Some properties of bacteriophages active on the obligate anaerobe Clostridium sporogenes

Abstract

The most commonly encountered bacteriophages active on Clostridium sporogenes have elongated six-sided heads and simple, tubular, noncontractile tails. These viruses have minimum latent periods of about 1 hour at 37° and yield average burst sizes from 17 to 150 PFU/cell. Phage F1 was selected as typical of this group and has been characterized in these studies. F1-directed DNA synthesis begins 20 minutes after infection, and the first mature intracellular virus particles are formed in 40 minutes. Infected cells begin to lyse 60 minutes after infection, and lysis is complete within 90 minutes. F1 particles sedimented with an S obs. of 301, and were composed of 40% protein and 60% DNA. The DNA gave a thermal denaturation profile typical of double-stranded DNA with a T M value of 85.2°. This indicates a 39.5% GC content which is somewhat higher than 33.2% GC found for its host, C. sporogenes 213. Two other viruses, active on strains of C. sporogenes but encountered less frequently, were a very large phage 420 mμ in length with an icosahedral head and a noncontractile tail, and a temperate phage with a smaller icosahedral head and a tail with a contractile sheath. All these viruses were similar to phages described for aerobic, gram-positive bacteria.