New records of the blacklegged tick, Ixodes scapularis (Acari: Ixodidae) in Minnesota.

The Minnesota distribution of the blacklegged tick, Ixodes scapularis, was studied during 1998 and 1999. The majority of tick collecting was done by grouse hunters, who sent in specimens collected during the fall of 1998 and 1999. I. scapularis specimens were received from 17 counties, including eight counties in northern and central Minnesota that previously had no reports of I. scapularis. This brings the number of Minnesota counties with reported populations of I. scapularis to 30, mostly in the east-central, central, and northern parts of the state.

A chemoattractant cytokine associated with granulomas in tuberculosis and silicosis.

Chronic inflammation and granuloma formation are associated with mononuclear cell infiltrates and are characteristic pathologic responses in tuberculosis. To identify host cell genes involved in tuberculous pathology, we screened macrophage cDNA libraries for genes induced by mycobacterial infection. One gene isolated in this screen, osteopontin (also known as early T lymphocyte activation protein 1 or Eta-1), was of particular interest because it is a cytokine and macrophage chemoattractant. Further study revealed that Mycobacterium tuberculosis infection of primary human alveolar macrophages causes a substantial increase in osteopontin gene expression. Osteopontin protein was identified by immunohistochemistry in macrophages, lymphocytes, and the extracellular matrix of pathologic tissue sections of patients with tuberculosis. Increased osteopontin expression also was found to be associated with silicosis, another granulomatous disease. The association of osteopontin with granulomatous pathology, together with the known properties of the protein, suggest that osteopontin may participate in granuloma formation. The strategy of identifying host genes whose expression is altered by infection thus can provide valuable clues to disease mechanisms and will be increasingly valuable as additional human genome sequences become available.

Sequence and transcriptional analysis of the Streptomyces glaucescens tcmAR tetracenomycin C resistance and repressor gene loci.

Sequence analysis of the tcmA tetracenomycin C resistance gene from Streptomyces glaucescens GLA.O (ETH 22794) identifies one large open reading frame whose deduced product has sequence similarity to the mmr methylenomycin resistance gene from Streptomyces coelicolor, the Streptomyces rimosus tet347 (otrB) tetracycline resistance gene, and the atr1 aminotriazole resistance gene from Saccharomyces cerevisiae. These genes are thought to encode proteins that act as metabolite export pumps powered by transmembrane electrochemical gradients. A divergently transcribed gene, tcmR, is located in the region upstream of tcmA. The deduced product of tcmR resembles the repressor proteins encoded by tetR regulatory genes from Escherichia coli and the actII-orf1 gene from S. coelicolor. Transcriptional analysis of tcmA and tcmR indicates that these genes have back-to-back and overlapping promoter regions.

The Streptomyces glaucescens TcmR protein represses transcription of the divergently oriented tcmR and tcmA genes by binding to an intergenic operator region.

Preliminary evidence has been presented by Guilfoile and Hutchinson (J. Bacteriol. 174:3651-3658, 1992) suggesting that the Streptomyces glaucescens TcmR protein is a transcriptional repressor. Here, we extend that work by showing that transcription of the S. glaucescens tcmA gene is inducible by tetracenomycin C and that inactivation of the tcmR gene results in constitutive transcription of the tcmA gene. Gel retardation studies show that the TcmR protein binds to the tcmA-tcmR intergenic region in vitro and that this binding is inhibited by tetracenomycin C. Footprinting experiments demonstrate that the TcmR protein binds to an operator region that encompasses both the tcmA and the tcmR promoters. This genetic and biochemical evidence strongly supports the model of the TcmR protein acting as a repressor in inhibiting transcription of both the tcmA and the tcmR genes, in much the same way that TetR from Tn10 inhibits transcription of tetA and tetR.

A bacterial analog of the mdr gene of mammalian tumor cells is present in Streptomyces peucetius, the producer of daunorubicin and doxorubicin.

Sequence analysis of the drrAB locus from Streptomyces peucetius (American Type Culture Collection 29050) reveals the presence of two genes, drrA and drrB, both of which are required for daunorubicin and doxorubicin (Adriamycin) resistance in the heterologous host Streptomyces lividans. The DrrA protein is similar to a large family of ATP-binding transport proteins, including the proteins encoded by the mdr genes from mammalian tumor cells, which confer resistance to daunorubicin, doxorubicin, and some other structurally unrelated chemotherapeutic agents. The DrrB protein shows no significant similarity to other known proteins but is probably very hydrophobic, suggesting that it is located in the bacterial membrane. These two proteins may act jointly to confer daunorubicin and doxorubicin resistance by an analog of the antiport mechanism established for mammalian tumor cells that contain amplified or overexpressed mdr genes. Transcriptional analysis of the drrAB region supports the presence of one transcript containing drrA and drrB and indicates that these genes are expressed only during antibiotic production.