Summary: The sequencing of the entire genetic complement of Streptomyces coelicolor A3(2) has been completed with the determination of the 365 023 bp sequence of the linear plasmid SCP1. Remarkably, the functional distribution of SCP1 genes somewhat resembles that of the chromosome: predicted gene products/functions include ECF sigma factors, antibiotic biosynthesis, a gamma‐butyrolactone signalling system, members of the actinomycete‐specific Wbl class of regulatory proteins and 14 secreted proteins. Some of these genes are among the 18 that contain a TTA codon, making them targets for the developmentally important tRNA encoded by the bldA gene. RNA analysis and gene fusions showed that one of the TTA‐containing genes is part of a large bldA‐dependent operon, the gene products of which include three proteins isolated from the spore surface by detergent washing (SapC, D and E), and several probable metabolic enzymes. SCP1 shows much evidence of recombinational interactions with other replicons and transposable elements during its history. For example, it has two sets of partitioning genes (which may explain why an integrated copy of SCP1 partially suppressed the defective partitioning of a parAB‐deleted chromosome during sporulation). SCP1 carries a cluster of probable transfer determinants and genes encoding likely DNA polymerase III subunits, but it lacks an obvious candidate gene for the terminal protein associated with its ends. This may be related to atypical features of its end sequences.

Summary: Interaction of the predatory myxobacterium Myxococcus xanthus with the non‐motile, antibiotic producer Streptomyces coelicolor was examined using a variety of experimental approaches. Myxococcus xanthus cells prey on S. coelicolor , forming streams of ordered cells that lyse the S. coelicolor hyphae in the contact area between the two colonies. The interaction increases actinorhodin production by S. coelicolor up to 20‐fold and triggers aerial mycelium production. Other bacteria are also able to induce these processes in S. coelicolor though to a lesser extent. These studies offer new clues about the expression of genes that remain silent or are expressed at low level in axenic cultures and open the possibility of overproducing compounds of biotechnological interest by using potent inducers synthesized by other bacteria.

Streptomyces, the main antibiotic-producing bacteria, responds to changing environmental conditions through a complex sensing mechanism and two-component systems (TCSs) play a crucial role in this extraordinary “sensing” device.

Streptomycetes are prokaryotic microorganisms that exhibit a complex, mycelial fungus-like cycle of morphological differentiation. Development involves at least two spatially separated types of cells: the branching hyphae of the substrate mycelium, which penetrate the stratum upon which the colony feeds, and the upwardly protruding hyphae of the aerial mycelium, which undergo metamorphosis into spores. The luciferase-encoding luxA and luxB operon of the luminescent marine bacterium Vibrio harveyi was used as a promoter probe to visualize gene expression in differentiating colonies of Streptomyces coelicolor. Promoters for developmental genes of several kinds gave distinctive temporal and spatial patterns of light emission.

Sequencing of Streptomyces genomes has revealed they harbor a high number of biosynthesis gene cluster (BGC), which uncovered their enormous potentiality to encode specialized metabolites. However, these metabolites are not usually produced under standard laboratory conditions. In this manuscript we report the activation of BGCs for antimycins, carotenoids, germicidins and desferrioxamine compounds in Streptomyces argillaceus, and the identification of the encoded compounds. This was achieved by following different strategies, including changing the growth conditions, heterologous expression of the cluster and inactivating the adpAa or overexpressing the abrC3 global regulatory genes. In addition, three new carotenoid compounds have been identified.