Bioprospecting of the novel isolate Microbacterium proteolyticum LA2(R) from the rhizosphere of Rauwolfia serpentina

Naushin Bano; Saba Siddiqui; Mohammad Amir; Qamar Zia; Saeed Banawas; Danish Iqbal; Roohi

doi:10.1016/j.sjbs.2021.10.038

Bioprospecting of the novel isolate Microbacterium proteolyticum LA2(R) from the rhizosphere of Rauwolfia serpentina

Saudi J Biol Sci. 2022 Mar;29(3):1858-1868. doi: 10.1016/j.sjbs.2021.10.038. Epub 2021 Oct 22.

Authors

Naushin Bano¹, Saba Siddiqui², Mohammad Amir¹, Qamar Zia^{3

4}, Saeed Banawas^{3

4

5}, Danish Iqbal⁴, Roohi¹

Affiliations

¹ Department of Bioengineering, Integral University, Lucknow 226026, India.
² Integral Institute of Agricultural Science and Technology, Integral University, Lucknow 226026, India.
³ Health and Basic Science Research Centre, Majmaah University, Al-Majmaah 11952, Saudi Arabia.
⁴ Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Al-Majmaah 11952, Saudi Arabia.
⁵ Department of Biomedical Sciences, Oregon State University, Corvallis, OR 97331, USA.

Abstract

The study aimed to assess the proficiency of secondary metabolites (SMs) synthesized by actinobacteria isolated from the rhizospheric soil of Rauwolfia serpentina for its antimicrobial and anti-biofilm activity. After morphological and biochemical identification of actinobacteria, primary and secondary screening was done for specific metabolite production. The secondary metabolites were then tested for their antioxidant, antibacterial, and antibiofilm potential. Out of 29 bacterial colonies isolated, only one emerged as a novel isolate, Microbacterium LA2(R). Partial 16S rRNA gene sequence of the isolate LA2(R) was deposited in NCBI GenBank with accession number MN560041. The highest antioxidant capacity of the methanolic extract the novel isolate was found to be 474.183 µL AAE/mL and 319.037 µL AAE/mL by DPPH assay and ABTS assay respectively; three folds higher than the control. These results were further supported by the high total phenolic (194.95 gallic acid equivalents/mL) and flavonoid contents (332.79 µL quercetin equivalents/mL) of the methanolic extract. GC-MS analysis revealed the abundance of antibacterial compounds; where, n-Hexadecanoic acid was found to be the major compound present with a peak of 14 min retention time (RT) and 95% similarity index. MIC value of the metabolite was noted to be around 132.28 ± 84.48 μg/mL. The IC₅₀ value was found to be 74.37, 71.33, 66.28 and 84.48 μg/mL against Escherichia coli, Staphylococcus aureus, Klebsiella pneumonia, and Salmonella abony, respectively. Treatment with IC₅₀ of the extract decreased the biofilm formation up to 70%-80% against pathogenic strains viz. Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Salmonella abony. These significant activities of Microbacterium sp. LA2(R) suggests that it could be utilized for antibiotic production for human welfare and in various important industrial applications.

Keywords: Actinobacteria; Antibiofilm; Antioxidant; GC–MS; Microbacterium; Secondary metabolites.