Microbial diversity in ostrich ceca as revealed by 16S ribosomal RNA gene clone library and detection of novel Fibrobacter species

The ostrich (Struthio camelus) is a herbivorous bird and although the hindgut is known as the site for fiber digestion, little is known about the microbial diversity in the ostrich hindgut. Our aim was to analyze the microbial diversity in ostrich ceca using a 16S ribosomal RNA gene (rDNA) clone library approach. A total of 310 clones were sequenced and phylogenetically analyzed and were classified into 110 operational taxonomy units (OTUs) based on a 98% similarity criterion. The similarity of the sequences ranged from 86 to 99% and 95 OTUs had less than 98% similarity to the sequences in the public databases. Coverage and the Shannon–Wiener index (H′) of the library were 83.9% and 4.29, respectively. The sequences were assigned to the following 6 phyla: Firmicutes (50.9% of the total number of sequences), Bacteroidetes (39.4%), Fibrobacteres (6.5%), Euryarchaeota (1.9%), Spirochaetes (1.0%), and Verrucomicrobia (0.3%); approximately 90% of the sequences were affiliated with Firmicutes and Bacteroidetes. The only OTU of Fibrobacteres (OTU 107), had 93 and 90% similarity to Fibrobacter succinogenes and F. intestinalis, respectively, suggesting a new species of Fibrobacter in ostrich ceca. Clostridium coccoides and C. leptum formed major groups within the Firmicutes. There was no OTU with high similarity (≥98%) to the 16S rDNA of cultivated fibrolytic bacteria in our library. Although two OTUs were affiliated with Euryarchaeota, no sequence was affiliated with methanogenic Archaea. This study presents the very complex ostrich cecal microbial community, in which the majority of the bacterial species have not yet been cultivated.     

Competition Between Ruminal Cellulolytic Bacteria for Adhesion to Cellulose

Competition for adhesion to cellulose among the three main ruminal cellulolytic bacterial species was studied using differential radiolabeling (¹⁴C/³H) of cells. When added simultaneously to cellulose, Ruminococcus flavefaciens FD1 and Fibrobacter succinogenes S85 showed some competition; however, both species were surpassed competitively by Ruminococcus albus 20. When R. flavefaciens FD1 and F. succinogenes S85 were already adherent, R. albus 20 adhesion occurred without inhibition but involved R. flavefaciens FD1 detachment. Received: 28 October 1996 / Accepted: 28 January 1997     

Sequence of a cellulase gene from the rumen anaerobe Ruminococcus flavefaciens 17

Summary A cellulase gene (endA) was isolated from a library of Ruminococcus flavefaciens strain 17 DNA fragments inserted in pUC13. The endA product showed activity against acid-swollen cellulose, carboxymethyl-cellulose, lichenan, cellopentaose and cellotetraose, but showed no activity against cellotriose or binding to avicel. Nucleotide sequencing indicated an encoded product of 455 amino acids which showed significant sequence similarity (ranging from 56% to 61%) with three endoglucanases from Ruminococcus albus, and with Clostridium thermocellum endoglucanase E. Little relatedness was found with a cellodextrinase previously isolated from R. flavefaciens FD1.     

The Effect of a Methanogen, Methanobrevibacter smithii, on the Growth Rate, Organic Acid Production, and Specific ATP Activity of Three Predominant Ruminal Cellulolytic Bacteria

Three predominant ruminal cellulolytic organisms, Fibrobacter succinogenes S85, Ruminococcus albus 8, and R. flavefaciens FD-1, were cultured with a methanogen, Methanobrevibacter smithii. Growth rates, bacterial protein, organic acids, and methane production were measured. When grown in diculture with the methanogen, a fermentative advantage was observed with F. succinogenes S85 as seen by an increase in specific rate of ATP production and organic acid concentration. The introduction of the methanogen did not improve the growth rate, organic acid yield, or specific rate of ATP production for R. albus 8. The growth rate and amount of organic acid end products increased when R. flavefaciens FD-1 was cultured with the methanogen; however, the specific activity of ATP production did not increase. Received: 3 August 1999 / Accepted: 4 September 1999     

Influence of Forage Phenolics on Ruminal Fibrolytic Bacteria and In Vitro Fiber Degradation

In vitro cultures of ruminal microorganisms were used to determine the effect of cinnamic acid and vanillin on the digestibility of cellulose and xylan. Cinnamic acid and vanillin depressed in vitro dry matter disappearance of cellulose 14 and 49%, respectively, when rumen fluid was the inoculum. The number of viable Bacteroides succinogenes cells, the predominant cellulolytic organism, was threefold higher for fermentations which contained vanillin than for control fermentations. When xylan replaced cellulose as the substrate, a 14% decrease in the digestibility of xylan was observed with vanillin added; however, the number of viable xylanolytic bacteria cultured from the batch fermentation was 10-fold greater than that of control fermentations. The doubling time of B. succinogenes was increased from 2.32 to 2.58 h when vanillin was added to cellobiose medium, and absorbance was one-half that of controls after 18 h. The growth rate of Ruminococcus albus and Ruminococcus flavefaciens was inhibited more by p-coumaric acid than by vanillin, although no reduction of final absorbance was observed in their growth cycles. Vanillin, and to a lesser extent cinnamic acid, appeared to prevent the attachment of B. succinogenes cells to cellulose particles, but did not affect dissociation of cells from the particles. B. succinogenes, R. albus, R. flavefaciens, and Butyrivibrio fibrisolvens all modified the parent monomers cinnamic acid, p-coumaric acid, ferulic acid, and vanillin, with B. fibrisolvens causing the most extensive modification. These results suggest that phenolic monomers can inhibit digestibility of cellulose and xylan, possibly by influencing attachment of the fibrolytic microorganisms to fiber particles. The reduced bacterial attachment to structural carbohydrates in the presence of vanillin may generate more free-floating fibrolytic organisms, thus giving a deceptively higher viable count.     

Degradation and fermentation of cellulose by the rumen anaerobic fungi in axenic cultures or in association with cellulolytic bacteria

Three rumen anaerobic fungi—Neocallinastix frontalis MCH3,Piromyces (Piromonas) communis FL, andCaecomyces (Sphaeromonas) communis FG10—were cultured on cellulose filter paper alone or in association with one of two rumen cellulolytic bacteria,Ruminococcus flavefaciens 007 andFibrobacter succinogenes S85. Cocultures ofN. frontalis orP. communis andR. flavefaciens were markedly less effective than the fungal monocultures in degrading cellulose but more effective than the bacterial monocultures.R. flavefaciens had an antagonistic effect against both of the fungal species. In contrast, no interaction was observed between the two fungal species andF. succinogenes. Cellulose was more effectively degraded by the cocultureC. communis-R. flavefaciens than by the corresponding fungal and bacterial monocultures. The effectiveness of degradation of the cocultureC. communis-F. succinogenes was comparable to that of the bacterial strains but greater than that of the fungi; no interaction was observed between these two microorganisms.     

Localization of Ruminal Cellulolytic Bacteria on Plant Fibrous Materials as Determined by Fluorescence In Situ Hybridization and Real-Time PCR

To visualize and localize specific bacteria associated with plant materials, a new fluorescence in situ hybridization (FISH) protocol was established. By using this protocol, we successfully minimized the autofluorescence of orchard grass hay and detected rumen bacteria attached to the hay under a fluorescence microscope. Real-time PCR assays were also employed to quantitatively monitor the representative fibrolytic species Fibrobacter succinogenes and Ruminococcus flavefaciens and also total bacteria attached to the hay. F. succinogenes was found firmly attached to not only the cut edges but also undamaged inner surfaces of the hay. Cells of phylogenetic group 1 of F. succinogenes were detected on many stem and leaf sheath fragments of the hay, even on fragments on which few other bacteria were seen. Cells of phylogenetic group 2 of F. succinogenes were often detected on hay fragments coexisting with many other bacteria. On the basis of 16S rRNA gene copy number analysis, the numbers of bacteria attached to the leaf sheaths were higher than those attached to the stems (P < 0.05). In addition, R. flavefaciens had a greater tendency than F. succinogenes to be found on the leaf sheath (P < 0.01) with formation of many pits. F. succinogenes, particularly phylogenetic group 1, is suggested to possibly play an important role in fiber digestion, because it is clearly detectable by FISH and is the bacterium with the largest population size in the less easily degradable hay stem.     

Identification of Ruminococcus flavefaciens as the Predominant Cellulolytic Bacterial Species of the Equine Cecum

Detection and quantification of cellulolytic bacteria with oligonucleotide probes showed that Ruminococcus flavefaciens was the predominant species in the pony and donkey cecum. Fibrobacter succinogenes and Ruminococcus albus were present at low levels. Four isolates, morphologically resembling R. flavefaciens, differed from ruminal strains by their carbohydrate utilization and their end products of cellobiose fermentation.     

Diet-Dependent Shifts in the Bacterial Population of the Rumen Revealed with Real-Time PCR

A set of PCR primers was designed and validated for specific detection and quantification of Prevotella ruminicola, Prevotella albensis, Prevotella bryantii, Fibrobacter succinogenes, Selenomonas ruminantium-Mitsuokella multiacida, Streptococcus bovis, Ruminococcus flavefaciens, Ruminobacter amylophilus, Eubacterium ruminantium, Treponema bryantii, Succinivibrio dextrinosolvens, and Anaerovibrio lipolytica. By using these primers and the real-time PCR technique, the corresponding species in the rumens of cows for which the diet was switched from hay to grain were quantitatively monitored. The dynamics of two fibrolytic bacteria, F. succinogenes and R. flavefaciens, were in agreement with those of earlier, culture-based experiments. The quantity of F. succinogenes DNA, predominant in animals on the hay diet, fell 20-fold on the third day of the switch to a grain diet and further declined on day 28, with a 57-fold reduction in DNA. The R. flavefaciens DNA concentration on day 3 declined to approximately 10% of its initial value in animals on the hay diet and remained at this level on day 28. During the transition period (day 3), the quantities of two ruminal prevotella DNAs increased considerably: that of P. ruminicola increased 7-fold and that of P. bryantii increased 263-fold. On day 28, the quantity of P. ruminicola DNA decreased 3-fold, while P. bryantii DNA was still elevated 10-fold in comparison with the level found in animals on the initial hay diet. The DNA specific for another xylanolytic bacterium, E. ruminantium, dropped 14-fold during the diet switch and was maintained at this level on day 28. The concentration of a rumen spirochete, T. bryantii, decreased less profoundly and stabilized with a sevenfold decline by day 28. The variations in A. lipolytica DNA were not statistically significant. After an initial slight increase in S. dextrinosolvens DNA on day 3, this DNA was not detected at the end of the experiment. S. bovis DNA displayed a 67-fold increase during the transition period on day 3. However, on day 28, it actually declined in comparison with the level in animals on the hay ration. The amount of S. ruminantium-M. multiacida DNA also increased eightfold following the diet switch, but stabilized with only a twofold increase on day 28. The real-time PCR technique also uncovered differential amplification of rumen bacterial templates with the set of universal bacterial primers. This observation may explain why some predominant rumen bacteria have not been detected in PCR-generated 16S ribosomal DNA libraries.     

Magnesium requirement of some of the principal rumen cellulolytic bacteria

Information available on the role of Mg for growth and cellulose degradation by rumen bacteria is both limited and inconsistent. In this study, the Mg requirements for two strains each of the cellulolytic rumen species Fibrobacter succinogenes (A3c and S85), Ruminococcus albus (7 and 8) and Ruminococcus flavefaciens (B34b and C94) were investigated. Maximum growth, rate of growth and lag time were all measured using a complete factorial design, 2(3)×6; factors were: strains (2), within species (3) and Mg concentrations (6). R. flavefaciens was the only species that did not grow when Mg was singly deleted from the media, and both strains exhibited a linear growth response to increasing Mg concentrations (P<0.001). The requirement for R. flavefaciens B34b was estimated as 0.54 mM; whereas the requirement for R. flavefaciens C94 was >0.82 as there was no plateau in growth. Although not an absolute requirement for growth, strains of the two other species of cellulolytic bacteria all responded to increasing Mg concentrations. For F. succinogenes S85, R. albus 7 and R. albus 8, their requirement estimated from maximum growth was 0.56, 0.52 and 0.51, respectively. A requirement for F. succinogenes A3c could not be calculated because there was no solution for contrasts. Whether R. flavefaciens had a Mg requirement for cellulose degradation was determined in NH₃-free cellulose media, using a 2×4 factorial design, 2 strains and 4 treatments. Both strains of R. flavefaciens were found to have an absolute Mg requirement for cellulose degradation. Based on reported concentrations of Mg in the rumen, 1.0 to 10.1 mM, it seems unlikely that an in vivo deficiency of this element would occur.     

Prokaryote diversity in the rumen of yak (Bos grunniens) and Jinnan cattle (Bos taurus) estimated by 16S rDNA homology analyses

Prokaryote diversity in the rumen of yak (Bos grunniens) and Jinnan cattle (Bos taurus) was estimated by 16S rDNA homology analysis. Two rumen 16S rDNA libraries were constructed. Of the 194 clones in the library of yak rumen, the sequences were mainly clustered to two phyla, low G+C Gram-positive bacteria (LGCGPB, 54.12% total clones) and Bacteroidetes (30.93%), respectively. While in the 197 clone-library of the cattle rumen, the sequences were mainly related to three phyla, Bacteroidetes (39.59%), gamma-Proteobacteria (26.9%) and LGCGPB (22.34%), respectively. The sequence analysis indicated that more than half of the species harbored in yak rumen belonged to the not-yet-cultured groups at <90% 16S rDNA similarity levels with cultured species, while 36% 16S rDNA sequences amplified from the rumen of Jinnan cattle fell in these catalogues. By comparing the uncultured sequences in yak rumen with those in Jinnan cattle and cow, the former formed distinct clusters loosely related to the later, implying that yak rumen could harbor some special prokaryote phyla. 10.8% sequences retrieved in yak rumen were related to the known rumen fibrolytic bacterial species; however none was related to the known amylolysis species. While 4% and 17.8% sequences retrieved from Jinnan cattle rumen were related to cultured fibrolytic and amylolysis species, respectively. The bacterial structures seemed to be in accordance with the feed of the two kinds of animals. In both rumens, retrieved methanogenic Archaea-related 16S rDNA sequences were at an unreasonable low level; in addition, none sequence was related to Ruminococcus albus, a classical rumen fibrolytic species. The reason can be due to the experimental biases.     

Phylogenetic analysis of 16S rRNA gene sequences reveals rumen bacterial diversity in Yaks (<Emphasis Type="Italic">Bos grunniens</Emphasis>)

Six matured male Yaks (Bos grunniens) with a mean live weight of 450 ± 23 kg (mean ± SD), were housed indoors in metabolism cages and fed pelleted lucerne (Medicago sativum). After an adjustment period of 24 days of feeding the diet, samples of rumen content were obtained for analysis of the bacteria in the liquor. The diversity of rumen bacteria was investigated by constructing a 16S rRNA gene clone library using the general bacterial primers F27 and R1492. A total of 130 clones, comprising nearly full length sequences (approx. 1.5 kb) were sequenced and submitted to BLAST and phylogenetic analysis. Using the criterion that similarity of 97% or greater with the sequences of cultivated bacteria, 16 clones were identified as Butyrivibrio fibrisolvens, Pseudobutyrivibrio ruminis, Ruminococcus flavefaciens, Succiniclasticum ruminis, Selenomonas ruminantium and Prevotella ruminicola, respectively. A further 10 clones shared similarity ranging from 90 to 97% with cultivated bacteria but the similarity in sequences for the remaining 104 clones were less than 90% of those of cultivated bacteria. Using a phylogenetic analysis it was found that the majority of the clones identified (63.8%) were located in the Low G + C Subdivision, with most of the remainder (35.4% of clones) located in the Cytophaga-Flexibacter-Bacteroides phylum and one clone (0.8%) was identified as a Proteobacteria. It was apparent that Yaks have a large and diverse range of bacteria in the rumen content which differ from those of cattle and other ruminants.     

Degradation of forage chicory by ruminal fibrolytic bacteria

Aims: Determine the susceptibility of forage chicory (Cichorium intybus L.) to degradation by ruminal fibrolytic bacteria and measure the effects on cell-wall pectic polysaccharides. Methods and Results: Large segments of fresh forage chicory were degraded in vitro by Lachnospira multiparus and Fibrobacter succinogenes, but not by Ruminococcus flavefaciens or Butyrivibrio hungatei. Cell-wall pectins were degraded extensively (95%) and rapidly by L. multiparus with a simultaneous release of uronic acids and the pectin-derived neutral monosaccharides arabinose, galactose and rhamnose. Fibrobacter succinogenes also degraded cell-wall pectins extensively, but at a slower rate than L. multiparus. Immunofluorescence microscopy using monoclonal antibodies revealed that, after incubation, homogalacturonans with both low and high degrees of methyl esterification were almost completely lost from walls of all cell types and from the middle lamella between cells. Conclusions: Only two of the four ruminal bacteria with pectinolytic activity degraded fresh chicory leaves, and each showed a different pattern of pectin breakdown. Degradation was greatest for F. succinogenes which also had cellulolytic activity. Significance and Impact of the Study: The finding of extensive removal of pectic polysaccharides from the middle lamella and the consequent decrease in particle size may explain the decreased rumination and the increased intake observed in ruminants grazing forage chicory.     

The <Emphasis Type="Italic">Fibrobacteres</Emphasis>: an Important Phylum of Cellulose-Degrading Bacteria

The phylum Fibrobacteres currently comprises one formal genus, Fibrobacter, and two cultured species, Fibrobacter succinogenes and Fibrobacter intestinalis, that are recognised as major bacterial degraders of lignocellulosic material in the herbivore gut. Historically, members of the genus Fibrobacter were thought to only occupy mammalian intestinal tracts. However, recent 16S rRNA gene-targeted molecular approaches have demonstrated that novel centres of variation within the genus Fibrobacter are present in landfill sites and freshwater lakes, and their relative abundance suggests a potential role for fibrobacters in cellulose degradation beyond the herbivore gut. Furthermore, a novel subphylum within the Fibrobacteres has been detected in the gut of wood-feeding termites, and proteomic analyses have confirmed their involvement in cellulose hydrolysis. The genome sequence of F. succinogenes rumen strain S85 has recently suggested that within this group of organisms a “third” way of attacking the most abundant form of organic carbon in the biosphere, cellulose, has evolved. This observation not only has evolutionary significance, but the superior efficiency of anaerobic cellulose hydrolysis by Fibrobacter spp., in comparison to other cellulolytic rumen bacteria that typically utilise membrane-bound enzyme complexes (cellulosomes), may be explained by this novel cellulase system. There are few bacterial phyla with potential functional importance for which there is such a paucity of phenotypic and functional data. In this review, we highlight current knowledge of the Fibrobacteres phylum, its taxonomy, phylogeny, ecology and potential as a source of novel glycosyl hydrolases of biotechnological importance.     

Effects of nitrate on methane production, fermentation, and microbial populations in in vitro ruminal cultures

The objective of this study was to examine the effects of nitrate on methane production, important fermentation characteristics, Fibrobacter succinogenes, Ruminococcus albus, Ruminococcus flavefaciens, total bacteria, and methanogens using in vitro ruminal cultures. Potential adaptation of the above microbes and persistency of nitrate to mitigate CH₄ production were also evaluated. Methane production was reduced by 70% at 12 μmol ml⁻¹ and nearly completely at ?24 μmol ml⁻¹ nitrate. Production of volatile fatty acids (VFAs) was affected to different extents at different nitrate concentrations. Over a series of six consecutive cultures receiving 12 μmol ml⁻¹nitrate, production of CH₄ and VFA did not change significantly. R. albus and R. flavefaciens seemed to adapt to nitrate, while F. succinogenes and methanogens did not. Nitrate may be used in achieving persistent mitigation of CH4 production by ruminants.     

Bacterial cell surface structures involved in lucerne cell wall degradation by pure cultures of cellulolytic rumen bacteria

Summary Pure cultures of the cellulolytic rumen bacterial strains Bacteroides succinogenes S85, Ruminococcus flavefaciens FD1 and Ruminococcus albus 7 were grown on lucerne cell walls (CW) or on cellobiose as the sole added carbohydrate substrate. Scanning electron microscopy visualization using cationized-feritin pretreatment have shown that cell surface topology of these strains grown on and attached to CW particles was specified by a dense coat of characteristic protuberant structures. In contrast, when grown on cellobiose, the surface topology of these bacterial strains was smoother, and contained fewer protuberant structures. The ability of these bacterial strains to attach to cellulose was higher for bacteria previously adapted to lucerne CW compared to cellobiose adaptation. Bacteroides succinogenes S85 was the best digester of lucerne CW (46.5%) and also had the best adhesion capability (65.6%) after adaption to grow on CW.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 2599-E, 1989 seriesOffprint requests to: J. Miron     

Molecular diversity of bacteria in Yunnan yellow cattle (Bos taurs) from Nujiang region, China

The rumen content of four Yunnan Yellow Cattle (Bos taurs) were collected to determine the bacteria diversity by using 16S rRNA gene sequence analysis. A total of 129 sequences were examined and the sequences were referred as 107 OTU (Operational Taxonomy Unit) according to the similarity level of 97% in gene sequence. Similarity analysis revealed that Yunnan Yellow Cattle had 12 sequences (10 OTU) shared 97% or greater similarity with cultured rumen bacteria Butyrivibrio fibrisolvens, Succiniclasticum ruminis, Ruminococcus bromii, Clostridium proteoclasticum, Ruminococcus flavefaciens, Pseudobutyrivibrio ruminis, Jeotgalicoccus psychrophilus, and Prevotella ruminicola, which accounting for 9.3% of the total clones (9.2% of the total OTU). The further 12 sequences (9 OTU) shared 90–97% similarity with cultured bacteria Clostridium aminobutyricum, butyrate-producing bacterium, Schwartzia succinivorans, Prevotella ruminicola, Eubacterium ruminantium, Ruminococcus albus, and Clostridium termitidis, also accounting for 9.3% of the total sequences (8.3% of the total OTU). The remaining 105 sequences (90 OTU) shared less than 90% similarity with cultured bacteria, accounting for 81.4% of the total sequences (82.5% of the total OTU). According to the phylogenetic analysis, all sequences were phylogenetically placed within phyla of low G+C subdivision (accounting for 72.1 and 72.5% of the total clones and OTU, respectively) and CFB subdivision (Cytophaga-Flexibacter-Bacteroides; accounting for 27.9 and 27.5% of the total clones and OTU, respectively). Among the examined clones, rare bacteria Jeotgalicoccus psychrophilus was detected in the rumen of cattle.     

Rumen Bacterial Community Transition During Adaptation to High-grain Diet

Transitional changes of the ruminal bacterial community structure in cows during the switch from roughage to high-grain diet were monitored by PCR amplification and sequencing of 16S rDNA clone libraries. In total, one hundred fifty 16S rDNA sequences of almost full-length (1.4 kb) were analysed from three libraries prepared from the rumen fluid on day 0, 3, and 28 of switch to high-grain diet. In the first library (day 0, hay diet) of 51clones, 90.2% of sequences were belonging to the low G+C Gram-positive bacteria (LGCGPB) phylum, with the minor inclusion of theCytophaga-Flavobacter-Bacteroides (CFB;3.9%), Proteobacteria (3.9%) and high G+C Gram-positive bacteria (HGCGPB;2.0%) phyla-related sequences. Six LGCGPB sequences were clustered with the well-known cellulolytics of the rumen, Ruminococcus flavefaciens and R. albus. In the second library (day 3 of high-grain diet) of 58 clones, the LGCGPB-related sequences still dominated (72.4%), albeit being represented by other species than in the first library. In particular, this library was enriched by representatives of Selenomonas-Succiniclasticum-Megasphaera group IX (17.2%), lactobacilli- (6.9%) and Butyrivibrio fibrisolvens lineage 3-related (8.6%) sequences. Other phyla were represented by CFB (22.4%) and HGCGPB (3.4%). In the third library (day 28 of high-grain diet) of 41 clones, 95% of sequences fell into the LGCGPB phylum. About half of them (46%) were clustered within theSelenomonas-Succiniclasticum-Megasphaera group in Clostridium cluster IX. No HGCGPB-related sequences were detected and CFB was represented by only a single clone. No Streptococcus bovis -related sequences were detected in any of the three clone libraries.     

Effects of different sources of physically effective fiber on rumen microbial populations

Physically effective fiber is needed by dairy cattle to prevent ruminal acidosis. This study aimed to examine the effects of different sources of physically effective fiber on the populations of fibrolytic bacteria and methanogens. Five ruminally cannulated Holstein cows were each fed five diets differing in physically effective fiber sources over 15 weeks (21 days/period) in a Latin Square design: (1) 44.1% corn silage, (2) 34.0% corn silage plus 11.5% alfalfa hay, (3) 34.0% corn silage plus 5.1% wheat straw, (4) 36.1% corn silage plus 10.1% wheat straw, and (5) 34.0% corn silage plus 5.5% corn stover. The impact of the physically effective fiber sources on total bacteria and archaea were examined using denaturing gradient gel electrophoresis. Specific real-time PCR assays were used to quantify total bacteria, total archaea, the genus Butyrivibrio, Fibrobacter succinogenes, Ruminococcus albus, Ruminococcus flavefaciens and three uncultured rumen bacteria that were identified from adhering ruminal fractions in a previous study. No significant differences were observed among the different sources of physical effective fiber with respect to the microbial populations quantified. Any of the physically effective fiber sources may be fed to dairy cattle without negative impact on the ruminal microbial community.     

Effects of glycerol on the growth,adhesion, and cellulolytic activity of rumen cellulolytic bacteria and anaerobic fungi

The effect of glycerol on the growth, adhesion, and cellulolytic activity of two rumen cellulolytic bacterial species,Ruminococcus flavefaciens andFibrobacter succinogenes subsp.succinogenes, and of an anaerobic fungal species,Neocallimastix frontalis, was studied. At low concentrations (0.1–1%), glycerol had no effect on the growth, adhesion, and cellulolytic activity of the two bacterial species. However, at a concentration of 5%, it greatly inhibited their growth and cellulolytic activity. Glycerol did not affect the adhesion of bacteria to cellulose. The growth and cellulolytic activity ofN. frontalis were inhibited by glycerol, increasingly so at higher concentrations. At a concentration of 5%, glycerol totally inhibited the cellulolytic activity of the fungus. Thus, glycerol can be added to animal feed at low concentrations.