In situ morphology of the gut microbiota of wood-eating termites [Reticulitermes flavipes (Kollar) and Coptotermes formosanus Shiraki]

Abstract

Light microscopy and scanning and transmission electron microscopy were used to examine the in situ morphology of the gut microbiota of Reticulitermes flavipes and Coptotermes formosanus. Laboratory-maintained termites were used and, for R. flavipes, specimens were also prepared immediately after collection from a natural infestation. The latter endeavor enabled a study of different castes and developmental stages ofR. flavipes and revealed differences in the microbiota of field versus laboratory specimens. The termite paunch microbiota consisted of an abundance of morphologically diverse bacteria and protozoa. Thirteen bacterial morphotypes in the paunch were described in detail: seven were observed only in R. flavipes, three were observd only in C. formosanus, and three were common to both termite species. The paunch epithelium was densely colonized by bacteria, many of which possessed holdfast elements that secured them tightly to this tissue and to other bacterial cells. Besides bacteria, the protozoan Pyrsonympha vertens adhered to the paunch epithelium of R. flavipes by means of an attachment organelle. Cuplike indentations were MATERIALS AND METHODS Termites. C. formosanus was collected near Lake Charles, La., whereas R. flavipes was collected in Janesville, Wis. Termite-infested wood, with adherent soil and debris from the collection site, was kept 406

‘Candidatus Arthromitus’ revised: segmented filamentous bacteria in arthropod guts are members of Lachnospiraceae

“…However, we did not find ectosymbionts showing the characteristic F420 autofluorescence of methanogens in the batch of termites used for our study. Instead, we found evidence that the Arthromitus filaments are colonized by uncultivated bacteria from the Bacteroidales cluster V, which agrees with the report of Breznak and Pankratz (1977), who demonstrated ectosymbionts of Arthromitus in R. flavipes that had a typical Gram-negative ultrastructure (see fig. 15 in Breznak and Pankratz, 1977) and, more specifically, the report of Nakajima and colleagues (2006), who documented the presence of ectosymbionts belonging to Bacteroidales Cluster V on Arthromitus filaments in Reticulitermes speratus.…”

“…Instead, we found evidence that the Arthromitus filaments are colonized by uncultivated bacteria from the Bacteroidales cluster V, which agrees with the report of Breznak and Pankratz (1977), who demonstrated ectosymbionts of Arthromitus in R. flavipes that had a typical Gram-negative ultrastructure (see fig. 15 in Breznak and Pankratz, 1977) and, more specifically, the report of Nakajima and colleagues (2006), who documented the presence of ectosymbionts belonging to Bacteroidales Cluster V on Arthromitus filaments in Reticulitermes speratus. Other members of Bacteroidales cluster V are known to be specific ectosymbionts of gut flagellates Desai et al, 2010).…”

“…Their association with the hindgut wall is further supported by their absence from a metagenomic analysis of the lumen-associated gut microbiota of Nasutitermes termites (Warnecke et al, 2007). Our study shows that members of this cluster are present also in other arthropods (Figs 2 and 4) and include many taxa in which Arthromitus filaments have been previously described, such as termites of the genera Coptotermes, Reticulitermes, Zootermopsis and Incisitermes (Leidy, 1881;Breznak and Pankratz, 1977;Margulis et al, 1998), blattid cockroaches (Bracke et al, 1979) and millipedes (Leidy, 1849). The presence of the Arthromitus cluster in the gut of scarab beetle larvae (Egert et al, 2003) agrees with our observation of Arthromitus-like filaments attached to the gut wall of P. marginata (Fig.…”

“…The presence of rod-shaped ectosymbionts on the surface of Arthromitus filaments has been already observed by Leidy (1881). Not all filaments are colonized, and the location of the ectosymbionts on filaments, their morphology, and also their mode of attachment vary (Breznak and Pankratz, 1977;Margulis et al, 1990;Leadbetter and Breznak, 1996). Leadbetter and Breznak (1996) observed ectosymbiotic methanogens on the surface of Arthromitus filaments in R. flavipes.…”

“…However, as there are at least three subgroups in R. santonensis that match both probes, it is also possible that one of them contains nonfilamentous forms. The surface of Arthromitus filaments is known to be colonized by ectosymbiotic bacteria (Leidy, 1881;Breznak and Pankratz, 1977;Margulis et al, 1990;Leadbetter and Breznak, 1996). In view of the abundance of Bacteroidales in the 16S clone libraries obtained from the filament suspensions, particularly of Bacteroidales Cluster V (comprising ectosymbionts of termite gut flagellates), it seemed likely that Arthromitus filaments are associated with bacteria from this group.…”