Characterisation of bacteria from Pinus sylvestris–Suillus luteus mycorrhizas and their effects on root–fungus interactions and plant growth

Abstract

Bacteria from Pinus sylvestris-Suillus luteus mycorrhizas were isolated, characterised, and their effects on P. sylvestris-S. luteus interactions and plant growth investigated in vitro. The isolates formed five distinct phenotypic and physiological groups. Two of the groups, accounting for 34 of the 55 isolates, consisted of Bacillus spp., with three subgroups represented. The other groups contained Burkholderia spp., Serratia spp. and Pseudomonas spp. Representatives from each bacterial group were used in microcosm experiments to investigate bacterial effects on P. sylvestris-S. luteus interactions. Most Bacillus isolates stimulated growth of S. luteus along the P. sylvestris root, while isolates of Pseudomonas and Serratia inhibited root colonisation by the fungus. Burkholderia and Serratia isolates inhibited ectomycorrhiza formation by 97 and 41% respectively, while a single Bacillus isolate doubled the formation of first order ectomycorrhizal roots. There were no clear relationships between effects of the bacteria on root colonisation by the fungus after 4 weeks, and chitinase production or subsequent ectomycorrhiza formation. However, isolates that inhibited ectomycorrhiza formation appeared to associate preferentially with ectomycorrhizal roots. Several isolates enhanced plant growth substantially, although these effects were unrelated to either root colonisation by the fungus or ectomycorrhiza formation.

Newly identified helper bacteria stimulate ectomycorrhizal formation in Populus

“…Bending et al ( 2002 ) also demonstrated that Pseudomonas isolates stimulated lateral root formation similar to our results. In total, these results suggest a diversity of growth promoting mechanisms operating on plant or fungi and/or both and illustrate the complexity of the evolving MHB concept.…”

“…Poole et al ( 2001 ) reported that bacteria ( Burkholderia and Pseudomonas ) isolated from Pinus sylvestris — Lactarius rufus mycorrhizas did not affect the total number of roots formed by the plants but only ectomycorrhizal formation. While Bending et al ( 2002 ) found bacteria isolates ( Burkholderia spp., Serratia spp., Pseudomonas spp., and Bacillus spp.) from Pinus sylvestris — Suillus luteus mycorrhizas stimulating root growth and even shoot growth by Bacillus spp.…”

Distinctive Feature of Microbial Communities and Bacterial Functional Profiles in Tricholoma matsutake Dominant Soil

“…In contrast, the bOTU richness of Firmicutes was higher in Tm -dominant soil. Firmicutes contains the genera Bacillus , Cohnella , and Paenibacillus , which are commonly found in mycorrhiza-associated environments [63–65]. Therefore, higher richness of Firmicutes may suggest a conserved trait associated with fungi-bacteria interaction or resistance to antibiotics.…”

“…Most of these genera were previously detected in the fairy ring of T . matsutake [13, 15], and are commonly found in the rhizosphere or mycorrhizosphere [63–65, 73]. In addition, these taxa may be similar on a functional level.…”

Selection of bacterial populations in the mycosphere of Laccaria proxima: is type III secretion involved?

“…The influence of the hyphal network at the base of fungal fruiting bodies on the local bacterial community structure in natural soil has, as far as we know, never been described in detail by a fingerprinting technique such as DGGE. Most research in this area so far has focused on specific groups of culturable bacteria selected under the influence of a certain fungus and not on bacterial community analyses (Frey et al, 1997;Bending et al, 2002;Rangel-Castro et al 2002;Tornberg et al 2003). Hence, for the first time we reveal a glimpse of an ecological effect on soil bacterial communities brought about by emerging fungal structures and presumably related to upshifts in growth-enhancing ecological opportunities for bacterial associates.…”