scholarly journals Knockout of an Azorhizobial dTDP-L-Rhamnose Synthase Affects Lipopolysaccharide and Extracellular Polysaccharide Production and Disables Symbiosis with Sesbania rostrata

2001 ◽  
Vol 14 (7) ◽  
pp. 857-866 ◽  
Author(s):  
Mengsheng Gao ◽  
Wim D'Haeze ◽  
Riet De Rycke ◽  
Beata Wolucka ◽  
Marcelle Holsters
Keyword(s):  
Uv Light ◽  
Light And Electron Microscopy ◽  
Extracellular Polysaccharide ◽  
Sesbania Rostrata ◽  
Peripheral Tissues ◽  
Polysaccharide Production ◽  
Phenol Extraction ◽  
Infection Threads ◽  
Ineffective Nodule ◽  
Bacterial Hydrophobicity

A nonpolar mutation was made in the oac2 gene of Azorhizobium caulinodans. oac2 is an ortholog of the Salmonella typhimurium rfbD gene that encodes a dTDP-L-rhamnose synthase. The knockout of oac2 changed the lipopolysaccharide (LPS) pattern and affected the extracellular polysaccharide production but had no effect on bacterial hydrophobicity. Upon hot phenol extraction, the wild-type LPS partitioned in the phenol phase. The LPS fraction of ORS571-oac2 partitioned in the water phase and had a reduced rhamnose content and truncated LPS molecules on the basis of faster migration in detergent gel electrophoresis. Strain ORS571-oac2 induced ineffective nodule-like structures on Sesbania rostrata. There was no clear demarcation between central and peripheral tissues, and neither leghemoglobin nor bacteroids were present. Light and electron microscopy revealed that the mutant bacteria were retained in enlarged, thick-walled infection threads. Infection centers emitted a blue autofluorescence under UV light. The data indicate that rhamnose synthesis is important for the production of surface carbohydrates that are required to sustain the compatible interaction between A. caulinodans and S. rostrata.

scholarly journals Effect of medium pH and cultivation period on mycelial biomass, polysaccharide, and ligninolytic enzyme production by Ganoderma lucidum from Montenegro

2006 ◽  
Vol 58 (3) ◽  
pp. 179-182 ◽  
Author(s):  
Jelena Vukojevic ◽  
Mirjana Stajic ◽  
Sonja Duletic-Lausevic ◽  
Jasmina Simonic
Keyword(s):  
Ganoderma Lucidum ◽  
Enzyme Production ◽  
Ligninolytic Enzymes ◽  
Extracellular Polysaccharide ◽  
Ligninolytic Enzyme ◽  
Extracellular Polysaccharides ◽  
Medium Ph ◽  
Polysaccharide Production ◽  
Intracellular Polysaccharide ◽  
Maximal Production

The effect of initial medium pH on biomass, extracellular and intracellular polysaccharide, and ligninolytic enzyme production by Ganoderma lucidum was investigated at different pH values after 7 and 14 days of cultivation. Maximal production of biomass was recorded at pH 4.5 and 5.0; maximal production of extracellular polysaccharides at pH 7.0 and 3.0; and maximal production of intracellular polysaccharides at pH 7.0 and 5.5. Ligninolytic enzymes were not produced at any pH of the medium. Maximal biomass production was obtained on the 11th day of cultivation; maximal extracellular polysaccharide production on the 7th day; and maximal intracellular polysaccharide production on the 6th and 10th day of cultivation. .

Nodulation competitiveness of Tn5-induced mutants of Rhizobium fredii USDA208 that are altered in motility and extracellular polysaccharide production

1991 ◽  
Vol 37 (1) ◽  
pp. 52-58 ◽  
Author(s):  
Robert E. Zdor ◽  
Steven G. Pueppke
Keyword(s):  
Parental Strain ◽  
Extracellular Polysaccharide ◽  
Triphenyltetrazolium Chloride ◽  
Polysaccharide Production ◽  
Production Type ◽  
Rhizobium Fredii ◽  
Induced Mutants ◽  
Nodulation Competitiveness

The role of motility and extracellular polysaccharide production in nodulation competitiveness of Rhizobium fredii was examined. Transposon Tn5 was used to mutagenize strain USDA208, and mutants with reduced motility on semisolid agar medium were isolated. One such mutant, 208M3, migrated to only one-seventh the distance of the parental strain. Solid medium amended with triphenyltetrazolium chloride was used to identify mutants altered in extracellular polysaccharide production. Type 1 colonies, typified by mutant 208T13, were heavily mucoid, while type 2 colonies, represented by mutant 208T3, were dry and nonmucoid. Compared with strain USDA208, these mutants produced 4- to 5-fold more extracellular polysaccharide and 20% as much extracellular polysaccharide, respectively. Marker exchange of 208T3 genomic DNA containing Tn5 into strain USDA208 resulted in a mutant, 208K1, that produced extracellular polysaccharide levels similar to mutant 208T3. Mutants 208M3, 208T3, and 208T13 contained single Tn5 insertions. All formed pink nodules on 'Peking' soybean that were structurally indistinguishable and contained proteins with similar profiles. Rates of nodulation were similar in the mutants and the parental strain. Mutants 208M3 and 208T13 were as competitive against an isolate of Bradyrhizobium japonicum serogroup 123 as was strain USDA208. In contrast, mutants 208T3 and 208K1 were competitively superior. Key words: nodulation competition, motility, extracellular polysaccharide, Rhizobium.

Ontogenèse des nodules caulinaires du Sesbania rostrata (légumineuses)

1984 ◽  
Vol 62 (5) ◽  
pp. 982-994 ◽  
Author(s):  
E. Duhoux
Keyword(s):  
Sesbania Rostrata ◽  
Cortical Cells ◽  
Root Cortex ◽  
Central Mass ◽  
Intracellular Release ◽  
Infection Threads ◽  
Bacterial Penetration ◽  
Infected Cells ◽  
Determinate Growth

Stem nodules of the legume Sesbania rostrata are ovoids, contain chlorophyll and have determinate growth. They possess a large central mass of infected cells. Stem mamillae are regularly arranged in vertical files along the stem and develop into nodules when they are infected by a specific Rhizobium. Each nodule arises from the development of an infected region of the incipient root cortex. The infection in S. rostrata has been shown to proceed in four sequential stages. Some of them have never been shown to occur in other legumes: (i) bacterial penetration takes place in degenerated (dead) cortical cells; (ii) proliferation of the bacteria occurs in the intercellular cavities and initiates a meristematic nodule; (iii) protusion of infection threads at first occurs intercellularly and then intracellularly from the cavities; (iv) finally there is an intracellular release of Rhizobia by an endocytotic process.

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