Journal: PLOS Biology
Article Title: Prophage induction can facilitate the in vitro dispersal of multicellular Streptomyces structures
doi: 10.1371/journal.pbio.3002725
Figure Lengend Snippet: ( A ) Growth and pH in BM and MP5 media. Each symbol represents an independent experiment. Due to the presence of large aggregates (see panel B ), the pseudo-opacimetry (OD 600 nm ) was not exploitable for DSM 40697 strain after 48 h of growth in BM medium. ( B ) Dispersed versus aggregated growth of S . ambofaciens strains in BM media. The results are representative of the appearance of the most frequently observed cultures, as the quantity and size of cell clusters may vary from one experiment to the other. The S . ambofaciens ATCC 23877 Δ Samy strain corresponds to clone #3, deleted from at least the phage integrase by a CRIPSR-based approach ( and ). Scale bar: 1.5 cm. ( C ) Microscopy of Streptomyces colonies after 4 d growth in BM medium. S . ambofaciens ATCC 23877 and its derivate CRISPR-deleted of Samy prophage (clone #3) were grown in BM medium and imaged using differential interference contrast microscopy (also see ). Scale bar: 10 μm. ( D ) Colony-forming units after 4 d of growth in BM medium. The S . ambofaciens ATCC 23877 Δ Samy strains correspond to 3 independent mutants (#1, #3, and #4) we obtained by a CRIPSR-based approach . The boxplot is plotted as described in the legend of . Each dot represents an independent experiment per condition. The p -values of two-sided Wilcoxon rank sum tests with continuity correction are indicated for each comparison. Please note that this number is the result of both cell survival and mycelium dispersal (propensity to form separate colonies). ( E ) Pattern of Samy MCP-mCherry expression in a S . ambofaciens colony. Bacteria encoding a MCP-mCherry fusion were inoculated from plates and grown 4 d in BM medium before red fluorescence imaging. The overlay of red fluorescence and bright field images is shown. Additional images and controls are presented in . Scale bar: 10 μm. ( F ) Correlation between Samy phage production and colony-forming units by diverse S . ambofaciens strains. S . ambofaciens strains obtained from distinct collections were grown during 4 d in BM medium, before counting colony-forming units and phage production in the supernatants. Even strains ATCC 23877 and DSM 40697 were cultured for this experiment from stocks produced by another laboratory. Each dot represents an independent experiment per strain. The correlation was analyzed by a Spearman rank correlation test. Results of 2 independent experiments. ( G ) Bioassay performed with the supernatants of S . ambofaciens ATCC 23877 WT strain and its derivatives deleted in Samy regions (clones #1, #3, and #4; and ). Then 50 μL of filtered supernatant from S . ambofaciens culture after 4 d in BM medium was deposited on a Micrococcus luteus mat, as previously described . The size of the M . luteus growth inhibition halo after 24 h incubation at 37°C was measured. The boxplot is plotted as described in the legend of . The p -values of two-sided Wilcoxon rank sum tests with continuity correction are indicated. ( H ) Model of the stress- and phage-induced dispersed growth of Streptomyces in liquid medium. After germination of the spore, the multicellular bacteria form successively primary and secondary mycelia. In the absence of prophage, the S . ambofaciens DSM 40497 tends to form particularly large and dense pellets in response to metabolic stress encountered in BM medium (nitrogen unbalance, translation inhibition, basic pH). Under the same conditions, phage production by S . ambofaciens ATCC 23877 is correlated with dispersed growth in sparse clumps and filaments. We propose that phage-induced cell death within the secondary mycelium leads to a dislocation of multicellular aggregates. The subsequent increase in the number of small colonies promotes strain dispersal under stressful conditions. The data and scripts underlying the A, D, F, and G panels can be found in and , respectively.
Article Snippet: The ATCC 23877 and DSM 40697 strains share 99.04% of average nucleotide identity calculated by using the BLASTn algorithm (ANIb) [ ], indicating that they belong to the same species.
Techniques: Microscopy, CRISPR, Comparison, Expressing, Bacteria, Fluorescence, Imaging, Cell Culture, Produced, Bioassay, Clone Assay, Inhibition, Incubation