Antioxidant and antimicrobial potential of the Bifurcaria bifurcata epiphytic bacteria.

Rui Pedrosa,André Horta,Nádia Fino,Celso Alves,Susete Pinteus,Joana Silva,Sara Fernandez,Américo Rodrigues

doi:10.3390/md12031676

Abstract

Surface-associated marine bacteria are an interesting source of new secondary metabolites. The aim of this study was the isolation and identification of epiphytic bacteria from the marine brown alga, Bifurcaria bifurcata, and the evaluation of the antioxidant and antimicrobial activity of bacteria extracts. The identification of epiphytic bacteria was determined by 16S rRNA gene sequencing. Bacteria extracts were obtained with methanol and dichloromethane (1:1) extraction. The antioxidant activity of extracts was performed by quantification of total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC). Antimicrobial activities were evaluated against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Salmonella enteritidis, Staphylococcus aureus, Saccharomyces cerevisiae and Candida albicans. A total of 39 Bifurcaria bifurcata-associated bacteria were isolated and 33 were identified as Vibrio sp. (48.72%), Alteromonas sp. (12.82%), Shewanella sp. (12.26%), Serratia sp. (2.56%), Citricoccus sp. (2.56%), Cellulophaga sp. (2.56%), Ruegeria sp. (2.56%) and Staphylococcus sp. (2.56%). Six (15.38%) of the 39 bacteria Bifurcaria bifurcata-associated bacteria presented less than a 90% Basic Local Alignment Search Tool (BLAST) match, and some of those could be new. The highest antioxidant activity and antimicrobial activity (against B. subtilis) was exhibited by strain 16 (Shewanella sp.). Several strains also presented high antimicrobial activity against S. aureus, mainly belonging to Alteromonas sp. and Vibrio sp. There were no positive results against fungi and Gram-negative bacteria. Bifurcaria bifurcata epiphytic bacteria were revealed to be excellent sources of natural antioxidant and antimicrobial compounds.

Highlights

The marine environment is extremely complex and contains a huge diversity of life forms, which is a huge source of biological and chemical diversity [1,2,3]
Like macro-algae, this association is an important strategy of survival in the environment where they live, since it is known that marine microorganisms strengthen the host defense mechanism by producing various kinds of secondary metabolites
39 phenotypic different bacteria from the Bifurcaria bifurcata surface were isolated, and the strains were subjected to molecular identification using 16S rRNA gene sequencing

Summary

Introduction

The marine environment is extremely complex and contains a huge diversity of life forms, which is a huge source of biological and chemical diversity [1,2,3]. The surfaces of marine eukaryotes provide a unique habitat for microorganisms colonization, where competition between members of these communities and chemically-mediated interactions with their host are thought to influence both microbial diversity and function [8] This close association of marine eukaryotes with microorganisms improves their physiological capacities, mainly providing microbial defenses [9]. Like macro-algae, this association is an important strategy of survival in the environment where they live, since it is known that marine microorganisms strengthen the host defense mechanism by producing various kinds of secondary metabolites. Many of these metabolites have been recognized to be rich in chemical and biological properties [10,11]. In recent years, microorganisms associated with the surfaces of marine eukaryotes have been major targets for the discovery of new bioactive metabolites [15]

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Results

Conclusion