The research team, led by Ivan Dudaš of the University of Novi Sad and Åbo Akademi University, tested five cyanobacterial strains alongside five fungal strains, both individually and in every possible cyanobacteria–fungi combination, on quartz sand tailings over a 90-day incubation period. The cyanobacteria included species from the genera Nostoc, Trichormus, Tolypothrix, and two strains of Chroococcidiopsis, while the fungal panel comprised Penicillium oxalicum, Purpureocillium lilacinum, Aspergillus clavatus, Penicillium brasilianum, and Talaromyces wortmannii. This systematic screening of all 25 pairings is what gives the study its unusual power: rather than assuming that mixing microbes is always beneficial, the researchers could measure exactly how each combination performed.

Biocrusts are natural features of arid and semi-arid ecosystems worldwide, where cyanobacteria, lichens, mosses, and fungi colonize the top millimeters of soil and hold it together. In natural settings, these crusts form slowly over years or decades. The concept behind induced biocrusts is to jump-start the process by seeding suitable substrates with pioneer organisms. Cyanobacteria are the classic choice because many filamentous species glide through sediment, excrete sticky exopolysaccharides, and even contribute to carbonate precipitation. But the authors of the new study argue that the fungal side of the partnership has been largely overlooked, even though fungi in natural biocrusts weave hyphal networks that enmesh sand grains and can supply nutrients and moisture to their photosynthetic partners.

To evaluate success, the team deployed a battery of physical and biochemical measurements. Scanning electron microscopy revealed whether the microbes had actually colonized the tailings and bound sediment particles together. Chlorophyll-a content served as a proxy for cyanobacterial biomass, while exopolysaccharide production—measured in both loosely bound and tightly bound fractions—indicated how much glue-like material the community was generating. The researchers also assessed fungal abundance, the thickness of the induced crust, water drop penetration time as a measure of surface water repellency, and sediment penetration resistance as an indicator of mechanical stability.

The results showed that pairing mattered enormously. Certain combinations produced striking synergies that far exceeded anything achieved by cyanobacteria alone. The pairing of Tolypothrix sp. with Penicillium oxalicum delivered substantial boosts in chlorophyll-a, exopolysaccharides, and water repellency, while Trichormus sp. combined with Purpureocillium lilacinum produced thicker induced crusts along with a modest increase in sediment stability. Scanning electron micrographs confirmed that in these successful combinations, the microbes had effectively colonized the sand and were binding particles through EPS-mediated stabilization, with fungal filaments and cyanobacterial filaments visibly entangling the quartz grains.

Just as revealing were the failures. Some pairings had little effect at all, and others actively harmed crust development. Tolypothrix sp. combined with either Penicillium brasilianum or Talaromyces wortmannii caused significant reductions in key indicators, demonstrating that incompatibility between strains can undermine the entire enterprise. The authors emphasize that the benefits of co-inoculation depend strongly on the compatibility of the specific microorganisms involved—a caution for anyone hoping to simply throw a microbial cocktail at a degraded landscape and expect improvement.

Correlation analysis added a layer of nuance that complicates any simple recipe for crust engineering. Chlorophyll-a and the loosely bound EPS fraction were positively correlated with each other and with water repellency, suggesting that photosynthetic biomass and polysaccharide glue reinforce one another and help the surface shed or repel water. Yet crust thickness told a different story: it was negatively correlated with water repellency, chlorophyll-a, and penetration resistance. In other words, thicker crusts were not automatically stronger or more photosynthetically active, and different functional traits of the induced biocrusts responded in contrasting ways. This decoupling means that restoration practitioners may need to decide which property matters most for a given site—surface sealing, mechanical resistance, or biomass accumulation—and select their microbial partners accordingly.

The implications extend well beyond a single laboratory experiment. Quartz sand tailings are generated in enormous quantities by mining and mineral processing operations around the world, and their fine, unconsolidated particles are prone to becoming airborne dust or washing into waterways. Conventional stabilization approaches often rely on physical barriers, chemical binders, or imported topsoil, all of which can be costly and environmentally problematic. An induced biocrust strategy, by contrast, works with living organisms that self-assemble, self-repair, and potentially begin the long process of building genuine soil, complete with organic matter and nutrient cycling. If tailored consortia can be matched to specific tailings chemistries and climates, rehabilitation could shift from heavy engineering toward ecological restoration.

The study also contributes to a broader scientific conversation about microbial interactions in extreme environments. Cyanobacteria–fungi partnerships echo the ancient symbioses that produced lichens, and understanding the rules that govern which pairings succeed could illuminate how early life colonized barren substrates on Earth—and perhaps how life might be established on other planets with regolith surfaces. The finding that compatibility, not mere co-presence, drives synergy suggests that the metabolic exchange between the partners—potentially involving carbon compounds, growth factors, and moisture retention—is finely tuned and species-specific. Mapping those exchanges is a likely next step for the field.

For now, the message of the research is one of cautious optimism. Co-inoculation of compatible cyanobacteria and fungi can markedly enhance induced biocrust formation and stabilize degraded mine tailings, offering what the authors describe as an effective biocrust-facilitated strategy for rehabilitating degraded substrates. But the same experiments show that the wrong pairing can stall or reverse progress. The era of microbial landscaping—seeding damaged landscapes with designer communities of photosynthetic and fungal pioneers—is coming into focus, and its success will depend on the kind of patient, systematic compatibility testing this study exemplifies. The desert’s own engineers, it turns out, work best in carefully chosen teams.

Subject of Research: Induced biocrust formation on mine tailings through cyanobacteria–fungi co-inoculation

Article Title: Co-inoculation of Cyanobacteria and Fungi Promotes Induced Biocrust Formation and Stabilization of Quartz Sand Tailings

Article References: Dudaš, I., Dulić, T., Čapelja, E., Nystrand, M., Palanački Malešević, T., Österholm, P., Svirčev, Z., & Meriluoto, J. (2026). Co-inoculation of Cyanobacteria and Fungi Promotes Induced Biocrust Formation and Stabilization of Quartz Sand Tailings. Microbial Ecology. https://doi.org/10.1007/s00248-026-02887-z

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02887-z

Keywords: biocrusts, cyanobacteria, fungi, mine tailings, exopolysaccharides, microbial consortia, ecosystem restoration, soil stabilization, microbial ecology, erosion control, Co-inoculation, Promotes