A highly active endo-β-1,4-mannanase produced by Cellulosimicrobium sp. strain HY-13, a hemicellulolytic bacterium in the gut of Eisenia fetida

A xylanolytic gut bacterium isolated from Eisenia fetida, Cellulosimicrobium sp. strain HY-13, produced an extracellular glycoside hydrolase capable of efficiently degrading mannose-based substrates such as locust bean gum, guar gum, mannotetraose, and mannopentaose. The purified mannan-degrading enzyme (ManK, 34,926 Da) from strain HY-13 was found to have an N-terminal amino acid sequence of DEATTDGLHVVDD, which has not yet been identified. Under the optimized reaction conditions of 50°C and pH 7.0, ManK exhibited extraordinary high specific activities of 7109 IU/mg and 5158 IU/mg toward locust bean gum and guar gum, respectively, while the enzyme showed no effect on sugars substituted with p-nitrophenol and various non-mannose carbohydrates. Thin layer chromatography revealed that the enzyme degraded locust bean gum to mannobiose and mannotetraose. No detectable amount of mannose was produced from hydrolytic reactions with the substrates. ManK strongly attached to Avicel, β-cyclodextrin, lignin, and poly(3-hydroxybutyrate) granules, but not bound to chitin, chitosan, curdlan, or insoluble oat spelt xylan. The aforementioned characteristics of ManK suggest that it is a unique endo-β-1,4-mannanase without additional carbohydrolase activities, which differentiates it from other well-known carbohydrolases.     

Inhibition of random amplified polymorphic DNAs (RAPDs) by plant polysaccharides

A survey of the inhibition of the amplification of spinach DNA by various plant polysaccharides revealed that neutral polysaccharides (arabinogalactan, dextran, gum guar, gum locust bean, inulin, mannan, and starch) were not inhibitory. In contrast, the acidic polysaccharides (carrageenan, dextran sulfate, gum ghatti, gum karaya, pectin, and xylan)were inhibitory. In the process of preparing random amplified polymorphic DNAs (RAPDs), the loss of large DNA bands appears to be an indicator that the fingerprint pattern has been affected by polysaccharides. The addition of various concentrations of Tween 20, DMSO, or PEG 400 to the PCR reaction mixture resulted in partial restoration of amplification of RAPDs for the acidic polysaccharides. The most effective way to eliminate the effects of polysaccharide inhibition was by diluting the DNA extracts, and thereby diluting the polysaccharide inhibitors.     

Incorporation of galactomannans in the diet of newly weaned piglets: Effect on bacteriological and some morphological characteristics of the small intestine

In search of substances replacing antibiotics as growth promoters for farm animals, non-digestible oligosaccharides (NDO) or non-starch polysaccharides (NSP) have been proposed as possible alternatives. In this context, the influence of galactomannans on bacteriological and morphological aspects of the gastrointestinal tract in weanling pigs was investigated. Four groups of five newly weaned piglets received one of the following diets: control feed (C), C supplemented with guar gum (1%), C supplemented with locust bean gum (1%) and C supplemented with 10% of carob tree seeds meal as source of locust bean gum. The animals were euthanized after 11?–?12 days and digesta were sampled in stomach, jejunum (proximal and distal) and caecum, while mucosal scrapings and ring shaped tissue samples were taken of proximal and distal jejunum. On these samples bacteriological, biochemical and morphological determinations were carried out. Total count of bacteria in digesta and mucosal scrapings was not influenced by the different diets, with the exception of the proximal jejunum where a small decrease (0.5 log₁₀ CFU) was noted with the guar gum and carob tree seeds diet. The number of E. coli increased by feeding both gums and carob tree seeds. With the latter diet, higher counts of streptococci were observed. In agreement with the lower concentration of lactic acid in jejunal contents, guar gum decreased the number of lactobacilli. Locust bean gum decreased the molar proportion of acetate in caecal contents while butyrate and valerate were augmented. Feeding the carob tree seeds resulted in shorter villi and a lower villus height/crypt depth ratio in the jejunum mucosa, which was an indication for a faster renewal rate of the epithelium. Both locust bean gum feeds significantly lowered the mitotic index in the crypts of the small intestine. Only with the carob tree seeds diet, viscosity of jejunal contents was increased. In conclusion, the effects of the addition of 1% of pure guar gum or locust bean gum were inconsistent and not very outspoken, whereas 10% of carob tree seeds meal in the diet resulted in influences on intestinal characteristics at the bacteriological and morphological level.     

Production of \-mannanases by Trichoderma harzianum E58

Summary The extracellular mannanase and endoglucanase activities of Trichoderma harzianum E58 were followed during growth of the fungus on 1% (w/v) mannose, Avicel, locust bean gum, konjac powder or the water-soluble fraction from stream-treated white spruce (SWS). Peak galactomannanase activities of 0.60 IU/ml and 0.66 IU/ml were detected in culture filtrates after 6–8 days growth on locust bean gum and Avicel respectively. When SWS or konjac powder were used as substrates, lower but relatively constant levels of activity were detected between 2 and 11 days of growth. Growth of the fungus on mannan-rich locust bean gum resulted in the highest specific glucomannanase and galactomannanase values. Although growth on 1% mannose failed to induce any mannanase activity, when 0.5% galactomannan was added with mannose, mannanase activity was detected in the culture filtrate. This indicated that mannanase production was not repressed in the presence of mannose. Samples were taken from each culture at the time of maximum galactomannanase activity. A protein profile obtained by isoelectric focusing was followed by a zymogram overlay to detect bands exhibiting galactomannanase, glucomannanase and endoglucanase activities. Several bands showed mannanase and endoglucananase activity. One band at pI 6.55 revealed both gluco- and galactomannanase activity and was free of detectable cellulase activity. Offprint requests to: J. N. Saddler     

枯草芽孢杆菌中性β—甘露聚糖酶的产生及性质

由土壤中分离出一株产中性β甘露聚糖酶的枯草芽孢杆菌（Ｂａｃｉｌｕｓｓｕｂｔｉｌｉｓ）,编号ＢＭ９６０２。该菌在液体培养条件下,产生中性β甘露聚糖酶。多糖能作为碳源,而单糖不能作为碳源;有机氮源优于无机氮源。产酶最适培养基组成：魔芋粉４％,牛肉蛋白胨和酵母膏各１％。产酶最适培养条件：培养基起始ｐＨ８５,３５℃,振荡培养３６ｈ。以槐豆胶为底物,培养滤液中性β甘露聚糖酶活力为９６ＩＵ／ｍＬ。酶在ｐＨ５０～１００和５０℃下稳定;作用最适条件为ｐＨ６０和５０℃;水解魔芋粉和槐豆胶均产生寡聚糖。     

Incorporation of galactomannans in the diet of newly weaned piglets: effect on bacteriological and some morphological characteristics of the small intestine

In search of substances replacing antibiotics as growth promoters for farm animals, non-digestible oligosaccharides (NDO) or non-starch polysaccharides (NSP) have been proposed as possible alternatives. In this context, the influence of galactomannans on bacteriological and morphological aspects of the gastrointestinal tract in weanling pigs was investigated. Four groups of five newly weaned piglets received one of the following diets: control feed (C), C supplemented with guar gum (1%), C supplemented with locust bean gum (1%) and C supplemented with 10% of carob tree seeds meal as source of locust bean gum. The animals were euthanized after 11-12 days and digesta were sampled in stomach, jejunum (proximal and distal) and caecum, while mucosal scrapings and ring shaped tissue samples were taken of proximal and distal jejunum. On these samples bacteriological, biochemical and morphological determinations were carried out. Total count of bacteria in digesta and mucosal scrapings was not influenced by the different diets, with the exception of the proximal jejunum where a small decrease (0.5 log10 CFU) was noted with the guar gum and carob tree seeds diet. The number of E. coli increased by feeding both gums and carob tree seeds. With the latter diet, higher counts of streptococci were observed. In agreement with the lower concentration of lactic acid in jejunal contents, guar gum decreased the number of lactobacilli. Locust bean gum decreased the molar proportion of acetate in caecal contents while butyrate and valerate were augmented. Feeding the carob tree seeds resulted in shorter villi and a lower villus height/crypt depth ratio in the jejunum mucosa, which was an indication for a faster renewal rate of the epithelium. Both locust bean gum feeds significantly lowered the mitotic index in the crypts of the small intestine. Only with the carob tree seeds diet, viscosity of jejunal contents was increased. In conclusion, the effects of the addition of 1% of pure guar gum or locust bean gum were inconsistent and not very outspoken, whereas 10% of carob tree seeds meal in the diet resulted in influences on intestinal characteristics at the bacteriological and morphological level.     

Biocatalytic activity of recombinant human β-mannosidase immobilized onto magnetic nanoparticles for bioprocess

Recombinant human β-mannosidase (rhMANB) is an important glycosidase enzyme that degrades mannose-linked glycoproteins and mannan polysaccharides. rhMANB was purified and covalently immobilized onto magnetic nanoparticles. The immobilization of the enzyme was confirmed by Fourier-transform infrared spectroscopy (FTIR) and magnetic nanoparticles linked immunosorbent assay (MagLISA). Antibodies against rhMANB were raised, purified and characterized for MagLISA. The binding of rhMANB onto magnetic nanoparticles was found to be 65%. The V( max ) and K( m ) of immobilized rhMANB was observed 3.0-fold higher and 2.024-fold lower, respectively, as compared to unbound rhMANB. The stability and activity of immobilized enzyme was observed at different pH, temperature, and after storage at 4°C. Metal chelators (oxalic acid, citric acid, and ascorbic acid) did not affect the enzyme activity of immobilized enzyme, whereas ethylenediamine tetraacetic acid reduced the activity. The results obtained from thin-layer chromatography indicate that immobilized rhMANB is more efficient than the unbound form to hydrolyze mannobiose, mannotriose, mannotetraose, mannopentose, galactoglucomannan, and locust bean gum. Magnetic nanoparticles suspended gel-permeation chromatography showed that 29% locust bean gum hydrolyzed efficiently during flow in the column. The immobilization of rhMANB will be a good process for gelling and saccharification of mannan polymers at industrial scale.     

The influence of locust bean gum and dextran on the gelation of κ-carrageenan

The interaction of κ-carrageenan with locust bean gum and dextran has been studied by rheology, differential scanning calorimetry (DSC), and electron spin resonance spectroscopy (ESR). Rheological measurements show that the carrageenan gel characteristics are greatly enhanced in the presence of locust bean gum but not in the presence of dextran. Carrageenan/locust bean gum mixtures show two peaks in the dsc cooling curves. The higher temperature peak corresponds to the temperature of gelation and its intensity increases at the expense of the lower temperature peak as the proportion of locust bean gum in the mixture increases. Furthermore, the DSC heating curves show enhanced broadening when locust bean gum is present, indicating increased aggregation. These results are taken as evidence of carrageenan/locust bean gum association. The gelation process has also been followed by ESR using spin-labeled carrageenan. On cooling carrageenan solutions, an immobile component appears in the ESR spectra signifying a loss of segmental mobility consistent with chain stiffening due to the coil → helix conformational transition and helix aggregation. For carrageenan/locust bean gum mixtures, carrageenan ordering occurs at temperatures corresponding to the higher temperature DSC setting peak and the temperature of gelation. Similar studies using spin-labeled locust bean gum show that its mobility remains virtually unaffected during the gelation process. It is evident, therefore, that carrageenan and locust bean gum interact only weakly. It is proposed that at low carrageenan concentrations the gel network consists of carrageenan helices cross-linked by locust bean gum chains. At high carrageenan concentrations the network is enhanced by the additional self-aggregation of the “excess” carrageenan molecules. For carrageenan/dextran mixtures, only one peak is observed in the dsc cooling curves. The onset of gelation shifts to higher temperatures only at very high (20%) dextran concentrations and this is attributed to volume exclusion effects. Furthermore, there is no enhanced broadening of the peaks in the DSC heating curves as for the carrageenan/locust bean gum systems. It is therefore concluded that carrageenan/dextran association does not occur. The difference in behavior between locust bean gum and dextran is attributed to the greater flexibility of the dextran chains. © 1996 John Wiley & Sons, Inc.     

Studies on κ-carrageenan/locust bean gum mixtures in the presence of sodium chloride and sodium iodide

The solution properties of κ-carrageenan and κ-carrageenan/locust bean gum mixtures have been studied by small deformation oscillation measurements and differential scanning calorimetry (DSC) in the presence of sodium chloride and sodium iodide. Both salts induced the κ-carrageenan to undergo a coil-helix conformational change as noted by an increase in the storage and loss moduli (G′, G′) and by an exothermic peak in the DSC cooling curves. The enthalpy ΔH_c-h and temperature of the conformational transition T_c-h were higher in Nal compared to NaCl and T_c-h increased with increasing the concentration of both electrolytes. Gelation was not observed for carrageenan or carrageenan/locust bean gum mixtures in the presence of up to 200 mM Nal. Although carrageenan alone did not gel in the presence of 100 mM NaCl, a weak gel was obtained for a mixture containing 0.9%/0.1% carrageenan/locust bean gum. Furthermore, the mixture showed hysteresis in both the rheological and DSC cooling and heating curves. A strong gel was produced for carrageenan alone in the presence of 200 mM NaCl and the gel strength increased on adding a small proportion of locust bean gum (0.9%/0.1%). © 1997 John Wiley & Sons, Inc. Biopoly 41: 657–671, 1997     

The extracellular polysaccharides of the red microalgae: Chemistry and rheology

Cells of red microalgae encapsulated within sulphated polysaccharides, are thought to have a wide range of potential industrial applications. Our group is thus carrying out a comprehensive research program aimed at bringing these biopolymers into industrial use. The program includes physiological studies on polysaccharide production, outdoor cultivation of the microalgae, and characterisation of the polysaccharides. Chemical composition and structure and physicochemical properties were investigated for the polysaccharides of three red microalgae, Porphyridium sp., P. aerugineum and Rhodella reticulata. Differences were found among the three species in the composition of the monosugars, half ester sulphate groups and glucuronic acid content, but a disaccharide isolated was identical in all the species examined. This disaccharide is thought to be the basic building block of these polysaccharides. In addition, monosugar sulphates were isolated and characterised. Fractionation by charge showed the polysaccharides to be heterogenous and composed of at least two fractions that differed in their composition. Although the polysaccharides differed in composition, their rheological characteristics were found to be similar. Aqueous solutions of the biopolymers were stable over a wide range of pH values and temperatures and were compatible with monovalent cations. Mixtures of the algal polysaccharides with locust bean gum exhibited synergism and syneresis. When the gel strength was compared with that of agar gel at the same concentration the polysaccharide gels were found to be weaker.     

Carbohydrates of Padina tetrastromatica

Extraction with hydrochloric acid (pH 2.5) of the brown alga Padina tetrastromatica afforded water-soluble and water-insoluble polysaccharides. The water-soluble polysaccharide was fractionated using cetyltritmethyl ammonium bromide and chromatography on DEAE-cellulose and Sephadex G-100. A neutral laminaran like glucan and two new sulphated heteropolysaccharides comprising d-glucuronic acid, l-fucose, l-rhamnose, d-xylose, d-arabinose, d-galactose, d-glucose and half-ester sulphate were obtained. The alginic acid isolated from this brown seaweed was found to be predominantly of poly 1 → 4β-d-mannuronic acid type. The water-soluble sulphated polymer showed high anticoagulant activity.     

Improved hypolipidemic effects of xanthan gum-galactomannan mixtures in rats

This study describes the effects of mixtures of xanthan gum and galactomannan, guar gum, or locust bean gum, on the lipids in plasma and liver in non-diabetic and diabetic rats. Non-diabetic rats were fed cholesterol-free diets with 3% guar gum, locust bean gum, or xanthan gum (3G, 3L, and 3X), or a mixture of xanthan gum and guar gum or locust bean gum (1:2, w/w) (2G1X, 2L1X) for 2 weeks. Rats fed diets not containing these polysaccharides were used as controls. The total cholesterol in plasma and the triacylglycerol in liver were significantly lowered in rats fed the 2G1X diet. The 3G, 3X, 3L, and 2L1X diets showed no significant effect on the total cholesterol and triacylglycerol in plasma and liver. In the streptozotocin-induced (STZ) diabetic rats, the total cholesterol in plasma was lowered in rats fed the 3G, 3X or 2G1X diet for 4 weeks, and the 2G1X diet was more effective than the 3G and 3X diets. The triacylglycerol in plasma in STZ diabetic rats was also significantly lowered by the 2G1X diet. These results showed that a mixture of xanthan gum and guar gum has an improved hypolipidemic effect on non-diabetic and STZ diabetic rats. The effects of the 2G1X diet on the diabetic symptoms in STZ diabetic rats, suppression of food and water intakes, decrease in glucose in urine, and lowering of plasma glucose, were also observed.     

Improved Hypolipidemic Effects of Xanthan Gum-Galactomannan Mixtures in Rats

This study describes the effects of mixtures of xanthan gum and galactomannan, guar gum, or locust bean gum, on the lipids in plasma and liver in non-diabetic and diabetic rats. Non-diabetic rats were fed cholesterol-free diets with 3% guar gum, locust bean gum, or xanthan gum (3G, 3L, and 3X), or a mixture of xanthan gum and guar gum or locust bean gum (1:2, w/w) (2G1X, 2L1X) for 2 weeks. Rats fed diets not containing these polysaccharides were used as controls. The total cholesterol in plasma and the triacylglycerol in liver were significantly lowered in rats fed the 2G1X diet. The 3G, 3X, 3L, and 2L1X diets showed no significant effect on the total cholesterol and triacylglycerol in plasma and liver. In the streptozotocin-induced (STZ) diabetic rats, the total cholesterol in plasma was lowered in rats fed the 3G, 3X or 2G1X diet for 4 weeks, and the 2G1X diet was more effective than the 3G and 3X diets. The triacylglycerol in plasma in STZ diabetic rats was also significantly lowered by the 2G1X diet. These results showed that a mixture of xanthan gum and guar gum has an improved hypolipidemic effect on non-diabetic and STZ diabetic rats. The effects of the 2G1X diet on the diabetic symptoms in STZ diabetic rats, suppression of food and water intakes, decrease in glucose in urine, and lowering of plasma glucose, were also observed.     

Oogonial release in Turbinaria conoides (J. Agardh) Kützing (Fucales,Sargassaceae)

The oogonium in Turbinaria conoides (J. Agardh) Kürzing at the time of release is 8-nucleate and consists of 3 wall layers namely exochiton, mesochiton and endochiton. The exochiton contains alginic acid. The mesochiton a mixture of alginic acid and sulphated polysaccharides. The endochiton that is evident in the unreleased 8-nucleate oogonium, stains for sulphated polysaccharides, but is PAS negative. In a released oogonium, the endochiton is Alcian blue and PAS positive and consists of both alginic acid and sulphated polysaccharides.Polysaccharide granules are secreted near the perinuclear region and in thecytoplasmic vacuoles during the initiation of mesochiton. Furthermore, at the distal end the mesochiton froms a pad that fuses with the exochiton. The pad consists of alternate thick and thin bands. The exochiton opens at one side due to the swelling of the oogonium and accumulation of sulphated polysaccharides between exochiton and mesochiton followed by formation and elongation of a mesochiton stalk. The 8-nucleate oogonium is, thus, extruded from the conceptacle, but remains attached to the exochiton by means of a long mesochiton stalk. The secretory paraphyses, at the time of oogonial release, produce copious amounts of polysaccharides. The oogonium is, thus, extruded through the ostiole by the combined efforts of the 3 wall layers that are histochemically and histologically different, in combination with secretion produced by secretory paraphyses.     

Production and characterization of the slime polysaccharide of Pseudomonas aeruginosa

The slime polysaccharides produced by Pseudomonas aeruginosa isolated from a variety of human infections were investigated. Slime production in culture seemed optimal when adequate amounts of carbohydrate were present and under conditions of either high osmotic pressure or inadequate protein supply. The polysaccharides produced by the organisms were similar to each other, to the slime of Azotobacter vinelandii, and to seaweed alginic acids. They were composed of beta-1,4-linked d-mannuronic acid residues and variable amounts of its 5-epimer l-guluronic acid. All bacterial polymers contained o-acetyl groups which are absent in the alginates. The polysaccharides differed considerably in the ratio of mannuronic to guluronic acid content and in the number of o-acetyl groups. The particular composition of the slime was not found to be characteristic for the disease process from which the mucoid variants of P. aeruginosa were obtained.     

Production of β-Mannanase and β-Mannosidase from Aspergillus awamori K4 and Their Properties

β-Mannanase and β-mannosidase from Aspergillus awamori K4 was produced by solid culture with coffee waste and wheat bran. The optimum composition for enzyme production was 40% coffee waste–60% wheat bran. Two enzymes were partially purified. Optimum pH was about 5 for both enzymes, and optimum temperature was around 80°C for β-mannanase and 60–70°C for β-mannosidase. These enzymes produced some oligosaccharides from glucomannan and galactomannan by their hydrolyzing and transferring activities. β-Mannanase hydrolyzed konjak and locust bean gum 39.1% and 15.8%, respectively. Oligosaccharides of various molecular size were released from glucomannan of konjak, but on the addition of cellulase, mannobiose was released selectively. In locust bean gum, tetra-, tri-, and disaccharides (mannobiose) were mainly released by K4 β-mannanase. Tetra- and trisaccharides were heterooligosaccharides consisting of galactose and mannose residues. K4 β-mannosidase had a transglycosylation action, transferring mannose residue to alcohols and sugars like fructose. Received: 24 April 2000/Accepted: 20 October 2000     

The effects of plant polysaccharides and buffer additives on PCR.

A survey of the inhibitory effects of various plant polysaccharides on PCR amplification of a 974-bp section of rbcL in spinach revealed that most of the polysaccharides tested (arabinogalactan, carrageenan, dextran, gum guar, gum karaya, gum locust bean, inulin, mannan, pectin, starch and xylan) were not inhibitory. In contrast, two of the acidic polysaccharides (dextran sulfate and gum ghatti) were inhibitory. The addition of 0.5% Tween 20 reversed the inhibitory effects of gum ghatti (polysaccharide:DNA ratio of 500:1). The inhibitory effect of dextran sulfate (50:1) could be reversed by the addition of Tween 20 (0.25% or 0.5%), DMSO (5%) or polyethylene glycol 400 (5%), but none of these three additives were effective at a 100:1 ratio of dextran sulfate/DNA.     

Binding of Volatile Organic Compounds to Food Biopolymers

Capillary gas chromatography was used to study the influence of the composition and structure of different food polymers (polysaccharides, vegetable fibers, and animal protein gelatin) on the binding of essential oil components. The retention of volatile organic compounds on biopolymers was shown to depend on their molecule structure and the presence, type, and position of a functional group. The maximum extent of the binding was observed for nonpolar terpene and sesquiterpene hydrocarbons, and the minimum extent was observed for alcohols. The components of essential oils were adsorbed due mostly to hydrophobic interactions. It was shown that the composition and structure of a compound, its physico-chemical state, and the presence of functional groups influence the binding. Gum arabic and guar gum were found to bind nonpolar compounds to a maximum and minimum extent, respectively. It was demonstrated the minimum adsorption ability of locust bean gum with respect to all studied compounds.     

Synthesis and Fungicidal Activity of Diaryl 1,1 -Dichloroethyl-phosphonates

Non-Newtonian behavior and dynamic viscoelasticity of a series of aqueous mixed solutions of xanthan and locust bean gum were measured using a rheogoniometer, and the rheological properties were analysed. A gelation occurred in the mixture at the concentration of 0.2% total gums at room temperature. The flow curves of the mixture solutions showed a yield value and approximated to plastic behavior at 50°C. The maximum dynamic modulus was obtained when the mixing ratio of xanthan to locust bean gum was 1:2, while comparable high moduli were also obtained in the mixing ratio of 1: 3 or 1:4. A mixture of deacetylated xanthan and locust bean gum showed the highest dynamic modulus, about two times that of the mixture of native or Na-form xanthan. The dynamic modulus of the mixtures decreased rapidly with increasing temperature. In contrast, the dynamic viscosity was scarcely changed during increasing temperature in the mixing ratio of 2: 1. The dynamic modulus was decreased by addition of urea (4.0 M), NaCl (0.1%) and MgCl₂. We concluded that the intermolecular interaction between xanthan and locust bean gum might occur between the side chains of the former and backbone of the latter, as in a lock-and-key effect.     

Meristoderm in Turbinaria conoides (Fucales,sargassaceae)

In Turbinaria conoides (J. Agardh) Kützing, the hapteron, thallus and receptacle meristoderm cells are columnar, polarized and have thick longitudinal walls. In the thallus apical cavity, however, these cells are elongate and possess cap-like structures and thin, longitudinal walls. The meristoderm cells, except for those present at the apical cavities and ostiole regions, are overarched by 1–5 extracellular layers that are deposited in an orderly manner.The histochemistry of the meristoderm suggests that its cell walls contain alginic acid, cellulose and sulphated polysaccharides. The extracellular layers and the materials in the cap-like structures contain a mixture of alginic acid and sulphated polysaccharides, and little cellulose. The possible role of meristoderm cells lining the apical cavity of the thallus and that of extracellular layers is discussed.