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. 2018 Dec;26(8):1089-1097.
doi: 10.1016/j.jsps.2018.05.019. Epub 2018 May 31.

Identification and characterization of a novel antimicrobial peptide compound produced by Bacillus megaterium strain isolated from oral microflora

Abdullah S A Al-Thubiani  1 , Yahia A Maher  2   3 , Adel Fathi  4   5 , Mohammed A S Abourehab  6   7 , Mohammed Alarjah  8 , Mohd S A Khan  9 , Saleh B Al-Ghamdi  10
Affiliations

Identification and characterization of a novel antimicrobial peptide compound produced by Bacillus megaterium strain isolated from oral microflora

Abdullah S A Al-Thubiani et al. Saudi Pharm J. 2018 Dec.

Abstract

In recent years, the decreased efficacy of existing antibiotics toward management of emergent drug-resistant strains has necessitated the search for novel antibiotics from natural products. In this regard, Bacillus sp is well known for producing variety of secondary metabolites of potential use. Therefore, we performed an investigation to isolate and identify Bacillus sp from oral cavity for production of novel antimicrobial compounds. We extracted, purified, and identified a novel bioactive compound by B. megaterium (KC246043.1). The optimal production of compound was observed on de Man Rogosa and Sharpe broth by incubating at 37 °C, and pH 7.0 for 4 days. The bioactive compound was extracted by using n-butanol (2:1 v/v), purified on TLC plates with detection at Rf 7.8 cm; further characterized and identified as a cyclic ploypeptide sharing structural similarity with bacitracin. Minimum inhibitory concentration of bioactive compound was found to be 0.25, 0.5, 1.0, 3.125 and 6.25 μg/ml against Micrococcus luteus ATCC10240, Salmonella typhi ATCC19430, Escherichia coli ATCC35218. Pseudomonas aeruginosa ATCC27853 and Staphylococcus aureus ATCC25923 respectively, with no activity against Candida albicans ATCC10231. Our findings have revealed a novel cyclic peptide compound from B. megaterium with broad spectrum antimicrobial activity against both Gram positive and Gram negative bacteria.

Keywords: Antibacterial; Bacillus megaterium; Bacitracin; Drug discovery; Peptide antibiotics.

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Figures

Fig. 1
Fig. 1
Phylogenetic tree for 16S rRNA sequence of the strain B. megaterium using the neighbor-joining method.
Fig. 2
Fig. 2
Separation of the crude antimicrobial components obtained from the B. megaterium supernatant on TLC plate.
Fig. 3
Fig. 3
FTIR spectrum of bacitracin standard and purified active antimicrobial components produced by the strain B. megaterium.
Fig. 4
Fig. 4
Bacitracin peptide sequencing and chemical structure.
Fig. 5
Fig. 5
HPLC analysis of (a) bacitracin standard (b) purified active antimicrobial components produced by the strain B megaterium.
Fig. 6
Fig. 6
1H NMR spectrum of the purified active antimicrobial components (lower) and the standard bacitracin zinc (upper).
Fig. 7
Fig. 7
Predicted structure of active antibacterial compound isolated from the strain B. megaterium based on 1H NMR data.
See this image and copyright information in PMC

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