Methanogenic Symbionts and the Locality of their Host Lower Termites.

Abstract

SSU rRNA genes of symbiotic methanogens in the hindgut of four lower Japanese termites and one Australian lower termite Mastotermes darwiniensis as well as a soil sample collected near a nest of Reticulitermes speratus were amplified, cloned and phylogenetically analyzed. Most of the clones found in the lower termites were of the genus Methanobrevibacter. The symbiotic methanogens in the Japanese termites and in the soil sample were related to each other. The clones obtained from M. darwiniensis grouped separately from the clones of Japanese termites. These results suggest that the methanogen community of lower termites reflects host locality rather than phylogeny.Key words: symbiosis, termite, methanogen, phylogeny, ThermoplasmaTermites harbor methanogenic archaea in the hindgut 9) , where methane is formed by the reduction of carbon-dioxide with hydrogen. Methanogens and acetogens in the termite hindgut play a role as a hydrogen-sink. The hydrogenconsuming process facilitates the anaerobic degradation of lignocellulose 14) . The microecology of the termite gut was recently reviewed 1) .A phylogenetic analysis of methanogens in the hindgut of the lower termite Reticulitermes speratus by Ohkuma et al. 11) found only one type of sequence in PCR clones. We have also analyzed symbiotic methanogens in the hindgut of R. speratus 15) . PCR clones of SSU rDNA sequences were grouped into three types. Type 1 clones were further classified into subtypes 1A, 1B, 1C and 1D. Most of the PCR clones of methanogen in R. speratus collected around the Japan Archipelago belonged to subtypes 1A and 1B in the genus Methanobrevibacter. Fluorescence in situ hybridization analysis showed that at least some of the type 1 species live on the hindgut epithelial surface. Ohkuma et al. 10,12) have reported two other types of sequences, Cd30 and MHj4, from Cryptotermes domesticus and Hodotermopsis sjostedti, respectively. Leadbetter et al. 5,6) have isolated three species of Methanobrevibacter, M. curvatus, M. cuticularis, and M. filiformis from R. flavipes. In the present study, we examined the molecular phylogeny of symbiotic methanogens of five species that belong to four families of lower termites. Phylogenetic relationships between methanogens and host termites were also discussed.Four lower termite species of three families, Neotermes koshunensis, Hodotermopsis sjostedti, Reticulitermes kanmonensis, and Coptotermes formosanus, were collected in the Japan Archipelago. Sampling points of the Japanese termites are listed in Table 1. Another lower termite Mastotermes darwiniensis was collected in Australia and kindly donated by Dr. O. Kitade. Ten individuals of pseudergate (worker) from each colony of termite were employed for DNA extraction. Total genomic DNA of the digestive tracts of the termites was prepared as described previously 15) . PCR primers and reaction conditions were also described in a previous report 15) . The primers used were ME855F and ME1354R, which were designed to se-

Phylogenetic Relationship of Symbiotic Archaea in the Gut of the Higher Termite Nasutitermes takasagoensis Fed with Various Carbon Sources

“…Because most of the clones obtained from N. takasagoensis were closely related to clones obtained from various termite species, it is likely that the majority of symbiotic archaea are unique to termites. Our data, as well as several previous studies 9,12,26,27) , support a coevolutionary relationship between termites and symbiotic archaea.…”

Identification of Endosymbiotic Methanogen and Ectosymbiotic Spirochetes of Gut Protists of the Termite Coptotermes formosanus

“…than that in S. leidyi. The endosymbiotic methanogens may be affected not by the host protists but by the termite taxonomy or their locality as discussed previously 18,20) . In each of the two independent single-cell samples of H. mirabile, two clone libraries of the 16S rRNA gene amplified with the general bacterial primers and the spirochete-specific primers were examined (Table 1).…”

“…The presence of diverse bacterial species and archaea has been reported in the gut community based on 16S rRNA gene sequences 18,19) . A recent observation has revealed that the intracellular endosymbionts of the largest protist species Pseudotrichonympha grassii (order Trichonymphida) are bacteria of a member of the order Bacteroidales and that the endosymbionts constitute the predominant bacteria accounting for more than two-thirds of gut bacteria 10) .…”

“…This strongly suggested that only one unique methanogen species was shared among the S. leidyi cells. The endosymbiotic methanogen associated with S. leidyi was affiliated with the genus Methanobrevibacter, a methanogen genus distributed widely and abundantly in the gut of diverse termites 3,18,20) . In the phylogenetic tree ( Fig.…”

Diverse Bacteria Related to the Bacteroides Subgroup of the CFB Phylum within the Gut Symbiotic Communities of Various Termites

“…Furthermore, approximately 18z of the clones cannot be readily assigned to any recognized group of Bacteria. The analogous culture-independent approaches have been successfully applied, in various termite species, to the studies of their gut microbial community of ‰agellated protists, 3) spirochetes, 4,5) methanogenic Archaea, [6][7][8] and diazotrophs. 9,10) These studies revealed that the majority of the gut community consists of novel and yet-uncultured species previously unknown to microbiologists.…”