Detection of methanogenic archaea associated with rumen ciliate protozoa (original) (raw)
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A re‐appraisal of the diversity of the methanogens associated with the rumen ciliates
FEMS microbiology …, 2006
The diversity of methanogenic archaea associated with different species of ciliated protozoa in the rumen was analysed. Partial fragments of archaeal SSU rRNA genes were amplified from DNA isolated from single cells from the rumen protozoal species Metadinium medium, Entodinium furca, Ophryoscolex caudatus and Diplodinium dentatum. Sequence analysis of these fragments indicated that although all of the new isolates clustered with sequences previously described for methanogens, there was a difference in the relative distribution of sequences detected here as compared to that of previous work. In addition, many of the novel sequences, although clearly of archaeal origin have relatively low identity to the sequences in database which are most closely related to them. (N.R. McEwan). www.fems-microbiology.org FEMS Microbiology Letters 238 (2004) 307-313 Unidentified rumen methanogen [AB034189] Unidentified rumen methanogen [AF029206] Unidentified rumen methanogen [AF029208] Unidentified rumen methanogen [AF029207] Unidentified rumen methanogen [AF029210] Unidentified rumen methanogen [AF029211] Unidentified rumen methanogen [Isolate from gut of xylophagous cockroaches [AB062332] Isolate from astewater sludge [AF424770] Archaeon from contaminated aquifer [AF050616] Unidentified rumen methanogen [AB034187] Unidentified rumen methanogen [AB034186] Unidentified rumen methanogen [AB034184]
Some rumen ciliates have endosymbiotic methanogens
FEMS Microbiology …, 1994
Most of the small ciliate protozoa, including Dasytricha ruminantium and Entodinium spp. living in the rumen of sheep, were found to have intracellular bacteria. These bacteria were not present in digestive vacuoles. They showed characteristic coenzyme F420 autofluorescence and they were detected with a rhodamine-labelled Archaea-specific oligonucleotide probe. The measured volume percent of autofluorescing bacteria (1%) was close to the total volume of intracellular bacteria estimated from TEM stereology. Thus it is likely that all of the bacteria living in the cytoplasm of these ciliates were endosymbiotic methanogens, using H 2 evolved by the host ciliate to form methane. Intracellular methanogens appear to be much more numerous than those attached to the external cell surface of ciliates.
European Journal of Protistology, 1996
In situ hybridization of rumen ciliate protozoa with 165 ribosomal RNA fluorescent oligonucleotide probes specific for Archaea and Bacteria provided semi-quantitative indication of the location, type and extent of prokaryotic colonization of various protozoal species. The isotrichid holotrich ciliates generally carried a smaller load of intracellular microorganisms than did the entodiniomorphid species. Thus, the vast majority of the Dasytricha ruminantium population had neither bacterial not archaeal endosymbionts, although a very small minority of these ciliates (only 11 out of 447: < 3%), contained numerous Bacteria cells. Their food vacoules contained only Bacteria. Thirty per cent of Isotricha spp. were without endosymbionts. Polyplastron multivesiculatum invariably had large numbers (> 250 cells per ciliate) of intracellular Bacteria, but no Archaea. Only some Epidinium spp. had intracellular prokaryotes, whereas Entodinium spp. and Ent. simplex almost always had. Many of the larger entodiniomorphid genera were heavily colonized by both bacterial and archaeal species. Eudiplodinium maggii had no obvious bacterial associates, although the autofluorescence of ingested plant material made difficult the detection of possible endosymbionts.
Multiple Acquisition of Methanogenic Archaeal Symbionts by Anaerobic Ciliates
Molecular Biology and Evolution, 2000
Anaerobic heterotrichous ciliates (Armophoridae and Clevelandellidae) possess hydrogenosomes that generate molecular hydrogen and ATP. This intracellular source of hydrogen provides the basis for a stable endosymbiotic association with methanogenic archaea. We analyzed the SSU rRNA genes of 18 heterotrichous anaerobic ciliates and their methanogenic endosymbionts in order to unravel the evolution of this mutualistic association. Here, we show that the anaerobic heterotrichous ciliates constitute at least three evolutionary lines. One group consists predominantly of gut-dwelling ciliates, and two to three, potentially four, additional clades comprise ciliates that thrive in freshwater sediments. Their methanogenic endosymbionts belong to only two different taxa that are closely related to free-living methanogenic archaea from the particular ecological niches. The close phylogenetic relationships between the endosymbionts and free-living methanogenic archaea argue for multiple acquisitions from environmental sources, notwithstanding the strictly vertical transmission of the endosymbionts. Since phylogenetic analysis of the small-subunit (SSU) rRNA genes of the hydrogenosomes of these ciliates indicates a descent from the mitochondria of aerobic ciliates, it is likely that anaerobic heterotrichous ciliates hosted endosymbiotic methanogens prior to their radiation. Therefore, our data strongly suggest multiple acquisitions and replacements of endosymbiotic methanogenic archaea during their host's adaptation to the various ecological niches.
Study of methanogen communities associated with different rumen protozoal populations
FEMS Microbiology Ecology, 2014
Protozoa-associated methanogens (PAM) are considered one of the most active communities in the rumen methanogenesis. This experiment investigated whether methanogens are sequestrated within rumen protozoa, and structural differences between rumen free-living methanogens and PAM. Rumen protozoa were harvested from totally faunated sheep, and six protozoal fractions (plus free-living microorganisms) were generated by sequential filtration. Holotrich-monofaunated sheep were also used to investigate the holotrich-associated methanogens. Protozoal size determined the number of PAM as big protozoa had 1.7–3.3 times more methanogen DNA than smaller protozoa, but also more endosymbiotic bacteria (2.2- to 3.5-fold times). Thus, similar abundance of methanogens with respect to total bacteria were observed across all protozoal fractions and free-living microorganisms, suggesting that methanogens are not accumulated within rumen protozoa in a greater proportion to that observed in the rumen as ...
Folia Microbiologica, 2000
The methanogenic activity in the presence ofEntodinium caudatum andEpidinium ecaudatum was well preserved after long-term cultivation. Microscopic observation revealed that methane production in the presence ofE. caudatum was probably caused by their intracellular methanogenic activity, while methane production in the presence ofE. ecaudatum f.caudatum etecaudatum could be atributed to both the methanogenic bacterial fraction of their external surface and their intracellular activity. Methane production per protozoan cell ofE. caudatum andE. ecaudatum was 2.1 nmol per cell per d and 6.0 nmol. per cell per d, respectively.E. caudatum was responsible for almost the entire methane production in the culture. The activity of free methanogens constituted approximately 50% of the total methane production in thee. ecaudatum culture. Decrease of digestibility of substrates and differences in the fermentation end products accompanied the inhibition of methanogenesis in both cultures by penicillin G. streptomycin, chloramphenicol, 2-bromoethanesulfonate, and pyromellitic diimideE. caudatum appeared to be more sensitive thanE. ecaudatum to the compounds tested. Hydrogen recoveries based on both volatile fatty acids and methane production suggested that the methanogenic population appeared not to be fully able to consume hydrogen produced in the protozoan cultures. The culture conditions tested were found to be suitable for experiments on the relationship between rumen ciliate and rumen bacteria.
The Role of Ciliate Protozoa in the Rumen
Frontiers in microbiology, 2015
First described in 1843, Rumen protozoa with their striking appearance were assumed to be important for the welfare of their host. However, despite contributing up to 50% of the bio-mass in the rumen, the role of protozoa in rumen microbial ecosystem remains unclear. Phylogenetic analysis of 18S rDNA libraries generated from the rumen of cattle, sheep, and goats has revealed an unexpected diversity of ciliated protozoa although variation in gene copy number between species makes it difficult to obtain absolute quantification. Despite repeated attempts it has proven impossible to maintain rumen protozoa in axenic culture. Thus it has been difficult to establish conclusively a role of ciliate protozoa in rumen fiber degradation. The development of techniques to clone and express ciliate genes in λ phage, together with bioinformatic indices to confirm the ciliate origin of the genes has allowed the isolation and characterization of fibrolytic genes from rumen protozoa. Elimination of t...
Examining diversity of free-living methanogens and those associated with protozoa in the rumen
Journal of Animal and Feed Sciences, 2004
The diversity of methanogens in the rumen of sheep fed three different diets was examined using denaturing gradient gel electrophoresis (DGGE). In addition, half of the sheep had pot scrubbers added to their rumen to increase fl ow rate. The methanogens were separated by a series of washing steps into three populations: free-living, ecto-symbiotic and endo-symbiotic. Preliminary DGGE banding patterns demonstrated considerable differences between populations, treatment groups, and within groups. This suggests that the diversity of methanogens is infl uenced by diet, fl ow rates of digesta and the niche they occupy in relation to the protozoa.