Antimicrobial and Antioxidant Properties of a Bacterial Endophyte, Methylobacterium radiotolerans MAMP 4754, Isolated from Combretum erythrophyllum Seeds

Abstract

is study reports on the isolation and identification of Methylobacterium radiotolerans MAMP 4754 from the seeds of the medicinal plant, Combretum erythrophyllum, for the purposes of investigating antimicrobial and antioxidant activities from this endophyte. e strain identity was confirmed by 16S rRNA-based phylogeny and Scanning Electron Microscopy (SEM). Ethyl acetate and chloroform (1 : 1 v/v) extracts from the endophyte were tested for antimicrobial and antioxidant activity on a total of 7 bacterial species (3 Gram-positive and 4 Gram-negative) using the standard Minimum Inhibitory Concentration (MIC) protocol and Quantitative Radical Scavenging activity using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay, respectively. e MICs were recorded at 250 μg/mL for B. subtilis ATCC 19659, B. cereus ATCC 1076, E. coli ATCC1053, and 62.5 μg/mL for K. oxytoca ATCC 13182 and M. smegmatis ATCC 21293, while an IC 50 of 5.65 μg/mL was recorded with the DPPH assay. Qualitative phytochemical analysis was positive for alkaloids, flavonoids, and steroids. Gas chromatography/mass spectrometry (GC/MS) analysis revealed the presence of 9-octadecene, 2,4-dinitrophenyl acetate, and 2(5H)-furanone, which have been previously reported for the targeted activities. M. radiotolerans MAMP 4754 tested positive for antimicrobial and antioxidant activity and this is linked to the production of plant-derived secondary metabolites by this strain. with only 3% of these being antimicrobial [4]. e pharmaceutical properties of medicinal plants have been linked to the production of a wide variety of structurally diverse phytochemicals which include alkaloids, flavonoids, terpenes, steroids, curcumins, saponins, and phenolics, all of which can potentially serve as drug lead candidates for the development of antimicrobials and resistance modifiers [5,6].According to the International Union for Conservation of Nature and the World Wildlife, there are an estimated 80 000 recognized medicinal flowering plant species globally,

Antimicrobial activity, phytochemical characterization and gas chromatography-mass spectrometry analysis of Aspilia pluriseta Schweinf. extracts

“…The MIC and MMC of A. pluriseta solvent fractions were analyzed as previously described [ 36 , 57 , 60 , 61 , 63 ]. Briefly, 50 μL of varying fraction concentrations (3.9–500 μg/mL petroleum ether, dichloromethane, and methanol; 1.95–250 μg/mL ethyl acetate) were added into 100 μL of nutrient broth held in a sterile 96-well plate followed by addition of 50 μL test organisms adjusted to 0.5 McFarland standard.…”

Contact Effect of a Methylobacterium sp. Extract on Biofilm of a Mycobacterium chimaera Strain Isolated from a 3T Heater-Cooler System

“…This antibiofilm effect has also been described in other rapidly growing non-tuberculous mycobacteria, such as Mycobacterium abscessus , Mycobacterium fortuitum , and Mycobacterium chelonae [ 35 ]. This antibacterial effect has been described in other Methylobacterium strains, for instance, the ERI-135 strain isolated from the soil whose ethyl acetate extract inhibited the growth of bacteria such as Bacillus subtilis , Klebsiella pneumoniae , Pseudomonas aeruginosa , Salmonella typhimurium , Shigella flexneri , Enterobacter aerogenes , Staphylococcus aureus and S. epidermidis and fungi, such as Candida albicans and Trichophyton rubrum [ 38 ]; the Methylobacterium radiotolerans MAMP 4754 isolated from the seeds of the river bushwillow ( Combretum erythrophyllum (Burch.) Sond), whose ethyl acetate and chloroform extracts also showed antibacterial effect on B. subtilis, B. cereus, Escherichia coli, K. oxytoca, and Mycobacterium smegmatis [ 40 ]; and Methylobacterium extorquens DSM13060, an intracellular meristem endophyte of scots pine ( Pinus sylvestris L.), whose defensin-like antimicrobial peptide MB1533 showed an inhibitory effect on S. aureus and B. subtilis [ 37 ].…”

“…Methylobacterium is a genus from Alphaproteobacteria isolated by Patt et al [ 34 ] that is a strictly aerobic bacterium and forms small rose colonies at its optimal growth temperature (25 °C) and usually inhabits water distribution systems [ 32 , 35 ]. Some strains of Methylobacterium genus have already demonstrated antibacterial effect against different microorganisms, both Gram-positive and Gram-negative bacteria [ 36 , 37 , 38 ], including mycobacteria [ 33 ], and fungi [ 36 ].…”

Microorganisms: A Potential Source of Bioactive Molecules for Antioxidant Applications

“…Sy et al [ 87 ] isolated Bacillus indicus HU36, producing carotenoids from human fecal and assessed the stability (sensitivity to iron-induced autoxidation) and antioxidant activity (inhibition of iron-induced lipid peroxidation). Photolo et al [ 88 ] reported Methylobacterium radiotolerans MAMP 4754 (IC 50 of 5.65 μg/mL) contains 9-octadecene, 2,4-dinitrophenyl acetate, and 2(5H)-furanone that can scavenge ROS [ 88 ]. Violacein, a purple pigment is a potent antioxidant primarily produced by Chromobacter violaceum and Pseudoalteromonas , stimulating mucosal defense mechanisms for protection against oxidative damage due to gastric ulcers [ 34 ].…”

“…Whenever there is a discussion about fungal metabolites, the story of penicillin has been told many times. Alexander Fleming, in 1929 discovered that mold juice’ from Penicillium notatum had antibacterial action and named this biological activity “Penicillin” [ 88 ]. In the past few years, researchers instigated to look for a fungal strain that could be grown quickly and produce bioactive metabolites in submerged culture.…”