This report describes the cloning and sequencing of a chromosomally encoded tetracycline resistance determinant from a clinical isolate of methicillin-resistant Staphylococcus aureus. On the basis of the sequence, the gene is in the tet(M) class, and it was shown that the S. aureus tetA(M) gene is induced at the level of transcription.

The Escherichia coli rpsU-dnaG-rpoD operon contains an internal transcription terminator T1 located in the intergenic region between the rpsU and dnaG genes (Smiley et al. 1982). By cloning T1 as a small 127 bp fragment into the terminator probe plasmid pDR720 between the trp operator promoter and the assayable galK gene, it was shown that T1 acts as a strong transcription terminator, comparable in strength to the 3′ operon terminator T2. However, an operon sequence that occurs 5′ to T1 within the coding region of the rpsU gene and which has homology with the lambda nut site, (Lupski et al. 1983) when placed 5′ to T1 in the pDR720 plasmid construct, modifies transcription through T1 allowing expression of the galK gene. This sequence, called the dnaG nut site also modifies the termination activity of the external operon terminator T2. It is proposed that the dnaG nut site is a cis-acting element of an antitermination system in E. coli.

The complete nucleotide sequence of 5-kb DNA fragment immediately 5' to the rpsU-dnaG-rpoD macromolecular-synthesis operon in Escherichia coli has been determined. It encodes for six open reading frames. Transcriptional and translational analysis have shown that three of them (orfx, orfz1 and orfz2) are expressed in exponentially growing E. coli cells. The orfx, directly 5' to the rpsU gene but transcribed in the opposite direction, may be part of the rpsU-dnaG-rpoD macromolecular-synthesis operon.

The nucleotide sequences of the left ends of bacteriophage Mu DNA and that of its close relative D108 have been determined. The first 100 bp of phages Mu and D108 are substantially the same except for an octanucleotide change from bp 53 to 61 and other small interspersed base-pair changes from bp 61 to 200. The first five host nucleotides preceding the host-phage junction are generally, but not always, G + C-rich and these five nucleotides display no obvious consensus sequence. Both phages Mu and D108 share striking similarity in their end DNA sequences to the end sequences of the newly described Escherichia coli movable genetic element IS30.

The major surface antigen (circumsporozoite-protein) of the sporozoite stage of Plasmodium knowlesi has been cloned and characterized. The gene is notable for the presence of a 36 base pair unit repeated in tandem 12 times. These repeats may function at the DNA level in regulating gene expression and at the protein level in providing multiple copies of a single epitope (repitope) as part of a protein designed to evade and decoy the immune system.

Complementary DNA clones that code for the immunogenic region of the Plasmodium knowlesi circumsporozoite protein were shown to contain a tandemly repeating 36-base pair unit. A synthetic dodecapeptide corresponding to the predicted reading frame of the repeating nucleotide unit behaved, in an immunoradiometric assay, identically with the native P. knowlesi circumsporozoite protein. The repeating 36-base pair unit occurred 12 times within the gene and accounts for at least one-third of the amino acid sequence of the surface antigen protein.