Isolation ofDesulfovibrio intestinalissp. nov. from the hindgut of the lower termiteMastotermes darwiniensis

Abstract

A Gram-negative, anaerobic sulfate-reducing bacterium was isolated from hindgut contents of the lower termite Mastotermes darwiniensis Froggatt (strain KMS2). Strain KMS2 is motile by a single polar flagellum. The isolate possesses desulfoviridin and catalase activity. The G+C content of its DNA is in the range of 54.5-55.5 mol% (strain KMS2). It respires hydrogen and different low molecular weight organic compounds in the presence of sulfate, thiosulfate, and sulfite, and also oxygen. The isolated strain ferments pyruvate. Fastest growth with a doubling time of 12.5 h was obtained at 37 degrees C and not at 28 degrees C, the temperature at which the termites were grown. The isolate showed a 16S rDNA sequence homology of 95.9% to Desulfovibrio desulfuricans ATCC 27774 and a DNA-DNA homology of 44.6% to D. desulfuricans Essex 6 (type strain). Based on its biochemical properties and 16S rDNA sequence, the isolate was assigned to a new species named Desulfovibrio intestinalis.

Hydrogen is the central free intermediate during lignocellulose degradation by termite gut symbionts

“…In addition, the model does not account for alternative fermentation pathways, for example, malate and succinate formation, or for the direct uptake of polysaccharide monomers in the midgut. Also, a contribution of sulfatereducing bacteria to hydrogen turnover cannot be ruled out, especially since Desulfovibrio spp have been repeatedly isolated from the termite hindgut (Brauman et al, 1990;Trinkerl et al, 1990;Kuhnigk et al, 1996;Frö hlich et al, 1999). However, molecular studies using cloning and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes suggest very low population densities of this metabolic group in Figure 6 Proposed model of hydrogen metabolism in Reticulitermes santonensis and Cryptotermes secundus.…”

In vitro and in vivo sulfate reduction in the gut contents of the termite Mastotermes darwiniensis and the rose-chafer Pachnoda marginata

“…An unexpected high cell count of sulfate reducers (2ϫ10 8 cells per ml gut content) of the beetle Pachnoda marginata corresponded to 4.6% of the total bacterial population (9.2ϫ10 9 cells per ml gut content) grown in Postgate medium B. So far, SRB have also been found in the human large intestine (Gibson et al, 1988a, b) and in lower and higher animals (Brauman et al, 1990;Fröhlich et al, 1999;Gebhart et al, 1993;Howard and Hungate, 1976;Kuhnigk et al, 1996;Ohkuma and Kudo, 1996;Trinkerl et al, 1990). All isolates from termites examined so far could be assigned to the genus Desulfovibrio.…”

“…Enrichment and identification of sulfate-reducing bacteria from gut contents of the rose-chafer Pachnoda marginata SRB have been detected or isolated from the gut of higher and lower termites and the wood-eating cockroach Cryptocercus punctulatus (Brauman et al, 1990;Fröhlich et al, 1999;Kuhnigk et al, 1996;Ohkuma and Kudo, 1996;Trinkerl et al, 1990). Therefore, we were interested to know whether SRB are more widespread and occur also in gut contents of insects which branched off later in the phylogenetic tree such as Coleoptera.…”

“…The termites were fed with pine, beech or poplar wood and cultured at 28°C in metallic vessels which contained humid vermiculit. Desulfovibrio intestinalis strain KMS2 (DSM 11275 T ; Fröhlich et al, 1999) was from the culture collection of our institute.…”

“…The guts were prepared under aseptic conditions (Fröhlich et al, 1999;Trinkerl et al, 1990). For cell count determination and enrichment of SRB strains, Postgate medium B (Postgate, 1984) containing sodium lactate (2 g/L) and sodium sulfate (1 g/L) as electron donor and acceptor, respectively, and FeSO 4 · 7H 2 O (500 mg/L) in addition was used.…”