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Lunar and Martian Simulant PGPB Lettuce SynCom

Community ID CommunityMech:000304
Ecological State ENGINEERED
Environment greenhouse regolith-simulant pot cultivation
ENVO:01001405

A defined four-strain plant growth-promoting bacterial (PGPB) consortium designed for space-agriculture (In-Situ Resource Utilization) research, composed of Azotobacter chroococcum 76A, Priestia megaterium EL5, Methylobacterium populi VP2, and Kosakonia pseudosacchari TL13. The strains belong to the microbial collection of the Department of Agricultural Sciences of the University of Naples Federico II and were selected for complementary plant growth-promoting traits (nitrogen fixation, phosphate solubilization, phytohormone biosynthesis) and for mutual non-antagonism in dual-culture assays. In a greenhouse pot experiment, the consortium was combined with green compost derived from plant residues (pH 8.25, low C/N ratio) to improve lettuce (Lactuca sativa cv. Grand Rapids) growth on commercial Lunar (LHS-1) and Martian (MMS-1) regolith simulants with zero external chemical input aside from the compost. Compost amendment increased lettuce biomass and nutrient bioavailability, and PGPB inoculation enhanced leaf biomass and mineral nutritional content while significantly increasing the copy number of functional marker genes for nitrogen fixation (nifH), alkaline phosphatase (phoD), and phytase (BPP) in non-amended substrates. The system is a Bioregenerative Life Support System model relevant to regolith-agriculture and long-term space missions.

Taxonomy

Taxon Ontology ID Functional Roles Abundance
Azotobacter chroococcum 76A NCBITaxon:353 N/A
Priestia megaterium EL5 NCBITaxon:1404 N/A
Methylobacterium populi VP2 NCBITaxon:223967 N/A
Kosakonia pseudosacchari TL13 NCBITaxon:1646340 N/A

Ecological Interactions

Ecological interaction network for Lunar and Martian Simulant PGPB Lettuce SynCom Bipartite graph where circle nodes represent taxa and colored rectangles represent ecological interactions (cross-feeding, mutualism, syntrophy, competition, commensalism).
Taxon
Cross-feeding
Mutualism
Syntrophy
Competition
Commensalism
Niche partitioning
Colonization facilitation
Strain competition
Predation

Non-antagonistic PGPB consortium assembly

COMMENSALISM

Evidence

PGPB rhizosphere colonization and functional-gene enrichment

COLONIZATION_FACILITATION

Target Taxon: Lactuca sativa (lettuce host)

Biological Processes:

Evidence

PGPB-enhanced lettuce growth and mineral nutrition

MUTUALISM

Target Taxon: Lactuca sativa (lettuce host)

Biological Processes:

  • indoleacetic acid biosynthetic process (GO:0009684)

Evidence

External Resources

Name Repository Resource ID
Primary publication - PGPB consortia and green compost on regolith simulants
Duri et al. 2025, Biology and Fertility of Soils - primary source describing the four-strain PGPB consortium and green compost improving lettuce growth on Lunar and Martian regolith simulants. 		OTHER doi:10.1007/s00374-025-01923-3
NCBI Taxonomy - Azotobacter chroococcum
NCBI Taxonomy record for Azotobacter chroococcum. 		OTHER NCBITaxon:353
NCBI Taxonomy - Priestia megaterium
NCBI Taxonomy record for Priestia megaterium. 		OTHER NCBITaxon:1404
NCBI Taxonomy - Methylorubrum populi
NCBI Taxonomy record for Methylorubrum populi (formerly Methylobacterium populi). 		OTHER NCBITaxon:223967
NCBI Taxonomy - Kosakonia pseudosacchari
NCBI Taxonomy record for Kosakonia pseudosacchari. 		OTHER NCBITaxon:1646340

Environmental Factors

Factor Value Unit
Regolith simulant substrate Lunar Highlands Simulant (LHS-1) and Mojave Mars Simulant (MMS-1) N/A
Regolith alkalinity and nutrient limitation alkaline pH (9 to 10), organic-matter-poor N/A
Green compost amendment green compost, pH 8.25, low C/N ratio, 20% v/v N/A
Greenhouse climate mean air temperature 13 C; 10/14 photoperiod N/A

Growth Media

PGPB inoculum production media (per-strain fermentor cultivation)

pH 7.00
Atmosphere AEROBIC

Preparation notes: Each strain was cultivated separately in a strain-specific complex medium: Brain Heart Infusion (BHI) for K. pseudosacchari TL13, Yeast Mannitol Broth (YMB) for A. chroococcum 76A, Plate Count Broth (PCB) for P. megaterium EL5, and Nutrient Broth (NB) for M. populi VP2. Fermentations were run at 30 C (K. pseudosacchari, P. megaterium), 28 C (A. chroococcum), and for M. populi, at pH 7.00, 130 rpm agitation, air sparging 0.5 vvm, with antifoam added. Biomass was centrifuged and freeze-dried; inocula were resuspended to 1e6 CFU/mL per strain and applied to lettuce by a root-dip method plus repeated collar application after transplanting.

Evidence

doi:10.1007/s00374-025-01923-3

"pH 7.00, agitation at 130 rpm, air sparging at 0.5"

doi:10.1007/s00374-025-01923-3

"freeze-dried for long term"

doi:10.1007/s00374-025-01923-3

"root dip method"