Abstract
Dehalococcoides ethenogenes strain 195 (DE195) was grown in a sustainable syntrophic
association with Desulfovibrio vulgaris Hildenborough (DVH) as a co-culture, as well as with DVH
and the hydrogenotrophic methanogen Methanobacterium congolense (MC) as a tri-culture using
lactate as the sole energy and carbon source. In the co- and tri-cultures, maximum dechlorination
rates of DE195 were enhanced by approximately three times (11.0±0.01 lmol per day for the
co-culture and 10.1±0.3 lmol per day for the tri-culture) compared with DE195 grown alone
(3.8±0.1 lmol per day). Cell yield of DE195 was enhanced in the co-culture (9.0±0.5107 cells per
lmol Cl released, compared with 6.8±0.9107 cells per lmol Cl released for the pure culture),
whereas no further enhancement was observed in the tri-culture (7.3±1.8107 cells per lmol
Cl released). The transcriptome of DE195 grown in the co-culture was analyzed using a wholegenome
microarray targeting DE195, which detected 102 significantly up- or down-regulated genes
compared with DE195 grown in isolation, whereas no significant transcriptomic difference was
observed between co- and tri-cultures. Proteomic analysis showed that 120 proteins were
differentially expressed in the co-culture compared with DE195 grown in isolation. Physiological,
transcriptomic and proteomic results indicate that the robust growth of DE195 in co- and tri-cultures
is because of the advantages associated with the capabilities of DVH to ferment lactate to provide H2
and acetate for growth, along with potential benefits from proton translocation, cobalamin-salvaging
and amino acid biosynthesis, whereas MC in the tri-culture provided no significant additional
benefits beyond those of DVH.
