Strain TR-1 Research Articles

Cloning and sequencing of the gene encoding the cell surface glycoprotein of Haloarcula japonica strain TR-1.

The triangular disk-shaped halophilic archaeon Haloarcula japonica strain TR-1 has a glycoprotein on its cell surface. The complete gene encoding the cell surface glycoprotein (CSG) was cloned and sequenced. The gene has an open reading frame of 2586 bp, and a potential archaeal promoter sequence approximately 150 bp upstream of the ATG initiation codon. The mature CSG is composed of 828 amino acids and is preceded by a signal sequence of 34 amino acid residues. A hydropathy analysis showed a hydrophobic stretch at the C-terminus, that probably serves as a transmembrane domain. The amino acid sequence of the Ha. japonica CSG showed 52.1% and 43.2% identities to those from the Halobacterium halobium and Haloferax volcanii CSGs, respectively. Five potential N-glycosylation sites were found in the mature Ha. japonica CSG, sites that were distinctly different from those in Hb. halobium and Hf. volcanii. The Ha. japonica CSG gene was expressed in Escherichia coli.

Egg transmission of avian reoviruses in chickens: Comparison of a trypsin‐sensitive and a trypsin‐resistant strain

Two groups of commercial Light Sussex hens with no cultural evidence of reovirus infection and very low titres of neutralising antibodies were mated with cockerels from 17 weeks of age. At 27 weeks of age the birds were separated into three groups, and were inoculated intranasally and intravenously with avian reovirus strain R2 which is resistant to trypsin, with strain TR1 which is sensitive to the enzyme or sham-inoculated. Of the eggs laid by the hens infected with strain R2, 13/29 infertile eggs and embryos which fails to hatch were positive for virus, as were 6/70 hatched chicks. Despite this, virus was never isolated from cloacal swabs from the hens. Virus-infected eggs were laid between days 5 to 17 post inoculation (p.i.). Virus was isolated from the liver of all six R2 virus-positive chicks, from the hock joint of four and from the intestine of three. In contrast, for the group infected with the trypsin-sensitive virus TR1, of 120 eggs laid in the 5-week period, virus was isolated once only, from a chick hatched from an egg laid 7 days p.i. This infected chick was one of 83 which hatched and virus was found only in the joint. In a further experiment, two groups of mature SPF hens were inoculated with the reoviruses as above. Cloacal swabs and tissue examination showed greater virus excretion and tissue distribution of R2 than TR1. These results helped to explain the much higher egg transmission rate of R2 than TR1. However, the rate of vertical transmission of chicken reoviruses in nature, where the infectious dose would normally be lower than given here, is likely to be low.

Purification and partial characterization of cell surface glycoprotein from extremely halophilic archaeon Haloarcula japonica strain TR-1

Haloarculajaponica has a glycoprotein on its cell surface. The cell surface glycoprotein of H. japonica was purified and characterized. It had an apparent molecular mass of 180 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The carbohydrate content was about 12% (wt/wt). The polypeptide portion contained a large proportion of acidic amino acids, and the sequence of 18 N-terminal amino acids was determined.

Early pathogenesis in chicks of infection with a trypsin‐sensitive avian reovirus

Experiments are described which show how the sensitivity to trypsin of avian reovirus strain TR1 restricts its replication in the intestine of the chicken in comparison with a trypsin-resistant strain R2. Following oral infection with a high dose (5.3 log10 TCID50), the trypsin-sensitive virus generally showed lower titres than the resistant one in all tissues examined. Infection of chicks with strain TR1 via the respiratory route enabled the virus to spread throughout the body and localize in the hock joint, an important target site for reoviruses. Trypsin-sensitive reoviruses might be transmitted via the respiratory route, even though TR1 caused little damage to the respiratory epithelium. Dose-response studies showed that TR1 injected via the footpad can localize in the hock joint after very low doses, but high oral doses (4-5 log10) are necessary for such localization. Intranasal infection was intermediate in effect.

The triangular halophilic archaebacteriumHaloarcula japonica strain TR-1

We have isolated a predominantly triangular disc-shaped halophilic archaebacterium, strain TR-1, from a Japanese saltern soil. The taxonomical characteristics of this strain led us to propose a new speciesHaloarcula japonica. The cell division ofHa. japonica strain TR-1 was analyzed by time lapse microscopic cinematography. Cell plates were laid down asymmetrically, generating triangular or rhombic daughter cells which then separated. We have demonstrated the occurrence of a glycoprotein with an apparent molecular mass of 170 kDa on the cell surface ofHa. japonica. The release of this cell surface glycoprotein (CSG), accompanied by a morphological change (triangular to spherical), was observed after lowering the magnesium concentration in the medium. Thus, it is likely that the CSG plays an important role in maintaining the characteristic shape ofHa. japonica.

Ultrastructure of the cell wall of the triangular halophilic archaebacterium Haloarcula japonica strain TR-1

Cells of the halophilic archaebacterium Haloarcula japonica strain TR-1 were prepared for electron microscopy using conventional fixation and the freeze-substitution method. Cell walls were not observed in thin sections of cells prepared by conventional procedures, whereas thin sections of cells prepared by the freeze-substitution method revealed a cell wall 20–25 nm in thickness composed of three layers. Arrays of hexagonal structures arranged on the cell surface were observed in grazing sections.

Ultrastructure of the cell wall of the triangular halophilic archaebacteriumHaloarcula japonicastrain TR-1

Cells of the halophilic archaebacterium Haloarcula japonica strain TR-1 were prepared for electron microscopy using conventional fixation and the freeze-substitution method. Cell walls were not observed in thin sections of cells prepared by conventional procedures, whereas thin sections of cells prepared by the freeze-substitution method revealed a cell wall 20–25 nm in thickness composed of three layers. Arrays of hexagonal structures arranged on the cell surface were observed in grazing sections.

A trypsin‐sensitive avian reovirus: Isolation and experimental infection of poults and chicks

A reovirus (strain TR1) was isolated from the hock joint of a turkey with arthritis. It was rarely excreted in the faeces of poults after oral or intranasal inoculation and only occasionally following footpad inoculation. The virus did not localise in the hock joints or cause lesions. Cyclophosphamide-induced immunosuppression of poults did not modify the infection. Oral inoculation of chicks with a high dose of strain TR1 resulted in joint localisation, of virus and erosive arthritis. Footpad inoculation caused deaths in 13 of 15 chicks by 8 days pi due to hepatic necrosis. Intranasal inoculation of chicks resulted in a delayed and limited faecal excretion. However, joint lesions were most marked in chicks infected via this route. The infectivity of strain TR1 in chick embryo liver cell monolayers was reduced by almost 3.0 log(10) after treatment with 0.01% trypsin for 30 min, but the infectivity of strain R2 was unaffected. Bile salts had no effect on either virus. This trypsin-sensitive reovirus was much more pathogenic for chicks than for poults. The respiratory route may be important in the dissemination of trypsin-sensitive avian reoviruses such as this.