Biology subjects

Willemse, J.

Publications and source records attributed to Willemse, J..

6 recordsLinked to original sources

bioRxiv2018

Classification of the gifted natural product producer Streptomyces roseofaciens sp. nov. by polyphasic taxonomy

A novel verticillate strain of streptomycetes, Streptomyces strain MBT76T, was isolated from the QinLing mountains, which harbours more than 40 biosynthetic gene clusters for natural products. Here we present full taxonomic classification of strain MBT76T, and show that it has chemotaxonomic, genomic and morphological properties consistent with its classification in the genus Streptomyces. Strain MBT76T is part of the cluster of Streptoverticillates, a group within the genus Streptomyces that has characteristic whorl-forming spores produced in chains along the lateral wall of the hyphae. Multi-locus sequence analysis based on five housekeeping gene alleles showed that MBT76T is closely related to Streptomyces hiroshimensis. Average Nucleotide Identification (ANI) and Genome to Genome Distance Calculation (GGDC) of the genomes of strain MBT76T and S. hiroshimensis separated them into distinct species. Strain MBT76T represents a novel species of the genus Streptomyces for which we propose the name Streptomyces roseofaciens sp. nov. The type strain is MBT76T (=NCCB 100637T =DSM 106196T). The whole genome of MBT76T has 7974 predicted open reading frames and a total genome size of 8.64 Mb. Further genomic analysis showed that verticillate streptomycetes lack the sporulation gene ssgE, and our data suggest that this is a useful genetic marker for the spore-chain morphology of the verticillates.

microbiology↗

bioRxiv2017

Inter- and intracellular colonization of Arabidopsis roots by endophytic actinobacteria and the impact of plant hormones on their antimicrobial activity

Many actinobacteria live in close association with eukaryotes like fungi, insects, animals and plants. Plant-associated actinobacteria display (endo)symbiotic, saprophytic or pathogenic life styles, and can make up a substantial part of the endophytic community. Here, we characterised endophytic actinobacteria isolated from root tissue of Arabidopsis thaliana (Arabidopsis) plants grown in soil from a natural ecosystem. Many of these actinobacteria belong to the family of Streptomycetaceae with Streptomyces olivochromogenes and Streptomyces clavifer as well represented species. When seeds of Arabidopsis were inoculated with spores of Streptomyces strain coa1, which shows high similarity to S. olivochromogenes, roots were colonised intercellularly and, unexpectedly, also intracellularly. Subsequent exposure of endophytic isolates to plant hormones typically found in root and shoot tissues of Arabidopsis led to altered antibiotic production against Escherichia coli and Bacillus subtilis. Taken together, our work reveals remarkable colonization patterns of endophytic streptomycetes with specific traits that may allow a competitive advantage inside root tissue.

microbiology↗

bioRxiv2017

YlmD and YlmE are required for correct sporulation-specific cell division in Streptomyces coelicolor A3(2)

Cell division during the reproductive phase of the Streptomyces life-cycle requires tight coordination between synchronous formation of multiple septa and DNA segregation. One remarkable difference with most other bacterial systems is that cell division in Streptomyces is positively controlled by the recruitment of FtsZ by SsgB. Here we show that deletion of ylmD (SCO2081) or ylmE (SCO2080), which lie in operon with ftsZ in the dcw cluster of actinomycetes, has major consequences for sporulation-specific cell division in Streptomyces coelicolor. Electron and fluorescence microscopy demonstrated that ylmE mutants have a highly aberrant phenotype with defective septum synthesis, and produce very few spores with low viability and high heat sensitivity. FtsZ-ring formation was also highly disturbed in ylmE mutants. Deletion of ylmD had a far less severe effect on sporulation. Interestingly, the additional deletion of ylmD restored sporulation to the ylmE null mutant. YlmD and YlmE are not part of the divisome, but instead localize diffusely in aerial hyphae, with differential intensity throughout the sporogenic part of the hyphae. Taken together, our work reveals a function for YlmD and YlmE in the control of sporulation-specific cell division in S. coelicolor, whereby the presence of YlmD alone results in major developmental defects.

microbiology↗

bioRxiv2017

SParticle, an algorithm for the analysis of filamentous microorganisms in submerged cultures

Streptomycetes are filamentous bacteria that produce a plethora of bioactive natural products and industrial enzymes. Their mycelial lifestyle typically results in high heterogeneity in bioreactors, with morphologies ranging from fragments and open mycelial mats to dense pellets. There is a strong correlation between morphology and production in submerged cultures, with small and open mycelia favoring enzyme production, while most antibiotics are produced mainly in pellets. Here we describe SParticle, a Streptomyces Particle analysis method that combines whole slide imaging with automated image analysis to characterize the morphology of submerged grown Streptomyces cultures. SParticle allows the analysis of over a thousand particles per hour, offering a high throughput method for the imaging and statistical analysis of mycelial morphologies. The software is available as a plugin for the open source software ImageJ and allows users to create custom filters for other microbes. Therefore, SParticle is a widely applicable tool for the analysis of filamentous microorganisms in submerged cultures.

microbiology↗

bioRxiv2016

Reversible metamorphosis in a bacterium

The cell wall is a shape-defining structure that envelopes almost all bacteria. One of its main functions is to serve as a protection barrier to environmental stresses. Bacteria can be forced in a cell wall-deficient state under highly specialized conditions, which are invariably aimed at interrupting cell wall synthesis. Therefore, the relevance of such cells has remained obscure. Here we show that many filamentous actinomycetes have a natural ability to generate a new, cell wall-deficient cell type in response to hyperosmotic stress, which we call S-cells. This wall-deficient state is transient, as S-cells are able to switch to the canonical mycelial mode-of-growth. Remarkably, prolonged exposure of S-cells to hyperosmotic stress yielded variants that are able to proliferate indefinitely without their cell wall. This is the first report that demonstrates the formation of wall-deficient cells as a natural adaptation strategy and their potential transition into stable wall-less forms solely caused by prolonged exposure to osmotic stress. Given that actinomycetes are potent antibiotic producers, our work also provides important insights into how biosynthetic gene clusters and resistance determinants may disseminate into the environment.

microbiology↗

bioRxiv2016

Hyphal aggregation and surface attachment of Streptomyces is governed by extracellular poly-β-1,6-N-acetylglucosamine

Streptomycetes are multicellular filamentous microorganisms, which are major producers of antibiotics, anticancer drugs and industrial enzymes. When grown in submerged cultures, the preferred enzyme producer, Streptomyces lividans, forms dense mycelial aggregates or pellets, which requires the activity of the proteins encoded by the matAB and cslA-glxA. Here we show that matAB encodes the biosynthetic genes for the extracellular polymeric substance (EPS) poly-{beta}-1,6-N-acetylglucosamine or PNAG. Heterologous expression of matAB in actinomycetes that naturally lack these genes was sufficient for PNAG production and induction of mycelial aggregation. Also, overexpression of matAB in a non-pelleting cslA mutant restored pellet formation, which could effectively be antagonized by the PNAG-specific hydrolase, dispersin B. Extracellular accumulation of PNAG allowed Streptomyces to attach to hydrophilic surfaces, unlike attachment to hydrophobic surfaces, which involves a cellulase-degradable EPS produced by CslA. Altogether, our data support a model in which pellet formation depends on hydrophilic interactions mediated by PNAG and hydrophobic interactions involving the EPS produced by CslA. These new insights may be harnessed to improve growth and industrial exploitation of these highly versatile natural product and enzyme producers.

microbiology↗