Girma Daniel, Feyisa Abu, Chaluma Ebisa, Mulu Daniel, Geta Selamawit, Tafesse Mesfin
Department of Biotechnology, Addis Ababa Science and Technology University, Addis Ababa, Ethiopia.
Biotechnology and Bioprocess Center of Excellence, Addis Ababa Science and Technology University, Addis Ababa, Ethiopia.
BMC Microbiol. 2025 Apr 23;25(1):236. doi: 10.1186/s12866-025-03959-9.
Actinomycetes are a diverse group of filamentous, Gram-positive bacteria recognized for their ability to produce various secondary metabolites, including pigments. These pigments have various industrial applications and safe alternatives to synthetic pigments associated with adverse side effects. This study aimed to investigate pigment-producing Actinomycetes from Sof-Umer cave rock and sediment samples, focusing on their potential applications.
Thirty isolates of Actinomycetes were selected based on their morphology and further screened based on their pigment diffusion ability. Through subsequent screening and characterization, three isolates designated AFSc1, AFSc6, and AFSc9 were identified as potent pigment-producing Actinomycetes. The pigment extracts from these isolates were tested for their antibacterial and antioxidant activities and also evaluated for use as fabric colorants. For further identification, the isolates were subjected to 16S rRNA gene sequencing, where AFSc1 showed 98.34% similarity to Curtobacterium flaccumfaciens, AFSc6 98.9% similarity to Rhodococcus cercidiphylli, and AFSc9 99.36% similarity to Arthrobacter species.
The pigment extracts demonstrated significant antibacterial activity, with inhibition zones ranging from 18 ± 0.75 mm to 22 ± 0.88 mm against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Notably, AFSc9 showed the highest antioxidant activity (IC50 value of 16.84 ± 0.56 µg/mL). The pigment extracts were efficiently fixed to the cotton fabrics. UV-spectrophotometric analysis revealed λ max values of 430 nm for AFSc1, 495 nm for AFSc6, and 426 nm for AFSc9. The Fourier-Transform Infrared Spectroscopy (FTIR) analyses indicated the presence of diverse functional groups, and GC-MS analysis identified 13 and 42 chemical compounds in the chromatograms of AFSc6 and AFSc9, respectively.
In this study, the pigment extracts of the isolates showed remarkable antibacterial, antioxidant, and fabric colorant properties, emphasizing the potential of Sof-Umar cave-dwelling Actinomycetes as sources of natural colorants and bioactive compounds.
放线菌是一类多样的丝状革兰氏阳性细菌，以其产生包括色素在内的各种次生代谢产物的能力而闻名。这些色素具有多种工业应用，是与不良副作用相关的合成色素的安全替代品。本研究旨在调查索夫-乌默尔洞穴岩石和沉积物样本中产生色素的放线菌，重点关注其潜在应用。
根据放线菌的形态选择了30株分离株，并根据其色素扩散能力进行进一步筛选。通过后续的筛选和鉴定，确定了三株分离株AFSc1、AFSc6和AFSc9为高效产色素放线菌。测试了这些分离株的色素提取物的抗菌和抗氧化活性，并评估了其作为织物着色剂的用途。为了进一步鉴定，对分离株进行了16S rRNA基因测序，其中AFSc1与萎蔫短小杆菌的相似性为98.34%，AFSc6与日本红豆红球菌的相似性为98.9%，AFSc9与节杆菌属的相似性为99.36%。
色素提取物表现出显著的抗菌活性，对大肠杆菌、铜绿假单胞菌和金黄色葡萄球菌的抑菌圈范围为18±0.75毫米至22±0.88毫米。值得注意的是，AFSc9表现出最高的抗氧化活性（IC50值为16.84±0.56微克/毫升）。色素提取物能有效地固定在棉织物上。紫外分光光度分析显示，AFSc1的λ max值为430纳米，AFSc6为495纳米，AFSc9为426纳米。傅里叶变换红外光谱（FTIR）分析表明存在多种官能团，气相色谱-质谱（GC-MS）分析分别在AFSc6和AFSc9的色谱图中鉴定出13种和42种化合物。
在本研究中，分离株的色素提取物表现出显著的抗菌、抗氧化和织物着色剂特性，强调了索夫-乌马尔洞穴栖息放线菌作为天然色素和生物活性化合物来源的潜力。
