Isolation and Identification of Exiguobacterium Profundum Strain from Cholesterol-Enriched Fetal Sample

Background: Cholesterol is metabolized into various sterol hormones in living organisms. Excessive use of cholesterol results in high amounts of sterol hormones with adverse effects on environment. Objective: The aim of this study was to identify and isolate a bacteria strain for cholesterol degradation. Methods: Bacterial enrichment, cultivation, serial dilution and agar plating were used for bacterium isolation. Isolated bacteria were identified and characterized through morphological, molecular, physiological and biochemical methods. Further, multi substrate metabolism and drug sensitivity tests were carried out on isolated bacteria. Results: Sanger sequencing and BLAST analysis showed high homology (99.78%) of the isolated bacterial strain with Exiguobacterium profundum strain 10C. The isolated bacterial strain was, therefore named EP01. Further analysis showed the strain was rod or spherical shaped, gram negative and peritrichous. In addition, the strain occurred in single or in pairs assembling bacterium, and produced orange or yellow clone on LB agar plate. The strain required a temperature range of 27-45℃ (optimum temperature was 37℃), pH range of 5-11 (optimum pH was 9), and NaCl range of 0% - 5% (optimal concentration of sodium chloride was 1%) for growth. The doubling time of the EP01 under the optimal conditions was 1.22h. EP01 showed positive catalase, amylase and alkaline protease activities. Further, EP01 tested positive for kinetics, hydrogen sulfide, gelatin hydrolysis and mannitol tests. On the contrary, tested negative for oxidase, urease, citrate, Tween-20, nitrate reductase and phenylalanine decarboxylase activities. EP01 metabolized glucose, xylose, raffinose, fructose and lactose. However, EP01 showed no growth on cholesterol, estradiol, testosterone, ergosterol, carbazole, phenanthrene, tetrachlorobiphenol A, 4-hydroxyphenylacetic acid, n-octanoic acid, n-nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid and arabinose as the only carbon source. Furthermore, EP01 was sensitive to 1μg/μL penicillin potassium, chloramphenicol and erythromycin, but not to metronidazole. Conclusion: EP01 is a Exiguobacterium profundum strain with strong alkaline resistance. EP01 can be used for environmental remediation to degrade contaminants.