Asian Journal of Bio Science

E. Prabhavati ¹, K. V. Mallaiah ¹

Affiliations
1 Department of Microbiology, Acharya Nagarjuna University, Nagarjunanagar, Guntur (A.P.), IN

Abstract

The ability of thirty two Rhizobium strains, isolated from ischolar_main nodules of Macrotyloma uniflorum (Lam.) Verdc. were tested for their production of extracellular polysaccharides (EPS) in Yeast Extract Mannitol (YEM) medium. Among the thirty two isolates, maximum amount of EPS was produced by the isolate HGR12 (4690 μg mL^-1). Both growth and EPS production started simultaneously. The production of EPS was maximum in the stationary phase of growth (72 hr) when the medium was supplemented with mannitol (1%). The EPS contained glucose, galactose, xylose, rhamnose and raffinose, which were identified by paper chromatography.

Keywords

Extracellular Polysaccharides, Rhizobium Sp., Macrotyloma uniflorum, Legume-Rhizobium Association.

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E. Prabhavati ¹, K. V. Mallaiah ¹

Affiliations
1 Department of Microbiology, Acharya Nagarjuna University, Nagarjuna Nagar, Guntur (A.P.), IN

Abstract

Thirty two Rhizobium strains isolated from ischolar_main nodules of Macrotyloma uniflorum (Lam.) Verdc. showed siderophore production on Chrome-Azurol S agar medium. Ten Rhizobium strains which showed varying siderophore production at control (without salt) were selected to study the effect of salt concentration on siderophore production. These strains showed low siderophore production at control and it increased with increasing salt concentration up to 1000mM by the strain HGR23 (80μg/mL^-1) while two strains HGR16 and HGR30 showed at 400mM concentration. Salt stress enhanced maximum siderophore production (90 μg/mL^-1) by the strains HGR5 and HGR8 at 600mM salt concentration over control. Later, the siderophore production decreased with increasing salt concentration. The strains HGR1, HGR4, HGR7, HGR12 and HGR18 showed maximum production at 800mM salt concentration (60.7 μg/mL^-1 to 70.8 μgmL^-1). Paper Electrophoresis of the siderophore extract showed the presence of trihydroxamate type of siderophores.

Keywords

Siderophore Production, Salt Concentration, Rhizobium species, Macrotyloma uniflorum.

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M. Sridevi ¹, K. V. Mallaiah ¹

Affiliations
1 Department of Microbiology, Acharya Nagarjuna University, Nagarjuna Nagar (A.P.), IN

Abstract

Twenty six Rhizobium strains isolated from ischolar_main nodules of Sesbania sesban (L.) Merr. were studied for their ability to produce siderophores. Of them, only nine strains have the ability to produce catechol-type of siderophores in culture after 4 h of incubation and at neutral pH. Mannitol and sucrose at the concentration 2% stimulated growth and siderophore production. Among nitrogen sources, arginine and proline stimulated growth and siderophore production. Maximum amount of siderophores was produced by SSR 19. 2, 3-dihydroxy benzoic acid (DHBA) was present in siderophore extract of this strain. Arginine and proline were identified as conjugated amino acids of the siderophore. The outer membrane protein profiles of the SSR 19 grown in iron containing medium revealed the presence of single protein band of molecular mass 40 K Da.

Keywords

Siderophore Production, 2,3-DHBA, Sesbania sesban, Rhizobium Species.

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