Genetic and metabolic diversity of streptomycetes in pulp and paper mill effluent treated crop fields

Irrigation of farm field with water mixed with pulp and paper mill effluent from Century pulp and paper mill in Uttrakhand state of India for over last 25 years in succession increased streptomycetes population (120 × 105) compared to the fresh water irrigated fields (48 × 103 in WIF). Denaturing gradient gel electrophoresis, amplified ribosomal DNA restriction analysis, 16S rRNA gene sequencing, BIOLOG™ substrate usage, production of extracellular enzymes (xylanase and cellulase) and plant growth promoting attributes were applied to monitor changes in genetic and metabolic diversity of streptomycetes. Significant variation was observed for production of extracellular enzymes, Indolic compounds, siderophore and P-solubilisation among isolates. Metabolic substrate usage of Streptomyces isolates was evaluated using the BIOLOG™ GP2 plates and unique carbon substrate usage profiles were observed. Based on 16S rRNA gene sequencing, the isolates were identified as Streptomyces variabilis, Streptomyces spp. S. glaucescens, S. viridochromogenes, S. cinnabarinus, S. aburaviensis, S. viridis, S. xylophagus, S. macrosporeus, S. thermocarboxydus, and S. albogriseolus. The diversity index parameters like Shannon index, reciprocal of Simpson’s index (1/D), and Pielou index of evenness based on ARDRA revealed that streptomycetes community in effluent irrigated field (EIF) was more diverse. DGGE profiles of Streptomyces specific 16S rRNA gene fragments (16S-DGGE) amplified directly from soil samples were highly similar in both soils.