5b, d and f), showed very little growth after 30 days, but significant growth and attachment after 45 days of incubation.
On the other hand, Bacillus cereus showed little if any growth on the fungal surface (data not shown). In contrast to the spore-collected bacteria, the non-soil control bacteria E. coli showed no growth on the water media and little affinity to the fungal surface (Fig. 5 h). AZD3965 molecular weight As expected, negative controls using sterile water inoculated either on the mycelium or on the media without mycelium showed no growth (data not shown). The growth and attachment of the bacterial isolates on the hyphal surface are summarized in the Supporting Information. This study aimed to isolate soil bacteria closely associated with the mycelium of the AMF G. irregulare grown in vitro. We developed an experimental Petri dish system to study the hyphal attachment of bacteria in the absence of nutrients other than those derived from the mycelium and monitored the interactions of bacteria inoculated at similar concentrations
on the mycelium and incubated for 15, 30 or 45 days before observation. It is well known in the literature that bacterial colonization of the rhizosphere is GDC-0199 chemical structure extremely important for plant–microorganism interactions including pathogenic and symbiotic interactions. In addition, research in microbial ecology has revealed that bacteria from soil adhere specifically to AMF hyphae. However, these interactions are quite complex and community structure changes are affected by many factors. In the present work, 29 bacterial morphotypes associated with the AMF G. irregulare spores were recovered successfully. 16S rRNA gene sequencing showed that they belong to only seven different bacterial species: B. cereus, Bacillus megaterium, B. simplex, K. rhizophila, M. ginsengisoli,
Sphingomonas sp. and V. paradoxus (Table 1). Interestingly, V. paradoxus was the most frequent bacterial taxon isolated from spores (13 morphotypes out of 29). All these bacterial taxa are commonly found in soil. The results supported the hypothesis that some bacteria adhering Succinyl-CoA onto the spore surface and likely living on the AMF mycelium surface were able to grow in vitro with AMF hyphae as the sole energy source. We tested the growth of the isolated bacteria on sterile water solidified with gellan gum lacking nutrients and we did not observe any bacterial growth. This test shows that these bacteria are not able to grow on gellan gum alone. It is likely that the bacterial taxa having grown around G. irregulare hyphae in vitro were mostly taxa adapted to metabolize the molecules released by the hypha because no other nutrients were available. However, it is also likely that this method would isolate only the most competitive and fast-growing taxa whose portion of the total bacterial biodiversity is unknown. Kirk et al. (2004) estimated that standard microbiological techniques may allow the growth of only about 1% of the soil bacterial taxa from environmental samples.