Search

The attachment of rumen microbes to feed particles is critical to feed fermentation, degradation and digestion. However, the extent to which the physicochemical properties of feeds influence the colonization by rumen microbes is still unclear. We hypothesized that rumen microbial communities may have differential preferences for attachments to feeds with varying lignocellulose properties. To this end, the structure and composition of microbial communities attached to six common forages with different lignocellulosic compositions were analyzed following in situ rumen incubation in male Taleshi cattle. The results showed that differences in lignocellulosic compositions significantly affected the inter-sample diversity of forage-attached microbial communities in the first 24 h of rumen incubation, during which the highest dry matter degradation was achieved. However, extension of the incubation to 96 h resulted in the development of more uniform microbial communities across the forages. Fibrobacteres were significantly overrepresented in the bacterial communities attached to the forages with the highest neutral detergent fiber contents. Ruminococcus tended to attach to the forages with low acid detergent lignin contents. The extent of dry matter fermentation was significantly correlated with the populations of Fibrobacteraceae, unclassified Bacteroidales, Ruminococcaceae and Spirochaetacea. Our findings suggested that lignocellulosic compositions, and more specifically the cellulose components, significantly affected the microbial attachment to and thus the final digestion of the forages.

Knowledge on the spatial distribution of prokaryotic taxa is an essential basis to understand microbial diversity and the factors shaping its patterns. Large-scale patterns of faunal distribution are thought to be influenced by physical environmental factors, whereas smaller scale spatial heterogeneity is maintained by species-specific life-history characteristics, the quantity and quality of food sources and local disturbances including both natural and man-induced events. However, it is still not clear which environmental parameters control the diversity and community structure of sedimentary microorganisms mediating important ecosystem processes. In this study, multiscale patterns were elucidated at seven stations in the Oyster Ground, North Sea (54°4'N/4°E), 100 m to 11 km apart. These were related to biotic (e.g. multicellular organisms) and abiotic parameters (e.g. organic carbon content in the sediment) to establish the relationship between the distribution of both bacterial and archaeal communities and their environment. A relatively high variability was detected at all scales for bacterial and archaeal communities, both of which were controlled by different suites of biotic and abiotic environmental variables. The bacterial community consisted mainly of members belonging to the Gammaproteobacteria and the Fibrobacteres/Acidobacteria group. Members of the Deltaproteobacteria, Bacteroidetes and Actinobacteria also contributed to the bacterial community. Euryarchaeota formed the majority of archaeal phylotypes together with three phylotypes belonging to the Crenarchaeota.

The bacterial diversity and abundance in two moraine lakes and two glacial meltwaters (5140, 5152, 5800 and 6350 m above sea level, respectively) in the remote Mount Everest region were examined through 16S rRNA gene clone library and flow cytometry approaches. In total, 247 clones were screened by RFLP and 60 16S rRNA gene sequences were obtained, belonging to the following groups: Proteobacteria (8% alpha subdivision, 21% beta subdivision, and 1% gamma subdivision), Cytophaga–Flavobacteria–Bacteroides (CFB) (54%), Actinobacteria (4%), Planctomycetes (2%), Verrucomicrobia (2%), Fibrobacteres (1%) and Eukaryotic chroloplast (3%), respectively. The high dominance of CFB distinguished the Mount Everest waters from other mountain lakes. The highest bacterial abundance and diversity occurred in the open moraine lake at 5152 m, and the lowest in the glacial meltwater at 6350 m. Low temperature at high altitude is considered to be critical for component dominancy. At the same altitude, nutrient availability plays a role in regulating population structure. Our results also show that the bacteria in Mount Everest may be derived from different sources.