YlmD and ylmE genes are dispensable for growth, cross-wall formation and sporulation in Streptomyces venezuelae

Fernando Santos-Beneit,Jing-Ying Gu,Ulrich Stimming,Jeff Errington

doi:10.1016/j.heliyon.2017.e00459

Abstract

Streptomycetes are Gram-positive filamentous soil bacteria that grow by tip extension and branching, forming a network of multinucleoid hyphae. These bacteria also have an elaborate process of morphological differentiation, which involves the formation of an aerial mycelium that eventually undergoes extensive septation into chains of uninucleoid cells that further metamorphose into spores. The tubulin-like FtsZ protein is essential for this septation process. Most of the conserved cell division genes (including ftsZ) have been inactivated in Streptomyces without the anticipated lethality, based on studies of many other bacteria. However, there are still some genes of the Streptomyces division and cell wall (dcw) cluster that remain uncharacterized, the most notable example being the two conserved genes immediately adjacent to ftsZ (i.e. ylmDE). Here, for the first time, we made a ylmDE mutant in Streptomyces venezuelae and analysed it using epifluorescence microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The mutant showed no significant effects on growth, cross-wall formation and sporulation in comparison to the wild type strain, which suggests that the ylmDE genes do not have an essential role in the Streptomyces cell division cycle (at least under the conditions of this study).

Highlights

Streptomyces venezuelae is being promoted as a useful new model organism for study of the streptomycetes, which are the world’s most prolific producers of natural product molecules for the drug and agrochemical industries (Bibb et al, 2012; Bush et al, 2013)
Several groups have been working on various aspects of the cell cycle in Streptomyces, much less is known about this general area of biology in comparison with bacteria such as Escherichia coli and Bacillus subtilis (Adams and Errington, 2009)
Streptomyces biology brings with it a number of very interesting problems that are not addressable in those other organisms, including cell wall growth at the tips of filaments or the nonessentiality of FtsZ and many others cell division players (Flärdh, 2003; McCormick et al, 1994)

Summary

Introduction

Streptomyces venezuelae is being promoted as a useful new model organism for study of the streptomycetes, which are the world’s most prolific producers of natural product molecules for the drug and agrochemical industries (Bibb et al, 2012; Bush et al, 2013). Streptomyces biology brings with it a number of very interesting problems that are not addressable in those other organisms, including cell wall growth at the tips of filaments (rather than the more common intercalating MreB-dependent mode of cylindrical elongation) or the nonessentiality of FtsZ and many others cell division players (Flärdh, 2003; McCormick et al, 1994). Streptomyces constitutes an exception to this event Both Streptomyces coelicolor and S. venezuelae ftsZ-null mutants are able to grow and to form aerial mycelium; are unable to convert aerial hyphal filaments into spores (McCormick et al, 1994; Santos-Beneit et al, 2017). We focus on the isolation of a S. venezuelae ATCC10712 ΔylmDE double mutant and in the characterization of its mutant phenotype using epifluorescence microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM)

Methods

Results

Conclusion