A total of 168 actinomycete colonies were isolated from 14 sediment samples of the northern parts of the Oman Sea and were screened for cytotoxic and antimicrobial activity. Among four media and two treatments, the glucose arginine agar medium (18%) and heat treatment (28.3%) showed maximum isolation rate of actinomycetes. Preliminary characterization revealed that the members of Streptomycetaceae were widely distributed (66%) in the most of the sampling stations followed by Micromonosporaceae (14%), Nocardiaceae (6%), and Pseudonocardiaceae (4%), respectively. Approximately, 23.8% of the isolates inhibited the growth of at least one of the microbial test strains, while the majority of them belonged to the Streptomycetaceae family. Minimum inhibitory concentrations of the ethyl acetate culture extracts of the five most putative isolates varied from 64 μg/mL against Micrococcus luteus and Candida albicans to 1 mg/mL against Aspergillus niger. These extracts showed significant cytotoxic activity at18.74–193.5 μg/mL on the human breast (MCF7), colon (HCT 116), and liver (HepG2) tumor cell lines while exhibited less or no cytotoxicity on the normal cell line (HUVEC). Interestingly, IFSRI 193 extract selectively inhibited the growth of HCT 116 cell line and gram-positive bacteria. 16S rRNA gene sequencing revealed that the potent isolates have 97 to 99% similarity with S. chartreusis, S. cacaoi, S. sampsonii, S. qinglanensis, and S. diastaticus. These results suggested that the five Streptomyces strains could be considered candidates for discovering the antitumor antibiotics.

中文翻译：

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从阿曼北部沉积物中海洋放线菌的细胞毒性和抗菌活性的筛选和表征。

从阿曼海北部的14个沉积物样品中分离出总共168个放线菌菌落，并对其细胞毒性和抗菌活性进行了筛选。在四种培养基和两种处理中，葡萄糖精氨酸琼脂培养基（18％）和热处理（28.3％）显示了放线菌的最大分离率。初步鉴定显示，链菌科的成员在大多数采样站中分布广泛（66％），其次是微单孢菌科（14％），诺卡氏菌（6％）和假心卡菌（4％）。约有23.8％的分离物抑制了至少一种微生物测试菌株的生长，而其中大多数属于链霉菌科。五个最推定的分离物的乙酸乙酯培养物提取物的最低抑菌浓度从对微球菌和白色念珠菌的64μg / mL到对黑曲霉的1 mg / mL 。这些提取物对人乳腺癌（MCF7），结肠癌（HCT 116）和肝癌（HepG2）肿瘤细胞系显示出明显的细胞毒性活性，为18.74–193.5μg/ mL，而对正常细胞系（HUVEC）则显示出较少或没有细胞毒性。 。有趣的是，IFSRI 193提取物选择性抑制HCT 116细胞系和革兰氏阳性细菌的生长。16S rRNA基因测序表明，强效分离株与S具有97％到99％的相似性。黄绿色，S. cacaoi，S.元宝，S. qinglanensis，和S.道格拉氏。这些结果表明，五种链霉菌菌株可以被认为是发现抗肿瘤抗生素的候选药物。