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The pSETT4 vector integrates into the Actinoplanes sp. SE50/110 chromosome via the bacteriophage φC31 integrase and allows cloning of a gene of interest by Golden Gate assembly (BsaI). T4 terminators surround the expression cassette to isolate the transcriptional unit and to prevent antisense transcription. The system can be used in other Actinomycetales by exchanging the promoter., (Copyright © 2020 Schaffert et al.)

Sinorhizobium meliloti Rm41 nodulates alfalfa plants, forming indeterminate type nodules. It is characterized by a strain-specific K-antigen able to replace exopolysaccharides in promotion of nodule invasion. We present the Rm41 genome, composed of one chromosome, the chromid pSymB, the megaplasmid pSymA, and the nonsymbiotic plasmid pRme41a.

Neisseria meningitidis is a commensal and accidental pathogen exclusively of humans. Although the production of polysaccharide capsules is considered to be essential for meningococcal virulence, there have been reports of constitutively unencapsulated strains causing invasive meningococcal disease (IMD). Here we report the genome sequence of a capsule null locus (cnl) strain of sequence type 198 (ST-198), which is found in half of the reported cases of IMD caused by cnl meningococcal strains.

Sinorhizobium fredii HH103 is a fast-growing rhizobial strain that is able to nodulate legumes that develop determinate nodules, e.g., soybean, and legumes that form nodules of the indeterminate type. Here we present the genome of HH103, which consists of one chromosome and five plasmids with a total size of 7.22 Mb.

Neisseria meningitidis serogroup B strains are responsible for most meningococcal cases in the industrialized countries, and strains belonging to the clonal complex ST-41/44 are among the most prevalent serogroup B strains in carriage and disease. Here, we report the first genome and transcriptome comparison of a serogroup B carriage strain from the clonal complex ST-41/44 to the serogroup B disease strain MC58 from the clonal complex ST-32. Both genomes are highly colinear, with only three major genome rearrangements that are associated with the integration of mobile genetic elements. They further differ in about 10% of their gene content, with the highest variability in gene presence as well as gene sequence found for proteins involved in host cell interactions, including Opc, NadA, TonB-dependent receptors, RTX toxin, and two-partner secretion system proteins. Whereas housekeeping genes coding for metabolic functions were highly conserved, there were considerable differences in their expression pattern upon adhesion to human nasopharyngeal cells between both strains, including differences in energy metabolism and stress response. In line with these genomic and transcriptomic differences, both strains also showed marked differences in their in vitro infectivity and in serum resistance. Taken together, these data support the concept of a polygenic nature of meningococcal virulence comprising differences in the repertoire of adhesins as well as in the regulation of metabolic genes and suggest a prominent role for immune selection and genetic drift in shaping the meningococcal genome.

The production of Shiga toxin (Stx) (verocytotoxin) is a major virulence factor of Escherichia coli O157:H7 strains (Shiga toxin-producing E. coli [STEC] O157). Two types of Shiga toxins, designated Stx1 and Stx2, are produced in STEC O157. Variants of the Stx2 type (Stx2, Stx2c) are associated with high virulences of these strains for humans. A bacteriophage designated 2851 from a human STEC O157 encoding the Stx2c variant was described previously. Nucleotide sequence analysis of the phage 2851 genome revealed 75 predicted coding sequences and indicated a mosaic structure typical for lambdoid phages. Analyses of free phages and K-12 phage 2851 lysogens revealed that upon excision from the bacterial chromosome, the loss of a phage-encoded IS629 element leads to fusion of phage antA and antB genes, with the generation of a recombined antAB gene encoding a strong antirepressor. In wild-type E. coli O157 as well as in K-12 strains, phage 2851 was found to be integrated in the sbcB locus. Additionally, phage 2851 carries an open reading frame which encodes an OspB-like type III effector similar to that found in Shigella spp. Investigation of 39 stx(2c) E. coli O157 strains revealed that all except 1 were positive for most phage 2851-specific genes and possessed a prophage with the same border sequences integrated into the sbcB locus. Phage 2851-specific sequences were absent from most stx(2c)-negative E. coli O157 strains, and we suggest that phage 2851-like phages contributed significantly to the dissemination of the Stx2c variant toxin within this group of E. coli.