Antimicrobial activities of culturable microorganisms (actinomycetes and fungi) isolated from Chaabe Cave, Algeria

Abstract

Abstract:The discovery of new antibiotics and other bioactive microbial metabolites is a priority given the frequency of the emerging multi-drug resistant pathogenic microorganisms. Thus, scientists are searching for new antibiotics in microorganisms isolated from extreme habitats such as caves. In the present study, we aimed to perform the first analysis on culturable microorganisms in the Chaabe Cave (Algeria), and to test the antimicrobial activities of the isolates (Streptomyces spp. and Penicillium spp.). The potential for antimicrobial activity of 47 strains of actinomycetes and 23 strains of fungi were tested on Candida albicans, Staphylococcus aureus, Micrococcus luteus, Listeria monocytogenes, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. The identification of the most active actinomycetes strains by 16S rRNA gene sequence analysis revealed that these isolates were exclusively affiliated to the genus Streptomyces. On the other hand, the fungi were determined by phylogenetic analysis based on the ITS region or on the β tubulin gene and were affiliated to the genera Readeriella, Cladosporium, Aspergillus, Penicillium, Beauveria, Alternaria, Rhizopus, and Rhizomucor. The strains showed strong inhibitory activity against pathogenic microorganisms and the diameters of the inhibition zones vary between 7.5 and 34 mm for Streptomyces strains, and between 6.5 and 19.50 mm for Penicillium strains. The data indicated that the majority (72.86%) of the 70 isolates were active against at least one of the tested microorganisms. The production of nonpolyenic antifungal substances by active Streptomyces isolates was investigated using several criteria (antibacterial activity, ergosterol inhibition, and UV-visible spectra) of active extracts. The results were promising and showed that the metabolites produced by the actinomycete strains do not have a UVvisible spectrum characteristic of a polyenic structure. The Chaabe Cave possesses a diversity of microorganisms that could lead to new antibiotics necessary in the fight against drug-resistant pathogens and warrant further study.

Screening the cultivable cave microbial mats for the production of antimicrobial compounds and antibiotic resistance

“…Interestingly, low levels or resistance (<10%) were found even for cefepime, a recently introduced 4 th generation cephalosporine. In these terms, the results of our study are consistent with previous studies which have noted high levels of antibiotic resistance genes in cave environments (Pawlowski et al, 2016;Lavoie, 2017;Belyagoubi et al, 2018) and even in ancient cave microbes that had no anthropogenic contact for the past four million years (Bhullar et al, 2012).…”

Actinobacteria Derived from Algerian Ecosystems as a Prominent Source of Antimicrobial Molecules

“…[91]. A series of polyether antibiotics including nigericin (40), epinigericin (41), abierixin (42), and the new grisorixin methyl ester (43) were isolated from the Streptomyces youssoufiensis SF10 strain collected from Chélia Mountain, in Khenchela (North-eastern Algeria) [105]. The online coupled HPLC-ESIMS analysis provided the full polyether profile, and the preparative HPLC technique in the reversed phase condition gave pure compounds, which were identified by extensive NMR and ESI-MS spectra in comparison with reported data.…”

“…Recently, the polyether antibiotics nigericin (40) and the new grisorixin methyl ester (43) isolated from Streptomyces youssoufiensis SF10 have provided significant cytotoxic activities against glioblastoma stem cells, with a higher activity for grisorixin methyl ester (GI 50 values of 3.85 and 3.05 µM for two human glioblastoma stem cell lines), corresponding to a higher growth-inhibion cell-proliferation than the drug temozolomide [105]. The data are remarkable due to both the nature of glioblastoma multiforme as the most malignant primary brain tumors and the effect against stem cells which are resistant to the conventional therapies.…”

“…This affects a great biodiversity, rich and diversified in actinobacteria, to which corresponds a wide chemodiversity of metabolites. A number of actinobacteria has been isolated from different ecosystems including Saharan plants [34,38,39], caves [40], waste water [41,42], river sediments [43], hypersaline areas [44][45][46][47][48][49][50][51], Saharan desert soil [22,52], and derived algae [53]. The most studied sampling sites for the isolation of actinobacteria are listed in Figure 1.…”

In vitro antibacterial activities and molecular characterization of bacterial species isolated from farmlands against selected pathogens

“…They also produce some antimicrobial compounds such as hydrogen cyanide, monoacetylphloroglucinol (MAPG) and microcin for growth inhibition. Actinobacteria are widely known for antimicrobial activities against an enormous number of pathogens [ 16 , 17 ]. They produce over 60 % of antimicrobial compounds used around the world today.…”