Information stored in a phage particle: Lactobacillus delbrueckii bacteriophage LL-H as a case

Abstract

The bacteriophage LL-H, that infects Lactobacillus delbrueckii ssp. lactis, is a typical pac-type double-stranded DNA phage. The genome, of about 34.7 kbp, is packaged inside an icosahedral proteinous capsid of approximately 50 nm diameter; LL-H possesses a 170 nm long noncontractile tail and one tail fiber of 30-35 nm length. This chapter summarizes some of the research data obtained with LL-H since the late 1970s. Here, besides brief considerations of its genomic organization, the major discussion focuses on the biology of LL-H, on its special structural features of prime importance for its survival and infectivity during the period when its DNA is in an inactive state, more precisely during the time that elapses between the DNA packaging and injection steps; during that time interval, the information for the specific phage-host interactions is stored in the phage particle itself. Models on the calcium/magnesium dependent adsorption and injection steps are also discussed for LL-H.