Microorganisms from clean environments may be better at helping plants survive heavy metal contamination than microbes that have adapted to polluted habitats, a study by Polish researchers suggests.
The finding challenges the assumption that microorganisms from heavily contaminated soils are the best candidates for helping plants grow in post-industrial areas.
Researchers from the Małopolska Centre of Biotechnology and the Institute of Botany at Jagiellonian University, led by Rafał Ważny, PhD, worked with Agnieszka Domka, PhD, from the Institute of Botany of the Polish Academy of Sciences in Kraków. Their study of the seed microbiota of sand rock-cress (Arabidopsis arenosa) was published in the journal Microbiome.
The researchers examined endophytes – bacteria and fungi living inside seeds and accompanying plants from the earliest stages of development – to determine how metal toxicity affects these microorganisms and their role in plant adaptation to post-industrial habitats.
They found that heavy metals dramatically reduced bacterial diversity in plant seeds and substantially altered the structure of bacterial communities. Endophytic fungi, however, proved much more resilient: their communities remained almost unaffected by the presence of metals. The effects were also observed in subsequent generations of plants.
To test whether the origin of microorganisms affected plants' tolerance to heavy metals, the researchers created microbial communities from fungal and bacterial isolates taken from plants growing in both contaminated and uncontaminated areas.
Microbes from metal-free sites clearly supported the growth of plants exposed to heavy metal stress.
Further analysis showed that this effect was primarily driven by endophytic fungi rather than bacteria. Fungi from uncontaminated environments increased the biomass of plants exposed to heavy metals, while fungi from post-industrial areas did not have the same effect.
The findings challenge the assumption that microorganisms useful for the biological reclamation and purification of polluted soils are most likely to be found in heavily contaminated environments.
Instead, the key to supporting plant growth appears to lie in the innate properties of individual microbial strains rather than their previous exposure to heavy metals.
The researchers suggest that the search for effective biostimulants and plant-growth-promoting microorganisms for degraded areas should therefore extend to clean, natural habitats. Endophytic fungi from these environments, despite having no previous exposure to heavy metals, may prove particularly valuable in helping plants cope with contamination.
PAP - Science in Poland
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