Abstract
Antiphage properties of many kinds of chemicals such as antibiotics, surface-active agents and chelating agents were examined on Brevibacterium lactofermentum No. 2256-phage P465 system using double-layer agar method, as a part of the basic study, for pre-venting phage infection in the industrial fermentation.
A great majority of inhibitors which were selected were usually nonspecific and inhibited also bacterial growth. Among about 200 chemicals tested, 5 antibiotics such as chloramphenicol and tetracycline, 6 chelating agents such as phytic acid and 19 surface-active agents such as PEG monoester and POE alkyl ether showed the selective inhibitions for phage infection at the concentrations which did not affect bacterial growth, or at the subbactericidal concentrations that suppressed bacterial growth slightly.
Of the above chemicals which showed selective inhibitions for phage infection, a possible mechanism of chelating agents chiefly of phytic acid was investigated. When 0.1 to 0.2%, of phytic acid was present in the medium, the effect of inhibition was most remarkable; this could be applied to the actual phage-infected L-glutamic acid fermentation. Phytic acid had no direct phagocidal action, nor did it inhibit the late step of the phage multiplication; but it prevented the adsorption of phages, which required inorganic co-factors such as Mg2+ or Ca2+ in this step, to the host bacteria. Moreover, a part of the infected bacteria was made incapable of forming plaques in the presence of phytic acid. These results suggested that the chelation between Mg2+ or Ca
and phytic acid would remove the metal ions essential for phage adsorption and prevent the phage adsorption and infection of phage DNA, consequently, the phage infection.
