Biology subjects

van der Aart, L.

Publications and source records attributed to van der Aart, L..

3 recordsLinked to original sources

bioRxiv2018

High-resolution analysis of the peptidoglycan composition in Streptomyces coelicolor

The bacterial cell wall maintains cell shape and protects against bursting by the turgor. A major constituent of the cell wall is peptidoglycan (PG), which is continuously modified to allow cell growth and differentiation through the concerted activity of biosynthetic and hydrolytic enzymes. Streptomycetes are Gram-positive bacteria with a complex multicellular life style alternating between mycelial growth and the formation of reproductive spores. This involves cell-wall remodeling at apical sites of the hyphae during cell elongation and autolytic degradation of the vegetative mycelium during the onset of development and antibiotic production. Here, we show that there are distinct differences in the cross-linking and maturation of the PG between exponentially growing vegetative hyphae and the aerial hyphae that undergo sporulation. LC-MS/MS analysis identified over 80 different muropeptides, revealing that major PG hydrolysis takes place over the course of mycelial growth. Half of the dimers lack one of the disaccharide units in transition-phase cells, most likely due to autolytic activity. De-acetylation of MurNAc to MurN was particularly pronounced in spores, suggesting that MurN plays a role in spore development. Taken together, our work highlights dynamic and growth phase-dependent construction and remodeling of PG in Streptomyces.\n\nIMPORTANCEStreptomycetes are bacteria with a complex lifestyle, which are model organisms for bacterial multicellularity. From a single spore a large multigenomic, multicellular mycelium is formed, which differentiates to form spores. Programmed cell death is an important event during the onset of morphological differentiation. In this work we provide new insights into the changes in the peptidoglycan architecture over time, highlighting changes over the course of development and between growing mycelia and spores. This revealed dynamic changes in the peptidoglycan when the mycelia age, showing extensive PG hydrolysis and in particular an increase in the proportion of 3-3-cross-links. Additionally, we identified a muropeptide that is highly abundant specifically in spores, which may relate to dormancy and germination.

biochemistry↗

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↗

bioRxiv2016

Structural and Functional Characterization of the Alanine Racemase from Streptomyces coelicolor A3(2)

The conversion of L-alanine (L-Ala) into D-alanine (D-Ala) in bacteria is performed by pyridoxal phosphate-dependent enzymes called alanine racemases. D-Ala is an essential component of the bacterial peptidoglycan and hence required for survival. The Gram-positive bacterium Streptomyces coelicolor has at least one alanine racemase encoded by alr. Here, we describe an alr deletion mutant of S. coelicolor which depends on D-Ala for growth and shows increased sensitivity to the antibiotic D-cycloserine (DCS). The crystal structure of the alanine racemase (Alr) was solved with and without the inhibitors DCS or propionate, at 1.64 [A] and 1.51 [A] resolution, respectively. The crystal structures revealed that Alr is a homodimer with residues from both monomers contributing to the active site. The dimeric state of the enzyme in solution was confirmed by gel filtration chromatography, with and without L-Ala or D-cycloserine. Specificity of the enzyme was 66 +/- 3 U mg-1 for the racemization of L-to D-Ala, and 104 +/- 7 U mg-1 for the opposite direction. Comparison of Alr from S. coelicolor with orthologous enzymes from other bacteria, including the closely related D-cycloserine-resistant Alr from S. lavendulae, strongly suggests that structural features such as the hinge angle or the surface area between the monomers do not contribute to D-cycloserine resistance, and the molecular basis for resistance therefore remains elusive.

molecular biology↗