Induction of cryptic metabolites from a rare Antarctic psychrophile, Marinobacter sp.

 

Microbes from extreme environments represent an untapped source of novel, bioactive metabolites with unique molecular frameworks, as they have evolved genes that are critical for surviving in unusual environments [1 – 3]. Antarctic subglacial environments are among the most challenging systems to study because they are locked under 100 – 1000 s of meters of glacial ice and require novel drilling technology to access materials cleanly for microbiological analyses. Only recently have microbiological samples been obtained from these cold, dark isolated ecosystems. Blood Falls, one of the better-characterized subglacial environments in Antarctica, is a cold (-7 °C), iron-rich (˜3.4 mM) subglacial brine (8% NaCl) that leaks out from below the Taylor Glacier, Antarctica [4]. We recently isolated and characterized a moderately halophilic, heterotrophic psychrophile from the Blood Falls brine that clusters within the Marinobacter genus. Bioinformatic analysis of this strain's genome indicated the presence of at least four gene clusters involved in secondary metabolism with low sequence identity (˜30%) to other known genes in GenBank. Two gene clusters are most similar to those that produce aryl polyenes, which function as pigments/antioxidants, protecting bacteria from reactive oxygen species. Another gene cluster appears to be involved in terpene biosynthesis and most likely produces pigments, as it contains includes lycopene cyclase from carotenoid biosynthesis. To identify some of these uncharacterized, cryptic gene products with potential bioactivity, we modified growth conditions as well as created a cosmid library in Escherichia coli to induce the production of pigments. We were able to induce gene expression and partially characterize metabolic products by high-resolution LC/MS by varying media as shown in the figure below. These data provide insight into the metabolome of Marinobacter sp., and its role in cold environments, such as those found in Antarctica.

Acknowledgements: We would like to acknowledge Professor Russell Kerr at the University of Prince Edward Island for kindly providing access to his high-resolution LC-MS.

Keywords: Cryptic metabolites, extremophilic microbes, bioactive compounds.

References:

[1] Giddings L-A, Newman DJ. Bioactive compounds from extremophiles: genomic studies, biosynthetic gene clusters, and new dereplication methods. In: Springer; 2015

[2] Giddings L-A, Newman DJ. Bioactive compounds from terrestrial extremophiles. In: Springer; 2015

[3] Giddings L-A, Newman DJ. Bioactive compounds from marine extremophiles. In: Springer; 2015

[4] Mikucki JA, Pearson A, Johnston DJ, Turchyn AV, Farquhar J, Schrag DP, Anbar AD, Priscu JC, Lee PA. A contemporary microbially maintained subglacial ferrous "Ocean". Science 2009; 324: 397 – 400