Marsigli (1658–1730), the Bolognese Count and polymath of the Enlightenment, was a man of extraordinary breadth. His interests spanned books, manuscripts, geology, mineralogy, cartography, oceanography, military affairs, botany and mycology. In 1685 he published a 47-page treatise entitled “Bevanda asiatica,” referring to coffee as an Asian drink. Although this might sound odd—Coffea arabica is endemic to Africa, not Asia—coffee at the time was sourced from Yemen, a country located in the southwestern region of the Asian continent. The treatise, written in Italian, is divided into three sections: a dedication to Cardinal Francesco Buonvisi, a parallel Italian–Ottoman Turkish translation of a manuscript, and Marsigli’s own hard-won knowledge of coffee preparation.

The manuscript Marsigli acquired in Constantinople (present-day Istanbul) in 1679 was written by Hezârfen Hüseyin Efendi, whose name Marsigli rendered variously as “Cuseim Efendi,” “Cosain Efendi” and “Cossain Effendi.” The manuscript was part of Hüseyin’s medicinal encyclopedia, entitled “Tuhfetü’l-Erîbi’n-Nâfia li’r-Rûhânî ve’t-Tabîb” (“Useful and Skillful Gift for Doctors and All Creatures”), of which nine copies are known. Whether Marsigli translated the manuscript himself or relied on an interpreter remains unclear, but the evidence suggests the latter: Marsigli himself admitted he was “pleased with the few Turkish words that I had learned,” and historical accounts note he was accompanied by Jewish interpreters and dragomans of the Venetian embassy during his first visit to Istanbul.

Hüseyin’s manuscript contains one of the earliest descriptions by someone who had observed coffee plants in situ in Yemen. He reported that the coffee tree grew in only two districts—the county of Usab and the county of Naharii—and described trees, some 20 to 30 years old, with white flowers, very similar to cherry trees, planted in a straight line. When the fruit reached maturity, it became “dark red like the color of a wild cherry, and sweet like it.” Hüseyin also discussed the drying of coffee on flat terraces, dehulling, and the preparation of the drink, noting that the dried peel was boiled in water as a summer refreshment. He further described the drink’s properties: it preserved the stomach, was useful against drunkenness and opium intoxication, removed sleep, and, when drunk moderately, brought happiness rather than melancholy.

Marsigli’s third section of “Bevanda asiatica” deals with “l’arte di cucinar questo frutto”—the art of cooking the coffee fruit—an art he learned in the most unusual way. In 1683, while serving in the army of the Habsburg Holy Roman Empire, he was wounded and became a prisoner of the Ottoman Empire prior to the two-month-long Siege of Vienna. He was held as a slave from July 2, 1683 to March 25, 1684, when ransom was paid for his freedom. Assigned to a cupboard-keeper who ran a public coffee shop, Marsigli had to roast, cook and distribute coffee to buyers. He learned, “at the cost of many lashes,” that roasting must be done with constant motion in a copper pan to a state of perfection manifesting as a dark umber color—beyond black, the grains became like coals, changing the strength, flavor and properties of the drink. He also learned that the roasting does not cover the surface of the grain, and that the middle can remain raw, damaging the flavor when reduced to powder.

The only engraving in “Bevanda asiatica” is a title-page attempt at illustrating a coffee plant. It depicts a landscape with hills and trees, and a terminal branch with two alternate leaves bearing serrated margins. Coffee leaves are not serrated but entire—smooth, without teeth or lobes. Cherry leaves, by contrast, are serrate or serrate-crenate. Three round fruits attached to the branch resemble cherry fruits, not coffee. Yet the engraving also shows three seeds perfectly recognizable as coffee seeds, which makes sense as coffee beans were the marketable product and widely available at the time. The engraver’s signature appears to be “Ac. G. f,” with the “f” an abbreviation for the Latin “fecit”—“made it.”

In 1703, Marsigli published a 14-page coffee monograph, “Notizie, di Costantinopoli; sopra la pianta del caffè,” with a bilingual title reflecting that both Italian and Latin are interspersed throughout. The lower part of the title page bears an engraving very similar to the one in “Bevanda asiatica,” with the same engraver initials. The “Praefatiuncula” was written in Latin by Johann Samuel Schoder, an assistant to Georg Christoph Eimmart, an engraver and astronomer in Nuremberg. Schoder makes clear he is simply relaying Marsigli’s information, noting that Marsigli was “abroad serving his Caesar.” Indeed, in 1703 Marsigli was engaged in the War of the Spanish Succession and would surrender the fortress of Breisach, resulting in his dishonorable discharge in early 1704. A similar delegation of authority had occurred with Marsigli’s 1698 “Dissertazione epistolare del fosforo,” where errors crept in during his absence.

Schoder’s Preface is followed by four pages of coffee plant descriptions and five pages of engravings depicting six supposed coffee plants. The original watercolors used to create these engravings are housed at the Biblioteca Universitaria di Bologna and are presented here for the first time since publication. Five of the depicted plants have alternate leaves with indistinctly lobed or weakly undulate margins, when coffee has opposite, entire leaves. The remaining plant, supposedly depicting an entire coffee tree, exhibits both opposite and alternate leaves with serrated margins. As de Jussieu stated in 1716, coffee leaves should be “without serrations or crenellations in their contours.” None of the six engravings represents a coffee plant.

The watercolors bear handwritten notes in Italian and Ottoman Turkish. Fig. 1A is identified as “Zellebi Caffesi, Caffè Nobilis ò, di Monti di Senaam,” referring to the mountains of Sanaa, while the Ottoman Turkish text reads “ḳahve-i Salāba”—“coffee of Salaba.” Fig. 1B is labeled “Coffee of Bayt al-Faqih,” an important coffee marketplace but not a coffee-growing area. Fig. 2 is labeled “coffee of Yemen.” Fig. 3, described as “Beitulfaki Caffè,” depicts a plant rendered with ample artistic license—taller than the surrounding mountains, with fruits almost as large as the leaves and an enormous trunk. Fig. 4, identified as the third coffee species, describes flowers as “sulfur-yellow and rose pink” and tri-petalous, when Arabica coffee flowers are white and usually have five corolla lobes. Fig. 5 shows leaves and flowers with the Ottoman Turkish text stating “the size of its leaves is like this”—yet none of the descriptive elements matches coffee in any way.

What makes this botanical failure so striking is that the correct depiction of coffee leaves was not rare. Prospero Alpino’s 1592 woodcut in “De plantis Aegypti liber” correctly showed opposite, entire leaves with five to six secondary veins, and this illustration was plagiarized by Parkinson (1640), Vesling (1640), Bauhin and Cherler (1650), Peters (1666), Chabrée (1666, 1677, 1678) and de Blegny (1687), among others. Elegant coffee botanical engravings were published by de la Roque in 1715, followed a year later by de Jussieu. The early 1700s was also a significant period for coffee botany due to de Jussieu’s botanical description, the creation of the genus Coffea by Linnaeus in 1735, and Linnaeus’s comprehensive botanical description in 1737.

The engravings from “Notizie, di Costantinopoli” were subsequently copied by others. In 1704, Michael Bernhard Valentini published the first edition of “Museum Museorum,” including an unsigned engraving copied from Fig. 4. All subsequent editions—the second edition of 1714 and the first and second Latin editions of 1716 and 1732—contained the same figure. In 1705, Jacob Spon published “Bevanda asiatica: hoc est; Pysiologia potus café,” the second edition of his Latin translation of Dufour’s book, which included all the coffee plant engravings from “Notizie, di Costantinopoli.” Spon’s Preface claimed that “very exact images” of the coffee plant “came to us from Arabia, by way of Constantinople,” and that their “genuine expression” should not be doubted. It is possible Spon used the same copper plates as those used in the original monograph.

Contemporary reactions were mixed. Valentini stated in 1714 that Marsigli’s book depicted “various species,” which is botanically impossible—at the time, only one commercially traded coffee species existed in Yemen, i.e., Arabica. In a 1715 letter, Volkamer commented critically that Marsigli’s figures, “lacking a certain character, disappoint the wishes and expectations of the curious.” His own letter included a beautiful engraving of a coffee branch depicting opposite ovate-lanceolate leaves and perfectly identifiable coffee fruits. De la Roque, in 1715, published “Voyage de l’Arabie heureuse” with more accurate botanical engravings, noting that observers “will easily perceive how very different this is from all those, which we have seen in many books.”

In recent times, however, bibliographers have praised Marsigli’s engravings. Hünersdorff and Hasenkamp (2002) called them “among the earliest faithful representations of the coffee plant in a western book,” and Schnyder-v. Waldkirch (1988) asserted that Marsigli’s engravings “significantly clarified Europe’s idea of the coffee plant.” These comments were made by outstanding bibliographers who might not necessarily have been familiar with the botanical characters of the coffee plant. The extreme rarity of “Notizie, di Costantinopoli”—only two copies have been located, one at the Universitätsbibliothek Erlangen-Nürnberg and one sold in 2023—raises the question of whether Marsigli realized the plants were not coffee, resulting in most copies being destroyed.

Linnaeus did not cite either of Marsigli’s coffee-related books in his description of Coffea in “Hortus Cliffortianus” (1737). Almost 25 years later, Linnaeus cited Spon’s 1705 book in the Linnaean dissertation “Potus coffeae” (1761). One wonders what Linnaeus’s response would have been after examining the botanical engravings purportedly representing plants in the genus he had erected. Marsigli’s two coffee-related books present a microcosm of the coffee world in the early 1700s: a popular drink from a distant country was still a novelty, and its botanical identity and medical properties were areas of widespread interest among the cognoscenti. If Marsigli tried to erase the evidence by not distributing “Notizie, di Costantinopoli,” his attempt completely failed when Valentini kept publishing an engraving of Fig. 4 until 1732, and when Spon published all the botanical engravings in 1705.

Subject of Research: History of Botany

Article Title: When is coffee not coffee? Luigi Ferdinando Marsigli's depictions of the coffee plant in “Notizie, di Costantinopoli; sopra la pianta del caffè” (1703)

Article References: Vega, F. E., & Davis, A. P. (2025). When is coffee not coffee? Luigi Ferdinando Marsigli's depictions of the coffee plant in “Notizie, di Costantinopoli; sopra la pianta del caffè” (1703). Italian Botanist, 19, 65-85. https://doi.org/10.3897/italianbotanist.19.146007

Image Credits: AI Generated

DOI: 10.3897/italianbotanist.19.146007

Keywords: coffee, botanical illustration, Luigi Ferdinando Marsigli, Coffea arabica, history of science, 17th century, Ottoman Empire, botany, Luigi, Ferdinando, Marsigli's, depictions

The yield numbers are striking. In the study, conducted between 2022 and 2023, ripe berries were manually harvested from 360 branches across six farms supplemented with stingless bee colonies. Branches close to the colonies averaged 0.50 kilograms of coffee each, while branches far from the colonies averaged 0.30 kilograms. The researchers analysed these data with linear mixed-effects models that accounted for the spatial non-independence of sampling sites, nesting plots within farms and treating farm identity as a random effect. The 67 percent gain survived all statistical scrutiny, confirming that supplemental pollination by a native bee can transform productivity in a crop once thought immune to pollinator deficits.

Why would a self-pollinating plant respond so dramatically to bee visits? The answer lies in the subtle biology of arabica coffee. Although the species does not require pollen transfer between different plants to set fruit, decades of research worldwide have shown that flowers isolated from visiting insects form about 28 percent fewer fruits than flowers open to natural pollinators. Bees appear to enhance fruit set even in self-compatible flowers, likely through more efficient pollen deposition on stigmas. Scaptotrigona depilis brings a suite of traits that make it unusually effective at this job: a small body of roughly 5.5 millimeters, short foraging trips of about 4.2 minutes, constant activity from morning to early afternoon, mass-recruitment foraging using scent trails to rapidly mobilize nestmates, and colonies of around 10,000 workers.

There is also a mechanical quirk that may give stingless bees an edge over honeybees. Like Apis mellifera, S. depilis foragers moisten collected coffee pollen with nectar and pack it into their metatibial pollen baskets. But apparently they carry more free pollen grains incidentally attached to their bodies, and those loose grains are the ones most likely to be available for pollination as bees move from flower to flower. Add the fact that stingless bees lack a functional sting, posing less hazard to farm workers, and their well-developed colony management protocols, and the case for renting them out to coffee growers becomes compelling. Bee rental is already routine for apples and melons in Brazil, and the authors expect arabica coffee to follow the same trajectory.

But the study was designed to answer a second, more contentious question: does thiamethoxam, a neonicotinoid insecticide widely used against the coffee leaf miner and coffee leaf rust, harm stingless bee colonies under real farming conditions? Neonicotinoids are systemic, meaning they are absorbed by the treated plant and translocated to all organs, including nectar and pollen in flowers. Laboratory studies have documented lethal and sublethal effects on social bees, including impaired foraging, learning and memory, colony development and disease resistance. Yet field-realistic colony-level studies on stingless bees have been scarce, and most regulatory ecotoxicology relies on honeybees as the model species.

The researchers installed thiamethoxam-based products, Verdadero 600 WG and Actara 250 WG, by soil drenching during the berry expansion stage of the 2021 season, following label recommendations at field rates of 1 kilogram per hectare. Colonies were introduced the following season, roughly 10 to 18 days before coffee blooming in September and October 2022, so that residues from the previous application could be assessed. Three colony strength parameters were tracked according to international standardized protocols: brood production, counted in pre-provisioning and oviposition stages; brood mortality, calculated as the percentage of empty pupal cells; and foraging activity, counted as foragers leaving the colony during 3-minute observation windows. Measurements were taken before and after blooming and again at 45, 75 and 105 days post-exposure, spanning approximately three complete generations of stingless bees.

The residue analysis told a nuanced story. Using liquid chromatography tandem mass spectrometry, the team detected thiamethoxam and its metabolite clothianidin in all coffee leaves sampled at conventional farms, with leaf concentrations ranging from 0.0093 to 0.1071 milligrams per kilogram. Low but detectable residues also appeared in nectar and pollen stored within the stingless bee nests, generally below 0.02 milligrams per kilogram. At the two organic control farms, residues were below the limit of quantification. Critically, these levels sat well beneath thresholds known to affect honeybee colonies: continuous feeding with 100 parts per billion thiamethoxam for six weeks impaired colony development in prior research, with no adverse effects at 50 parts per billion and a no-observed-effect concentration of 37.5 parts per billion, roughly 1.8 to 2-fold higher than the residues found in the stingless bee food stores.

The colony health data matched the residue picture. Brood production and brood mortality were statistically indistinguishable between colonies on conventional and organic farms, with no significant interaction between farming system and sampling period. Foraging activity did differ between farm types, but the lower baseline activity at conventional farms was observed before coffee flowering began, before foragers had any exposure to coffee nectar or pollen, pointing instead to pre-existing differences in floral resource availability in the surrounding landscape. Both systems showed similar proportional increases in foraging activity once blooming started, and the temporary difference normalized in subsequent assessments. The authors argue that thiamethoxam exposure should not be considered the primary cause of the foraging difference, and that transient effects on foraging do not threaten colony viability when they recover without translating into brood impacts.

Why do laboratory findings of neonicotinoid harm so often fail to materialize in the field? The study explores several explanations. Coffee flowers remain open for only 3 to 4 days and open synchronously in brief but intense flowering periods driven by rainfall, which concentrates foraging into narrow windows and limits exposure duration. Stingless bees visit a wide array of flowering plants, mixing pollen and nectar from treated crops with resources from untreated plants and diluting residue levels. Applications made an average of 8 months before blooming, as the label requires, leave systemic residues on flowers very low, a pattern also seen in apple orchards where fall foliar sprays produced no detectable spring residues. Social bee colonies also possess recovery mechanisms and nutritional buffers that can compensate for some sublethal costs of losing foragers.

The implications ripple outward from the farm gate. Introducing stingless bee colonies gives farmers a direct method to increase coffee yield and generate sustainable profit, which the authors suggest can be invested in native forest restoration, creating a synergistic loop between agriculture and conservation. Brazil produces a record forecast of 178.7 million bags of coffee for 2025/26 across 2.25 million hectares, 82 percent of it arabica, so even modest pollination gains scale into enormous volumes. The study is among the first to combine a pollinator abundance manipulation with a higher-tier colony strength assessment for a non-Apis bee under field-realistic pesticide exposure, and the authors caution that different application timings or rates could yield different results. Still, the message is clear: with responsible label-compliant pesticide use, native stingless bees can markedly boost coffee production while remaining healthy themselves, offering a practical template for sustainable intensification in the tropics.

Subject of Research: Crop pollination and pesticide risk assessment in Brazilian arabica coffee

Article Title: Stingless bees in coffee: yield gains and assessing neonicotinoid impact

Article References: Ramos, J. D., Santos, G. S., dos Santos, C. F., De Oliveira Kaminski, T. S., Cione, A. P., Alves, D. A., Quenzer, F. C. L., Campbell, A. J., Pereira, A. M., Thompson, H., Martins de Queiroz, A. C., Bento, J. M. S., & Menezes, C. (2026). Stingless bees in coffee: yield gains and assessing neonicotinoid impact. Frontiers in Bee Science, 3, Article 1644205. https://doi.org/10.3389/frbee.2025.1644205

Image Credits: AI Generated

DOI: 10.3389/frbee.2025.1644205

Keywords: stingless bees, Scaptotrigona depilis, coffee pollination, Coffea arabica, thiamethoxam, neonicotinoids, clothianidin, colony strength, Brazil, sustainable agriculture, crop yield, pesticide residues

The pea aphid, Acyrthosiphon pisum, is a deceptively small problem with enormous consequences. Feeding on the phloem sap of legumes such as peas, faba beans, lentils, chickpeas, and alfalfa, it weakens plants directly, promotes sooty mould through its sugary honeydew excretions, and, most damagingly, transmits more than thirty plant viruses. Legume crops occupy a special place in sustainable agriculture because of their nutritional value, their ability to fix nitrogen, and their role in crop rotations, which makes protecting them from aphids a priority for food security.

The stakes are high across agriculture as a whole. Crop pests and diseases are estimated to cause 20 to 40 percent of global yield losses, rising to as much as 80 percent in regions where crop protection is limited. Meanwhile, synthetic pesticide use has nearly doubled since 1990, reaching roughly 3.73 million tons of active ingredients in 2023. Yet only a tiny fraction, between 0.1 and 0.5 percent, of applied pesticides actually reaches its target, with the rest drifting into water, soil, and air, harming pollinators and other beneficial insects along the way. Regulatory pressure and public demand are pushing farmers toward alternatives, and plant-derived volatiles have emerged as leading candidates.

In the new study, the researchers screened seven commercially available plant extracts for repellent activity against young pea aphid nymphs using a simple but elegant apparatus: a T-shaped glass tube in which aphids had to choose between an arm treated with extract and an arm treated only with ethanol, each ending in a pouch of artificial diet. After 24 hours in darkness, the researchers counted where the insects settled and calculated a repellency index. Chemical compositions of the extracts were determined by gas chromatography-mass spectrometry, revealing the dominant compounds responsible for each extract’s scent profile.

Three extracts repelled the aphids: andiroba seed oil, the coffee supercritical carbon dioxide extract, and the mandarin essential oil. Mandarin oil, dominated by R-(+)-limonene at nearly 89 percent of its composition, was the strongest, while the coffee extract, rich in hexadecanoic and linoleic acids, followed close behind. One extract, lemongrass, actually attracted the aphids, underscoring how differently these insects respond to various volatile blends. The two most potent extracts, mandarin and coffee, were then selected for detailed dose-response analysis and for testing as a 1:1 blend.

The results were striking. On its own, mandarin oil repelled half of the aphids at a dose of about 26.7 micrograms per square centimeter, while the coffee extract required roughly twice as much. But when the two were combined, the blend repelled half of the insects at just 9.1 micrograms per square centimeter, and 90 percent at 61.1, meaning the mixture was about 3.4 times more potent than mandarin alone and 9.4 times more potent than coffee alone at the 90 percent level. To determine whether this was true synergy rather than simple addition, the team compared the observed effect doses with predictions from two standard reference models: concentration addition, which assumes components act through similar mechanisms, and independent action, which assumes distinct mechanisms. Both models yielded deviation ratios well above the synergy threshold of two, confirming a genuine synergistic interaction.

To trace the source of that synergy, the researchers then tested the seven major compounds of the blend individually and in all 21 possible pairings. Remarkably, none of the compounds showed detectable repellency on its own, and one, p-cymene, was actually attractive to the aphids. Yet one pairing stood out: hexadecanoic acid combined with R-(+)-limonene produced a repellency index of 66 percent, far exceeding the roughly 7 percent expected from their individual effects, a statistically significant positive interaction. The full reconstructed mixture of major compounds reproduced the repellency of the original blend, suggesting that the combined activity emerges from multiple compounds acting together, with the limonene-hexadecanoic acid pair as a key contributor.

How can two chemically dissimilar molecules, a nonpolar cyclic monoterpene and an amphiphilic long-chain fatty acid, amplify each other’s behavioral effect? The researchers propose several non-mutually-exclusive mechanisms. Structurally, the electron-rich limonene and the polar-headed fatty acid may form transient associations through van der Waals forces, potentially altering bioavailability, solubility, or spreadability on surfaces. Physiologically, one compound may enhance cuticular penetration of the other, inhibit degrading enzymes, or act on complementary neurophysiological targets. On the sensory side, the authors point to aphid odorant-binding proteins, which shuttle hydrophobic molecules to olfactory receptors. OBP3 from a related aphid species is known to bind R-(+)-limonene, while fatty acids appear to be detected largely through chemosensory proteins, hinting that the two compounds may stimulate distinct but complementary olfactory pathways, consistent with the independent action model.

Beyond the laboratory, the practical implications are considerable. Both R-(+)-limonene and hexadecanoic acid can be recovered from abundant, low-value agro-industrial by-products, citrus peel from juice processing and spent coffee grounds, respectively. Limonene is already produced globally at around 70,000 tonnes per year and growing. By reducing the effective dose several-fold, synergy could make plant-based aphid repellents economically competitive with synthetic pesticides while lowering environmental exposure. The authors caution that their results come from laboratory assays on a single clonal aphid line with a 24-hour endpoint, and that field validation, formulation strategies such as encapsulation, and regulatory pathways for botanical repellents remain to be addressed. Still, the study delivers a clear proof of concept: the future of green crop protection may lie not in finding single miracle molecules, but in understanding how the compounds plants already make work together.

Subject of Research: Synergistic repellent effects of mandarin and coffee plant extracts against the pea aphid Acyrthosiphon pisum

Article Title: Synergistic repellency of Citrus reticulata and Coffea arabica extracts mediated by R-(+)-limonene and hexadecanoic acid against the pea aphid Acyrthosiphon pisum

Article References: Benhamou, S., Jouve, C., Rahioui, I., Peignier, S., Mercier, P.-E., Rey, M., Livi, S., & Da Silva, P. (2026). Synergistic repellency of Citrus reticulata and Coffea arabica extracts mediated by R-(+)-limonene and hexadecanoic acid against the pea aphid Acyrthosiphon pisum. Journal of Agriculture and Food Research, 31, Article 103317. https://doi.org/10.1016/j.jafr.2026.103317

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103317

Keywords: pea aphid, Acyrthosiphon pisum, plant extracts, R-(+)-limonene, hexadecanoic acid, synergy, repellency, essential oils, Citrus reticulata, Coffea arabica, crop protection, botanical pesticides

Brazil cultivates coffee across approximately 2.25 million hectares, and the crop’s famously high productivity rests on heavy applications of mineral fertilizers, particularly nitrogen. Nitrogen is the engine of plant metabolism, forming the structural backbone of proteins, nucleic acids, and chlorophyll, and coffee plants grown in full-sun monocultures demand enormous quantities of it during vegetative growth, flowering, and fruit filling. But synthetic nitrogen inputs are notoriously inefficient: a large fraction is lost to leaching, volatilization, and denitrification before the plant can use it, driving up production costs while polluting waterways and warming the atmosphere. That inefficiency has pushed scientists to look beneath their feet for alternatives.

The research team focused on two adjacent coffee-producing areas in the municipality of Araponga, in the state of Minas Gerais, both planted with the Catuaí Vermelho variety at roughly 900 meters altitude and both cultivated for more than fifteen years. One farm followed conventional mineral fertilization, receiving 1,250 kilograms per hectare of NPK fertilizer split into two doses, along with lime. The other practiced organic fertilization, applying 400 kilograms per hectare of urea together with 6,000 kilograms per hectare of composted chicken litter. Soil samples were collected in November 2023 during the flowering stage, with ten composite samples gathered per farm from bulk soil around the tree trunks.

To coax out bacteria capable of living without fixed nitrogen, the team plated soil dilutions onto two nitrogen-free culture media, LGI and JMV, traditionally used to enrich diazotrophic bacteria. In total, thirty-eight morphologically distinct bacterial isolates were purified—nineteen from each farm—and identified by Sanger sequencing of the 16S rRNA gene, the standard molecular barcode for bacteria. The isolates spanned four phyla and fifteen genera, with members of Pseudomonadota and Actinomycetota dominating both farms. Intriguingly, isolates from the phyla Bacillota and Bacteroidota emerged exclusively from the organically fertilized soil, hinting that compost inputs had opened ecological niches that mineral fertilizer alone could not.

Only three genera—Pseudomonas, Streptomyces, and Acinetobacter—were shared between the two management systems. The organic farm exclusively yielded Paraburkholderia, Priestia, Flavobacterium, Curtobacterium, and Dyella, while the conventional farm alone harbored Burkholderia, Ralstonia, Luteibacter, Kosakonia, and Rhizobium. The researchers attribute these management-specific profiles to differences in carbon inputs and nutrient dynamics, noting that organic amendments generally increase soil organic carbon and niche heterogeneity, whereas mineral fertilization favors fast-growing copiotrophic microbes that exploit sudden nutrient pulses. The recovery of Rhizobium and Luteibacter under conventional fertilization was particularly noteworthy, expanding knowledge of these genera’s distribution in coffee agroecosystems.

The functional screening was where the study’s biotechnological promise crystallized. Eleven isolates from the organic farm and nine from the conventional farm grew in nitrogen-free semi-solid NFb medium, forming the subsurface microaerophilic pellicles and alkalinizing the indicator dye that signal a putative diazotrophic phenotype—the ability to convert atmospheric nitrogen into biologically usable forms. Even more striking, every single isolate recovered from the organically fertilized soil could solubilize tricalcium phosphate in vitro, dissolving an otherwise inaccessible mineral pool of phosphorus into forms plants can absorb. Standout performers included Streptomyces, Bacillus, Flavobacterium, and Acinetobacter strains with solubilization indices above 3, the threshold for classification as high-efficiency solubilizers.

Phytohormone production added a third dimension to the isolates’ toolkit. Quantified spectrophotometrically after growth in tryptophan-supplemented medium, indole-3-acetic acid—the principal auxin that stimulates root development—was produced by isolates from both farms, with no statistically significant difference between the two management systems. The most prolific producers included Priestia, Dyella, Paraburkholderia, and Bacillus from the organic soil, and Streptomyces and Luteibacter from the conventional soil. One Streptomyces isolate reached concentrations of up to 68.82 micrograms per milliliter, exceeding values previously reported for well-characterized plant growth-promoting Streptomyces strains, a result the authors describe as reinforcing the biotechnological potential of these genera.

What makes these findings compelling is the convergence of multiple traits within single isolates. A bacterium that simultaneously fixes nitrogen, unlocks phosphorus, and secretes auxins is a candidate for multifunctional microbial inoculants—living fertilizers that could reduce the environmental footprint of coffee cultivation while lowering input costs for farmers. The authors caution that their assays represent an initial in vitro screening. Confirming true diazotrophy will require quantitative nitrogen fixation assays such as acetylene reduction or nitrogen-15 isotope dilution, molecular detection of nitrogenase genes like nifH, and ultimately greenhouse and field inoculation trials to verify agronomic performance under real conditions.

Nevertheless, the study fills an important gap. While culture-independent metagenomic studies have catalogued the vast microbial diversity of coffee plantations across Latin America, cultivable isolates remain indispensable for experimentally validating microbial functions and translating ecological knowledge into practical agricultural products. By demonstrating that both organic and conventionally managed coffee soils harbor a resilient core microbiota alongside management-specific taxa with valuable plant growth-promoting traits, the research establishes a foundation for developing microbial consortia adapted to local edaphoclimatic conditions. For an industry confronting rising fertilizer prices, nitrogen losses, and mounting environmental scrutiny, the humble bacteria of Minas Gerais may prove to be coffee’s most valuable untapped resource.

Subject of Research: Cultivable plant growth-promoting bacteria in Brazilian Coffea arabica soils under organic and conventional mineral fertilization

Article Title: Cultivable diversity and plant growth-promoting traits of free-living bacteria from coffee soils under contrasting fertilization systems

Article References: Guimarães, C. V., Velozo, T. G. R., da Luz, J. M. R., Públio, G. C., da Silva, J. P. T., Pereira, L. L., & de Cássia Soares da Silva, M. (2026). Cultivable diversity and plant growth-promoting traits of free-living bacteria from coffee soils under contrasting fertilization systems. International Microbiology. https://doi.org/10.1007/s10123-026-00893-2

Image Credits: AI Generated

DOI: 10.1007/s10123-026-00893-2

Keywords: coffee, plant growth-promoting bacteria, nitrogen fixation, phosphate solubilization, indole-3-acetic acid, soil microbiome, organic fertilization, mineral fertilization, Coffea arabica, microbial inoculants, Brazil, sustainable agriculture