Fitness effect of temperate phages vTRX321 and SM 113.1 on Rhizobium leguminosarum biovar trifolii TRX19 in vitro and in plant (clover) rhizosphere.

Rhizobia are nitrogen-fixing bacteria, which form symbioses with leguminous plants such as clover, beans and peas, in the form of globular structures on roots, known as root nodules. Rhizobia can be used as organic nitrogen fertilisers but their efficiency in nitrogen fixation varies in fields due to competition from native rhizobia which may be not so efficient as nitrogen fixation. This study was done to research whether temperate phages could be used to improve rhizobia by killing competitive rhizobia. Temperate phages are viruses, which can infect and integrate into host bacteria and are spontaneously released under different environmental conditions such as UV light as lytic viruses that can infect and kill competitive but highly susceptible rhizobia.In this study, we measured the relative fitness effects of two phages i.e. TRX19v32-1 and SM113.1 on Rhizobium leguminosarum biovar trifolii strain TRX19. We measured these effects in vitro and in the clover rhizosphere. In the lab, fitness effects were found to be variable at 24, 48 and 72 hours while in the plant experiment, we did not find any differences in the fitness effects, meaning that there were no fitness benefits of phage presence to the host bacteria competition in these experiments.