Arthospira platensis and Bacillus subtilis Synergies for Sustainable Agriculture

Abstract

The aim of this study is to analyze the biofertilizer value of B. subtilis by estimating its phosphate solubilizing potential and its antagonistic activity against pathogenic strains of E. coli and Bacillus cereus. Prolonged use of chemical fertilizers have adverse effects on the soil and through food chain they cause hazards to organisms including humans. Moreover pests and pathogenic microbes are becoming immune to the chemical pesticides and herbicides. Hence the need of biofertilizers that are ecofriendly and good biocontrol agents are gaining importance. Use of biofertilizers leads us towards the path of sustainable agriculture yielding better productivity without compromising the fertility of agricultural fields. Bacillus subtilis is a PGPR (Plant growth promoting rhizobacteria) capable of phosphate and zinc solubilizing and it increases the bioavailability of nutrients to the plants. Due to its antagonistic nature, B. subtilis can be utilized in biocontrol management practices. Arthospira platensis is a well explored microalgal species that is rich in micronutrients and a wide array of amino acids that has immense biofertilizer value. The methodology involves UV spectrometric estimation of bioavailable phosphate in Pikovskaya’s broth at 690nm and percentage of inhibition of B. subtilis against E. coli and Bacillus cereus using OD600values. Evidences for utilizing mixed culture of A. platensis and B. subtilis as biofertilizer are explored from literature. B. subtilis strain AMLA5 isolated from oil contaminated soil from Coimbatore had phosphate solubilizing potential of 1.3ppm and showed good antagonistic effects against E. coli and B. cereus. The NCBI genebank accession number of the strain SUB13179211 AMLA5 is OQ874086 that showed 99.77% sequence identical to Bacillus subtilis. This strain was a surfactin producer that utilized A. platensis as its economical substrate. A. platensis & B. subtilis are GRAS level organisms that can be utilized in agriculture as biofertilizer as mixed culture. The synergism existing between these two organisms can be exploited in multiple sectors