An anaerobic rhizobacterium primes rice immunity

Abstract

we established a new protocol to isolate anaerobic bacteria from three root compartments, rhizosphere (soil surrounding the root), rhizoplane (root surface), and endosphere (root interior; Uekiet al., 2007; Edwardset al., 2015), in paddy soil, which is an ideal ecological niche for anaerobic bacteria. Then, the ability of Clostridium spp. to colonize plant root and improve plant fitness by activating induced systemic resistance (ISR) was evaluated. Lastly, we identified bacterial metabolites that function as ISR determinants, and demonstrated the potential application of BA as a bioprotectant. Collectively, we show that Clostridium spp. elicit ISR and improve plant fitness through root colonization. Collectively, we demonstrate thatClostridium spp. (mostly obligate anaerobes) function as PGPR, and that Clostridium spp. produce BA. Additional interesting questions remain: How do Clostridium spp. interact with other anaerobic and aerobic bacteria in soil? What is the direct effect of BA on rice soil microbiome? What other bacterial determinants, if any, activate plant immunity under anaerobic conditions? Further studies are needed to investigate the effects of Clostridium spp. on upland crops such as wheat, pepper, and tomato. Given their critical advantage, such as ability to maintain stable spore formation under aerobic conditions, allowing their preparation before their application in fields, Clostridium spp. could have potential as a biofertilizer and bioprotective agent that only germinates under anaerobic conditions, such as the rice rhizosphere.