Evidence That Ceriporiopsis subvermispora Degrades Nonphenolic Lignin Structures by a One-Electron-Oxidation Mechanism

The white-rot fungus Ceriporiopsis subvermispora is able to degrade nonphenolic lignin structures but appears to lack lignin peroxidase (LiP), which is generally thought to be responsible for these reactions. It is well established that LiP-producing fungi such as Phanerochaete chrysosporium degrade nonphenolic lignin via one-electron oxidation of its aromatic moieties, but little is known about ligninolytic mechanisms in apparent nonproducers of LiP such as C. subvermispora. To address this question, C. subvermispora and P. chrysosporium were grown on cellulose blocks and given two high-molecular-weight, polyethylene glycol-linked model compounds that represent the major nonphenolic arylglycerol-(beta)-aryl ether structure of lignin. The model compounds were designed so that their cleavage via one-electron oxidation would leave diagnostic fragments attached to the polyethylene glycol. One model compound was labeled with (sup13)C at C(inf(alpha)) of its propyl side chain and carried ring alkoxyl substituents that favor C(inf(alpha))-C(inf(beta)) cleavage after one-electron oxidation. The other model compound was labeled with (sup13)C at C(inf(beta)) of its propyl side chain and carried ring alkoxyl substituents that favor C(inf(beta))-O-aryl cleavage after one-electron oxidation. To assess fungal degradation of the models, the high-molecular-weight metabolites derived from them were recovered from the cultures and analyzed by (sup13)C nuclear magnetic resonance spectrometry. The results showed that both C. subvermispora and P. chrysosporium degraded the models by routes indicative of one-electron oxidation. Therefore, the ligninolytic mechanisms of these two fungi are similar. C. subvermispora might use a cryptic LiP to catalyze these C(inf(alpha))-C(inf(beta)) and C(inf(beta))-O-aryl cleavage reactions, but the data are also consistent with the involvement of some other one-electron oxidant.     

Biodegradation of lignocellulose in Bermuda grass by white rot fungi analyzed by solid-state 13C nuclear magnetic resonance.

Following the solid-state fermentation of Bermuda grass by two lignin-degrading white rot fungi, compositional changes have been observed in situ by utilization of cross-polarization and magic angle spinning 13C nuclear magnetic resonance difference spectra and interrupted decoupling spectra. Intensity differences in the 13C resonances assigned to specific components of the cell wall were used to observe these changes. Bermuda grass treated with Phanerochaete chrysosporium K-3 exhibited losses primarily in the polysaccharide components, with a smaller proportion of phenolic components also being degraded. In contrast, Ceriporiopsis subvermispora FP 90031-sp removed a proportionate amount of phenolic components compared with polysaccharide components. The results also indicated that C. subvermispora preferentially removes guaiacyl phenolic components relative to syringyl phenolic components, while P. chrysosporium was nonspecific in its attack on phenolic components.     

Ceriporic acid B, an extracellular metabolite of Ceriporiopsis subvermispora, suppresses the depolymerization of cellulose by the Fenton reaction

The white rot fungus, Ceriporiopsis subvermispora, is able to degrade lignin in wood without intensive damage to cellulose. Since lignin biodegradation by white rot fungi proceeds by radical reactions, accompanied by the production of a large amount of Fe3+-reductant phenols and reductive radical species in the presence of iron ions, molecular oxygen, and H2O2, C. subvermispora has been proposed to possess a biological system which suppresses the production of a cellulolytic active oxygen species, *OH, by the Fenton reaction. In the present paper, we demonstrate that 1-nonadecene-2,3-dicarboxylic acid (ceriporic acid B), an extracellular metabolite of C. subvermispora, strongly inhibited *OH production and the depolymerization of cellulose by the Fenton reaction in the presence of iron ions, cellulose, H2O2, and a reductant for Fe3+, hydroquinone (HQ), at the physiological pH of the fungus.     

Isolation and evaluation of tannin-degrading fungal strains from the Mexican desert

Eleven fungal strains (4 Penicillium commune, 2 Aspergillus niger, 2 Aspergillus rugulosa, Aspergillus terricola, Aspergillus ornatus and Aspergillus fumigatus) were isolated, characterized morphologically and by their capacity to degrade tannins. Aspergillus niger Aa-20 was used as control strain. Several concentrations of hydrolysable tannin (tannic acid) were used as sole carbon source. All strains were able to degrade hydrolysable tannins. Aspergillus niger GH1 and PSH showed the highest tannin-degrading capacity (67 and 70%, respectively). Also, the fungal capacity to degrade condensed tannin (catechin) was tested. Aspergillus niger PSH and Penicillium commune EH2 degraded 79.33% and 76.35% of catechin. The results demonstrated the capacity of fungi to use hydrolysable and condensed tannins as carbon source.     

Microbial scission of sulfide linkages in vulcanized natural rubber by a white rot basidiomycete, Ceriporiopsis subvermispora

A white rot basidiomycete, Ceriporiopsis subvermispora, degraded vulcanized natural rubber (NR) sheets on a wood medium. The fungus decreased the total sulfur content of the rubber by 29% in 200 days, accompanied by the cleavage of sulfide bonds between polyisoprene chains. X-ray photoelectron spectroscopy (XPS) demonstrated that C. subvermispora reduced the frequency of S-C bonds by 69% with a concomitant formation of S-O bonds during the culture period. Dipolar decoupling/magic angle spinning (DD/MAS) solid state 13C NMR revealed that the fungus preferentially decomposed monosulfide bonds linked to a cis- and trans-1,4-isoprene backbone but the cleavage of polysulfide bonds was also observed. In contrast, no decrease in weight or devulcanization of rubber was observed in cultures of a white rot fungus, Dichomitus squalens. The oxidative cleavage of sulfide bonds by C. subvermispora demonstrates that ligninolytic basidiomycetes are potential microbes for the biological devulcanization of rubber products.     

Manganese-Dependent Cleavage of Nonphenolic Lignin Structures by Ceriporiopsis subvermispora in the Absence of Lignin Peroxidase

Many ligninolytic fungi appear to lack lignin peroxidase (LiP), the enzyme generally thought to cleave the major, recalcitrant, nonphenolic structures in lignin. At least one such fungus, Ceriporiopsis subvermispora, is nevertheless able to degrade these nonphenolic structures. Experiments showed that wood block cultures and defined liquid medium cultures of C. subvermispora rapidly depolymerized and mineralized a (sup14)C-labeled, polyethylene glycol-linked, high-molecular-weight (beta)-O-4 lignin model compound (model I) that represents the major nonphenolic structure of lignin. The fungus cleaved model I between C(inf(alpha)) and C(inf(beta)) to release benzylic fragments, which were shown in isotope trapping experiments to be major products of model I metabolism. The C(inf(alpha))-C(inf(beta)) cleavage of (beta)-O-4 lignin structures to release benzylic fragments is characteristic of LiP catalysis, but assays of C. subvermispora liquid cultures that were metabolizing model I confirmed that the fungus produced no detectable LiP activity. Three results pointed, instead, to the participation of a different enzyme, manganese peroxidase (MnP), in the degradation of nonphenolic lignin structures by C. subvermispora. (i) The degradation of model I and of exhaustively methylated (nonphenolic), (sup14)C-labeled, synthetic lignin by the fungus in liquid cultures was almost completely inhibited when the Mn concentration of the medium was decreased from 35 (mu)M to approximately 5 (mu)M. (ii) The fungus degraded model I and methylated lignin significantly faster in the presence of Tween 80, a source of unsaturated fatty acids, than it did in the presence of Tween 20, which contains only saturated fatty acids. Previous work has shown that nonphenolic lignin structures are degraded during the MnP-mediated peroxidation of unsaturated lipids. (iii) In experiments with MnP, Mn(II), and unsaturated lipid in vitro, this system mimicked intact C. subvermispora cultures in that it cleaved nonphenolic (beta)-O-4 lignin model compounds between C(inf(alpha)) and C(inf(beta)) to release a benzylic fragment.     

Phenolic glycosides and condensed tannins in Salix sericea, S. eriocephala and their F1 hybrids: not all hybrids are created equal

The performance of hybrids depends upon the inheritance and expression of resistance traits. Secondary chemicals are one such resistance trait. In this study, we measured the concentrations of phenolic glycosides and condensed tannins in parental and F1 hybrid willows to examine the sources of chemical variation among hybrids. S. sericea produces phenolic glycosides, salicortin and 2'-cinnamoylsalicortin, and low concentrations of condensed tannin in its leaves. In contrast, S. eriocephala produces no phenolic glycosides but high concentrations of condensed tannins in its leaves. These traits are inherited quantitatively in hybrids. On average, F1 hybrids are intermediate for condensed tannins, suggesting predominantly additive inheritance or balanced ambidirectional dominance of this defensive chemical from the parental species. In contrast, the concentration of phenolic glycosides is lower than the parental midpoint, indicating directional dominance. However, there is extensive variation among F1 hybrids. The concentration of tannin and phenolic glycosides in F1 hybrid families is either (1) lower than the midpoint, (2) higher than the midpoint, or (3) indistinguishable from the midpoint of the two parental taxa. It appears that the production of the phenolic glycosides, especially 2'-cinnamoylsalicortin, is controlled by one or more recessive alleles. We also observed a two-fold or greater difference in concentration between some hybrid families. We discuss how chemical variation may effect the relative susceptibility of hybrid willows to herbivores.     

Evidence for the role and fate of water-insoluble condensed tannins in the short-term reduction of carbon loss during litter decay

Warmer temperatures associated with climate change have the potential to accelerate litter decay and subsequently release large amounts of carbon stored in soils. Condensed tannins are widespread secondary metabolites, which accumulate to high concentrations in many woody plants and play key roles in forest soil nutrient cycles. Future elevated atmospheric CO₂ concentrations are predicted to reduce nitrogen content and increase tannin concentrations in plant tissues, thus reducing litter quality for microbial communities and slowing decomposition rates. How the distinct condensed tannin fractions (water-soluble, acetone:MeOH-soluble and solvent-insoluble) impact soil processes, has not been investigated. We tested the impact of condensed tannin and nitrogen concentrations on decay rates of poplar and Douglas-fir litter at sites spanning temperature and moisture gradients in coastal rainshadow forests in British Columbia, Canada. The three condensed tannin fractions were quantified using recent improvements on the butanol-HCl assay. Decay was assessed based on carbon remaining, while changes in litter chemistry were primarily observed using two methods for proximate chemical analyses. After 0.6 and 1 year of decay, more carbon remained in poplar litter with high, compared to low, condensed tannin concentrations. By contrast, more carbon remained in Douglas fir litter than poplar litter during this period, despite lower condensed tannin concentrations. Rapid early decay was especially attributed to loss of soluble compounds, including water-soluble condensed tannins. Water-insoluble condensed tannin fractions, which were transformed to acid-unhydrolyzable residues over time, were associated with reduced carbon loss in high condensed tannin litter.     

Metabolism of tannin-protein complex by facultatively anaerobic bacteria isolated from koala feces

The metabolic pathways involved in degradation of tannin-protein complex (T-PC) were investigated in various facultatively anaerobic bacteria, with specific reference to fecal isolates from the koala including T-PC-degrading enterobacteria (T-PCDE),Streptococcus bovis, Klebsiella pneumoniae, andK. oxytoca. It was demonstrated that T-PCDE andS. bovis biotype I were capable of degrading protein complexed with gallotannin (a hydrolyzable tannin), but not that complexed with quebracho (a condensed tannin). Subsequent studies showed that these strains metabolized gallic acid to pyrogallol. Strains ofKlebsiella pneumoniae andK. oxytoca, which did not degrade T-PC, also metabolized gallic acid into pyrogallol. Pyrogallol was not degraded by any strains studied, but it was not detected in fresh feces of the koalas. The majority of strains isolated from feces could degrade phloroglucinol. Based on these findings, we propose that members of the gut microflora of the koala cooperate in the degradation of T-PC.     

Bioorganosolve pretreatments for simultaneous saccharification and fermentation of beech wood by ethanolysis and white rot fungi

Ethanol was produced by simultaneous saccharification and fermentation (SSF) from beech wood chips after bioorganosolve pretreatments by ethanolysis and white rot fungi, Ceriporiopsis subvermispora, Dichomitus squalens, Pleurotus ostreatus, and Coriolus versicolor. Beech wood chips were pretreated with the white rot fungi for 2-8 weeks without addition of any nutrients. The wood chips were then subjected to ethanolysis to separate them into pulp and soluble fractions (SFs). From the pulp fraction (PF), ethanol was produced by SSF using Saccharomyces cerevisiae AM12 and a commercial cellulase preparation, Meicelase, from Trichoderma viride. Among the four strains, C. subvermispora gave the highest yield on SSF. The yield of ethanol obtained after pretreatment with C. subvermispora for 8 weeks was 0.294 g g(-1) of ethanolysis pulp (74% of theoretical) and 0.176 g g(-1) of beech wood chips (62% of theoretical). The yield was 1.6 times higher than that obtained without the fungal treatments. The biological pretreatments saved 15% of the electricity needed for the ethanolysis.     

Genetic Manipulation of Condensed Tannins in Higher Plants : II. Analysis of Birdsfoot Trefoil Plants Harboring Antisense Dihydroflavonol Reductase Constructs

We have produced and analyzed transgenic birdsfoot trefoil (Lotus corniculatus L.) plants harboring antisense dihydroflavonol reductase (AS-DFR) sequences. In initial experiments the effect of introducing three different antisense Antirrhinum majus L. DFR constructs into a single recipient genotype (S50) was assessed. There were no obvious effects on plant biomass, but levels of condensed tannins showed a statistical reduction in leaf, stem, and root tissues of some of the antisense lines. Transformation events were also found, which resulted in increased levels of condensed tannins. In subsequent experiments a detailed study of AS-DFR phenotypes was carried out in genotype S33 using pMAJ2 (an antisense construct comprising the 5′ half of the A. majus cDNA). In this case, reduced tannin levels were found in leaf and stem tissues and in juvenile shoot tissues. Analysis of soluble flavonoids and isoflavonoids in tannin down-regulated shoot tissues indicated few obvious default products. When two S33 AS-DFR lines were outcrossed, there was an underrepresentation of transgene sequences in progeny plants and no examples of inheritance of an antisense phenotype were observed. To our knowledge, this is the first report of the genetic manipulation of condensed tannin biosynthesis in higher plants.     

A comparison of two strategies to modify the hydroxylation of condensed tannin polymers in Lotus corniculatus L

A full-length sense Antirrhinum majus dihydroflavonol reductase (DFR) sequence was introduced into birdsfoot trefoil (Lotus corniculatus L.) in experiments aimed at modifying condensed tannin content and polymer hydroxylation in a predictable manner. Analysis of transgenic plants indicated lines that showed enhanced tannin content in leaf and stem tissues. In contrast to previous data from root cultures, levels of propelargonidin units were not markedly elevated in lines with enhanced tannin content. RT-PCR analysis of four selected lines indicated a correlation between enhanced tannin content and expression of the introduced DFR transgene. Using a contrasting approach we introduced a flavonoid 3'5' hydroxylase (F3'5'H) sequence derived from Eustoma grandiflorum into Lotus root cultures. Expression of the transgene was associated with increased levels of condensed tannins and in this case there was also no alteration in polymer hydroxylation. These results suggest that additional mechanisms may exist that control the hydroxylation state of condensed tannins in this model species.     

Alterations in structure, chemistry, and biodegradability of grass lignocellulose treated with the white rot fungi Ceriporiopsis subvermispora and Cyathus stercoreus.

The white rot fungi Ceriporiopsis subvermispora FP-90031-sp and Cyathus stercoreus ATCC 36910 were evaluated for their ability to delignify Bermuda grass (Cynodon dactylon) stems and improve biodegradability. Compositional and structural alterations in plant cell walls effected by the fungi were determined by nuclear magnetic resonance spectroscopy, gas chromatography of alkali-treated residues, microspectrophotometry, and electron microscopy. Contaminating bacteria and fungi, which grew from unsterilized Bermuda grass stems, did not alter the improvement in grass biodegradability by either of the fungi from that of gas-sterilized stems. The biodegradation of stems by ruminal microorganisms, after treatment for 6 weeks with C. subvermispora or C. stercoreus, was improved by 29 to 32% and by 63 to 77%, respectively; dry weight losses caused by pretreatment with the fungi were about 20% over that in untreated, control stems. Both fungi preferentially removed aromatics to carbohydrates, and C. subvermispora removed proportionately more guaiacyl units than did C. stercoreus. Substantial amounts of ester-linked p-coumaric and ferulic acids were removed by both fungi, and about 23 and 41% of total aromatics (determined after 4 M NaOH direct treatment) were removed from the plant biomass after incubation with C. subvermispora and C. stercoreus, respectively. UV absorption microspectrophotometry indicated that ester-linked phenolic acids were totally removed from the parenchyma cell walls, and these cells were readily and completely degraded by both fungi. However, aromatic constituents were only partially removed from the more recalcitrant sclerenchyma cell walls, resulting in variation in electron density and random digestion pits after incubation with fiber-degrading bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tree resistance to Lymantria dispar caterpillars: importance and limitations of foliar tannin composition

The ability of foliar tannins to increase plant resistance to herbivores is potentially determined by the composition of the tannins; hydrolyzable tannins are much more active as prooxidants in the guts of caterpillars than are condensed tannins. By manipulating the tannin compositions of two contrasting tree species, this work examined: (1) whether increased levels of hydrolyzable tannins increase the resistance of red oak (Quercus rubra L.), a tree with low resistance that produces mainly condensed tannins, and (2) whether increased levels of condensed tannins decrease the resistance of sugar maple (Acer saccharum Marsh.), a tree with relatively high resistance that produces high levels of hydrolyzable tannins. As expected, when Lymantria dispar L. caterpillars ingested oak leaves coated with hydrolyzable tannins, levels of hydrolyzable tannin oxidation increased in their midgut contents. However, increased tannin oxidation had no significant impact on oxidative stress in the surrounding midgut tissues. Although growth efficiencies were decreased by hydrolyzable tannins, growth rates remained unchanged, suggesting that additional hydrolyzable tannins are not sufficient to increase the resistance of oak. In larvae on condensed tannin-coated maple, no antioxidant effects were observed in the midgut, and levels of tannin oxidation remained high. Consequently, neither oxidative stress in midgut tissues nor larval performance were significantly affected by high levels of condensed tannins. Post hoc comparisons of physiological mechanisms related to tree resistance revealed that maple produced not only higher levels of oxidative stress in the midgut lumen and midgut tissues of L. dispar, but also decreased protein utilization efficiency compared with oak. Our results suggest that high levels of hydrolyzable tannins are important for producing oxidative stress, but increased tree resistance to caterpillars may require additional factors, such as those that produce nutritional stress.     

Biochemical pulping of bagasse

This study deals with pretreatment of wheat straw with lignin-degrading fungi and its effect on chemical pulping. Ceriporiopsis subvermispora strains, which preferentially attack the lignin, were used for biochemical pulping of bagasse. Treatment of depithed bagasse with different strains of C. subvermispora reduced the kappa number by 10-15% and increased unbleached pulp brightness by 1.1-2.0 ISO points on chemical pulping at the same alkali charge. Bleaching of biopulps at the same chemical charge increased final brightness by 4.7-5.6 ISO points and whiteness by 10.2-11.4 ISO points. Fungal treatment did not result in any adverse effect on the strength properties of pulp.     

Developmental Differences in the Location of Polyphenols and Condensed Tannins in Leaves and Stems of Sericea Lespedeza, Lespedeza cuneata

This histologkal study was performed to determine whether differencesin location and concentration of polyphenols and condensed tanninscould be observed in leaves and stems of sericea lespedeza genotypesof high (HP) or low (LP) phenolic content. Polyphenols and condensedtannins were especially evident in the vacuoles of paraveinalmesophyll cells from leaves of both genotypes. However, higherlevels of these substances were observed in paraveinal cellsof HP leaves. Cross-sections through young stem internodes revealedmany perivascular and vascular parenchyma cells staining prominentlyfor polyphenols in both genotypes. Their location in vacuolesof paraveinal mesophyll cells that function in photosynthatetransport within the leaf suggests that these substances playan active role in physiological processes of sericea lespedezaplants. Alternatively, they could represent a form in whichthese plants store excess photosynthates. Lespedeza cuneata (Dumont de Courset) G. Don, sericea lespedeza, polyphenols, condensed tannins, leaf anatomy, stem anatomy     

马尾松与阔叶树种混合凋落叶分解过程中总酚和缩合单宁的变化

采用凋落物分解袋法,研究四川低山丘陵区马尾松与檫木、香椿、香樟3种阔叶树种的混合凋落叶及纯马尾松凋落叶分解过程中总酚和缩合单宁的变化特征.设置马尾松:檫木质量比为6:4、7:3、8:2,马尾松:香椿质量比为6:4、7:3、8:2,马尾松:香樟质量比为6:4、7:3、8:2混合处理.结果表明:经过180 d的分解,纯马尾松凋落叶缩合单宁的降解率为84.4%,混合凋落叶缩合单宁的降解率均高于纯马尾松凋落叶.在所有组合中,马尾松:香樟6:4混合凋落叶的缩合单宁和总酚降解率最高,分别为90.3%和68.6%,凋落叶的混合促进了马尾松凋落叶缩合单宁和总酚的分解.随着分解时间的延长,马尾松与3种阔叶凋落叶所有混合处理缩合单宁的降解率均呈现先上升后趋于稳定的趋势.而纯马尾松凋落叶、马尾松:香樟(7:3)和马尾松与香椿的所有混合处理总酚的降解率呈现在分解前90 d上升此后下降的趋势;马尾松与檫木的所有混合处理及马尾松:香樟6:4和8:2混合处理总酚降解率呈现上升趋势.混合凋落叶分解过程中,单宁和总酚的变化特征还与凋落物基质质量、凋落物分解相关酶(多酚氧化酶、过氧化物酶、亮氨酸氨基肽)的活性有关.     

Effect of nitrogen fertilization upon the secondary chemistry and nutritional value of quaking aspen (Populus tremuloides Michx.) leaves for the large aspen tortrix (Choristoneura conflictana (Walker))

Summary We investigated the effects of nitrogen fertilization upon the concentrations of nitrogen, condensed tannin and phenolic glycosides of young quaking aspen (Populus tremuloides) leaves and the quality of these leaves as food for larvae of the large aspen tortrix (Choristoneura conflictana), a Lepidopteran that periodically defoliates quaking aspen growing in North America. Nitrogen fertilization resulted in decreased concentrations of condensed tannin and phenolic glycosides in aspen leaves and an increase in their nitrogen concentration and value as food for the large aspen tortrix. These results indicate that plant carbon/nutrient balance influences the quality of aspen leaves as food for the large aspen tortrix in two ways, by increasing the concentrations of positive factors (e.g. nitrogen) and decreasing the concentrations of negative factors (eg. carbon-based secondary metabolites) in leaves. Addition of purified aspen leaf condensed tannin and a methanol extract of young aspen leaves that contained condensed tannin and phenolic glycosides to artificial diets at high and low levels of dietary nitrogen supported this hypothesis. Increasing dietary nitrogen increased larval growth whereas increasing the concentrations of condensed tannin and phenolic glycosides decreased growth. Additionally, the methanol extract prevented pupation. These results indicate that future studies of woody plant/insect defoliator interactions must consider plant carbon/nutrient balance as a potentially important control over the nutritional value of foliage for insect herbivores.     

Wound-induced accumulations of condensed tannins in turtlegrass, Thalassia testudinum

Turtlegrass, Thalassia testudinum, produces high concentrations of proanthocyanidins (condensed tannins) which we hypothesized are induced by grazing, as a component of a general wound response. To test this we quantified condensed tannins in a variety of turtlegrass tissues following simulated fish grazing, grazing by the urchin Lytechinus variegatus, and treatment with the natural plant wound hormone jasmonic acid. We observed that simulated fish grazing triggered rapid induction of condensed tannins by an average of 10 mg tannin g⁻¹ dry mass (DM) after 5 days. Condensed tannin accumulations were correlated with a reduction of blade extension rates. Further, we observed that constitutive tannin levels in developing first-rank leaves were strongly correlated with the width of second-rank leaves on each shoot, with an increase of 7.7 mg tannin g⁻¹ tissue dry mass per millimeter blade width on average. We propose that wider source leaves provide additional resources for phenolic biosynthesis. There was no induction of tannins in leaves, meristematic or sheath tissues in response to grazing by the urchin L. variegatus, the presence of potential waterborne cues from nearby grazed plants, or to treatment with 5 mM jasmonic acid. However, urchin grazing did induce tannin production in root/rhizome tissues, where they accumulated to levels 3–4 times higher than in blades (up to 350 mg tannin g⁻¹ tissue dry mass). These results confirm the potential for rapid wound-induced condensed tannin accumulations in T. testudinum. The link between blade widths and the tannin content of new leaves indicates that leaf morphology may be a useful bioindicator for predicting herbivore and disease-resistance in the field.     

Bactericidal effect of hydrolysable and condensed tannin extracts on <Emphasis Type="Italic">Campylobacter jejuni</Emphasis> in vitro

Strategies are sought to reduce intestinal colonisation of food-producing animals by Campylobacter jejuni, a leading bacterial cause of human foodborne illness worldwide. Presently, we tested the antimicrobial activity of hydrolysable-rich blackberry, cranberry and chestnut tannin extracts and condensed tannin-rich mimosa, quebracho and sorghum tannins (each at 100 mg/mL) against C. jejuni via disc diffusion assay in the presence of supplemental casamino acids. We found that when compared to non-tannin-treated controls, all tested tannins inhibited the growth of C. jejuni and that inhibition by the condensed tannin-rich mimosa and quebracho extracts was mitigated in nutrient-limited medium supplemented with casamino acids. When tested in broth culture, both chestnut and mimosa extracts inhibited growth of C. jejuni and this inhibition was much greater in nutrient-limited than in full-strength medium. Consistent with observations from the disc diffusion assay, the inhibitory activity of the condensed tannin-rich mimosa extracts but not the hydrolysable tannin-rich chestnut extracts was mitigated by casamino acid supplementation to the nutrient-limited medium, likely because the added amino acids saturated the binding potential of the condensed tannins. These results demonstrate the antimicrobial activity of various hydrolysable and condensed tannin-rich extracts against C. jejuni and reveal that condensed tannins may be less efficient than hydrolysable tannins in controlling C. jejuni in gut environments containing high concentrations of amino acids and soluble proteins.