Gut-associated Micrococcus yunnanensis RK-06 from Scylla serrata in Khor Al-Zubair waters, Basrah, Iraq: A Novel Source of a Halotolerant Alkaline Protease

Authors

• Rafid M. Karim, Marine Biology Department, Marine Science Centre, University of Basrah, Basrah, IraqFollow
• Reham M. Al-Mosawi, Marine Biology Department, Marine Science Centre, University of Basrah, Basrah, IraqFollow
• Wissal A. Alhilfi, Marine Biology Department, Marine Science Centre, University of Basrah, Basrah, IraqFollow
• Anwar A. Maki, Department of Biological Development, Marine Science Centre, University of Basrah, Basrah, IraqFollow
• Nida J. Al-Mousawi, Department of Biology, College of Science, University of Basrah, Basrah, IraqFollow
• Mohammed F. Abbas, Marine Biology Department, Marine Science Centre, University of Basrah, Basrah, IraqFollow

Abstract

Proteolytic bacteria have been isolated from diverse environments, but the crab gut remains a relatively unexplored source. This study aimed to isolate and identify protease-producing bacteria from the gut of the mud crab Scylla serrata collected from Khor Al-Zubair, Basrah, Iraq, and to characterize the produced protease. The gut homogenate was plated on Nutrient agar and 52 bacteria were recovered, of which 12 exhibited proteolytic activity on skim milk agar. Isolate RK-06 showed the highest activity, producing a clear zone exceeding 22 mm and was identified as Micrococcus yunnanenss (GenBank accession No. PZ312149). M. yunnanensis RK-06 was cultivated in the casein-supplemented basal medium and produced 1250 U mL^–1 protease. By performing protease assays under various conditions and the enzyme showed optimum activity at 35°C and pH 8.0. The protease retained over 90% activity when assayed in presence of 15% NaCl indicating remarkable halotolerance. Protease activity was enhanced by Ca²⁺ and Mg²⁺ but inhibited by EDTA and PMSF, indicating a metallo-serine protease. Gene sequence and bioinformatics analysis revealed a 363-amino-acid protease containing conserved serine protease motifs with a predicted pI of 4.16. Structural predictions indicated a predominantly a-helical conformation and favorable stability. These findings suggest that M. yunnanensis RK-06 is a promising source of industrially important protease with potential biotechnological and biomedical applications.

Keywords

Gut microbiota, Halo-tolerant enzymes, Micrococcus yunnanensis, Mud crab, Serine protease

Subject Area

Biology

Article Type

Article

First Page

3475

Last Page

3485

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

How to Cite this Article

Karim, Rafid M.; Al-Mosawi, Reham M.; Alhilfi, Wissal A.; Maki, Anwar A.; Al-Mousawi, Nida J.; and Abbas, Mohammed F. (2026) "Gut-associated Micrococcus yunnanensis RK-06 from Scylla serrata in Khor Al-Zubair waters, Basrah, Iraq: A Novel Source of a Halotolerant Alkaline Protease," Baghdad Science Journal: Vol. 23: Iss. 10, Article 4.
DOI: https://doi.org/10.21123/2411-7986.5425