Mycosporine-like amino acids (MAAs) are an important class of secondary metabolites known for their protection against UV radiation and other stress factors. Cyanobacteria produce a variety of MAAs, including shinorine, the active ingredient in many sunscreen creams. Bioinformatic analysis of the genome of the soil-dwelling cyanobacterium Cylindrospermum stagnale PCC 7417 revealed a new gene cluster with homology to MAA synthase from Nostoc punctiforme. This newly identified gene cluster is unusual because it has five biosynthesis genes (mylA to mylE), compared to the four found in other MAA gene clusters. Heterologous expression of mylA to mylE in Escherichia coli resulted in the production of mycosporine-lysine and the novel compound mycosporine-ornithine. To our knowledge, this is the first time these compounds have been heterologously produced in E. coli and structurally characterized via direct spectral guidance. This study offers insight into the diversity, biosynthesis, and structure of cyanobacterial MAAs and highlights their amenability to heterologous production methods. M ycosporine-like amino acids (MAAs) are commonly found in marine microbes exposed to high levels of UV radiation, including aquatic fungi, eukaryotic algae, and cyanobacteria (1-6). These small (Ͻ400 Da), colorless, water-soluble compounds are composed of a 4-deoxygadusol core conjugated with an amino acid or alcohol (7). Their absorption maxima typically range from 310 to 360 nm and their molar extinction coefficients (ε) range from 28,100 to 50,000 M Ϫ1 cm Ϫ1 (8, 9). Commonly termed "microbial sunscreens," MAAs can dissipate UV energy as heat without generating free oxygen radicals (7).While UV exposure is necessary to elicit the synthesis of MAAs (10), some studies suggest that other factors, including osmotic stress, may also be involved in MAA regulation (11). Indeed, MAAs are widely considered to be multifunctional compounds offering protection against oxidative, osmotic, and thermal stress as well as UV radiation (12-17). However, this may not be true for all MAAs (11). Due to their diverse biological properties, MAAs are promising candidates for pharmaceutical and cosmetic applications (3, 18). For example, shinorine, produced by the cyanobacterium Anabaena variabilis, has already been commercialized as an active ingredient in sunscreen creams (Helioguard 365 and Helionori) (14).The biosynthesis of shinorine ( Fig. 1) was recently elucidated via heterologous expression in Escherichia coli (19,20) and is a model pathway for MAA biosynthesis. In A. variabilis ATCC 29413, the shinorine biosynthesis gene cluster consists of four genes: ava_3855 to ava_3858. The first step in the biosynthesis of shinorine is the conversion of sedoheptulose-7-phosphate (SH-7P) to 2-demethyl-4-deoxygadusol (DDG) by a DDG synthase (Ava_3858). Following this, DDG is converted to the mycosporine core compound 4-deoxygadusol (4-DG) by an O-methyltransferase (O-MT) (Ava_3857). Glycylation of 4-DG is catalyzed by a C-N ligase (Ava_3856), resulting ...

No abstract

BackgroundPresent study focuses on diversity and distribution analysis of endophytic fungi associated with different tissues of the Monarda citriodora Cerv. ex Lag. (Lamiaceae/Labiatae). Anticancer and antimicrobial potential of isolated endophytes have also been investigated.ResultsA total of twenty eight fungal endophytes belonging to 11 different genera were isolated from this plant. All the endophytic fungi belonged to the Ascomycota phylum. The leaves were immensely rich in fungal species, while roots showed the highest tissue specific fungal dominance. Out of 28 fungal species, 72% endophytic extracts were found cytotoxic against one or more human cancer cell lines. The most prominent anticancer activity (IC50 value <10 μg/mL) was shown by MC-14 L (Fusarium oxysporum), MC-14 F (F. oxysporum), MC-18 L (Aspergillus fumigatus), MC-24 L (Cladosporium tenuissimum), MC-25 L (Fusarium sp.), MC-26 F (F. oxysporum) extracts. 75% of the extracts showed antimicrobial activities in agar disc-diffusion assay and 27% in the tube dilution method (MIC <100 μg/mL) respectively against the tested pathogens. Extracts of MC-14 L (F. oxysporum) and MC-18 L (A. fumigatus) displayed broad spectrum antimicrobial activity.ConclusionsThese results indicated that M. citriodora harbors a rich fungal endophytic community with anticancer and antimicrobial activities. The isolated endophyte MC-24 L (C. tenuissimum) has the potential to be a source of novel cytotoxic/antimicrobial compounds. This is the first report of diversity of fungal endophytes isolated from M. citriodora.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-017-0961-2) contains supplementary material, which is available to authorized users.

BackgroundEndophytes, which reside in plant tissues, have the potential to produce novel metabolites with immense benefits for health industry. Cytotoxic and antimicrobial activities of endophytic fungi isolated from Bacopa monnieri (L.) Pennell were investigated.MethodsEndophytic fungi were isolated from the Bacopa monnieri. Extracts from liquid cultures were tested for cytotoxicity against a number of cancer cell lines using the MTT assay. Antimicrobial activity was determined using the micro dilution method.Results22% of the examined extracts showed potent (IC50 of <20 μg/ml) cytotoxic activity against HCT-116 cell line. 5.5%, 11%, 11% of the extracts were found to be cytotoxic for MCF-7, PC-3, and A-549 cell lines respectively. 33% extracts displayed antimicrobial activity against at least one test organism with MIC value 10–100 μg/ml. The isolate B9_Pink showed the most potent cytotoxic activity for all the cell lines examined and maximum antimicrobial activity against the four pathogens examined which was followed by B19.ConclusionsResults indicated the potential for production of bioactive agents from endophytes of Bacopa monnieri.