Isolation and characterization of multifunctional Streptomyces species with antimicrobial, nematicidal and phytohormone activities from marine environments in Egypt

Abstract

Different strategies have been employed for selective isolation of Streptomycetes from 20 marine samples varied in their biological nature. The recovery of Streptomycetes isolates (112) was influenced preferentially by different strategies; sediment samples were the best source of potential candidate Streptomycetes. All isolates exhibited antimicrobial activities with variable spectrum; the most promising isolates (31) were phenotypically characterized and identified as Streptomyces sp.; these isolates exhibited variable capacity for secretion of numerous hydrolytic enzymes such as catalase, protease, amylase, lipase, lecithinase, asparaginase, chitinase and pectinase. All the strains resisted both penicillin and streptomycin, 29 were sensitive to neomycin; the majority of strains (25) showed multiple antibiotic resistance index greater than 0.2; 23, 22 and 13 degraded the shrimp shell, chicken feather and corn cob, respectively, producing bioactive substance(s) which indicates their diversity and their ecological role in the marine ecosystem. At least 28 strains exhibited nematicidal activity in vitro and in vivo against root-knot nematode and supported plant growth. In vitro, the assessed Streptomyces species exhibited the ability to produce gibberellic acid, indole acetic acid, abscisic acid, kinetin and benzyladenine. Except for indole acetic acid, this is the first report concerning the ability of marine Streptomyces to produce such phytohormones and the use of shrimp shell waste as a mono component medium for production of phytohormones. The study is efficacious in selecting effective biodiverse strains of marine Streptomyces that may work under diverse agro-ecological conditions as a useful element in plant nutrition and as biocontrol agents involved in integrated management programs.

Keywords: Antimicrobial activity; Biodegradation; Marine Streptomyces; Nematicidal activity; Phytohormones.