Animal (2012), 6:5, pp 815–823 & The Animal Consortium 2011
Effects of disodium fumarate on ruminal fermentation andmicrobial communities in sheep fed on high-forage diets
Y. W. Zhou1, C. S. McSweeney2, J. K. Wang1 and J. X. Liu1-
1Institute of Dairy Science, MoE Key Laboratory of Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, China; 2CSIRO LivestockIndustries, 306 Carmody Road, St Lucia, QLD 0467, Australia
(Received 1 September 2010; Accepted 23 September 2011; First published online 11 November 2011)
This study was conducted to investigate effects of disodium fumarate (DF) on fermentation characteristics and microbialpopulations in the rumen of Hu sheep fed on high-forage diets. Two complementary feeding trials were conducted. In Trial 1, sixHu sheep fitted with ruminal cannulae were randomly allocated to a 2 3 2 cross-over design involving dietary treatments of either0 or 20 g DF daily. Total DNA was extracted from the fluid- and solid-associated rumen microbes, respectively. Numbers of 16SrDNA gene copies associated with rumen methanogens and bacteria, and 18S rDNA gene copies associated with rumen protozoaand fungi were measured using real-time PCR, and expressed as proportion of total rumen bacteria 16S rDNA. Ruminal pHdecreased in the DF group compared with the control (P , 0.05). Total volatile fatty acids increased (P , 0.001), but butyratedecreased (P , 0.01). Addition of DF inhibited the growth of methanogens, protozoa, fungi and Ruminococcus flavefaciens in fluidsamples. Both Ruminococcus albus and Butyrivibrio fibrisolvens populations increased (P , 0.001) in particle-associated samples. Trial 2 was conducted to investigate the adaptive response of rumen microbes to DF. Three cannulated sheep were fed on basaldiet for 2 weeks and continuously for 4 weeks with supplementation of DF at a level of 20 g/day. Ruminal samples were collectedevery week to analyze fermentation parameters and microbial populations. No effects of DF were observed on pH, acetate andbutyrate (P . 0.05). Populations of methanogens and R. flavefaciens decreased in the fluid samples (P , 0.001), whereas additionof DF stimulated the population of solid-associated Fibrobacter succinogenes. Population of R. albus increased in the 2nd to4th week in fluid-associated samples and was threefold higher in the 4th week than control week in solid samples. Analysis ofdenaturing gradient gel electrophoresis fingerprints revealed that there were significant changes in rumen microbiota after addingDF. Ten of 15 clone sequences from cut-out bands appearing in both the 2nd and the 4th week were 94% to 100% similar toPrevotella-like bacteria, and four sequences showed 95% to 98% similarity to Selenomonas dianae. Another 15 sequences wereobtained from bands, which appeared in the 4th week only. Thirteen of these 15 sequences showed 95% to 99% similarity toClostridium sp., and the other two showed 95% and 100% similarity to Ruminococcus sp. In summary, the microorganismspositively responding to DF addition were the cellulolytic bacteria, R. albus, F. succinogenes and B. fibrisolvens as well asproteolytic bacteria, B. fibrisolvens, P. ruminicola and Clostridium sp.
Keywords: disodium fumarate, ruminal metabolism, microbial community, sheep
and the positive effects on the population of cellulolyticmicrobes, Ruminococcus albus and fungi.
The rumen microorganisms can be classified into hydrogen-producing (protozoa, cellulolytic bacteria and fungi) andhydrogen-consuming microbes (methanogens and fumarate-
reducers) according to their hydrogen metabolic pathway.
Hydrogen metabolism plays a central role in regulating rumen
Supplementation of disodium fumarate in the sheep diet could
fermentation (Hungate, 1967; Williams and Coleman, 1997).
improve ruminal fermentation by changing the microbial com-
Efficient removal of hydrogen from the rumen is beneficial to
munities, indicative of the decreased methanogen population
increase the rate of fermentation by eliminating its inhibitoryeffect on the microbial degradation of plant material (Wolin,
1979; McAllister and Newbold, 2008). There are other potential
electron acceptors in rumen (Wolin, 1979), such as sulfate,
In Trial 2, three 1.5-year-old rumen-cannulated Hu sheep
nitrate and fumarate, etc. (Morgavi et al., 2010). Among them
(,45 kg BW) were fed on the same basal diet as in Trial 1
fumarate is non-toxic and an intermediate of the pathways of
continuously for 6 weeks, including 2 weeks of adaptation
propionate formation (Russell and Wallace, 1997), and has been
(without DF) and 4 weeks with DF supplementation (20 g/day).
extensively studied as an alternative electron sink (Castillo et al.,
Ruminal samples were collected in the morning before feeding
2004). Fumarate has been associated with favorable changes in
after the first 2 weeks of adaptation and every week thereafter.
ruminal fermentation in vitro as well as in vivo (Asanuma et al.,
Sampling points were indicated as 0 w (no DF addition), 1 w, 2
1999a; Ungerfeld et al., 2007; Wood et al., 2009).
w, 3 w and 4 w, respectively. Rumen fermentation and microbial
Methanogens (hydrogen-utilizing microbes) and fibrolytic
populations were measured. Microbial diversity was analyzed
microorganisms (hydrogen-producing microbes) play a pivotal
using denaturing gradient gel electrophoresis (DGGE) using
role in the rumen ecosystem. Interspecies hydrogen transfer has
rumen samples taken from 0 w, 2 w and 4 w.
been well described in vitro, especially between cellulolyticsand methanogens (Wolin et al., 1997). Ruminococcus albus,
Ruminococcus flavefaciens and all the rumen fungi and
The rumen samples were filtered through four layers of
protozoa produce hydrogen and they interact positively with
gauze into tubes for analysis of pH, ammonia nitrogen (N)
methanogens (Joblin et al., 1990; Pavlostathis et al., 1990;
and volatile fatty acids (VFA). The pH of rumen fluid was
determined immediately using a pH meter (Model PB-20,
Addition of disodium fumarate (DF) in the diet might stimu-
Sartorius, Go¨ettingen, Germany). Concentration of ammonia
late alternative pathways that use fumarate as electron accep-
N was determined (Model 721/721-100, Shanghai, China)
tors other than carbon dioxide in the rumen, and might induce
colorimetrically using a spectrometer (Searle, 1984) with
major effects on the population of hydrogen utilizers and pro-
ammonium chloride solution as a standard. The VFA were
ducers. Fumarate tended to increase rumen microbial growth on
determined using a gas chromatograph (GC-2010, Shimadzu,
high-forage diet, and generally the effect of fumarate on rumen
Kyoto, Japan) equipped with a Flame Ionization Detector
fermentation depended on the nature of the incubated substrate
and a capillary column (HP-INNOWAX, 1909N-133, Agilent
with high-forage diets showing a greater response compared
Technologies, Santa Clara, CA, USA ), as described elsewhere
with low-forage diet (Garcı´a-Martı´nez et al., 2005).
Microbial adaptation to fumarate metabolism is important,
and the whole community of hydrogen-producing microbes
(cellulytic microbes, protozoa and fungi) and hydrogen-using
The rumen samples were strained through four layers of
microbes (methanogens) could be modified when fumarate is
gauze and separated into fluid and particle parts. Total DNA
added to diet. Furthermore, the effect on rumen function and
was extracted from liquid- and solid-associated microbes,
bacteria community of fumarate addition for an extended
respectively, as described elsewhere (Chen et al., 2007 and
period could be different from addition during a short-term, and
2008). Number of 16S rDNA gene copies associated with
microbial populations in different ruminal fractions (fluid- and
rumen methanogens and bacteria, and 18S rDNA gene copies
solid-associated microbes) could respond differently to DF
associated with rumen protozoa and fungi were measured
addition. Thus, the objective of this study was to investigate the
using real-time PCR. Primer pairs of total bacteria, fungi, pro-
effects of DF on ruminal fermentation, methanogens and
tozoa, methanogen, R. albus, Fibrobacter succinogenes, Butyr-
fibrolytic populations in ruminal fluid and solid samples when
ivibrio fibrisolvens and R. flavefaciens are listed in Table 1.
supplementing for both a short and an extended period.
Species-specific real-time qPCR was performed using Bio-RadiCycler iQ real-time PCR detection system (Bio-Rad laboratoriesInc., Hercules, CA, USA) with fluorescence detection of SYBR
Green dye, as described elsewhere (Chen et al., 2008).
Animals, diets and experimental designsIn Trial 1, six Hu sheep (,45 kg BW) fitted with ruminal
cannulae were randomly allocated to a 2 3 2 cross-design either
Microbial diversity was analyzed by DGGE of PCR-amplified
or not supplemented with 20 g DF daily. Each period lasted for
genes coding for 16S rRNA (Muyzer et al., 1993). The V3 vari-
15 days. Animals were maintained in individual pens with
able regions of the bacterial 16S rRNA gene from rumen sam-
a daily basal diet consisting of 300 g concentrate and 700 g
ples (0 w, 2 w, 4 w) in Trial 2 were amplified by a touchdown
forage (concentrate/forage, 30/70) per sheep per day. The diet
PCR approach using forward primer 341F-GC clamp and 534R
was presumed to meet the energy requirement for maintenance
(Table 1). Fast silver staining of DGGE gels was used (Ji et al.,
(Ministry of Agriculture of China, 2004), and contained 100 g/kg
2007). The DGGE bands of interest were cut-out. PCR products
of CP, 530 g/kg of NDF and 470 g/kg of ADF. They were fed twice
were cloned using TOPO TA cloning kit according to the
daily at 0830 and 1630 h with free access to water. Ruminal
manufacturer’s instructions (Invitrogen Corporation, San
samples were collected from the cannulae in the morning before
Diego, CA, USA). All products were sequenced using the
the morning feeding on the last day during each period. Samples
Terminator v3.1 kit (Applied Biosystems, Foster
for DNA extraction were stored at 2808C. Rumen fermentation
city, CA, USA). All the DNA sequences were edited manually
parameters and microbial populations were measured.
and trimmed for vector contamination by ContigExpress
Fumarate effect on rumen function and microbiota
Table 1 Primers for real-time PCR assay and DGGE-V3
DGGE 5 denaturing gradient gel electrophoresis.
aCited from Denman and McSweeney (2006).
dCited from Koike and Kobayashi (2001).
Project (Vector NTI Advance 10, Invitrogen). Sequences from
Table 2 Effects of DF on ruminal pH, ammonia N, and total and indi-
excised DGGE bands were searched for homology with Basic
vidual VFA expressed as molar proportions of the total (n 5 3; Trial 1)
Local Alignment Search Tool program.
Quantification for methanogens, protozoa, F. succinogenes,
R. albus, R. flavefaciens, B. fibrisolvens and rumen fungi,
were expressed as a proportion to total rumen bacterial
16S rDNA, according to the equation: relative quantifica-
tion 5 22(ct target2ct total bacteria), where Ct represents
threshold cycle. The results of Trial 1 were analyzed according to
univariate analysis by GLM procedure of SPSS (SPSS, 2006) with
time and group as fixed factors. Multiple comparisons among
means of Trial 2 were performed using the least significant
DF 5 disodium fumarate; N 5 nitrogen; VFA 5 volatile fatty acids.
difference analysis (SPSS, 2006). Differences among means
*P , 0.05; **P , 0.01; ***P , 0.001; ns 5 non-significant.
with P , 0.05 were accepted as representing statisticallysignificant differences; differences among means with0.05 , P , 0.10 were accepted as representing tendencies.
The abundance of microbial populations relative to the total
bacterial 16S rDNA is shown in Table 3. Methanogens andprotozoa were less abundantly represented in the total bacterial16S rDNA of fluid samples (from 0.80% and 0.80% to
0.14% and 0.03%, respectively). R. albus represented a greater
Trial 1: fermentation parameters and microbial populations
proportion of the solid bacteria, but was less predominant in the
The rumen fermentation parameters in Trial 1 are presented
liquid bacterial population of the animals fed DF. The abun-
in Table 2. Average ruminal pH increased sharply in the DF
dance of fungi within the microbial community decreased in the
group compared with the control (P , 0.05). Ammonia N con-
fluid (P , 0.001), but increased in the solid (P 5 0.03) samples.
centration did not change (P . 0.05). Total VFA concentrationsincreased (P , 0.001), and minor increases (P , 0.05) in
acetate (2 molar percent) were at the expense of similar
No apparent effect of DF was observed (P . 0.05) on pH
decreases in molar byturate proportions (P , 0.05).
value (Table 4). Addition of DF induced dynamic changes on
ammonia N concentration (P 5 0.0006), with an increase by
0.20% in 1 w and 4 w relative to total bacterial 16S rDNA,
67% in 2 w compared with 0 w and a decease to the 0 w
respectively (Table 5). Solid-associated methanogens increased
level in 3 w and 4 w. Total VFA increased during the 4 weeks
in 1 w and then decreased in 2 w and 3 w, but again increased
when DF was added, and the concentration in 2 w, 3w and 4
to 0 w levels in 4 w. The abundance of methanogens was
w were 28%, 23% and 22% higher than that of control,
higher in fluid than in solid samples, whereas the protozoa
respectively. Proportions of acetate and butyrate were not
represented more of the solid as compared with liquid microbes
altered by DF addition. The proportion of propionate was not
(Table 5). The protozoal abundance in fluid samples was
decreased to the lowest numbers at the end of 2 w, butrecovered to original (0 w) values in 4 w.
The abundance of solid-associated F. succinogenes (fuma-
rate-reducers) within the solid-associated microbial population
The abundance of methanogens within the microbial com-
increased four times in 1 w, remained stable in 2 w, but its
munity in fluid samples decreased from 1.00% to 0.69% and
importance in the microbial population decreased from 3 w. However, after 4 weeks of DF supplementation this bacterial
Table 3 Effect of DF on microbial population in fluid and solid ruminal
group seemed twice as important as compared with a situation
samples (% of total bacterial 16S rDNA; n 5 3; Trial 1)
without DF supplementation (0 w). The abundance of R. albus
within the fluid-associated microbial population remainedstable in 1 w, increased twice and three times in 2 w and 3 w,
respectively, and its importance increased 11 times after4 weeks of DF supplementation, compared with that in
0 w. Although the abundance of R. albus within the solid-
associated microbial population remained stable during the
first 3 weeks, at the end of experiment it increased to four
times that in 0 w. A decrease (P , 0.05) was observed on the
populations of R. flavefaciens in both solid and fluid samples
at the end of 4 w, compared with that at 0 w. Addition of DF
increased the importance of fungi in both fluid and solid
samples throughout Trial 2 (P , 0.001). The number of fungi
in the microbial population of fluid and solid samples in 4 w
was approximately three times that of 0 w.
The DGGE fingerprints revealed significant changes in rumen
microbiota after DF addition (Figure 1). Bands a, b and c
were shown in each animal only in 2 w and 4 w, whereas
bands g, h and i were only shown in 4 w. DGGE profiles were
relatively consistent within three replicate animals. Cut-out
of DGGE bands and sequencing results are summarized in
Table 6. Ten of 15 clone sequences in the six bands, a, b and
c, which were more pronounced after 2 w and 4 w, showed
*P , 0.05; **P , 0.01; ***P , 0.001; ns 5 non-significant.
94% to 100% similarity to Prevotella-like bacteria. Four
Table 4 Dynamic change in pH and fermentation parameters with addition of DF (n 5 3; Trial 2)
DF 5 disodium fumarate. *P , 0.05; ns 5 non-significant.
Fumarate effect on rumen function and microbiota
Table 5 Trial 2: Effect of long-term addition of DF on the dynamic changes of microbial population in fluid and solid samples (n 5 3)
Time (week) after after adding DF (20 g/day)
appeared in 4 w were 95% to 99% related to Clostridium
sp., and the other two showed 95% and 100% similarity to
g h i
Ruminococcus sp. A total of 17 sequences were submitted toGenbank with the accession number: HQ162700 to HQ162716.
Ruminal fermentationAddition of monosodium fumarate in vitro increased acetate,propionate and total VFA and decreased the ratio of acetateto propionate (Yu et al., 2010). Carro and Ranilla (2003)showed that fumarate could beneficially affect in vitro rumenfermentation of concentrate feeds by increasing the pro-
a b a b c c
ductions of both acetate and propionate. An increase in totalVFA concentration and basically no change in the proportionof the individual fatty acids were observed in this study,although a slight increase in acetate and decrease in butyratewere observed in Trial 1 (Table 2). It seems that both acetateand propionate are formed to a same extent from DF. Thepossibility for both acetate and propionate formation from DF
Figure 1 Denaturing gradient gel electrophoresis profiles of the ruminalbacterial community with disodium fumarate (DF) addition for 4 weeks in
was indicated before (Ungerfeld and Kohn, 2006). The increase
Hu-sheep. A1, A2, A3 represent the sheep number in Trial 2; symbols a, b
of total VFA concentration in both trials indicates the positive
and c represent bands appearing in each animal through DF supplementa-
effects of DF addition on ruminal fermentation.
tion in both 2 w and 4 w; and g, h and i represent bands appearing insamples of animals after 4 weeks of DF supplementation (2 w and 4 w aresampling points).
Interaction between methanogens and protozoaThe abundance of methanogens within the microbial popula-
sequences were related to Selenomonas dianae (95% to
tion decreased significantly in the fluid-associated samples in
98% similarity); and one was 100% similar to B. fibrisolvens.
both trials (Tables 3 and 5). The abundance of methanogens
Thirteen of 15 sequences in three bands g, h and i that
in solid samples in Trial 1 showed no significant changes;
however, particle-associated abundance in Trial 2 increased
fermentation, and decrease the negative feed-back effect of
in 1 w, and decreased in 2 and 3 w compared with 0 w,
hydrogen on microbes, which in turn improves the growth of
respectively, and then increased to the same level as 0 w in
fiber-degrading microorganisms. F. succinogenes, R. flave-
4 w. These results indicated that DF addition provides dif-
faciens and R. albus are the representative cellulolytic spe-
ferent effects on fluid- and solid-associated methanogens
cies in the rumen (Forsberg et al., 1997). Moreover, several
with solid abundance showing more variable changes.
of them also might reduce fumarate. F. succinogenes are
It had been estimated that under ruminal conditions,
known to have high fumarate-reducing activity (Asanuma
fumarate reduction should be more exergonic than metha-
et al., 1999b). R. flavefaciens could hydrolyze cellulose and
nogenesis in terms of Gibbs-free energy released per pair of
use fumarate as the main electron acceptor producing suc-
electrons incorporated. The DG (kJ/2H) for fumarate reduc-
cinate (Stewart et al., 1988). Accordingly, these bacteria
tion and methanogenesis is 263.6 and 216.9, respectively
were expected to be stimulated either due to their fumarate-
(Ungerfeld and Kohn, 2006). Therefore, the decrease of fluid-
reducing capacity or due to effective removable of hydrogen.
associated methanogens in this study verified that the capacity
However, changes due to fumarate addition were variable
of methanogens to compete for hydrogen with fumarate-
and different between fluid and solid phase as well as long-
reducers was weakened by fumarate addition. However, it is
surprising that this is not associated with changes in propionate
As one of the main fumarate-reducers, the change of F.
succinogenes in both solid and fluid phases was not con-
Some methanogens are associated with the external sur-
sistent between two trials. In Trial 1, for a short-term of
face of protozoa, and/or are endosymbionts, living free
15 days, a decrease in the solid phase was observed with no
within the protozoal cytoplasm (Williams and Coleman,
change in the fluid phase, whereas in Trial 2, solid-associated
1997). In this study, the abundance of the protozoa popu-
F. succinogenes were more abundant during the 4 weeks of
lation within the fluid samples was decreased compared
DF addition compared with 0 w levels (Table 5). R. albus
with control in Trial 1 (Table 3), whereas in Trial 2 the
abundance increased in solid samples, but declined in fluid
extended feeding of DF caused their abundance in both solid
samples in Trial 1 (Table 3); whereas in Trial 2, R. albus
and fluid samples to recover to 0 w levels (Table 5). It is
increased in fluid samples throughout the 4 weeks of DF
suggested that DF may cause a transient effect on protozoa.
addition, although their abundance in solid samples did not
Protozoa serve not only as host for methanogens, but also
change during the first 3 weeks and increased to nearly four
produce hydrogen in large quantities in a specialized orga-
times the number of 0 w in 4 w (Table 5). Stimulation of
nelle (hydrogenosome; Morgavi et al., 2010). This hydrogen
R. albus could be linked to interspecies hydrogen transfer,
is metabolized by methanogens that are found inside (Finlay
that is, hydrogen produced by R. albus could be consumed by
et al., 1994) or in close association with protozoal cells
fumarate-reducing bacteria resulting in little accumulation of
(Stumm et al., 1982). The interaction between methanogens
hydrogen. The low partial pressure of hydrogen could facil-
and protozoa is a typical example of interspecies hydrogen
itate electron disposal in R. albus and result in faster growth
transfer, which favors both of them (Hillman et al., 1988;
Ushida and Jouany, 1996). Both populations of methanogens
B. fibrisolvens is one of the protein-degrading species in
and protozoa in fluid samples decreased significantly with
rumen with abilities to digest cellulose, although not as
the addition of DF, but remained relatively stable in particle
effective as Ruminococcus or Fibrobacter sp. Interestingly,
samples in both trials. Krumholz et al. (1983) found that the
some similarity can be seen in the concentration of ammonia
methanogenic activity in the rumen fluid was highest in
N and the abundance of solid-associated (Tables 2, 4 and 5)
fractions containing large numbers of protozoa. It is also
or fluid-associated B. fibrisolvens (Tables 2 and 3). Never-
reported that the capacity of competition by methanogens
theless, in Trial 1, solid-associated B. fibrisolvens is inversely
for hydrogen with fumarate-reducers was increased when
related with ammonia N, whereas fluid-associated bacteria
associated with protozoa (Finlay et al., 1994). This is in line
are positively correlated with ammonia N concentration.
with good growth by methanogens and protozoa when liv-
B. fibrisolvens require ammonia N for optimal growth when
ing in symbiosis (Wolin, 1974), and with the fact that
feeding fibrous basal diets (Williams and Coleman, 1997).
fumarate is more effective in reducing methane production
The effects of DF addition on protein degradation need
in protozoa-depleted ruminal fluid (Asanuma et al., 1999b).
Interaction between methanogens and fibrolytic
Most of the clone sequences from bands a, b and c in both 2 w
From the point of view of the syntrophy between R. albus
and 4 w were similar with Prevotella-like bacteria and
(hydrogen-producing) and methanogens (hydrogen-consuming),
S. dianae (Figure 1; Table 6), suggesting that the addition of
the increased importance of R. albus and the decreased
fumarate had a stable and stimulating effect on their growth.
abundance of methanogens implied that fumarate-reducing
Two of the sequences in band a were affiliated to Prevotella
bacteria could successfully compete with methanogens for
ruminicola (98%; AB501151.1). Two of the sequences in band
hydrogen when enough fumarate was supplied. Addition
b were affiliated to Selenomonas ruminantium isolate M40
of DF in vivo may stimulate the use of hydrogen during
(AY685142.1; Table 6). Fumarate reduction has been reported
Fumarate effect on rumen function and microbiota
Table 6 Affiliation of partial 16S rDNA (V3 region) gene sequences obtained from excised bands of DGGE fingerprint with their closeisolates in GenBank (sequence length 5 182 to 194 bp)
Close cultured relative (Genbank accession no.)
Selenomonas ruminantium isolate M40 (AY685142.1)
to be catalyzed by fumarate reductase in P. ruminicola and
Ruminococcus sp. in 4 w. The appearance of Ruminococcus
S. ruminantium (Henderson, 1980). There is also evidence that
sp. in 4 w was verified by real-time PCR results, suggesting
S. ruminantium can utilize hydrogen produced by other rumen
that R. albus increased throughout the experiment and
microorganisms (Marvin-Sikkema et al., 1990). There were
reached its highest abundance in 4 w in the current experi-
93% of the clone sequences in both 2 w and 4 w represented
ment, but the abundance of R. flavefaciens decreased.
by Prevotella sp. and Selenomonas sp., which could indicate
R. flavefaciens may not compete with R. albus for the supply
the involvement of Prevotella and Selenomonas-like bacteria
of hydrogen during interspecies hydrogen transfer. The
in fumarate reduction both during the early and late stage of
15 sequences in bands a, b and c belonged to the phylumn of
fumarate treatment. Nevertheless, an indirect effect of fumarate
bacteroidetes (67%) and firmicutes (33%), whereas all the
on these bacterial species cannot be excluded.
15 sequences in bands g, h and i belonged to the phylum of
One of the sequences from band a had 100% similarity with
firmicutes. It is indicated that a certain group of bacteria
B. fibrisolvens. The reveal of B. fibrisolvens in DGGE bands
belonging to the phylum of Bacteroidetes (Prevotella sp.)
agreed with the results of real-time PCR. The abundance of
and Firmicutes (S. dianae) grows faster after adding DF and
B. fibrisolvens increased and their abundance in fluid samples
may keep their activity stable for 4 weeks. Another group of
was higher in 3 w and 4 w than during earlier samplings.
Firmicutes, such as Clostridium sp., responded to DF addition
P. ruminicola and B. fibrisolvens are important proteolytic bac-
in week 4, but not at the early stage.
teria in the rumen (Wallace et al., 1997), indicating that some
This DGGE study suggested that the dominant group
protein-degrading bacteria responded to DF addition.
in the microbial community composition shifted from the
Of the10 clone sequences in bands a and b, 40% showed
phylum of Bacteroidetes to Firmicutes (Clostridia Class) after
95% to 98% similarity to S. dianae (AF287801.1). As discussed
addition of fumarate. Analysis of DGGE based on partial
above, the abundance of R. albus increased significantly in
16S rDNA sequences could capture some corresponding
both fluid and solid samples during the 4 weeks, especially in
predominant species, but only gives a general view of com-
4 w. Increased growth of R. albus through fumarate addition
munity shifts (Kocherginskaya et al., 2005). There is a need
was reported before in co-cultures with Selenomonas lactilytica
of more precise analysis based on functional fumarate
(Asanuma and Hino, 2000). It is further confirmed and
reductase (frdA) gene or full-length of 16S rDNA gene clone
approved by the appearance of Selenomonassp. in DGGE
libraries (Makkar and McSweeney, 2005). In their study on
analysis in 2 w and 4 w (Figure 1; Table 6). Interspecies
diverisity of frdA clones recovered from the rumen of cattle
hydrogen transfer might be the reason for their co-growth. The
on high-forage diets (Hattori and Matsui, 2008), three clusters
hydrogen produced by R. albus may be consumed by S. dianae.
represented by cultured isolates Proteus vulgaris, Pasteurel a
Asanuma and Hino (2000) indentified two strains of Seleno-
multocida and Shewanella putrefaciens were detected in the
monas having a high capacity for fumarate reduction by using
library from one animal; two abundant clusters were repre-
hydrogen as an electron donor. Therefore, S. dianae could be
sented by S. putrefaciens and Pasteurel a spp., accounting for
one of the potential fumarate-reducers as well.
56% and 33% of total clones, whereas a less abundant cluster
Of the clone sequences in bands g, h and i, 87% was
(9% of total frd clones) represented by P. vulgaris detected as
closely related to Clostridium sp., and the rest related to
their nearest neighbor. In our study, both Proteus spp. and
Shewanella spp. were detected in bands a, b and c from 2 w
Henderson C 1980. The influence of extracellular hydrogen on the metabolism
and 4 w, but Pasteurel a spp. was not found.
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