Post on 03-Jan-2016
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The Secret Life of BacteriophagesLysogenic interactions
in soil ecosystems
Kurt WilliamsonWommack LabMarch 9, 2006
Introduction - terms
Phage – bacteriophage, a virus that infects bacteria.
Temperate phage – virus able to integrate into its host’s chromosome.
Prophage –integrated virus genome.
Lysogen – a bacterium containing an integrated temperate phage.
Immunity to infections from other, similar viruses
In bacteria: lysogenic conversionDiptheria toxin (Barksdale and Pappenheimer, 1954)
Cholera toxin (Waldor and Mekalanos, 1996)
Less dramatic examples:Prophage down-regulates host metabolism (Chen et al., 2005)
… may be significant evolutionary repercussions.
Impact of Temperate Infections
Sampling Locations
White Clay Creek Preserve
Ag Experimental Stn., Newark
Blackbird Forest
Ag Experimental Stn., Georgetown
Gauging Induction
40-mlLog-phase cultures1 2
T2C2T1C1
Split into duplicate 20-ml cultures
Incubate 18h, 28C, 150 rpm
Enumerate viruses & bacteria with EFM
Initial ResultsSoil pH OM %W %
sand % silt
% clay
Lysogenic fraction
Matapeake silt loam 5.9 1.7 22 9 75 16 2/5 Evesboro loamy sand 6.1 0.1 11 85 12 3 2/5 Blackbird Wetland 4.9 12.4 175 39 56 16 1/5 Piedmont Wetland 5.9 3.0 60 59 36 5 1/5
• Agricultural soils: 2 of 5 isolates harbored inducible temperate phages.
• Wetland soils: 1 of 5 isolates contained inducible phages.
• Overall: 6 of 20 isolates tested (30%) contained inducible phages.
Induction TrialsConducted by Yingbo Wang with Matapeake isolate, MP3
1.00E+07
1.00E+08
1.00E+09
1.00E+10
1.00E+11
VD
C/m
l
-260.00
-210.00
-160.00
-110.00
-60.00
-10.00
40.00
90.00
140.00
1
bu
rst
size
MC MCMC30 UV MC30 UV
* *Prophage Induced Burst Size
Conclusions• Lysogens/inducible temperate phages found in all 4 soils.
• Six of 20 soil isolates contained inducible phages.
• Treatment with mitomycin C resulted in higher induction responses than UV exposure.
• Treatment with mitC for 30 resulted in significantly higher induction response and burst sizes for some (but not all) isolates.
• Induction response and burst size depends on specific induction conditions…
Conclusions
• Five of six lysogens produced siphophage particles with genome sizes similar to lambda – these lysogens are Bacillus species.
• One of the six lysogens produced small numbers of myophage particles with very small genome (12 KB) – host is Ochrobactrum spp.
Future work:
Community inductions from same 4 soils.