Evolution-guided engineering of trans-acyltransferase polyketide synthases

Bacterial multimodular polyketide synthases (PKSs) are giant enzymes that generate a wide range of therapeutically important but synthetically challenging natural products. Diversification of polyketide structures can be achieved by engineering these enzymes. However, notwithstanding successes made with textbook cis-acyltransferase (cis-AT) PKSs, tailoring such large assembly lines remains challenging. Unlike textbook PKSs, trans-AT PKSs feature an extraordinary diversity of PKS modules and commonly evolve to form hybrid PKSs. In this study, we analyzed amino acid coevolution to identify a common module site that yields functional PKSs. We used this site to insert and delete diverse PKS parts and create 22 engineered trans-AT PKSs from various pathways and in two bacterial producers. The high success rates of our engineering approach highlight the broader applicability to generate complex designer polyketides.

Trends and variability of climate and river flow in the region of Costa das Baleias, Brazil

There is an ongoing effort by the scientific community to regionalize climate studies to support local development plans. The area of interest is the Costa das Baleias on the east coast of northeast Brazil. It is located in a transition region of precipitation trends, and so assessing the local signal and magnitude is necessary. A series of annual anomalies of surface air temperature, precipitation and river discharge were analyzed from 1946 to 2010. The modified Mann-Kendall test was applied to detect trends. Temperature anomalies showed a consistent positive trend since 1950. Precipitation anomalies tended to decrease, though not significantly. River discharge rates showed a consistent positive trend. However, from the 1980s onwards, both the precipitation and the river discharge anomalies had the same decreasing tendency. The precipitation and discharge behavior are likely due to the combined effect of human interventions in the river basins including local, synoptic and global climate effects. The inter-annual variability was characterized by spectral analysis. Cycles were identified for the precipitation and the river discharge with periods of 2-3 years, 3-4 years, 7-8 years and 11-12 years. The decadal frequency is consistent with the South Atlantic and El Niño indices. This work strongly indicates that climate is changing in Costa das Baleias and further work is needed to investigate the mechanisms that link local to large-scale variability.