larvae of the pine wood nematode
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Dauer larvae characteristics

• Non-developing
• Non-feeding
• Long-lived
• Altered metabolism
• Resistance to SDS

• Glyoxylate pathway
• No high-energy phosphate
• Lipid metabolism

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C. elegans dauer pathway
PREDAUER
DAUER
L2d
EGG
L1
L4
ADULT
L2
L3
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Pheromone Cue
(DAF-22, Biosynthesis of pheromoneunknown
receptor)
Tgf-? Signal
Cyclic GMP Signal
3-Phosphoinositide Signal
(DAF-7, Ligand DAF-1, DAF-4, Receptor)
(DAF-11, Guanylyl Cyclase)
(AGE-1, Pl-3 Kinase)
Steroid Or Retinoid Signal?
(Unknown hormone DAF-12, Nuclear receptor)
Dauer Morphogenesis
Continuous Development
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ENVIRONMENTAL CUES
SENSORY PROCESSING
MORPHOGENESIS
def-3 def-5 def-12
def-18 def-20
def-22
def-10
def-18
def-17
def--6
def-8
def--15
PHEROMONE
def-14
def-1
def-4
def-7
def-11
def--9
Dauer larva
other
def--2
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Some bacteria sporulate in response to stress and
environmental perturbation
Courtesy Tom Hewlett
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The life-cycle of Pasteuria penetrans in excised
root-knot nematodes a re-evaluation
Sporogenesis
Attachment Germination
Rhizoid Formation Exponential Growth
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Sporulation

• The vulnerable vegetative cell partitions. A
  tough layer of protein and polysaccharide is laid
  down encapsulating the chromosome. The cell lyses
  and the protective spore is formed.

Cell Lysis
Nutrient Starvation Temperature or pH
extremes Cell crowding Antibiotic exposure
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Sporulation and competance genes occur in clusters
2537600
2531200
2519200
2517600
spoIIIAB
spoIIIAF
spo0A
spoIIIAD
spoIVB
spoIIIAH
spoIIIAG
spoIIIAE
spoIIIAC
spoIIIAA
yghV
efp
2443200
2640000
2636800
2445600
sigF
dacF
comEC
comEB
comEA
spoIIAB
AA
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Comparison of endospore formation in Bacillus
thuringiensis and Pasteuria penetrans
From Chen et al., (1997) Phytopathology 87,
273-283
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Pasteuria penetrans (Sayre Starr 1985)
Bacillus anthracis (Driks 2002)
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Occurrence of endospore coat proteins
Bs Ba Pp Genes ___________________________________
_ - - CotC CotM CotR
CotSA CotT CotV CotW CotX CotY
CotZ (38) - SpoVM SpoVID
CotB CotE CotF CotH
CotJC CotS YaaH YabG (38) -
CotA CotD CotG (12)
Spo1VA SafA CotJA
(12) _____________________________________
Positive hits using Artemis
(June 2004)
Driks (2002), Trends Microbiol. 10251
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60.8
47.3
NA
Filament length (nm)
48.7
28.4
29.8
24.8
25.1
13.9
BclA collagen-like repeats and their
relationship to filament length in B. anthracis
after Sylvestre et al. (2003), J. Bact., 185
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B. anthracis BclA vs. P. penetrans 79 identity
B. anthracis BclA vs. P. penetrans 78 identity
B. cereus Protein H vs. P. penetrans 64 identity
Pasteuria Collagen-like G-X-Y repeats
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How is regulation of sporulation controlled?
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KinB
Cell Membrane
KinA
RapB
Spo0F
PI
RapA
Spo0B
Spo0A
Spo0A
sporulation
DNA binding domain
DNA binding domain
abrB
Inactive
Active
Diagram of proteins involved in the phosphorelay
required for initiating the sporulation signal
transduction pathway in B. subtilis (from Feher
et al., 1998). The open arrows represent
environmental signals which initiate the transfer
of the phosphoryl group via the phosphorelay.
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Multi-component phosphorelay
P
P
P
P
H
H
ATP
D
D
ATP
Spo0F
KinA
Spo0A
H
H
P
Signaling pathway of sporulation two-component
phosphorelay
In many bacteria, the onset of sporulation is
assured by the activation of this very signal
specific signal transduction pathway
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ß1
a2
a1
a3
ß2
ß3
1nat ..
. . .
. . .
. SPOF_BACSU MMNEK..ILIVDDQYGIRILLNEVFNKEGYQTFQAAN
GLQALDIVTKERPDLVLLDMKIPGMDGIEILKR
1 10 20 30 40
50 60
SPOF_BACAN .MEGK..ILIVDDQYGIRVLLHEVFQKEGYQTFQAANGF
QALDIVKKDNPDLVVLDMKIPGMDGIEILKH
SPOF_BACTK .MEGK..ILIVDDQYGIRVLLHEVFQKEGYQTFQAANGF
QALDIVKKDNPDLVVLDMKIPGMDGIEIFKA
SPOF_BACHA ..MNK..ILVVDDQYGIRVLLNEILQKDGYQMFQAANGI
QALAIVEEETPDLVLLDMKIPGMDGLEILRR
SPOF_PASTU MMNEKKLILIVDDQYAIRLLLKEIFSQDGIIVLQAAGGX
EAIELVAQQQPDLMLLDMKMPGMDGIEILRR
ß4
a4
a5
70 80 90 100 110
120
. . . .
. . SPOF_BACSU MKVIDENIRVIIMTAYGELDMIQ
ESKELGALTHFAKPFDIDEIRDAVKKYLPLKSN
SPOF_BACAN VKEIDESIKVILMTAYGELDMIQEAKDLGALMHFAKPFD
IDEIRQAVRNELAVEA.
SPOF_PASTU VRQVIPALKVIVMTAYGELEMMEKIRSLGVVMHFAKPFD
VRAVRCGVLRYL.....
SPOF_BACHA IKDMNPNIEVIMMTAYGELNMINEAMQLGAVTHFAKPFD
IDDVRAVIAENMKSS..
SPOF_BACTK CKEIDESIKVILMSAYGELDMIQEAKDLGALMHFAKPFD
IDEIRQAVRNELAVEA.
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