Ecology of Uncultivated Oscillospira Species in the Rumen of Cattle, Sheep, and Reindeer as Assessed by Microscopy and Molecular Approaches

Abstract

The ecology of the uncultured, but large and morphologically conspicuous, rumen bacterium Oscillospira spp. was studied. Oscillospira-specific 16S rRNA gene sequences were detected in North American domestic cattle, sheep from Australia and Japan, and Norwegian reindeer. Phylogenetic analysis of the sequences obtained allowed definition of three operational taxonomic units within the Oscillospira clade. Consistent with this genetic diversity, we observed atypical smaller morphotypes by using an Oscillospira-specific fluorescence in situ hybridization probe. Despite the visual disappearance of typical large Oscillospira morphotypes, the presence of Oscillospira spp. was still detected by Oscillospira-specific PCR in the rumen of cattle and sheep. These observations suggest the broad presence of Oscillospira species in various rumen ecosystems with the level, and most likely the morphological form, dependent on diet. An ecological analysis based on enumeration of the morphologically conspicuous, large-septate form confirms that the highest counts are associated with the feeding of fresh forage diets to cattle and sheep and in two different subspecies of reindeer investigated.Morphologically unique, large bacteria of the genus Oscillospira, which have not been grown in pure culture yet, can be routinely detected microscopically in the rumen contents of cattle and sheep (11,18). A number of Oscillospira spp. are responsive to the advent of green pastures and fluctuate seasonally (13, 17) (see also Table 1). The only species of Oscillospira described in Bergey's Manual of Systematic Bacteriology (8) is Oscillospira guilliermondii, and this entry refers to the original morphological description by Chatton and Perard in 1913. Warner (34) proposed that at least two strains or species be included in the Oscillospira group based on cell diameter and the tendency to form spores as the main characteristic differences. This implies that there are different morphological forms or species related to different diets or in different gut ecosystems.Detection and identification of microbial populations are the most basic prerequisites for microbial ecology studies. Over the last decade, several molecular techniques have been developed that when applied to the rumen microbiota have revealed enormous microbial diversity not recognized previously because of limitations and biases inherent in the cultivation approach (24,(30)(31)(32)37). The cultivation-independent approach provides technology for detection and monitoring of microorganisms such as Oscillospira, for which growth requirements are unknown and undetermined. The only requirement for the development of molecular detection techniques is the availability of a marker molecule. Fortunately, several 16S rRNA gene sequences have recently been retrieved from this large bacterium isolated by flow cytometric sorting (39), and this enabled the design of various molecular probes for detection and monitoring. We designed and validate here PCR and PCR-denaturing gradient gel electroph...

Physiological and microbial adjustments to diet quality permit facultative herbivory in an omnivorous lizard

“…Individuals that exhibited a higher abundance of Oscillospira in the hindgut and feces displayed higher fiber digestibility, consistent with the notion that this genus may play a role in fiber degradation (Mackie et al, 2003). Additionally, individuals that harbored a higher abundance of Desulfovibrio in the small intestine exhibited higher fiber digestibility.…”

“…While the functions of the genus Oscillospira are unknown, it is likely that it plays a role in fiber fermentation given its presence in the in the guts of many ruminants and other herbivores (Kohl et al, 2014;Mackie et al, 2003). Additionally, ruminants fed fresh forage exhibit a higher abundance of Oscillospira compared with those fed low-fiber grain, and microscopy reveals that these bacteria associate with the surfaces of plant material in the gut (Mackie et al, 2003). From our study, it is unclear whether these changes are driven by the increase in fiber content of the diet or perhaps by a decrease in protein content.…”

Pan-genome of the dominant human gut-associated archaeon, Methanobrevibacter smithii , studied in twins

“…Two of these OTUs are highly related to Oscillospira guilliermondii, an as yet uncultured, large, and morphologically conspicuous organism found in ruminants (32,33). The most closely related cultured isolate that we could find for any of these OTUs is Sporobacter termitidis, a hydrogen-consuming acetogen from the termite gut (34).…”

Microbiota conservation and BMI signatures in adult monozygotic twins

“…Several Oscillospira species react to the diets of their host, increasing strongly when the hosts are feeding on fresh green fields (Mackie et al, 2003). It is likely that these organisms are adapted to degrade the fibers of young plants.…”