Products of anaerobic phloroglucinol degradation by Coprococcus sp. Pe15

The acute effects of rumen pulse-dosing of hydrogen acceptors during methane inhibition with nitrate or 3-nitrooxypropanol in dairy cows

Dietary methane (CH4) mitigation is in some cases associated with an increased hydrogen (H2) emission. The objective of the present study was to investigate the acute and short-term effects of acceptors for H2 (fumaric acid, acrylic acid or phloroglucinol) supplemented via pulse-dosing to dairy cows fed CH4 mitigating diets (using nitrate or 3-nitrooxypropanol), on gas exchange, rumen gas and VFA composition. For this purpose, 2 individual 4 × 4 Latin square experiments were conducted with 4 periods of 3 d (nitrate supplementation) and 7 d (3-nitrooxypropanol supplementation), respectively. In each study, 4 rumen cannulated Danish Holstein cows were used. Each additive for CH4 mitigation was included in the ad libitum fed diet within the 2 experiments, to which the cows were adapted for at least 14 d. Acceptors for H2 were administered twice daily in equal portions through the rumen fistula immediately after feeding of the individual cow. In Exp. 1 (nitrate), the treatments were CON-1 (no H2-acceptor), FUM-1 (fumaric acid), ACR-1 (acrylic acid) and FUM+ACR-1 (50% FUM-1 + 50% ACR-1). In Exp. 2 (3-nitrooxypropanol), the 3 treatments, CON-2, FUM-2, and ACR-2, were similar to CON-1, FUM-1 and ACR-1 treatments, however the fourth treatment was PHL-2 (phloroglucinol). Gas exchanges were measured in respiration chambers, while samples of rumen liquid and headspace gas were taken in time series relative to feeding and dosing on specific days. Headspace gas was analyzed for gas composition and rumen liquid was analyzed for volatile fatty acid composition and dissolved gas concentrations. Headspace gas composition and dissolved gas concentration were only measured in Exp. 2. Dry matter intake was reduced upon acrylic acid supplementation. There were no significant effects of any treatments in any experiments on H2 emission, except for a decrease in hourly H2 emission rate (g/h) at 1 h after feeding in both experiments. In Exp. 2, H2 headspace proportions increased by ACR-2 supplementation, whereas dissolved concentrations were unaffected. In Exp. 1, cows on ACR-1 increased propionate proportion at 1 h after feeding. In Exp. 2, both FUM-2 and ACR-2 increased rumen propionate proportion in the hours after feeding and dosing. There was no effect on rumen acetate for cows on PHL-2. There was a strong positive correlation between rumen dissolved CH4 and headspace CH4 (r = 0.84), whereas the equivalent correlation was weaker for H2 (r = 0.41). For the relationship between dissolved concentrations and emissions of CH4 and of H2, there was a moderate positive correlation for CH4 (r = 0.54), whereas it was weak for H2 (r = 0.28) with zero slope. In conclusion, the results suggested that fumaric acid and acrylic acid to some extent was reduced to propionate without associative effects on measures for H2 redirection. Furthermore, phloroglucinol seemed not to be metabolized in the rumen in the present study, as no effects on rumen acetate or measures of H2 were observed. Changes in H2 headspace and emission may be a poor proxy for actual changes in the rumen fluid concentration of H2.

Effects of monensin and cashew nut-shell extract on bacterial community composition in a dual-flow continuous culture system

The objective of this study was to evaluate the effects of including monensin and two doses of CNSE in a high producing dairy cow diet on ruminal bacterial communities. A dual-flow continuous culture system was used in a replicated 4 × 4 Latin Square design. A basal diet was formulated to meet the requirements of a cow producing 45 kg of milk per d (17% crude protein and 27% starch). There were four experimental treatments: the basal diet without any feed additive (CON), 2.5 μM monensin (MON), 100 ppm CNSE granule (CNSE100), and 200 ppm CNSE granule (CNSE200). Samples were collected from the fluid and solid effluents at 3, 6, and 9 h after feeding; a composite of all time points was made for each fermenter within their respective fractions. Bacterial community composition was analyzed by sequencing the V4 region of the 16S rRNA gene using the Illumina MiSeq platform. Treatment responses for bacterial community structure were analyzed with the PERMANOVA test run with the R Vegan package. Treatment responses for correlations were analyzed with the CORR procedure of SAS. Orthogonal contrasts were used to test the effects of (1) ADD (CON vs. MON, CNSE100, and CNSE200); (2) MCN (MON vs. CNSE100 and CNSE200); and (3) DOSE (CNSE100 vs. CNSE200). Significance was declared at P ≤ 0.05. We observed that the relative abundance of Sharpea (P < 0.01), Mailhella (P = 0.05), Ruminococcus (P = 0.03), Eubacterium (P = 0.01), and Coprococcus (P < 0.01) from the liquid fraction and the relative abundance of Ruminococcus (P = 0.03) and Catonella (P = 0.02) from the solid fraction decreased, while the relative abundance of Syntrophococcus (P = 0.02) increased in response to MON when compared to CNSE treatments. Our results demonstrate that CNSE and monensin have similar effects on the major ruminal bacterial genera, while some differences were observed in some minor genera. Overall, the tested additives would affect the ruminal fermentation in a similar pattern.

Enhancing rumen microbial diversity and its impact on energy and protein metabolism in forage-fed goats

Introduction

This study explores if promoting a complex rumen microbiota represents an advantage or a handicap in the current dairy production systems in which ruminants are artificially reared in absence of contact with adult animals and fed preserved monophyte forage.

Methods

In order to promote a different rumen microbial diversity, a total of 36 newborn goat kids were artificially reared, divided in 4 groups and daily inoculated during 10 weeks with autoclaved rumen fluid (AUT), fresh rumen fluid from adult goats adapted to forage (RFF) or concentrate (RFC) diets, or absence of inoculation (CTL). At 6 months of age all animals were shifted to an oats hay diet to determine their ability to digest a low quality forage.

Results and discussion

Early life inoculation with fresh rumen fluid promoted an increase in the rumen overall microbial diversity which was detected later in life. As a result, at 6 months of age RFF and RFC animals had higher bacterial (+50 OTUs) and methanogens diversity (+4 OTUs) and the presence of a complex rumen protozoal community (+32 OTUs), whereas CTL animals remained protozoa-free. This superior rumen diversity and presence of rumen protozoa had beneficial effects on the energy metabolism allowing a faster adaptation to the forage diet, a higher forage digestion (+21% NDF digestibility) and an energetically favourable shift of the rumen fermentation pattern from acetate to butyrate (+92%) and propionate (+19%) production. These effects were associated with the presence of certain rumen bacterial taxa and a diverse protozoal community. On the contrary, the presence of rumen protozoa (mostly Entodinium) had a negative impact on the N metabolism leading to a higher bacterial protein breakdown in the rumen and lower microbial protein flow to the host based on purine derivatives urinary excretion (-17% to -54%). The inoculation with autoclaved rumen fluid, as source of fermentation products but not viable microbes, had smaller effects than using fresh inoculum. These findings suggest that enhancing rumen microbial diversity represents a desirable attribute when ruminants are fed forages in which the N supply does not represent a limiting factor for the rumen microbiota.

Evaluating the effect of phenolic compounds as hydrogen acceptors when ruminal methanogenesis is inhibited in vitro – Part 2. Dairy goats

Most mitigation strategies to reduce enteric methane (CH₄) production in the rumen induce an excess of rumen dihydrogen (H₂) that is expelled and consequently not redirected to the synthesis of metabolites that can be utilised by the ruminant. We hypothesised that phenolic compounds can be potential H₂ acceptors when added to the diet, as they can be degraded to compounds that may be beneficial for the animal, using part of the H₂ available when ruminal methanogenesis is inhibited. We performed four in vitro incubation experiments using rumen inoculum from Murciano-Granadina adult goats: Experiment 1 examined the inhibitory potential of Asparagopsis taxiformis (AT) at different concentrations (0, 1, 2, 3, 4 and 5% of the substrate on a DM basis) in 24 h incubations; Experiment 2 investigated the effect of a wide range of phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, gallic acid and formic acid) at different doses (0, 2, 4, and 6 mM) on rumen fermentation for 24 h; Experiment 3 evaluated the combined effect of each phenolic compound at 6 mM with AT at 2% DM in sequential batch cultures for 5 days; and Experiment 4 examined the dose-response effect of phloroglucinol at different concentrations (0, 6, 16, 26 and 36 mM) combined with AT in sequential batch cultures for 5 days. Results from Experiment 1 confirmed that AT at 2% DM substantially inhibited CH₄ production while significantly increasing H₂ accumulation and decreasing the acetate:propionate ratio. Results from Experiment 2 showed that phenolic compounds did not negatively affect rumen fermentation at any dose. In Experiment 3, each phenolic compound at 6 mM combined with AT at 2% DM inhibited CH₄ production. Phloroglucinol numerically decreased H₂ accumulation and significantly increased total gas production (TGP), volatile fatty acid (VFA) production and the acetate:propionate ratio. In Experiment 4, phloroglucinol at increasing doses supplemented with AT at 2% DM significantly decreased H₂ accumulation and the abundances of archaea, protozoa and fungi abundances, and increased TGP, total VFA production and the acetate:propionate ratio in a dose-dependent way. In conclusion, combined treatment with AT and phloroglucinol was successful to mitigate CH₄ production while preventing the accumulation of H₂, leading to an increase in acetate and total VFA production and therefore an improvement in rumen fermentation in goats.

Evaluating the effect of phenolic compounds as hydrogen acceptors when ruminal methanogenesis is inhibited in vitro – Part 1. Dairy cows

Some antimethanogenic feed additives for ruminants promote rumen dihydrogen (H₂) accumulation potentially affecting the optimal fermentation of diets. We hypothesised that combining an H₂ acceptor with a methanogenesis inhibitor can decrease rumen H₂ build-up and improve the production of metabolites that can be useful for the host ruminant. We performed three in vitro incubation experiments using rumen fluid from lactating Holstein cows: Experiment 1 examined the effect of phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, and gallic acid) at 0, 2, 4, and 6 mM on ruminal fermentation for 24 h; Experiment 2 examined the combined effect of each phenolic compound from Experiment 1 at 6 mM with two different methanogenesis inhibitors (Asparagopsis taxiformis or 2-bromoethanesulfonate (BES)) for 24 h incubation; Experiment 3 examined the effect of a selected phenolic compound, phloroglucinol, with or without BES over a longer term using sequential incubations for seven days. Results from Experiment 1 showed that phenolic compounds, independently of the dose, did not negatively affect rumen fermentation, whereas results from Experiment 2 showed that phenolic compounds did not decrease H₂ accumulation or modify CH₄ production when methanogenesis was decreased by up to 75% by inhibitors. In Experiment 3, after three sequential incubations, phloroglucinol combined with BES decreased H₂ accumulation by 72% and further inhibited CH₄ production, compared to BES alone. Interestingly, supplementation with phloroglucinol (alone or in combination with the CH₄ inhibitor) decreased CH₄ production by 99% and the abundance of methanogenic archaea, with just a nominal increase in H₂ accumulation. Supplementation of phloroglucinol also increased total volatile fatty acid (VFA), acetate, butyrate, and total gas production, and decreased ammonia concentration. This study indicates that some phenolic compounds, particularly phloroglucinol, which are naturally found in plants, could improve VFA production, decrease H₂ accumulation and synergistically decrease CH₄ production in the presence of antimethanogenic compounds.

Microbial Dynamics and In Vitro Degradation of Plant Secondary Metabolites in Hanwoo Steer Rumen Fluids

Plant secondary metabolite (PSM) degradations and feed breakdown into small particles may occur primarily in the rumen. It is possible to predict the rate and extent of feed disappearance in the rumen during incubation by different in vitro techniques, which differ based on the PSM structures, including phenolics, and flavonoids. However, PSM degradation and conversion efficiency in the rumen remains unclear. This study's objective was to evaluate the in vitro degradation of a group of PSMs in the rumen fluid, collected from Hanwoo steer samples. PSMs including rutin, vitexin, myricetin, p-coumaric acid, ferulic acid, caffeic acid, quercetin, luteolin, propyl gallate, and kaempferol were used in their pure forms at 1mg/250 mL in a rumen fluid buffer system. The mixture of selected PSMs and buffer was incubated at 39 °C for 12-72 h, and samples were collected every 12 h and analyzed by a high-performance liquid chromatography-diode array detector (HPLC-DAD) to determine the biotransformation of the polyphenolics. The results revealed that the luteolin, ferulic acid, caffeic acid, coumaric acid, rutin, myricetin, vitexin, kaempferol, and quercetin were decreased after 12 h of incubation in the rumen fluid (p ≤ 0.05) and were more than 70% decreased at 72 h. In contrast, the propyl gallate concentrations were not significantly changed after 24 h of incubation in rumen fluid compared to other metabolites. Finally, microbial dynamics study showed that the Firmicutes, Bacterodetes, Actinobacteria, and Syngergistetes were the dominant phyla found in rumen fluids. The data suggest that most polyphenolic compounds may degrade or reform new complex structures in the rumen.

Inter-trophic Interaction of Gut Microbiota in a Tripartite System

Gut microbiota can be transmitted either environmentally or socially and vertically at intraspecific level; however, whether gut microbiota interact along trophic levels has been largely overlooked. Here, we characterized the gut bacterial communities of weevil larvae of Curculio arakawai that infest acorns of Mongolian oak (Quercus mongolica) as well as acorn-eating mammals, Siberian chipmunk (Tamias sibiricus), to test whether consumption of seed-borne larvae remodels the gut bacterial communities of T. sibiricus. Ingestion of weevil larvae of C. arakawai significantly altered the gut bacterial communities of T. sibiricus. Consequently, T. sibiricus fed larvae of C. arakawai showed higher capability to counter the negative effects of tannins, in terms of body weight maintenance, acorn consumption, N content in feces, urine pH, and blood ALT activity. Our results may first show that seed-borne insects as hidden players have a potential to alter the gut microbiota of seed predators in the tripartite system.

The bacterial and archaeal community structures and methanogenic potential of the cecal microbiota of goats fed with hay and high-grain diets

The cecum plays an important role in the feed fermentation of ruminants. However, information is very limited regarding the cecal microbiota and their methane production. In the present study, the cecal content from twelve local Chinese goats, fed with either a hay diet (0% grain) or a high-grain diet (71.5% grain), were used to investigate the bacterial and archaeal community and their methanogenic potential. Microbial community analysis was determined using high-throughput sequencing of 16S rRNA genes and real-time PCR, and the methanogenesis potential was assessed by in vitro fermentation with ground corn or hay as substrates. Compared with the hay group, the high-grain diet significantly increased the length and weight of the cecum, the proportions of starch and crude protein, the concentrations of volatile fatty acids and ammonia nitrogen, but decreased the pH values (P < 0.05). The high-grain diet significantly increased the abundances of bacteria and archaea (P < 0.05) and altered their community. For the bacterial community, the genera Bifidobacterium, Prevotella, and Treponema were significantly increased in the high-grain group (P < 0.05), while Akkermansia, Oscillospira, and Coprococcus were significantly decreased (P < 0.05). For the archaeal community, Methanosphaera stadtmanae was significantly increased in the high-grain group (P < 0.05), while Methanosphaera sp. ISO3-F5 was significantly decreased (P < 0.05). In the in vitro fermentation with grain as substrate, the cecal microorganisms from the high-grain group produced a significantly higher amount of methane and volatile fatty acids (P < 0.05), and produced significantly lower amount of lactate (P < 0.05). Conclusively, high-grain diet led to more fermentable substrates flowing into the hindgut of goats, resulting in an enhancement of microbial fermentation and methane production in the cecum.

Alfalfa Intervention Alters Rumen Microbial Community Development in Hu Lambs During Early Life

The pre-weaning period is crucial for rumen developmental plasticity, which can have a long-term impact on animal performance. Understanding the rumen microbiota during early life is important to elucidate its potential role in rumen development. In this study, the rumen microbiota of 10-day-old Hu lambs fed either milk replacer (B-10), milk replacer and starter (STA) or milk replacer and starter supplemented with alfalfa (S-ALF) in the pre- (d17, 24, and 38) and post-weaning periods (d45 and 66) were assessed to characterize rumen microbial colonization during early life and its response to fiber intervention. In the rumens of B-10 lambs, 498 operational taxonomic units belonging to 33 predominant genera were observed, and the top six predicted functions included “Membrane transport,” “carbohydrate metabolism,” “amino acid metabolism,” “replication and repair,” “translation,” and “energy metabolism.” Prevotella, Succinivibrio, Bifidobacterium, and Butyrivibrio abundances were increased at d38 for both STA and S-ALF groups compared to the B-10 group, whereas fibrolytic bacteria of the taxa Lachnospiraceae and Treponema were only increased in the S-ALF group at d38. A number of saccharolytic bacteria (Bacteroidaceae), organic acid-producing bacteria (Coprococcus and Actinomyces), proteolytic and amino acid fermenters (Fusobacterium) and fibrolytic bacteria (unclassified Ruminococcaceae) were significantly decreased in the STA lambs but not in the S-ALF lambs at d38. After weaning and exposed to alfalfa, the rumen microbial composition in the STA group started to appear similar to that of the S-ALF lambs. The relative abundance of unclassified Clostridiales was higher in S-ALF lambs than STA lambs after weaning. Spearman’s correlation analysis showed positive relationships between unclassified Lachnospiraceae, unclassified Clostridiales, Treponema, unclassified Bacteroidales, Coprococcus and crude protein intake, neutral detergent fiber intake, and plasma β-hydroxybutyrate. The unclassified Lachnospiraceae and Treponema were also positively correlated with average daily gain. Our results revealed that alfalfa stimulated changes in rumen microbiota during the pre- and post-weaning periods and was consistent with rumen development for better feed intake and animal performance before and after weaning. The findings of this study provide clues for strategies to improve rumen function through manipulation of the rumen microbiota during early life.

Phloroglucinol Degradation in the Rumen Promotes the Capture of Excess Hydrogen Generated from Methanogenesis Inhibition

Strategies to manage metabolic hydrogen ([H]) in the rumen should be considered when reducing ruminant methane (CH₄) emissions. However, little is known about the use of dietary treatments to stimulate rumen microorganisms capable of capturing the [H] available when CH₄ is inhibited in vivo. The effects of the phenolic compound phloroglucinol on CH₄ production, [H] flows and subsequent responses in rumen fermentation and microbial community composition when methanogenesis is inhibited were investigated in cattle. Eight rumen fistulated Brahman steers were randomly allocated in two groups receiving chloroform as an antimethanogenic compound for 21 days. Following that period one group received chloroform + phloroglucinol for another 16 days, whilst the other group received only chloroform during the same period. The chloroform treatment resulted in a decrease in CH₄ production and an increase in H₂ expelled with a shift in rumen fermentation toward higher levels of propionate and formate and lower levels of acetate at day 21 of treatment. Bacterial operational taxonomic units (OTUs) assigned to Prevotella were promoted whilst Archaea and Synergistetes OTUs were decreased with the chloroform treatment as expected. The shift toward formate coincided with increases in Ruminococcus flavefaciens, Butyrivibrio fibrisolvens, and Methanobrevibacter ruminantium species. The addition of chloroform + phloroglucinol in the rumen resulted in a decrease of H₂ expelled (g) per kg of DMI and moles of H₂ expelled per mol of CH₄ decreased compared with the chloroform only treated animals. A shift toward acetate and a decrease in formate were observed for the chloroform + phloroglucinol-treated animals at day 37. These changes in the rumen fermentation profile were accompanied by a relative increase of OTUs assigned to Coprococcus spp., which could suggest this genus is a significant contributor to the metabolism of this phenolic compound in the rumen. This study demonstrates for the first time in vivo that under methanogenesis inhibition, H₂ gas accumulation can be decreased by redirecting [H] toward alternative sinks through the nutritional stimulation of specific microbial groups. This results in the generation of metabolites of value for the host while also helping to maintain a low H₂ partial pressure in the methane-inhibited rumen.

Biocatalytic Properties and Structural Analysis of Phloroglucinol Reductases

Phloroglucinol reductases (PGRs) are involved in anaerobic degradation in bacteria, in which they catalyze the dearomatization of phloroglucinol into dihydrophloroglucinol. We identified three PGRs, from different bacterial species, that are members of the family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs). In addition to catalyzing the reduction of the physiological substrate, the three enzymes exhibit activity towards 2,4,6-trihydroxybenzaldehyde, 2,4,6-trihydroxyacetophenone, and methyl 2,4,6-trihydroxybenzoate. Structural elucidation of PGRcl and comparison to known SDRs revealed a high degree of conservation. Several amino acid positions were identified as being conserved within the PGR subfamily and might be involved in substrate differentiation. The results enable the enzymatic dearomatization of monoaromatic phenol derivatives and provide insight into the functional diversity that may be found in families of enzymes displaying a high degree of structural homology.

Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation

The valorization of aromatic heteropolymer lignin is an important unsolved problem in the development of a biomass-based biorefinery, for which novel high-activity biocatalysts are needed. Sequencing of the genomic DNA of lignin-degrading bacterial strain Sphingobacterium sp. T2 revealed no matches to known lignin-degrading genes. Proteomic matches for two manganese superoxide dismutase proteins were found in partially purified extracellular fractions. Recombinant MnSOD1 and MnSOD2 were both found to show high activity for oxidation of Organosolv and Kraft lignin, and lignin model compounds, generating multiple oxidation products. Structure determination revealed that the products result from aryl-Cα and Cα-Cβ bond oxidative cleavage and O-demethylation. The crystal structure of MnSOD1 was determined to 1.35 Å resolution, revealing a typical MnSOD homodimer harboring a five-coordinate trigonal bipyramidal Mn(II) center ligated by three His, one Asp, and a water/hydroxide in each active site. We propose that the lignin oxidation reactivity of these enzymes is due to the production of a hydroxyl radical, a highly reactive oxidant. This is the first demonstration that MnSOD is a microbial lignin-oxidizing enzyme.

Ruminal degradation of quercetin and its influence on fermentation in ruminants

The aim of the present study was to investigate the ruminal degradation of the flavonol quercetin and to determine its potential antimicrobial effects on ruminal fermentation in cows. Ruminal degradation of quercetin (0 or 100μmol/L, respectively) as well as its influence on ruminal gas production (0, 50, or 100μmol of quercetin equivalents/L, respectively, either applied as aglycone or as its glucorhamnoside rutin) using concentrate, grass hay, and straw as substrates were investigated in vitro using the Hohenheim gas test. Additionally, the influence of quercetin on ruminal concentrations of volatile fatty acids and their molar ratio in rumen-fistulated, nonlactating cows (n=5) after intraruminal application of quercetin as aglycone or as rutin (0, 10, or 50mg of quercetin equivalents/kg of BW, respectively) was evaluated. Quercetin was rapidly and extensively degraded, whereby the disappearance of quercetin was accompanied by the simultaneous appearance of 2metabolites 3,4-dihydroxyphenylacetic acid and 4-methylcatechol. In vitro total gas and methane production were not reduced by the addition of quercetin aglycone or rutin, respectively, using concentrate, grass hay, and straw as substrates. As expected, however, effects of the substrates used were detected on total gas and methane production. Highest gas production was found with concentrate, whereas values obtained with grass hay and straw were lower. Relative methane production was highest with grass hay compared with concentrate and straw (27.1 vs. 25.0 and 25.5%). After intraruminal application of the quercetin aglycone or rutin, respectively, neither total concentration nor the molar ratio of volatile fatty acids in the rumen fluid were influenced. Results of the present study show that quercetin underlies rapid ruminal degradation, whereby 3,4-dihydroxyphenylacetic acid and 4-methylcatechol are the main metabolites, whereas the latter one most likely is formed by dehydroxylation from 3,4-dihydroxyphenylacetic acid. Regarding antimicrobial effects of quercetin, results obtained indicate that fermentation processes in the forestomachs are not substantially influenced by quercetin or rutin, respectively. With regard to potential health-promoting effects of quercetin, its application in cows, especially in the form of the better available rutin, might not be accompanied by negative effects on ruminal fermentation.

Pyrosequencing 16S rRNA genes of bacteria associated with wild tiger mosquito Aedes albopictus: a pilot study

The Asian tiger mosquito Aedes (Stegomya) albopictus is an invasive species that has spread across the world in the last two decades, showing a great capacity to adapt to contrasting climates and environments. While demonstrated in many insects, the contribution of bacterial symbionts in Aedes ecology is a challenging aspect that needs to be investigated. Also some bacterial species have already been identified in Ae. albopictus using classical methods, but a more accurate survey of mosquito-associated bacterial diversity is needed to decipher the potential biological functions of bacterial symbionts in mediating or constraining insect adaptation. We surveyed the bacteria associated with field populations of Ae. albopictus from Madagascar by pyrosequencing 16S rRNA gene amplicons. Different aspects of amplicon preparation and sequencing depth were tested to optimize the breadth of bacterial diversity identified. The results revealed that all mosquitoes collected from different sites have a bacterial microbiota dominated by a single taxon, Wolbachia pipientis, which accounted for about 99% of all 92,615 sequences obtained. As Ae. albopictus is known to harbor two Wolbachia strains (wAlbA and wAlbB), a quantitative PCR was used to estimate the relative densities, (i.e., the bacteria-to-host gene ratios) of each strains in individual mosquitoes. Relative densities were between 6.25 × 10(0.01) and 5.47 × 10(0.1) for wAlbA and between 2.03 × 10(0.1) and 1.4 × 10(1) for wAlbB. Apart from Wolbachia, a total of 31 bacterial taxa were identified at the genus level using different method variations. Diversity index values were low and probably underestimated the true diversity due to the high abundance of Wolbachia sequences vastly outnumbering sequences from other taxa. Further studies should implement alternative strategies to specifically discard from analysis any sequences from Wolbachia, the dominant endosymbiotic bacterium in Ae. albopictus from this area.

Flavor compounds and quality parameters of chevon as influenced by sericea lespedeza hay

This research assessed the utilization of sericea lespedeza (SL, Lespedeza cuneata ) hay, a highly condensed tannin (CT) forage (87-181 g CT/kg), as a dietary regimen of meat goats, and thereby the effects on physicochemical properties of goat meat (chevon) and flavor compounds in cooked chevon chops were evaluated. Although it is commonly believed that higher amounts of CT can have deleterious effects on animal performance due to low digestibility and low voluntary intakes in ruminants, feeding meat goats with SL hay increased the body weight compared to goats fed bermudagrass hay without altering the chemical composition and meat quality of chevon. Feeding SL hay to meat goats also did not significantly influence the flavor volatiles in cooked chevon chops. The findings indicate that SL hay can be used as a low-input forage to replace expensive forages.

Effects of feed-supplementation and hide-spray application of two sources of tannins on enteric and hide bacteria of feedlot cattle

Pathogenic bacteria attached to the hide or shed in the feces of cattle at slaughter can contaminate carcasses intended to be processed for human consumption. Therefore, new pre-harvest interventions are needed to prevent the carriage and excretion of foodborne pathogens in cattle presented to the processing plant. The objectives of this study were to examine the antimicrobial effects of hydrolysable tannin-rich chestnut and condensed tannin-rich mimosa extracts on bacterial indicators of foodborne pathogens when applied as a hide-intervention and as a feed additive to feedlot cattle. Water (control) or solutions (3 % wt/vol) of chestnut- and mimosa-extract treatments were sprayed (25 mL) at the left costal side of each animal to a 1000 cm² area, divided in four equal quadrants. Hide-swabs samples obtained at pre-, 2-min, 8-h, and 24-h post-spray application were cultured to enumerate Escherichia coli/total coliforms and total aerobic plate counts. In a second experiment, diets supplemented without (controls) or with (1.5 % of diet dry matter) chestnut- or mimosa-extracts were fed during a 42-day experimental feeding period. Weekly fecal samples starting on day 0, and rumen fluid obtained on days 0, 7, 21 or 42 were cultured to enumerate E.coli/total coliforms and Campylobacter. Tannin spray application showed no effect of treatment or post-application-time (P > 0.05) on measured bacterial populations, averaging 1.7/1.8, 1.5/1.6 and 1.5/1.7 (log₁₀CFU/cm²) for E. coli/total coliforms, and 4.0, 3.4 and 4.2 (log₁₀CFU/cm²) in total aerobes for control, chestnut and mimosa treatments, respectively. Mean (± SEM) ruminal E. coli and total coliform concentrations (log(10) CFU/mL) were reduced (P < 0.01) in steers fed chestnut-tannins (3.6 and 3.8 ± 0.1) in comparison with the controls (4.1 and 4.2 ± 0.1). Fecal E. coli concentrations were affected by treatment (P< 0.01), showing the highest values (log₁₀ CFU/g) in fecal contents from mimosa-fed steers compared to controls (5.9 versus 5.6 ± 0.1 SEM, respectively). Total coliforms (log CFU/g) showed the highest values (P < 0.01) in feces from chestnut- and mimosa-fed steers (6.0 and 6.1 ± 0.1 respectively) in comparison with controls (5.7 ± 0.1). Fecal Campylobacter concentrations (log₁₀CFU/g) were affected by treatment (P < 0.05), day (P < 0.001) and their interaction (P < 0.01) with the controls having lower concentrations than chestnut- and mimosa-fed steers (0.4, 1.0, and 0.8 ± 0.3, respectively). It was concluded that under our research conditions, tannins were not effective in decreasing measured bacterial populations on beef cattle hides. Additionally, chestnut tannin reduced E. coli and total coliforms within the rumen but the antimicrobial effect was not maintained in the lower gastrointestinal tract. Further research is necessary to elucidate the possible antimicrobial effects of tannins at site-specific locations of the gastrointestinal tract in beef cattle fed high-grain and high-forage diets.

Catabolism of phloroglucinol by the rumen anaerobe coprococcus

A rumen isolate, Coprococcus, sp. Pe(1)5, was found to carry phloroglucinol reductase, which catalyzed the initial step in the breakdown of phloroglucinol. The organism uses phloroglucinol as the sole source of carbon and energy when grown in the absence of oxygen. Induced levels of enzyme were detected in cells grown either on phloroglucinol or on other carbon sources in the presence of limiting quantities of phloroglucinol. Although the organism is a strict anaerobe, the enzyme from anaerobically grown cells was insensitive to air. The partially purified enzyme required reduced nicotinamide adenine dinucleotide phosphate as an electron donor and was specific for phloroglucinol. However, partial enzyme activity (14 to 17%) was also detected in the presence of 2-methyl-1,4-naphthoquinone but not in the presence of several other phenolic compounds. The enzyme exhibited a higher affinity for phloroglucinol than for reduced nicotinamide adenine dinucleotide phosphate, with K(m) values of 3.0 x 10 M and 29.0 x 10 M, respectively. The optimum pH for maximal enzyme activity was 7.4, and the molecular weight of the native protein was about 130,000, as determined by the Sephadex gel filtration technique.

Enteric Disposition and Recycling of Flavonoids and Ginkgo Flavonoids

OBJECTIVE

The objective of this study was to determine the intestinal and microbial disposition of flavonoids and how these disposition processes affect their enteric recycling.

DESIGN

Studies were performed using a perfused rat intestinal model or using enrichment cultures and a pure isolate of Enterococcus avium (LY1).

RESULTS

In the rat intestine, aglycones, such as quercetin and apigenin, were as permeable (P*(eff) > or = 2) as compounds such as propranolol (100% absorption). However, a significant portion of the absorbed aglycones was conjugated and the metabolites were excreted into the lumen. Flavonoid glycosides, such as isoquercitrin and apigenin-7-O-glucoside, also had high apparent P*(eff) values (> or = 2) in the upper small intestine because of rapid hydrolysis. However, isoquercitrin was absorbed much slower (P*(eff) < or = 0.7, p < 0.05) when hydrolysis was absent or inhibited by 20 mmol gluconolactone. Absorption of other intact glycosides was similar to intact isoquercitrin and was much slower than the corresponding aglycones (P*(eff) < or = 0.7, p < 0.05). Intestinal bacteria, such as LY1, hydrolyzed the flavonoid glycosides used in the study. Excreted glycosidases were involved in the hydrolysis of glycosides because glycosides were poorly taken up by LY1. In conclusion, glycosidase-catalyzed hydrolysis is a critical first step in the intestinal and microbial disposition of flavonoid glycosides. Aglycones were not only rapidly absorbed, but also rapidly metabolized into phase II conjugates, which were then excreted back into the lumen. Therefore, intestinal and microbial glycosidases and intestinal phase II enzymes make a significant contribution to the disposition of flavonoids via the proposed enteric and enterohepatic recycling scheme.

Effect of phenolic monomers on biomass and hydrolytic enzyme activities of an anaerobic fungus isolated from wild nil gai (Baselophus tragocamelus)

AIMS

To test the anaerobic fungus, Piromyces sp. FNG5, for its tolerance to phenolic monomers released in the rumen by degradation of lignocellulosic poor-quality feeds.

METHODS AND RESULTS

Effects of phenolic monomers on biomass and fibrolytic enzyme activities of a pure culture of lignocellulolytic anaerobic fungus (Piromyces sp. FNG5) isolated from faeces of wild nil gai (blue bull, Baselophus tragocamelus) were evaluated. There was a reduction in fungal biomass at 1 mm concentration of catechol with complete inhibition at 10 mm. p-Coumaric acid caused a reduction in biomass at 10 mm and no growth was observed above 20 mm concentration. The fungal isolate could tolerate up to 5 mm of ferulic acid without any reduction in biomass level, and was able to grow to some extent up to the highest level of ferulic acid tested (20 mm). Vanillic acid had no effect on biomass of the fungus even up to 50 mm level. The phenolic monomers varied in their potential to inhibit the secretion of carboxymethyl cellulase, xylanase, beta-glucosidase and acetyl esterase activities with catechol being the most inhibitory and vanillic acid being the least inhibitory. After 14 days of incubation, 38.49-65.14%p-Coumaric acid, 65.22-74.10% ferulic acid and 34.13-66.78% vanillic acid disappeared from the medium under anaerobic conditions.

CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY

It is concluded that the anaerobic fungus Piromyces sp. FNG5 is tolerant to phenolic monomers and has ability to degrade them. Therefore, such anaerobic fungi may play an important role in fibre degradation in the rumen.

Utilization of 1,3,5-trihydroxybenzene (phloroglucinol) by a soil isolate, Rhodococcus species BPG-8

A Gram-positive bacterial strain was isolated from oil rich soil in Newfoundland and found to utilize various di- and trihydroxylated aromatic compounds as a source of carbon and energy. This bacterium exhibited rod/coccus dimorphism during its growth cycle. Chemical analysis of cell wall composition (amino acids, sugars, and fatty acids) was performed using gas chromatography-mass spectrophotometry and high pressure liquid chromatography. Comparison of both acid production and growth substrates showed complete homology with Rhodococcus erythropolis. Growth of the isolate on phloroglucinol (1,3,5 trihydroxybenzene) occurred in the pH range 5-8; with a substrate and temperature optima of 8.0 mM and 25 degrees C. The oxidation of PG was examined using whole cells as well as crude cell extracts. PG oxidation was shown to be due to an inducible enzyme system. Tentatively the isolate was identified as Rhodococcus species BPG-8 which is able to utilize phloroglucinol as the sole source of carbon and energy.

Metabolism of gallate and phloroglucinol in Eubacterium oxidoreducens via 3-hydroxy-5-oxohexanoate

The pathway for the anaerobic catabolism of gallic acid by Eubacterium oxidoreducans was studied by using both in vivo and cell-free systems. Cells grown with gallate and crotonate, but with no formate or H2, excreted pyrogallol and phloroglucinol into the medium. Gallate was decarboxylated by crude cell extracts, with pyrogallol as the only detectable product. Whole cells converted pyrogallol to phloroglucinol. A phloroglucinol reductase catalyzed the conversion of phloroglucinol to dihydrophloroglucinol when NADPH was used as the source of electrons. Both formate dehydrogenase (EC 1.2.1.43) and hydrogenase (EC 1.18.99.1) were present in cell extracts of gallate-formate-grown cells. These two enzymes were both NADP linked. Since either H2 or formate is required for cell growth with gallate or phloroglucinol, these results suggest that the oxidation of the reduced substrate may be indirectly linked to the reduction of phloroglucinol. A dihydrophloroglucinol hydrolase was present, which hydrolyzed dihydrophloroglucinol to 3-hydroxy-5-oxohexanoate. This six-carbon ring cleavage product then presumably can be broken down by a series of reactions similar to beta-oxidation. These reactions cleaved the six-carbon acid to 3-hydroxybutyryl-coenzyme A yielding acetate and butyrate as end products. A number of key enzymes involved in beta-oxidation and substrate-level phosphorylation were demonstrated in cell extracts.

The origin of urinary aromatic compounds excreted by ruminants. 4. The potential use of urine aromatic acid and phenol outputs as a measure of voluntary food intake

1. Studies were made of the extent to which p-cresol, catechol, quinol and orcinol infused through rumen or abomasal cannulas to sheep were recovered in their urine. 2. Rumen fermentation of dietary phenolic compounds caused the excretion of simple phenols in the urine. In decreasing order of magnitude these were: p-cresol, catechol, phenol and 4-methylcatechol with only traces of quinol and orcinol. 3. The percentages of rumen-infused p-cresol or orcinol recovered as increments in the urinary phenol outputs of sheep (94 and 99% respectively) following infusion showed that rumen degradation of these phenols was negligible. 4. After rumen infusion of catechol and quinol, mean recoveries of these phenols in urine were only 55 and 77% respectively. Possible reasons for these incomplete recoveries are discussed. 5. Studies were also made of the use of the urinary phenol output of phenols characteristics of particular forages as indices of their voluntary intake by sheep. Calluna vulgaris L. (Hull) (heather) may contain 1300-3600 mg/kg dry matter (DM) of orcinol and 200-800 mg/kg DM of quinol as beta-glycosides. When heather was offered ad lib. to sheep given one of five levels of grass, linear relationships were found between heather intake and urinary quinol and orcinol outputs. 6. The urinary output of aromatic acids was also determined when sheep ate grass and heather. Urinary phenylacetic acid output was linearly related to grass but not to heather intake. The relationship between urinary phenylacetic acid output and grass intake could vary with different forages but that between orcinol output and heather intake was considered a useful index of heather intake. 7. Methods for the assay of urine phenols are discussed.

The origin of urinary aromatic compounds excreted by ruminants. 3. The metabolism of phenolic compounds to simple phenols

Dietary phenolic cinnamic acids are hydrogenated in the side-chain, demethylated and dehydroxylated in the rumen and are responsible for the large urinary output of benzoic acid by ruminants. 2. Decarboxylation of phenolic acids to simple phenols is another reaction of the intestinal microflora and experiments were made to determine the extent of this reaction in the rumen of sheep. 3. In five experiments phenolic compounds, quinic acid or casein were infused into the rumen or abomasum of sheep and increments in urinary outputs of phenolic acids and phenols determined by thin-layer and gas-liquid chromatography. 4. Production of phenols was almost exclusively confined to reactions in the rumen. 5. Rumen administration of phenolic benzoic or phenylacetic acids which contained a 4-hydroxy substituent yielded large increments in urinary phenol outputs. Other phenolic benzoic and phenylacetic acids were not decarboxylated. Rumen decarboxylation of 4-hydroxy-3-phenylpropionic acid did not occur and decarboxylation of 4-hydroxycinnamic acids was slight. 6. Nearly half the tyrosine content of rumen-administered casein was excreted as p-cresol, a decarboxylation product of 4-hydroxyphenylacetic acid, p-Cresol was the principal phenol found in sheep urine. 7. Catechol and phenol were consistently found in sheep urine samples and p-ethylphenol, resorcinol, quinol, 4-methylcatechol, orcinol and pyrogallol were also found when suitable precursors were infused to the rumen. 8. It is concluded that p-cresol is a rumen metabolite of tyrosine. The other phenols found are microbial metabolites of phenolic precursors which are either widely distributed in plants such as 4-hydroxybenzoic, protocatechuic and vanillic acids or of more limited distribution such as the orcinol glycosides of some Ericaceous plants.