Abstract:Abstract: [Objective] We analyzed bacterial colonization associated with spores of arbuscular mycorrhizal fungi (AMF) Gigaspora margarita, to indicate their ecological niche, and to provide information for further researches on their populations or functions. [Methods] Six bacteria strains (Peanibacillus sp. M060106-1, Peanibacillus sp. M061122-2, Peanibacillus sp. M061122-6, Bacillus sp. M061122-4, Bacillus sp. M061122-10 and Brevibacillus sp. M061122-12) isolated from G. margarita spores were tagged with green fluorescence protein (GFP) using the carrier plasmid pNF8 (gfp-mut1). We analyzed the ecological niche and population dynamics of tagged strains on G. margarita under different conditions by using fluorescent microscope and/or plate counts. [Results] Four strains (M060106-1, M061122-6, M061122-10 and M061122-12) were tagged with GFP, showing high plasmid stability. These tagged strains possessed the basic characteristics identical to their original strains and, hence, were fit for short-term study of environmental colonization. All four GFP-tagged strains colonized the spore wall of G. margarita, and M061122-6 and M061122-12 further colonized the fungal hyphae. Under different pH conditions, the population dynamic of each GFP-tagged strain on the spores showed the same trend, i.e. first increased and then decreased, and the effects on the population size varied with different pH value. GFP-tagged strains colonized the spores of low viability more easily than those of high viability, and the population dynamic on the spores of high viability was different for each tagged strain. [Conclusion] The isolated bacteria associated with G. margarita spores can re-colonize the fungal spores, whereas their colonizing ability depends on their characteristics and environmental factors. These data contributes to the further understanding of populations and functions of AMF-associated bacteria.
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