ORIGINAL RESEARCH
A Study on Larvicidal Activity and Phylogenetic
Analysis of Staphylococcus epidermidis
as a Biosurfactant-Producing Bacterium
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1
Department of Microbiology, College of Sciences, Shiraz Branch, Islamic Azad University, Shiraz, Iran
2
Department of Entomology, College of Science, Shiraz Branch, Islamic Azad University, Shiraz, Iran
Submission date: 2020-12-04
Final revision date: 2021-01-15
Acceptance date: 2021-01-25
Online publication date: 2021-07-13
Publication date: 2021-09-22
Corresponding author
Nima Bahador
Dept. Microbiology, IAU, college of Science, Iran
Pol. J. Environ. Stud. 2021;30(5):4511-4519
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ABSTRACT
Biosurfactants, produced by microorganisms, are surface-active compounds with abundant
applications in miscellaneous industries like food, cosmetics, bioremediation, agriculture, and so on.
The primary objective of this study was to investigate the larvicidal activity of biosurfactants produced
by Staphylococcus epidermidis (S. epidermidis) isolated from petrochemical wastes. As the secondary
objective, this study was to perform a phylogenetic analysis of this bacterium. To this end, the type
of the extracted biosurfactant was characterized using the thin-layer chromatography (TLC) and the
gas chromatography/mass spectrometry (GC-MS). The isolated bacterium was then identified through
molecular tests based on 16S ribosomal ribonucleic acid (16S rRNA) and serum response factor (srf )
genes. Likewise, the phylogenetic tree of the bacterium was deduced via the Molecular Evolutionary
Genetics Analysis (MEGA-X) software. Besides, the larvicidal activity of the biosurfactant on the
larvae of flour beetles, Tribolium castaneum (T. castaneum), was examined. The mean mortality rate
and the lethal dose (LD50) were further calculated using the Statistical Analysis System (SAS) and the
Probit Analysis-MSChart software. Totally, nine diverse types of colonies were isolated and three of
them were found with potential activity to produce biosurfactants. The best bacterium was accordingly
selected for subsequent experiments recruiting the oil displacement process and the emulsification index
(E24). The extracted biosurfactant was then characterized as a lipopeptide. Moreover, biochemical tests
showed that the bacterium was Gram-positive cocci of gamma species. Hemolysis and molecular tests
also confirmed that the bacterium was S. epidermidis. As well, the presence of the SRF gene in the
isolation was established via the polymerase chain reaction (PCR). The mean mortality rate revealed
that the mentioned bacterial biosurfactant at the concentration of 10000 μg/g and on the ninth day of
the treatment had the highest larval mortality rate (63.33%). In addition, the LD50 equal to 25001.7
μg/g was calculated for S. epidermidis on the ninth day. The results demonstrated that the biosurfactant produced by this bacterium was endowed with an acceptable ability to control T. castaneum and it could
be used in further research on the larvae of other insects.