RESUMO
BACKGROUND: Stevia has been proposed as a potential antidiabetic sweetener, mainly based on inconsistent results from stevioside or the plant extract, yet lacking relative experimental evidence from individual steviol glycosides (SGs) and their metabolites. RESULTS: The results systematically revealed that the typical SGs and their final metabolite (steviol) presented an antidiabetic effect on streptozotocin (STZ) diabetic mice in all assayed antidiabetic aspects. In general, the performance strength of the samples followed the sequence steviol > steviol glucosyl ester > steviolbioside > rubusoside > stevioside > rebaudioside A, which is opposite to their sweetness strength order, and generally in accordance with the glucosyl group numbers in their molecules. This may imply that the antidiabetic effect of the SGs might be achieved through steviol, which presented antidiabetic performance similar to that of metformin with a dose of 1/20 that of metformin. Moreover, the 18 F-fluorodeoxyglucose traced micro-PET experiment revealed that stevioside and steviol could increase the uptake of glucose in the myocardium and brain of the diabetic mice within 60 min, and decrease the accumulation of glucose in the liver and kidney. CONCLUSIONS: The SGs and steviol presented an antidiabetic effect on STZ diabetic mice in all assayed aspects, with an induction time to start the effect of the SGs. Stevioside and steviol could increase uptake of glucose in the myocardium and brain of the diabetic mice, and decrease accumulation of glucose in the liver and kidney. The performance strength of the SGs is generally in accordance with glucosyl group numbers in their molecules.
Assuntos
Diabetes Mellitus Experimental/tratamento farmacológico , Diterpenos do Tipo Caurano/administração & dosagem , Glucosídeos/administração & dosagem , Hipoglicemiantes/administração & dosagem , Extratos Vegetais/administração & dosagem , Stevia/química , Animais , Diabetes Mellitus Experimental/metabolismo , Diterpenos do Tipo Caurano/metabolismo , Glucose/metabolismo , Glucosídeos/metabolismo , Humanos , Hipoglicemiantes/metabolismo , Rim/efeitos dos fármacos , Rim/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos ICR , Extratos Vegetais/metabolismo , Folhas de Planta/química , EstreptozocinaRESUMO
Water-mediated fertilization is ubiquitous in early land plants. This ancestral mode of fertilization has, however, generally been considered to have been lost during the evolutionary history of terrestrial flowering plants. We investigated reproductive mechanisms in the subtropical ginger Cautleya gracilis (Zingiberaceae), which has two pollen conditions - granular and filiform masses - depending on external conditions. We tested whether rain transformed granular pollen into filiform masses and whether this then promoted pollen-tube growth and fertilization of ovules. Using experimental manipulations in the field we investigated the contribution of water-mediated fertilization to seed production. Rain caused granular pollen to form filiform masses of germinating pollen tubes, which transported sperm to ovules, resulting in fertilization and seed set. Flowers exposed to rain produced significantly more seeds than those protected from the rain, which retained granular pollen. Insect pollination made only a limited contribution to seed set because rainy conditions limited pollinator service. Our results reveal a previously undescribed fertilization mechanism in flowering plants involving water-mediated fertilization stimulated by rain. Water-mediated fertilization is likely to be adaptive in the subtropical monsoon environments in which C. gracilis occurs by ensuring reproductive assurance when persistent rain prevents insect-mediated pollination.
Assuntos
Fertilização/fisiologia , Água , Zingiberaceae/fisiologia , Animais , Abelhas/fisiologia , Flores/fisiologia , Germinação/fisiologia , Modelos Lineares , Polinização , Chuva , Sementes/fisiologia , AutofertilizaçãoRESUMO
A series of novel anionic e-surfactants n-C cP pS was molecular designed and synthesized from long-chain fatty alcohols by polypropoxylation and sulfation followed by neutralization. Excellent all-round performance of extended surfactants (e-surfactants) interests us how a simple polypropylene oxide (PPO) spacer has great effects on properties. By a comparative study of conventional/ethoxylated/extended n-alkylsulfate surfactants, we were surprised to find that e-surfactants are in an obvious rugby shape at the air/water surface according to molecular surface area ( am), and it comes down to the intramolecular PPO spacer coiling and surface-induced collapse. On the basis of the interfacial properties of the e-surfactants, it is found that the PPO spacer can provide both hydrophilic and lipophilic contributions to an e-surfactant molecule. The synergism between PPO spacers and alkyl chains indicates that a certain PPO spacer can adjust the contributions in view of different alkyl chain lengths. Therefore, it is both the rugby-shaped molecular geometry of e-surfactants and the dynamic amphipathicity of a PPO spacer that makes e-surfactants behave with excellent interfacial and solution properties for household cleaning. Therefore, this work gives us a hint that the molecular geometry of surfactants plays a vital role in interfacial and solution properties similar to molecular amphipathicity.
RESUMO
Steviol glycosides, a natural sweetener, may perform bioactivities via steviol, their main metabolite in human digestion. The metabolising kinetics, i.e. glucuronidation kinetics and interaction between steviol glycosides or their metabolites and metabolising enzyme, are important for understanding the bioactivity and cytotoxicity. The present study investigated kinetics of steviol glucuronidation in human liver microsome and a recombinant human UDP-glucuronosyltransferases isomer, UGT2B7, along with molecular docking to analyse interaction between UGT2B7 and steviol or glucose. The active pocket of UGT2B7 is consisted of Arg352, Leu347, Lys343, Phe339, Tyr354, Lys355 and Leu353. The influence of stevioside, rebaudioside A, glucose and some chemotherapy reagents on the glucuronidation was also studied. The predicted hepatic clearence suggested that steviol could be classified as high-clearence drug. The steviol glycosides did not affect the glucuronidation of steviol notably.
Assuntos
Diterpenos do Tipo Caurano/metabolismo , Glucose/metabolismo , Glucosídeos/metabolismo , Glucuronosiltransferase/metabolismo , Microssomos Hepáticos/metabolismo , Humanos , Cinética , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Proteínas RecombinantesRESUMO
The development of zinc-ion storage cathode materials for aqueous zinc-ion batteries (AZIBs) is a necessary step for the construction of large-scale electrochemical energy conversion and storage devices. Iron-doped alpha-manganese dioxide (α-MnO2) nanocomposites were achieved in this study via pre-intercalation of Fe3+ during the formation of α-MnO2 crystals. A polypyrrole (PPy) granular layer was fabricated on the surface of α-MnO2 using acid-catalyzed polymerization of pyrroles. The pre-intercalation of Fe3+ effectively enlarges the lattice spacing of α-MnO2 and consequently decreases the hindrance for Zn2+ insertion/extraction in the iron-doped α-MnO2 coated by PPy (Fe/α-MnO2@PPy) composite. Meanwhile, the PPy buffer layer can ameliorate electron and ion conductivity and prevent dissolution of α-MnO2during the charge/discharge process. This unique structure makes the Fe/α-MnO2@PPy composite an efficient zinc-ion storage cathode for AZIBs. The targeted Fe/α-MnO2@PPy cathode achieves superior performance with reversible specific capacity (270 mA h g-1 at 100 mA g-1) and exhibits highdiffusioncoefficientof 10-10-10-14 cm-2 s-1. Therefore, a feasible approach is implemented on advanced electrode materials using in AZIBs for practical applications.
RESUMO
Current understanding of the classical ABC model of floral development has provided a new set of characters to evaluate floral evolution. However, what is still lacking is a clear assessment of this genetic program across monocots. Here, to investigate the evolution of members of class A and B genes in monocots, we report the sequence characteristic and transcript expression of three new MADS-box genes in Alpinia oblongifolia Hayata. Sequence and phylogenetic analysis reveals that these genes are FUL-like and AP3-like. Therefore, they were termed AoFL1, AoFL2 and AoAP3. AoFL1 contains the FUL motif, but AoFL2 lacks this motif. Their expression revealed by in situ hybridization may reflect the ancestral function of FUL-like genes in the specification of inflorescence and floral meristems. The AoAP3 gene contains two conserved motifs, the PI-derived and paleoAP3 motifs. The AoAP3 transcripts located to the corolla and stamen, and hybridization signals were detected in the central whorl. These expression patterns suggest that the functions of homologous organ identity genes are diversified in A. oblongifolia. The implications of these findings on the conservation of homologous gene function are discussed.
Assuntos
Alpinia/genética , Flores/crescimento & desenvolvimento , Genes Homeobox , Proteínas de Domínio MADS/genética , Alpinia/crescimento & desenvolvimento , Sequência de Aminoácidos , Sequência de Bases , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Hibridização In Situ , Dados de Sequência Molecular , Família Multigênica , Filogenia , Alinhamento de Sequência , Análise de Sequência de DNARESUMO
In the title compound, C(8)H(13)N(2)O(2) (+)·Cl(-)·H(2)O, the methyl C atom of the ethyl group is slightly out of the imidazole plane, with an N-C(ring)-C-C torsion angle of -15.1â (2)°. In the crystal structure, there are strong inter-molecular hydrogen-bonding inter-actions between the solvent water mol-ecule, the free chloride anion and the organic cation, resulting in a two-dimensional supra-molecular network in the ab plane.
RESUMO
The authors studied the fluorescence change of immobilized lipase from Rhizomucor miehei in the microwave assisted enzymatic esterification of caprylic acid and butanol in organic medium by investigating the fluorescence spectra in solvent or aqueous buffer after incubating the lipase with the solvent, caprylic acid and butanol under microwave irradiation, respectively. A comparison was made with the conventional heated enzymatic esterification in the solvents. Both of the heating modes, the microwave irradiation and conventional heating, can enhance the fluorescence intensity without shifting the emission wavelength of the lipase. In the circumstance that the irradiation can accelerate the esterification, the irradiation can enhance the exposure of the lipase protein molecules in the aqueous environment after incubating the lipase with solvents or the substrates. The effect of the reaction mixture on the fluorescence intensity was dominated by the solvents. The trend of the plot of log P versus the initial reaction rate was similar to that of log P versus fluorescence intensity of lipase in aqueous buffer after esterification; but was different from that of log P versus fluorescence intensity of lipase in organic medium.
Assuntos
Lipase/metabolismo , Micro-Ondas , Compostos Orgânicos/química , Solventes/química , Butanóis/metabolismo , Caprilatos/metabolismo , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Esterificação/efeitos da radiação , Temperatura Alta , Cinética , Lipase/química , Rhizomucor/enzimologia , Espectrometria de FluorescênciaRESUMO
HYPOTHESIS: The properties of conventional surfactants (c-surfactants) are generally accepted to be amphipathicity-dominated, but extended surfactants (e-surfactants) are additionally polypropylene oxide (PPO)-dependent; this additional property makes us wonder how an intramolecular PPO spacer would be "extended" at various interfaces and what is responsible for the excellent all-round properties of e-surfactants. EXPERIMENTS: A series of novel sodium medium alkyl chain PPO-b-PEO sulfates (2-ethylhexyl polypropylene oxide-block-polyethylene oxide sulfates, C8PpEeS) were designed, synthesized and structurally identified. Tensiometry was applied to estimate the surfactant shape at the air/water surface. Surface tension, interfacial tension, emulsifying power, electrolyte tolerance, adsorption onto oil sands and thermal hydrolysis stability were measured to evaluate the effect of the PPO coil on the interfacial and micellar properties of the e-surfactants. FINDINGS: On the basis of obtaining greater values for e-surfactants than c-surfactants for both surface area (am) per surfactant molecule and the corresponding shape factor (S), we were surprised to find that e-surfactants form a rugby ball shape not only at the air/water surface but also at the oil/water interface; this result is potentially explained by the PPO spacer coiling and collapsing to produce dense packing at the monolayer adsorption, which is rationally borrowed by other interfaces. Many positive or negative correlations were observed between the interfacial/micellar properties of C8PpEeS and am values, which seems that the surfactant shape dominants the properties of the e-surfactants. In fact, the properties of C8PpEeS are dominated by the dynamic amphipathicity and assisted by the rugby ball shape of the molecules because of both being driven by the dynamic biphasic affinity of the PPO coil in response to the external environment; these findings provide soft interfacial materials specially adapted for surfactant flooding.
RESUMO
In the title compound, C(11)H(14)N(2)O(5), the nitro group is approximately coplanar with the benzene ring, making a dihedral angle of 4.26â (17)°. The dihedral angle between the methyl-carbamate group and the benzene ring is 72.47â (6)°. There is a strong inter-molecular N-Hâ¯O hydrogen bond between the N and O atoms from adjacent methyl-carbamate groups, forming a one-dimensional network along the a axis.
RESUMO
Steviol is the colonic metabolite of the natural sweetener steviol glycosides. It does not diffuse to the blood and the half maximal inhibitory concentration of steviol is longer compared with that of current chemotherapy agents, including 5-fluorouracil and doxorubicin. The present study demonstrated that steviol inhibits the proliferation of the human osteosarcoma U2OS cell line in a dose- and time-dependent manner, and that the inhibition rate is comparative with that of doxorubicin and 5-fluorouracil. The mechanism of this anticancer activity is also investigated. The results indicated that steviol inhibits U2OS cells through inducing G1 phase cell cycle arrest, downregulating the ability of colony formation via a mitochondrial apoptotic pathway, which was indicated by an increase of the Bax/Bcl-2 ratio and activation of cyclin-dependent kinase inhibitor 1, tumor protein 53 and cyclin-dependent kinase; whereas a Survivin and Caspase 3-independent mechanism was involved. Considering that steviol appears minimally in the plasma during metabolism, and possesses a median lethal dose of 100-fold greater compared with that of 5-fluorouracil, it may become a potential chemotherapy agent.
RESUMO
A ß-galactosidase from Kluyveromyces lactis was found to specifically catalyze hydrolysis of the glycosyl ester linkage of stevioside to yield steviolbioside, a rare sweetener that also exists in Stevia rebaudiana leaves. In a packed bed reactor, a reaction coupling separation was realized and a production yield of steviolbioside reached 90% in 6 h. The hydrolysis product steviolbioside presented higher cytoxicity on human normal cells (hepatocytes cell L02 and intestinal epithelial cell T84) than stevioside did. Comparing to the typical chemotherapy agent, 5-fluorouracil (5-FU), steviolbioside presents much lower cytotoxicity on all assayed human normal cells; it presented notable inhibition on human hepatocarcinoma cell Hep3B, human breast cancer cell MDA-MB-231 and human pancreatic cancer cell BxPC-3. The remarkable inhibition on MDA-MB-231 cells makes steviolbioside a potential remedy for human breast cancer, when steviolbioside is served as a natural sweetener.
Assuntos
Diterpenos do Tipo Caurano/química , Glucosídeos/química , Edulcorantes/química , beta-Galactosidase/química , HumanosRESUMO
Polysaccharides from Ganoderma lucidum (GLPs) have been taken as effective supplements by both healthy people and cancer patients for many years. However, this short survey indicates that instead of inhibiting cancer cell growth, both submerge-cultured intracellular GLP and fruiting body GLP can stimulate the growth of human carcinoma cell lines lacking functional p53, such as HCT-116 p53(-/-), Saos-2, H1299, HL-60, MDA-MB-157. Conversely, the two GLPs inhibit all other assayed cells with functional p53. These results could be an alert since mutational inactivation of the tumor suppressor protein p53 is the most frequent genetic alteration found in human tumors.
Assuntos
Carcinógenos/metabolismo , Medicamentos de Ervas Chinesas/administração & dosagem , Neoplasias/tratamento farmacológico , Polissacarídeos/administração & dosagem , Reishi/química , Proteína Supressora de Tumor p53/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Humanos , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/fisiopatologia , Deleção de Sequência , Proteína Supressora de Tumor p53/genética , Proteínas Supressoras de Tumor/genéticaRESUMO
The effect of four metal ions Cu(2+), Ni(2+), Zn(2+) and Co(2+) on the interaction between bovine serum albumin (BSA) and berberine chloride (BC) extracted from a traditional Chinese Herb coptis chinensis franch, was investigated mainly by means of UV and fluorescence spectroscopy in this paper. The four metal ions make the quenching efficacy of BC to BSA higher than that in the absence of these metal ions because of the possible transition of BSA molecular conformation caused by metal ions. It was found that the quenching mechanism is a combination of static quenching with nonradiative energy transfer. In the presence of metal ions, the apparent association constant K(A) and the number of binding sites of BC on BSA are both decreased in a range of 8-19% and 25-28%, respectively, which indicates that the metal ions decrease the binding efficacy of BC on BSA and increase the concentration of free BC simultaneously. The scheme of interaction between BC and BSA in the presence of metal ions is a strong quenching but a weak binding.
Assuntos
Berberina/química , Coptis/química , Medicamentos de Ervas Chinesas/química , Metais Pesados/química , Soroalbumina Bovina/química , Berberina/isolamento & purificação , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Ligação Proteica , Espectrometria de Fluorescência , Espectrofotometria UltravioletaRESUMO
The interaction between bovine serum albumin (BSA) a nd umbelliferone, an active component of Chinese herbs, with or without metal ions was investigated using fluorescence spectroscopy (FS) and UV. The experimental results showed that the umbelliferone molecules inserted into the hydrophobic pockets of BSA and quenched the intrinsic fluorescence of BSA by forming umbelliferone-BSA complex. The mechanism of fluorescence quenching was confirmed combining by both static quenching and nonradiative energy transferring. It was discovered that the apparent association constant (K(A)) increases in the presence of Cu2+ and Zn2+, whereas the spatial-distance (r) between umbelliferone molecule and fluorescent amino acid residues of the BSA and the binding sites (n) of umbelliferone molecules on BSA have no obviously change. Binding of umbelliferone molecules to BSA was a spontaneous supramolecular interaction in which entropy increased and Gibbs free energy decreaed. The interaction of the umbelliferone-BSA was driven mainly by electrostatic force which was enhanced by Cu2+ and Zn2+, thus the contribution of AH to AG increased in the presence of metal ions.
Assuntos
Cobre/química , Soroalbumina Bovina/química , Umbeliferonas/química , Zinco/química , Algoritmos , Animais , Bovinos , Cobre/metabolismo , Transferência de Energia , Fluorescência , Cinética , Modelos Químicos , Ligação Proteica , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Eletricidade Estática , Termodinâmica , Umbeliferonas/metabolismo , Zinco/metabolismoRESUMO
Enzymatic hydrolysis and transgalactosylation of stevioside (St) were investigated using a ß-galactosidase from Sulfolobus sp. The hydrolysis yielded steviol as the main final product. Under the optimal transgalactosylation conditions, the highest conversion of stevioside was 87.3% with lactose as a donor, several galactosylated products (St-Gals) were obtained. Metal ions such as Na(+), K(2+), Ca(2+), Ba(2+), Mn(2+) and Mg(2+) (2 mM) did not affect the transgalactosylation activity, while Fe(2+), Fe(3+) and Cu(2+) reduced the transgalactosylation activity of ß-galactosidase to 64%, 33% and 18%, respectively.
Assuntos
Diterpenos do Tipo Caurano/química , Glucosídeos/química , Sulfolobus/enzimologia , beta-Galactosidase/metabolismo , Hidrólise , Lactose/químicaRESUMO
Excessive extracellular matrix degradation caused by the hyperfunction of matrix metalloproteinases (MMPs) has been implicated in the failure of pressure ulcers healing. EMMPRIN, as a widely expressed protein, has emerged as an important regulator of MMP activity. We hypothesize that EMMPRIN affects the process of pressure ulcer healing by modulating MMP activity. In the rat pressure ulcer model, the expression of EMMPRIN in ulcers detected by Western blot was elevated compared with that observed in normal tissue. To investigate the role of EMMPRIN in regulating ulcer healing, specific antibodies against EMMPRIN were used via direct administration on the pressure ulcer. Local blockage of EMMPRIN resulted in a poor ulcer healing process compared with control ulcers, which was the opposite of our expectation. Furthermore, inhibiting EMMPRIN minimally impacted MMP activity. However, the collagen content in the pressure ulcer was reduced in the EMMPRIN treated group. Angiogenesis and the expression of angiogenic factors in pressure ulcers were also reduced by EMMPRIN local blockage. The results in the present study indicate a novel effect of EMMPRIN in the regulation of pressure ulcer healing by controlling the collagen contents and angiogenesis rather than MMPs activity.
Assuntos
Anticorpos/farmacologia , Proteínas Sanguíneas/antagonistas & inibidores , Úlcera por Pressão/metabolismo , Pele/efeitos dos fármacos , Cicatrização/efeitos dos fármacos , Proteínas Angiogênicas/metabolismo , Animais , Basigina/imunologia , Basigina/metabolismo , Proteínas Sanguíneas/imunologia , Proteínas Sanguíneas/metabolismo , Colágeno/metabolismo , Modelos Animais de Doenças , Masculino , Metaloproteinase 2 da Matriz/metabolismo , Metaloproteinase 9 da Matriz/metabolismo , Neovascularização Fisiológica , Úlcera por Pressão/imunologia , Úlcera por Pressão/patologia , Ratos Sprague-Dawley , Pele/irrigação sanguínea , Pele/imunologia , Pele/metabolismo , Pele/patologia , Fatores de TempoRESUMO
Specificity of glycosyl donors is a critical issue in transglycosylation of stevioside, the main methodology to improve edulcorant quality of stevioside. The most popular glucanotransferase applied in this reaction is cyclodextrin glucanotransferase (CGTase) that catalyses cyclisation, coupling, hydrolysis and disproportionation simultaneously; which results a crosstalk in the glycosyl donors that comes from initial reactants, reaction intermediates as well as side products in parallel reactions. In this work, the specificity of glycosyl donors was studied to understand the transglucosylation pathways with the designed experiments and material balance analysis on the products using a commercial CGTase. It has been found that cyclodextrins and starches provided the best transglucosylation yield, while the assayed mono- and disaccharides were not effective glycosyl donors to stevioside with the CGTase. It is proposed that α- and ß-cyclodextrins performed transglycosylation via coupling to produce intermediates of reducing sugar and followed by disproportionation with stevioside; while starches may perform the transglycosylation combined the cyclodextrins pathway and hydrolysis pathway of starches.
Assuntos
Diterpenos do Tipo Caurano/metabolismo , Glucosídeos/metabolismo , Glucosiltransferases/metabolismo , Edulcorantes/metabolismo , Catálise , Glicosilação , Hidrólise , Amido/químicaRESUMO
Medicinal mushroom polysaccharides such as Ganoderma lucidum polysaccharides (GLPs) have been commonly hypothesized to suppress tumor cells proliferation through immune effects. To verify this hypothesis through investigating comprehensive miRNA expression in polysaccharide treated cancer cells, an anticancer mycelia GLP was employed to disclose miRNA differential expression of human hepatocarcinoma cells (HepG2), by using a miRNA microarray assay based on Sanger miR-Base Release 16. The experiment and the analysis result indicates that among the 61 differential expressed miRNAs (p ≤ 0.01), 17 of them were regulated significantly. GLP can inhibit HepG2 cells directly through regulation of hepatocarcinoma genes. A newly found miR-3131 exhibited the strongest upregulation (92-folds, Log2 = 6.53, p = 0.000016). The miRNAs responded synergistically in both hepatocarcinoma and immune-related aspects.
Assuntos
Fermentação , MicroRNAs/metabolismo , Polissacarídeos/metabolismo , Reishi/metabolismo , Células Hep G2 , Humanos , MicroRNAs/genética , Polissacarídeos/química , Reishi/químicaRESUMO
The antitumor activity of intracellular polysaccharides from submerged fermentation of Ganoderma lucidum was investigated focusing on the inhibition on human liver cancer cells. The polysaccharides inhibited human hepatocarcinoma cell HepG2 during earlier phase with lower dosage but obviously became less functional in later phase regardless of the dosage applied. However, apoptosis of the drugged HepG2 cells appeared in later incubation phase with high dosage, and the apoptosis could be enhanced by supplemental dose of the intracellular polysaccharides. Nevertheless, the intracellular polysaccharides inhibited other human hepatocarcinoma cells such as BEL-7402 and Huh-7 but luckily stimulated human normal liver cell L02 only in a positive dose- and time-dependent manner; so did the sulfated extracellular polysaccharides when it inhibited HepG2 and L02 cells. However, the toxicity of sulfated extracellular polysaccharides to L02 cells can be eliminated by the intracellular polysaccharides.