Patterns of sole-carbon-source utilization by fast-growing coastal sand dune rhizobia of the southwest coast of India

Abstract

Coastal sand dunes harbor a variety of free living and symbiotic microorganisms, which are adapted to stress conditions such as temperature, salinity and pH. The current paper explores the ability of sole-source-carbon utilization by symbiotic rhizobia isolated from tropical coastal sand dune wild legumes. Fast-growing rhizobia isolated from five legume plant species (Canavalia cathartica, Canavalia maritima, Crotalaria retusa, Crotalaria verrucosa, and Derris triflorum) grown on the two coastal sand dunes of the southwest coast of India (Someshwara, S1-S5; Padubidri, P1-P5) were assessed for sole-carbon-source utilization patterns based on BIOLOG GN2 microplate technique. All the isolates showed high extents of utilization of the different carbon sources within 24 h of incubation at 30 °C. Cluster analysis based on quantitative and qualitative utilization of a sole carbon source revealed two distinct clusters. Cluster I consists of four isolates (S1, P2, P4, and P5), of which P2 and P5 showed greater similarities. The cluster II encompasses six isolates (S2-S5, P1 and P3), among them S3 and S5 showed high similarities. Based on the utilization of six guilds by the isolates S1, S2, P1, and P2 (polymers, carbohydrates, carboxylic acids, amides and amines, amino acids and miscellaneous), S2 and P1 exhibited high functional diversity. Principal component analysis revealed a close catabolic potential between the isolates S5 and P1; S1 and P3; S3, P2, and P5. The symbiotic rhizobia of the southwest coastal sand dune wild legumes of India studied might serve as novel inoculants to achieve legume production through nitrogen fixation under the varied conditions of tropical soils. These rhizobia were able to utilize a wide range of carbon sources, possessed functional diversity, withstood extreme conditions (temperature, salinity, pH), exhibited non-host specificity and induced high biomass in edible legumes. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.