Lysogenic (or temperate) phages are capable of specifically or nonspecifically integrating their genomic material into that of the bacterial host, whereas lytic phages immediately
induce rapid phage replication followed by destruction of the host cell. Lysogenic phages are therefore characterized by vertical transmission, meaning that the phage genetic material is replicated together with the host genome. Upon integration into the bacterial genome, the phage becomes a so-called prophage, which is able to replicate alongside the host’s genetic material without killing the host. This establishes a long-term dynamic between the prophage and the bacterium, in which bacterial survival is prioritized. Bacteriophage SPβ has a 134 kbp genome that contains a biosynthetic gene cluster (BGC). BGCs encode proteins and enzymes that enable the synthesis of specialized metabolites that may benefit the bacterial host in various ways. Within phage genomes, BGCs are extremely rare and predominantly encode bacteriocins. Because bacteriocins enable bacteria to eliminate closely related strains and thereby reduce competition, in this master’s thesis we focused on investigating the hypothesis that the host range of the Bacillus subtilis bacteriophage SPβ does not overlap with the activity spectrum of sublancin. B. subtilis is commonly found in soil, on plants, and in the gastrointestinal tracts of mammals. The aim of this study was to develop a method that enables high-throughput screening of a large number of B. subtilis strains in a single experiment to determine their sensitivity to sublancin and to be able to also quantify the results. For method development, the wild-type strain MB8_B7 was used; this strain is a soil isolate and already harbors the SPβ phage, which enables it to produce sublancin. Through the production of sublancin,bacteriophage SPβ inhibits the growth of sensitive strains (lacking the BGC that also contains the resistance gene) by inhibiting DNA replication, transcription, and RNA translation. To compare the host range of the bacteriophage with the activity spectrum of sublancin we tested B. subtilis and other closely related isolates from several collections housed at the Chair of Microbial Ecology and Physiology, including isolates from the banks of the Sava River, pollen isolates, desert strains, strains from Denmark, and others. The results showed that the activity spectra of sublancin and phage SPβ do not overlap. Most strains were resistant to the phage but sensitive to sublancin, whereas only one strain was sensitive to the phage and resistant to sublancin. Several strains were resistant to both the phage and sublancin, which suggests the possible presence of a prophage or related elements in their genomes.
|
