Hello, readers!

This edition is a good chance to reflect on how much of a microorganism’s potential is shaped by its interaction with the plant and with other beneficial microorganisms already present in the soil.

We look at a Streptomyces that suppresses Fusarium wilt in banana by recruiting bacteria instead of attacking the pathogen directly; how small changes in aeration and the carbon-to-nitrogen ratio during fermentation can shape what a microbial product becomes; a well-deserved milestone for Brazil’s microbial innovation ecosystem: its first International Depositary Authority for patentable microorganisms; and four fungi with agricultural potential isolated from the crater of an active volcano in Mexico.

Researchers studying Streptomyces yongxingensis Sy2-11 found that its ability to suppress Fusarium wilt in banana goes beyond directly antagonizing the pathogen.

In natural soil, plants treated with Sy2-11 showed a 60% reduction in disease incidence. When the experiment was repeated in sterilised soil, where the resident microbiome had been removed, that reduction fell to 13%.

A major part of the protection appears to come from a microbial recruitment mechanism.

Sy2-11 produces two sesquiterpenes, aristolene and ledene, that trigger banana roots to increase the production of 10-hydroxycapric acid (10-HCA). This root exudate attracts beneficial Bacillus to the rhizosphere, including B. velezensis Bac155, B. subtilis Bac21, B. xiamenensis Bac147 and B. zanthoxyli Bac58, where they contribute to disease suppression.

The mechanism can be summarized like this:

Streptomyces → plant signaling → root exudate remodeling → Bacillus recruitment → disease suppression

The study suggests a different way of thinking about microbial biocontrol.

Instead of screening a strain against the pathogen alone, which mainly measures its direct antagonistic activity, we may need to ask whether it can reshape the microbial community already living around the plant. This could have important implications for biological product development.

Researchers and companies developing microbial technologies often need to deposit living microorganisms in officially recognized collections as part of the patent process, because some inventions cannot be fully protected through a written description alone.

Embrapa Genetic Resources and Biotechnology, in Brasília, will become Brazil's first International Depositary Authority (IDA) for microorganisms, allowing microbial samples to be deposited with international validity under the Budapest Treaty.

Until now, Brazilian researchers and companies requiring this type of deposit had to send microbial samples abroad. With an IDA in Brazil, the process can happen locally, potentially reducing logistical barriers associated with international deposits.

For microbial biologicals, this means Brazilian companies can deposit and protect new strains locally instead of relying on an overseas depositary institution.

An active volcano in Mexico became the source of a collection of fungi with traits that could be valuable for agriculture.

Researchers at the Centro de Investigación en Biotecnología of the Universidad Autónoma del Estado de Morelos isolated four fungi with traits associated with temperature tolerance from the rhizosphere of plants growing inside the crater of El Chichón: a Trichoderma asperellum, an Aspergillus brasiliensis, an Aspergillus pseudoviridinutans and a Penicillium velutinum. They screened all four for indoleacetic acid, gibberellins, phosphate solubilisation, siderophores and hydrolytic enzymes, at 28 °C and again at 40 °C.

All four produced siderophores at both temperatures, but only T. asperellum and A. brasiliensis still solubilised phosphate at 40 °C, and cellulase activity at that temperature held up only in A. brasiliensis.

T. asperellum isolate R_34 showed the strongest activity against Botrytis cinerea among the isolates tested. On tomato leaves, control lesions reached around 3 cm after five days while treated leaves stayed under 0.5 cm, and on fruit it left practically no lesion.

A strain that maintains biological activity at 40 °C represents a different starting point for development than one selected only under standard laboratory conditions.

Researchers at Embrapa Meio Ambiente showed that fermentation conditions can influence the fungal structures and metabolites produced before formulation.

Working with Clonostachys rosea, they modified oxygen availability and the carbon-to-nitrogen ratio. More oxygen raised propagule yields overall. A high C:N ratio (50:1) pushed the fungus towards conidia, while microsclerotia formed only at a low ratio (10:1) combined with good aeration. The fermentation also generated antifungal metabolites known as sorbicillinoids.

The resulting fungal material and fermentation liquids were formulated into water-dispersible granules and tested against Botrytis cinerea in cherry tomato. All of the formulations tested reduced gray mold incidence. The work was published in MicrobiologyOpen.

For microbial biologicals, strain selection is only one part of product development. Fermentation conditions help determine what kind of biocontrol product a microorganism becomes.