Abstract

Mangrove plants are located on coastal area of sea and harbor diverse communities of microorganisms. The aim of our present study was to isolate bacteria from two different mangroves collected from the coastal area of Thuwal, Saudi Arabia and to further screen them for their antimicrobial activities. We have isolated 317 different rhizo and endophytic bacteria from mangroves using soil, roots and leave tissues. Bacteria were screened for their antifungal activities against oomycetes pathogens, Phytophthora capsici, Pythium ultimum. Only 25 bacterial strains found to be active against oomycetes fungal pathogens. These bacteria were tested further against other fungal pathogens like Magnaporthe grisea, Altenaria malli, and Fusarium oxysporum. Antagonistic bacteria were further screened for antibacterial activities against human pathogenic bacteria. Only few isolates exhibited antagonistic activity against these pathogenic bacteria. Hydrolytic enzymes production (cellulase, protease, lipase, and amylase) was also assessed. Most of the active isolates exhibited amylase and protease activities. Identification based on 16S rRNA gene revealed 92.8 to 99.9% sequence, similar to type strains of related species. Antagonistic bacteria belong to 5 different classes that is Gammaproteobacteria (γ-Proteobacteria), Alphaproteobacteria (α-Proteobacteria), Firmicutes, Bacteroidetes and Actinobacteria. Our results provide evidence that, mangroves plants harbor potentially useful bacteria producing active metabolites and enzymes.

Key words: Mangrove plants, antagonistic bacteria, enzymatic activities, 16S rRNA gene sequence, phylogenetic analysis.