V' A few species clump significantly during syntrophic growth

1
Diverse Desulfovibrio species vary in
characteristics of syntrophic growth with
Methanococcus maripaludis Kristina L Hillesland,
Christopher Walker, David Stahl Department of
Civil and Environmental Engineering, University
of Washington, Seattle, WA

• Desulfovibrio, sulfate respiration and syntrophic
  growth
• Although sulfate reducing bacteria are thought to
  typically grow by respiration of sulfate, they
  have been detected in environments lacking this
  compound and other electron acceptors. It is
  thought that they survive under such conditions
  by participating in syntrophic interactions with
  hydrogen-consuming methanogens.
• Syntrophic growth by Desulfovibrio
• Several issues fundamental to understanding the
  physiological ecology of Desulfovibrio and
  syntrophic interactions in general have not been
  addressed. These include
• 1. How common is the capacity for syntrophic
  growth among sulfate reducers, esp.
  Desulfovibrio?

• V. A few species clump significantly during
  syntrophic growth
• Selected D. vulgaris Hildenborough genes that
  are absent from strains Woolwich and Brockhurst
  hill.

I. Variation in growth rate and biomass yield of
Desulfovibrio species growing syntrophically on
lactate II. Relationships between
syntrophic growth and sulfate respiration
III. Pyruvate fermentation by Desulfovibrio in
relationship to syntrophic growth IV.
Growth characteristics of some exceptional
syntrophs
D. vulgaris Woolwich coculture on lactate
D. vulgaris Hildenborough coculture on lactate
OD, 600 nm
Lactate (or another organic acid)
H2
CO2
Methane
Acetate ?
D. vulgaris Brockhurst Hill coculture on lactate
D. sp. Pt2 in coculture on pyruvate
Formate ?
Methanogen
Desulfovibrio

• Correlations between sulfate respiration and
  syntrophic growth in the Desulfovibrio

In each box, the top, boldface number is the
Pearson correlation coefficient. The bottom
number indicates the probability that the
coefficient is equal to zero (n8, growth of some
strains is still being determined)

• VI. D. vulgaris Llanelly was the only strain that
  would not grow syntrophically
• Llanelly grows more slowly than most strains on
  both lactate and pyruvate.
• But Llanelly has almost all of the same genes as
  Hildenborough.
• Hildenborough genes shown to be missing in
  Llanelly

D. vulgaris Hildenborough
D. vulgaris Llanelly
Strains were listed and color-coded according to
their growth rate in the same media in coculture
with M. maripaludis, with red being fastest
growth rate and brown indicating strains with the
slowest growth rate. Growth rate of dark grey
strains is ambiguous because of clumping or still
being determined.
OD, 600 nm

• Future plans
• Use experimental evolution to test further
  whether there is a trade-off between optimal
  syntrophic growth and sulfate reduction
• Further explore the potential for syntrophic
  growth by D. vulgaris Llanelly
• - Look for hydrogen burst during growth on
  lactate
• - Test for syntrophic growth on pyruvate
• - Search for mutations in candidate loci

Lowest syntrophic growth rate and biomass D.
oxamicus
Highest biomass in syntrophy D.
fructosivorans (lactate measurements in progress)
Highest syntrophic growth rate D. desulfuricans
27774
Acknowledgements We would like to thank S Stolyar
for helpful discussion of this work and ZK Yang,
Z He, and J Zhou for performing gDNA microarray
hybridizations.
Clumping strains were excluded from this analysis