The use of a chromosome integration vector to map erythromycin resistance and production genes in Saccharopolyspora erythraea (Streptomyces erythraeus)

The thiostrepton-resistance-conferring plasmid pIJ702 was integrated into the ermE region of the chromosome of erythromycin (Er)-producing bacterium Saccharopolyspora erythraea (Streptomyces erythraeus) by single, reciprocal (Campbell) recombination between DNA cloned in the vector and homologous nucleotide sequences in the chromosome. Genetic mapping experiments by conjugational transfer were used to establish that the ErR gene, ermE, was located close to the Er-production loci eryA34 and eryB25.     

Extracellular complementation of a developmental mutation implicates a small sporulation protein in aerial mycelium formation by S. coelicolor

The filamentous bacterium S. coelicolor differentiates by forming aerial hyphae, which protrude into the air and metamorphose into chains of spores. Aerial hyphae formation is associated with the production of a small, abundant protein, SapB, which is present in a zone around colonies of differentiating bacteria. Production of SapB is impaired in bld mutants, which are blocked in aerial hyphae formation, but not in whi mutants in which spore formation is prevented. We report that aerial hyphae formation by a newly identified bld mutant is restored by juxtaposition of the mutant near colonies of SapB-producing bacteria or by the application of the purified protein near mutant colonies. These observations implicate SapB in aerial mycelium formation and suggest that SapB is a morphogenetic protein that enables hyphae on the surface of colonies to grow into the air.     

A novel method for the rapid cloning in Escherichia coli of Bacillus subtilis chromosomal DNA adjacent to Tn917 insertions

Summary A rapid and general procedure has been devised for the pBR322-mediated cloning in Escherichia coli of Bacillus subtilis chromosomal DNA extending in a specified direction from any Tn917 insertion. Derivatives of Tn917 have been constructed that contain a pBR322-derived replicon, together with a chloramphenicol-resistance (Cm^r) gene of Gram-positive origin (selectable in B. subtilis), inserted by ligation in two orientations into a SalI restriction site located near the center of the transposon. When linearized plasmid DNA carrying such derivatives was used to transform to Cm^r B. subtilis bacteria already containing a chromosomal insertion of Tn917, the pBR322 sequences efficiently became integrated into the chromosomal copy of the transposon by homologous recombination. It was then possible to clone chromosomal sequences adjacent to either transposon insertion junction into E. coli, using a selection for ampicillin-resistance, by transforming CaCl₂-treated cells with small amounts of insert-containing DNA that had been digested with various restriction enzymes and then ligated at a dilute concentration. Because pBR322 sequences may be inserted by recombination in either orientation with respect to the transposon arms, a single restriction enzyme (such as EcoRi or SphI) that has a unique recognition site in pBR322 DNA may be used to separately clone chromosomal DNA extending in either direction from the site of any transposon insertion. A family of clones generated from the region of an insertional spo mutation (spoIIH::Tn917) was used in Southern hybridization experiments to verify that cloned material isolated with this procedure accurately reflected the arrangement of sequences present in the chromosome. Strategies are discussed for taking advantage of certain properties inherent in the structure of clones generated in this way to facilitate the identification and study of promoters of insertionally mutated genes.     

An additional GerE-controlled gene encoding an abundant spore coat protein from Bacillus subtilis.

We describe the identification and characterization of a gene, herein designated cotG, encoding an abundant coat protein from the spores of Bacillus subtilis. The cotG open reading frame is 195 codons in length and is capable of encoding a polypeptide of 24 kDa that contains nine tandem copies of the 13-amino-acid long, approximately repeated sequence H/Y-K-K-S-Y-R/C-S/T-H/Y-K-K-S-R-S. cotG is located at 300 degrees on the genetic map close to another coat protein gene, cotB. The cotG and cotB genes are in divergent orientation and are separated by 1.3 kb. Like the promoter for cotB, the cotG promoter is induced at a late stage of sporulation under the control of the RNA polymerase sigma factor sigma K and the DNA-binding protein GerE. The -10 and -35 nucleotide sequences of the cotG promoter resemble those of other promoters recognized by sigma K-containing RNA polymerase, and centered 70 bp upstream of the apparent start site is a sequence that matches the consensus binding site for GerE. Spore coat proteins from a newly constructed cotG null mutant lack not only CotG but also CotB, a finding that suggests that CotG may be a morphogenetic protein that is required for the incorporation of CotB into the coat.     

Assembly of the cell division protein FtsZ into ladder-like structures in the aerial hyphae of Streptomyces coelicolor

In the filamentous bacterium Streptomyces coelicolor , the cell division protein FtsZ is required for the conversion of multinucleoidal aerial hyphae into chains of uninucleoidal spores, although it is not essential for viability. Using immunofluorescence microscopy, we have shown that FtsZ assembles into long, regularly spaced, ladder-like arrays in developing aerial hyphae, with an average spacing of about 1.3 μm. Within individual hyphae, ladder formation was relatively synchronous and extended for distances over 100 μm. These ladders were present only transiently, decreasing in intensity as chromosomes separated into distinct nucleoids and disappearing upon the completion of septum formation. Evidence from the overall intensity of immunofluorescence staining suggested that ladder formation was regulated in part at the level of the accumulation and degradation of FtsZ within individual aerial hyphae. Finally, FtsZ ladder formation was under developmental control in that long arrays of FtsZ rings could not be detected in certain so-called white mutants ( whiG , whiH and whiB ), which are blocked in spore formation. The assembly of FtsZ into ladders represents the earliest known molecular manifestation of the process of spore formation, and its discovery provides insight into the role of whi genes in the conversion of aerial hyphae into chains of spores. We have also described a novel use of a cell wall-staining technique to visualize apical tip growth in vegetatively growing hyphae.     

Characterization of the Bacillus subtilis sporulation gene spoVK.

The sporulation gene spoVK of Bacillus subtilis was cloned by use of the insertional mutation spoVK::Tn917 omega HU8. The spoVK gene was shown to be the site of an incorrectly mapped mutation called spoVJ517. Thus, a separate spoVJ gene as defined by the 517 mutation does not exist and is instead identical with spoVK.