Exploring Bioactive Potential of Streptomyces thinghirensis WAE1 from Wadi El-Natron, Egypt

Abstract

This study aimed to investigate the bioactive metabolites produced by Streptomyces thinghirensis WAE1, an actinomycete isolated from El-Hamara Lake in Egypt. The discovery of new bioactive compounds from natural sources is crucial for the advancement of therapeutic treatments, and this study aimed to contribute to this field by exploring the potential of Streptomyces thinghirensis WAE1 as a source of such compounds. Streptomyces thinghirensis WAE1 was screened for its ability to produce antimicrobial, antioxidant, and anti-inflammatory metabolites. The results revealed that S. thinghirensis WAE1 exhibited strong antimicrobial activity against Streptococcus pneumoniae and moderate activity against Listeria monocytogenes, Staphylococcus aureus, and Candida albicans. Streptomyces thinghirensis WAE1 also displayed antioxidant activity through scavenging free radicals and chelating iron, and moderate anti-inflammatory activity as determined by its IC₅₀ value. The isolate's demonstration of L-asparaginase activity suggests that S. thinghirensis WAE1 is a promising source of bioactive compounds with potential therapeutic uses. The high salinity and alkalinity of El-Hamara Lake, which create favorable conditions for the production of bioactive metabolites, further add to its potential as a source of actinomycetes strains with bioactive properties. These findings make both S. thinghirensis WAE1 and El-Hamara Lake valuable subjects for further exploration in the field of bioactive compounds.

Keywords: Actinobacteria; Anti-inflammatory; Antimicrobial; Antioxidant; L-asparaginase.

Fig. 1

shows the location of El-Hamara Lake in Wadi El-Natron, Egypt, where the potent antimicrobial-producing actinomycete isolate WAE1 was obtained from a soil sample

Fig. 2

Antimicrobial activity of WAE1 isolate against various pathogenic bacterial and fungal strains as determined by agar well diffusion assays. The activities were evaluated against, a S. pneumoniae ATCC 49619, b L. monocytogenes ATCC 19116, c S. aureus ATCC 29213, d K. pneumoniae ATCC 27736, e C. albicans ATCC 10231, with no activity observed against, f C. sporogenes ATCC 3584, g S. enterica ATCC 25566, h E. coli ATCC 25922, i C. sakazakii ATCC 29544 and j P. aeruginosa ATCC 27853

Fig. 3

Phenotypic appearance of the actinobacterial isolate S. thinghirensis WAE1 grown on starch nitrate agar showing whitish-grey colonies exhibiting yellow-colored exopigment production

Fig. 4

Phylogenetic tree of 16S rRNA gene sequence of WAE1 isolate and closely related type strains constructed using the neighbour-joining method, showing S. thinghirensis (NR_116901.1) as the closest type strain with 100% sequence similarity

Fig. 5

Phylogenetic tree of S. thinghirensis WAE1 was created by neighbour-joining technique

Fig. 6

PCR amplification of PKS-I (a), PKS-II (b) and NRPS (c) gene sequences with an amplicon size of 1200–1400, 600–700 and 700–800 bp using primers K1F/M6R, KSαF/KSαR and A3F/A3R, respectively, on agarose gel 1%. The S. thinghirensis WAE1 isolate was found to only include the adenylation domain of NRPS genes, as indicated by an amplicon size of 700–800 bp

Fig. 7

Assessment of the antioxidant properties of the WAE1 extract and ascorbic acid used as a control by using different antioxidant assays

Fig. 8

Anti-inflammatory activity of WAE1 extract and indomethacin used as a control

Fig. 9

Qualitative detection of extracellular L-asparaginase secretion by S. thinghirensis WAE1 cultured in modified M9 solid medium. L-asparaginase activity was visualized using a pH indicator dye phenol red, where enzymatic hydrolysis of L-asparagine resulted in localized alkalinization and consequent color change from yellow to pink surrounding colonies after (a) 3 days and (b) 7 days of incubation. Control plates showed (c) inoculated medium lacking phenol red (positive control), and (d) uniform yellow coloration for uninoculated medium containing phenol red (negative control)