Antarctic Streptomyces fildesensis So13.3 strain as a promising source for antimicrobials discovery

Abstract

Antarctic have been suggested as an attractive source for antibiotics discovery and members of Streptomyces genus have historically been studied as natural producers of antimicrobial metabolites. Nonetheless, our knowledge on antibiotic-producing Streptomyces from Antarctic is very limited. In this study, the antimicrobial activity of organic extracts from Antarctic Streptomyces strains was evaluated by disk diffusion assays and minimum inhibitory concentration. The strain Streptomyces sp. So13.3 showed the greatest antibiotic activity (MIC = 15.6 μg/mL) against Gram-positive bacteria and growth reduction of Gram‒negative pathogens. The bioactive fraction in the crude extract was revealed by TLC‒bioautography at R f = 0.78 with molecular weight between 148 and 624 m/z detected by LC-ESI-MS/MS. The strain So13.3 was taxonomically affiliated as Streptomyces fildesensis . Whole genome sequencing and analysis suggested a 9.47 Mb genome size with 42 predicted biosynthetic gene clusters (BGCs) and 56 putative clusters representing a 22% of total genome content. Interestingly, a large number of them (11 of 42 BGCs and 40 of 56 putative BGCs), did not show similarities with other known BGCs. Our results highlight the potential of the Antarctic Streptomyces strains as a promising source of novel antimicrobials, particularly the strain Streptomyces fildesensis So13.3, which first draft genome is reported in this work.

Streptomyces sp. Strain MUSC 125 from Mangrove Soil in Malaysia with Anti-MRSA, Anti-Biofilm and Antioxidant Activities

“…Thus far, Streptomyces pluripotens MUSC 135 T is the only reported Streptomyces strain isolated from mangrove Malaysia showing anti-MRSA activity in well diffusion assay [58]. Although methanolic extract of MUSC 125 exhibited anti-MRSA activity, the MIC values are relatively high when compared with other recent works [82,83], suggesting that the active compound that targets MRSA could be present in the complex mixture of crude extract at a relatively low concentration. It is known that the cultivation conditions greatly influence the secondary metabolites production in Streptomyces.…”

Genome Mining Revealed a High Biosynthetic Potential for Antifungal Streptomyces sp. S-2 Isolated from Black Soot

“…At the same time, the genome mining of S-2 revealed 55 BGCs. A higher-than-average number of BGCs (20-30) that has been reported for mesophilic Streptomyces [13,63]. It is also more BGCs than identified in Streptomyces isolated from extreme environments, like Artic soil, caves or coal mine soil [1,13,24].…”

“…ICC1 and ICC4, isolated from the Iron Curtains Cave have been reported to have a higher number of BGCs than their closest terrestrial counterpart, S. lavendulae, has [24]. To the best of our knowledge, only two strains with a higher number of BGCs than S-2 have been described: S. griseochromogenes ATCC-14511 [13] and Streptomyces sp. GMR22 [64], with 59 and 63 BGCs respectively.…”

“…In co-cultures with pre-cultured S-2, the effect was even more pronounced, resulting in the complete inhibition of fungal growth on plates with bacteria pre-cultured for 7 and 14 days for N. oryzae roseF7 and for all tested fungi, respectively. Recently, there have been a number of reports of new Streptomyces strains isolated from extreme and non-conventional environments that are showing antimicrobial activity [1,13,24,25]. Streptomyces strains have also been previously studied for their potential to protect plants against fungal infections [2,35].…”

“…Sequencing has shown that the size of the S-2 genome (<7 Mbp) as well as number of coding sequences (CDS) (<7000) are on the lower end for Streptomyces genus whose members' genomes are 8.6 Mbp on average and contain more than 7000 CDS [5,13]. At the same time, the genome mining of S-2 revealed 55 BGCs.…”