Isolation and environmental adaptation of endophytic Actinomycetes in Acanthus ilicifolius of different mangrove

Abstract:

[Objective] To investigate geographical distribution of Acanthus ilicifolius endophytic actinomycetes of different mangrove regions, and their environmental adaptation. [Methods] Endophytic actinomycete strains were isolated from different part of Acanthus ilicifolius plant collected from 5 mangrove sites using 9 different selective isolation media. Isolates were identificated to genus level using 16S rRNA gene sequence analysis. NaCl tolerance was tested using ISP 2 liquid medium supplement with different NaCl concentrations. Potential of nitrogen-fixation isolates were surveyed using nitrogen-free medium. [Results] A total of 52 endophytic actinomycete strains were successfully isolated from Acanthus ilicifolius plant, among which 5 isolates were from surface- sterilized leaves, 2 isolates from stems and the re-maining 45 isolates were from roots. Analysis of 16S rRNA gene sequences of these isolates showed that they belonged to members of the genera Jishengella (1 isolate), Micromonospora (47 isolates), Streptomycetes (3 isolates) and Verrucosispora (1 isolate). Forty eight isolates were halo-tolerant or halophilic, including 18 isolates exhibited highest tolerance come up to 20% NaCl, 4 isolates can’t grow in salt-free medium, and 12 isolates exhibited good growth in presence of 3.3% NaCl. Meanwhile, 4 strains can grow on nitrogen-free medium that showed potential of nitrogen-fixation. [Conclusion] Analysis of 47 Micromonospora isolates from 5 mangrove locations indicated that there were different endophytic Micromonospora groups of Acanthus ilicifolius among different geographical sites. The results obtained revealed the en-vironmental adaptation of the Acanthus ilicifolius endophytic actinomycetes.