Streptomyces natalensis programmed cell death and morphological differentiation are dependent on oxidative stress

Abstract

Streptomyces are aerobic Gram-positive bacteria characterized by a complex life cycle that includes hyphae differentiation and spore formation. Morphological differentiation is triggered by stressful conditions and takes place in a pro-oxidant environment, which sets the basis for an involvement of the oxidative stress response in this cellular process. Characterization of the phenotypic traits of Streptomyces natalensis ΔkatA1 (mono-functional catalase) and ΔcatR (Fur-like repressor of katA1 expression) strains in solid medium revealed that both mutants had an impaired morphological development process. The sub-lethal oxidative stress caused by the absence of KatA1 resulted in the formation of a highly proliferative and undifferentiated vegetative mycelium, whereas de-repression of CatR regulon, from which KatA1 is the only known representative, resulted in the formation of scarce aerial mycelium. Both mutant strains had the transcription of genes associated with aerial mycelium formation and biosynthesis of the hyphae hydrophobic layer down-regulated. The first round of the programmed cell death (PCD) was inhibited in both strains which caused the prevalence of the transient primary mycelium (MI) over secondary mycelium (MII). Our data shows that the first round of PCD and morphological differentiation in S. natalensis is dependent on oxidative stress in the right amount at the right time.

A Challenging View: Antibiotics Play a Role in the Regulation of the Energetic Metabolism of the Producing Bacteria

“…However, when Pi becomes too scarce to support the ATP generating function of the respiratory chain, a blockage of the latter occurs, resulting in electron leakage toward secondary acceptors and thus generation of oxidative stress (ROS/RNS). Many reports in the literature suggest that oxidative stress might be an important trigger of the biosynthesis of some antibiotics in Streptomyces as in fungi [27][28][29][30], called "Type II" antibiotics. Some of these antibiotics, including ACT, contain quinone groups that are able to capture electrons [31].…”

Fungal Morphogenesis, from the Polarized Growth of Hyphae to Complex Reproduction and Infection Structures

“…The self-assembly of the hydrophobin EAS into fibrillar rodlets occurs spontaneously at hydrophobic-hydrophilic interfaces, forming an amphipathic monolayer (312). Similarly, in Streptomyces coelicolor, after stress and the death of the substrate mycelium, "aerial hyphae" that express the hydrophobin-like proteins chaplin and rodlin are formed; both cell death and morphogenesis depend on oxidative stress (313). As O 2 normally diffuses from the extracellular aqueous medium into the cytoplasm, hydrophobins might hinder direct O 2 diffusion from air, forcing O 2 ministration to the aerial hyphae mainly through the mycelial substrate.…”

Biotechnological production and application of the antibiotic pimaricin: biosynthesis and its regulation

“…The future application of this knowledge at the industrial scale will hopefully permit to satisfy the growing PIM commercial demands. In this sense, the present availability of the genome sequences of PIM producers such as S. natalensis (GenBank JRKI01; Beites et al 2015 ) and S. chattanoogensis (GenBank LGKG01) will certainly constitute a very valuable tool in the efforts to improve PIM production.…”