Synthesis and Uptake of the Compatible Solutes Ectoine and 5-Hydroxyectoine by Streptomyces coelicolor A3(2) in Response to Salt and Heat Stresses

Abstract

Streptomyces coelicolor A3(2) synthesizes ectoine and 5-hydroxyectoine upon the imposition of either salt (0.5 M NaCl) or heat stress (39°C). The cells produced the highest cellular levels of these compatible solutes when both stress conditions were simultaneously imposed. Protection against either severe salt (1.2 M NaCl) or heat stress (39°C) or a combination of both environmental cues could be accomplished by adding low concentrations (1 mM) of either ectoine or 5-hydroxyectoine to S. coelicolor A3(2) cultures. The best salt and heat stress protection was observed when a mixture of ectoine and 5-hydroxyectoine (0.5 mM each) was provided to the growth medium. Transport assays with radiolabeled ectoine demonstrated that uptake was triggered by either salt or heat stress. The most effective transport and accumulation of [ 14 C]ectoine by S. coelicolor A3(2) were achieved when both environmental cues were simultaneously applied. Our results demonstrate that the accumulation of the compatible solutes ectoine and 5-hydroxyectoine allows S. coelicolor A3(2) to fend off the detrimental effects of both high salinity and high temperature on cell physiology. We also characterized the enzyme (EctD) required for the synthesis of 5-hydroxyectoine from ectoine, a hydroxylase of the superfamily of the non-heme-containing iron(II)-and 2-oxoglutarate-dependent dioxygenases (EC 1.14.11). The gene cluster (ectABCD) encoding the enzymes for ectoine and 5-hydroxyectoine biosynthesis can be found in the genome of S. coelicolor A3(2), Streptomyces avermitilis, Streptomyces griseus, Streptomyces scabiei, and Streptomyces chrysomallus, suggesting that these compatible solutes play an important role as stress protectants in the genus Streptomyces.

A Comparative Metabolomics Analysis ofSaccharopolyspora spinosaWT, WH124, and LU104 Revealed Metabolic Mechanisms Correlated with Increases in Spinosad Yield

“…For example, the concentration of intracellular ectonie in Streptomyces coelicolor significantly increased when it was cultured in a highly osmotic environment. 37,38) Intracellular ectonie was also detected in our study. Notably, the concentration of intracellular ectonie increased during the fermentation process (Fig.…”

A Specialized Aspartokinase Enhances the Biosynthesis of the Osmoprotectants Ectoine and Hydroxyectoine in Pseudomonas stutzeriA1501

“…Microbial cells accumulate compatible solutes through either synthesis or uptake from environmental resources (7,65,69). They can employ them not only as effective osmostress protectants, but also as protectants against heat (8,10,13,17,26) and cold (2,25,33) stress.…”

“…Biosynthesis of ectoine is catalyzed by L-2,4-diaminobutyric acid transaminase (EctB), N-␥-acetyltransferase (EctA), and ectoine synthase (EctC) (40,44). A subset of the ectoine producers hydroxylate ectoine to 5-hydroxyectoine (9,17,48) in a stereospecific fashion using the ectoine hydroxylase EctD (8,9,50). The structural genes (ectABC) for the ectoine biosynthetic enzymes are typically organized as a gene cluster whose transcription can be induced by increased osmolarity of the growth medium (9,11,32,33,40,43).…”

“…The structural genes (ectABC) for the ectoine biosynthetic enzymes are typically organized as a gene cluster whose transcription can be induced by increased osmolarity of the growth medium (9,11,32,33,40,43). In some microorganisms (e.g., in several bacilli) the ectABC genes are transcribed as an operon (8,32,33), but more complex patterns of ect transcription have been reported for Chromohalobacter salexigens (17) and Halomonas elongata (57). The ectABC operon might also contain the structural gene (ectD) for the ectoine hydroxylase (8,48), but this gene can often also be found in a genomic location unlinked from the ectoine biosynthetic gene cluster (9,17).…”

“…In some microorganisms (e.g., in several bacilli) the ectABC genes are transcribed as an operon (8,32,33), but more complex patterns of ect transcription have been reported for Chromohalobacter salexigens (17) and Halomonas elongata (57). The ectABC operon might also contain the structural gene (ectD) for the ectoine hydroxylase (8,48), but this gene can often also be found in a genomic location unlinked from the ectoine biosynthetic gene cluster (9,17). Database searches by different groups have shown that the ability to synthesize ectoine and hydroxyectoine is widespread in the microbial world (9,39,45,50,62).…”