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. 2017 Mar 13:8:438.
doi: 10.3389/fmicb.2017.00438. eCollection 2017.

Exploring the Antimicrobial and Antitumor Potentials of Streptomyces sp. AGM12-1 Isolated from Egyptian Soil

Maged S Ahmad  1 , Ahmed O El-Gendy  2 , Rasha R Ahmed  3 , Hossam M Hassan  4 , Hussein M El-Kabbany  5 , Ahmed G Merdash  1
Affiliations

Exploring the Antimicrobial and Antitumor Potentials of Streptomyces sp. AGM12-1 Isolated from Egyptian Soil

Maged S Ahmad et al. Front Microbiol. .

Abstract

The occurrence of extensive antibiotics resistant bacteria increased the demands for mining out new sources of antimicrobial agents. Actinomycetes, especially Streptomyces sp. have grasped considerable attention worldwide due to production of many useful bioactive metabolites. In the present study, a total of 52 actinomycetes were isolated from agricultural soil samples in Beni-Suef, Egypt. All isolates were characterized based on colony morphology, mycelium coloration, and pigment diffusion. They were screened for their capabilities to show antimicrobial activities against different indicator microorganisms, and only 20 isolates have shown significant antimicrobial activities against at least one of the tested indicator microorganisms. The isolate AGM12-1 was active against all tested microorganisms and showed a marked antitumor activity with IC50 3.3 and 1.1 μg/ml against HCT-116 and HepG-2 cell lines respectively. It was genotypically characterized as Streptomyces sp. with the presence of PKS Π biosynthetic gene cluster. Mannitol, ammonium sulfate, pH 7, 2% inoculum size and incubation for 11 days at 30°C were the optimum conditions that used to maximize the production and hence allowed purification of one active antimicrobial compound to homogeneity using high performance liquid chromatography with a molecular mass of m/z 488.05. Nuclear magnetic resonance structural elucidation showed that this compound was a diketopiperazine derivative.

Keywords: Streptomyces sp.; Streptomyces vinaceusdrappus; actinomycetes; antimicrobial; antitumor; diketopiperazine.

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Figures

FIGURE 1
FIGURE 1
In vitro anti-tumor cytotoxicity bioassay. (A) Normal human liver cancer cell line (HepG2) while the effect of three tested concentrations 25, 50, 100 μg/ml of the AGM12-1 extract on the survival percent of HepG-2 are illustrated in (B–D), respectively.
FIGURE 2
FIGURE 2
Anti proliferative effect of total ethyl acetate extract, produced by AGM12-1, on HCT116 cell lines in vitro (A) and on HepG2 cell lines in vitro (B).
FIGURE 3
FIGURE 3
Phylogenetic tree of AGM12-1 isolate based on partial 16S rRNA gene sequences. The phylogenetic tree was inferred using the Neighbor-Joining method (Saitou and Nei, 1987). The distances were computed using the Kimura 2-parameter method (Kimura, 1980) and are in the units of the number of base substitutions per site. Numbers at nodes indicate percentages of 1000 bootstrap re-samplings, only values above 50% are shown. The analysis involved 20 nucleotide sequences. Codon positions included were 1st+2nd+3rd+Noncoding. All positions containing gaps and missing data were eliminated. There were a total of 827 positions in the final dataset. Evolutionary analyses were conducted in MEGA7 (Kumar et al., 2016).
FIGURE 4
FIGURE 4
High performance liquid chromatography (HPLC) chromatograms of a re-purified sample using a Nucleosil C18 column showing the active compound eluted at 20.32 min (fraction tube number 18).
FIGURE 5
FIGURE 5
Nuclear magnetic resonance (NMR) spectrum of antimicrobial and antitumor agent produced by Streptomyces sp. AGM12-1.
FIGURE 6
FIGURE 6
Chemical structure of the identified compound (a derivative of diketopiperazine) from Streptomyces sp. AGM12-1.
See this image and copyright information in PMC

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