Maize Root Simplified Bacterial Community

Host-mediated selection yielded a seven-strain bacterial model that reproducibly assembled on axenic maize roots and retained all seven members through 15 days, despite changing relative and absolute abundances. This is conditional persistence in a gnotobiotic system, not asymptotic stability, universal host compatibility or direct bacterial facilitation of colonization. Community structure differed in unplanted MS agar, supporting host dependence. The canonical seven bacterial terms and maize host identify the studied system; source strain names and unresolved taxonomy mappings are preserved, not independently recertified.

Participating Taxa: Enterobacter cloacae AA4, Stenotrophomonas maltophilia AA1, Ochrobactrum pituitosum AA2, Herbaspirillum frisingense, Pseudomonas putida, Curtobacterium pusillum, Chryseobacterium indologenes, Zea mays

Biological Processes:

• biological process involved in interspecies interaction between organisms (GO:0044419 · PathwayMech)

Evidence

• PMID:28275097 - SUPPORT (IN_VIVO)
  "In this work, from the distinctive microbiota assembled by maize roots, through host-mediated selection, we obtained a greatly simplified synthetic bacterial community consisting of seven strains (Enterobacter cloacae, Stenotrophomonas maltophilia, Ochrobactrum pituitosum, Herbaspirillum frisingense, Pseudomonas putida, Curtobacterium pusillum, and Chryseobacterium indologenes) representing three of the four most dominant phyla found in maize roots"

Removing E. cloacae from the seven-strain inoculum caused C. pusillum overgrowth and loss or strong decline of the other five bacteria on maize roots by day 15. Selective-plate absolute CFUs distinguish both C. pusillum expansion and decreases of other members, not merely relative-composition dilution. In unplanted MS agar, the same removal did not produce C. pusillum takeover. This perturbation establishes a host-dependent community keystone effect, not direct pairwise competition between E. cloacae and C. pusillum or a resolved molecular route. Removing P. putida also increased C. pusillum, but less dramatically. All seven bacterial participants and maize define the comparison, including the omitted member in its control inoculum.

Participating Taxa: Enterobacter cloacae AA4, Stenotrophomonas maltophilia AA1, Ochrobactrum pituitosum AA2, Herbaspirillum frisingense, Pseudomonas putida, Curtobacterium pusillum, Chryseobacterium indologenes, Zea mays

Biological Processes:

• biological process involved in interspecies interaction between organisms (GO:0044419 · PathwayMech)

Evidence

• PMID:28275097 - SUPPORT (IN_VIVO)
  "Only the removal of E. cloacae led to the complete loss of the community, and C. pusillum took over"
• PMID:28275097 - SUPPORT (IN_VIVO)
  "This result suggests that E. cloacae plays the role of keystone species in this model ecosystem"

The seven-strain community delayed visible Fusarium verticillioides colonization of maize seeds and reduced seedling-blight severity in laboratory assays; it also inhibited fungal growth on PDA and nutrient agar. Seed colonization was delayed, not eradicated: group differences became nonsignificant on day 10. All seven individual strains showed weaker protection to varying degrees, with E. cloacae strongest among them; the whole community performed better. This supports biocontrol without establishing every member as necessary, synergistic interaction, resource competition or host immune activation. Uninfected seed germination and root-growth tests did not show significant promotion. Participants include seven bacteria, the maize host for in-planta endpoints, and the fungal target, not a nine-member bacterial inoculum.

Participating Taxa: Enterobacter cloacae AA4, Stenotrophomonas maltophilia AA1, Ochrobactrum pituitosum AA2, Herbaspirillum frisingense, Pseudomonas putida, Curtobacterium pusillum, Chryseobacterium indologenes, Zea mays, Fusarium verticillioides

Evidence

• PMID:28275097 - SUPPORT (IN_VIVO)
  "In planta and in vitro, this model community inhibited the phytopathogenic fungus Fusarium verticillioides, indicating a clear benefit to the host"