Circular structure of the genome of phage ϕH in a lysogenic Halobacterium halobium

✍ Scribed by Schnabel, Heinke ;Zillig, Wolfram

• Publisher: Springer
• Year: 1984
• Tongue: English
• Weight: 777 KB
• Volume: 193
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00382078

✦ Synopsis

is a temperate phage, i.e., it can establish lysogeny in the archaebacterium Halobacterium halobium. d~H-lysogens are immune to phage infection and phage production is spontaneously induced at a rate of about 10 -r. In the prophage state, ~H DNA exists as a covalently closed circle of 57 kb.

The frequent occurrence of clones carrying the phage genome but unable to produce phage is another proof of the high variability of DNA in H. hatobium. In one such strain. R~-3, the phage genome has undergone a structural change which may have abolished an essential phage gene.

Resistance to Infection by (~H. Cells in late exponential or early stationary culture (0.3 ml) were plated in soft agar. A 5 lal drop of phage solution (2 x 10 9 p.f.u./ml) was placed in the middle of the plate followed by incubation for 3 days. On sensitive bacteria a clear zone was left in the lawn where the drop had been placed; on resistant strains no effect was seen.

Assay of Phage Production. A 0.1 ml sample of undiluted or diluted culture was plated in soft agar together with 0.3 ml of a late exponential culture of tt. halobium R~ as indicator strain.