Microplastics (MPs) occur widely in terrestrial ecosystems. However, information on the interaction of MPs with metals in terrestrial ecosystems is lacking in the literature. The present study investigated the effects of two types of MPs (high-density polyethylene (HDPE) and polystyrene (PS)) with different dosages (i.e., 0, 0.1%, 1%, and 10%) on the uptake and effects of Cd in maize plants grown in an agricultural soil. Results showed that addition of Cd at a 5 mg/kg caused inhibited plant growth and resulted in high Cd accumulation in plant tissues. Polyethylene alone showed no significant phytotoxic effects, but a high-dose of HDPE (10%) amplified Cd phytotoxicity. Polystyrene negatively affected maize growth and phytoxicity further increased in the presence of Cd. Both HDPE and PS caused soil diethylenetriaminepentaacetic acid (DTPA)-extractable Cd concentrations to increase but did not significantly affect Cd uptake into plant tissues. In the soil without Cd addition, HDPE decreased soil pH, while PS did not significantly alter soil pH. However, in the soil spiked with Cd, both HDPE and PS increased pH. Overall, impacts on plant growth and Cd accumulation varied with MP type and dose, and PS induced substantial phytotoxicity. In conclusion, co-occurring MPs can change Cd bioavailability, plant performance, and soil traits. Our findings highlight the ecological impacts that could occur from the release of MPs into soil.

Plants make chemical compounds to protect themselves. For example, chili peppers produce the spicy compound capsaicin to inhibit pathogen damage and animal feeding. In humans, capsaicin binds to a membrane channel protein, creating the sensation of heat, while in microbes, capsaicin limits energy production by binding respiratory enzymes. However, some data suggest that capsaicin also disrupts membranes. Here, we studied fungal pathogens ( Alternaria , Colletotrichum , Fusarium , and Phomopsis ) isolated from a wild chili pepper, Capsicum chacoense . By measuring growth rates in the presence of antibiotics with known respiratory targets, we inferred that wild-plant pathogens might be rich in alternative respiratory enzymes. A zone of clearance around the colonies, as well as liquid chromatography-mass spectrometry data, further indicated that these fungi can break down capsaicin. Finally, the total inhibitory effect of capsaicin was not fully explained by its effect on respiratory enzymes. Our findings lend credence to studies proposing that capsaicin may disrupt cell membranes, with implications for microbiology, as well as human health.

Both marine and terrestrial organisms produce light enzymatically in a process called bioluminescence. Though the ecological role of light production is known for some species, such as fireflies and bacteria, the ecological role in mushroom-producing fungi remains relatively unexplored, particularly in Central America. Here, we discovered a bioluminescent mushroom in the high-elevation oak forests of Costa Rica. We developed mushroom models with Light-Emitting Diodes (LEDs) producing various colors: green, blue, red, and yellow. Over three consecutive evenings after sunset, we applied Tanglefoot invertebrate-trapping glue to both mushroom models and actual mushrooms, and collected the traps before sunrise, then identified the trapped invertebrates to Order. We found green LED traps attracted more invertebrates than non-lit control traps, suggesting that light functions to attract invertebrates. The majority of invertebrates attracted to the green lights were Dipteran flies, who would be capable of dispersing fungal spores. The higher-intensity green LEDs attracted more total invertebrates than the dimmer mushrooms, but the results were not significant. Though we predicted that the invertebrate assemblages attracted to green lights would be similar to the invertebrate assemblage attracted to actual mushrooms, the results were not significant. Similarly, the red, blue, and yellow LEDs attracted fewer invertebrates than the green LEDs, but the differences in community composition were not statistically significant. Our findings corroborate other similar studies in tropical regions that found bioluminescent mushrooms may attract invertebrates.

The wild chili pepper Capsicum chacoense produces the spicy defense compounds known as capsaicinoids, including capsaicin and dihydrocapsaicin, antagonistic to the growth of fungal pathogens. Compared to other microbes, fungi isolated from infected seeds of C. chacoense possess much higher tolerance to these spicy compounds, having their growth slowed, but not entirely inhibited. Previous research has shown capsaicinoids inhibit microbes by disrupting ATP production via the binding of NADH dehydrogenase in the Electron Transport Chain (ETC), throttling Oxidative Phosphorylation (OXPHOS). Capsaicinoids may also disrupt cell membranes. Here, we investigated capsaicinoid tolerance in fungal seed pathogens isolated from C. chacoense . We selected 16 fungal isolates from four Ascomycete genera ( Alternaria, Colletotrichum, Fusarium and Phomopsis) . Using relative growth rate as a readout for tolerance, fungi were challenged with ETC inhibitors to infer if fungi possess alternative respiratory enzymes, and if effects on the ETC fully explained inhibition by capsaicinoids. In all isolates, we found evidence for at least one alternative NADH dehydrogenase. In many isolates we also found evidence for an alternative oxidase. These data suggest wild plant pathogens may be a rich source of alternative respiratory enzymes. We further demonstrate these fungal isolates are capable of the breakdown of capsaicinoids. Lastly, we determine the OXPHOS theory weakly explains the primary mechanism by which dihydrocapsaicin slows fungal growth, but not capsaicin. Our findings suggest capsaicinoids likely disrupt membranes in addition to energy poisoning, with implications for microbiology and human health. Importance: Plants make chemical compounds to protect themselves. For example, chili peppers produce the spicy compound capsaicin to inhibit animal feeding and pathogen damage. In humans, capsaicin binds to a membrane channel protein, creating the sensation of heat, while in microbes, capsaicin limits energy production by binding respiratory enzymes. However, some data suggest capsaicin also disrupts membranes. Here we studied fungal pathogens ( Alternaria , Colletotrichum , Fusarium , and Phomopsis ) isolated from a wild chili pepper, Capsicum chacoense . By measuring growth rate in the presence of antibiotics with known respiratory targets, we infer wild plant pathogens may be rich with alternative respiratory enzymes. A zone of clearance around the colonies, as well as LCMS data, further indicate these fungi can break down capsaicin. Lastly, the total inhibitory effect of capsaicin was not fully explained by its effect on respiratory enzymes. Our findings lend credence to studies proposing capsaicin may disrupt cell membranes, with implications for microbiology as well as human health.

1.1. The death cap mushroom, Amanita phalloides , is well known for containing amatoxins such as alpha- and beta-amanitin, which inhibit eukaryotic RNA polymerase II. While these toxins have been used in research for almost a century, they have recently garnered attention for their role in drug-antibody conjugates. The amatoxins are still largely extracted from wild mushrooms, which cannot be made to fruit in the lab. We propose simplified extraction methods that could reduce hazardous exposures to dust and expedite sample analysis without sacrificing accuracy. We recently developed a Lateral Flow Immunoassay (LFIA), for which we identified that sample maceration was not needed to extract the amatoxins and that the incubation time for extraction could be accomplished in 1 minute. In this current work, we hypothesized that these same extraction adjustments–minimal tissue maceration and reduced incubation time–could be transferable to instrumental detection methods. To test the need for sample maceration, we utilized three different techniques: 1) traditional mortar and pestle, 2) a similarly disruptive method of bead beating, and 3) no grinding, but rather hand shaking dried mushroom tissue in extraction buffer. In addition, we performed the solvent extraction step at varying times to observe if more time allows for more toxin to be removed from the tissue. Lastly, we utilized two comparable solvent evaporation methods (rotovap or speedvac) to establish if multiple samples could be processed simultaneously, thus improving sample throughput. We adjusted aspects of the typical extraction protocol, which resulted in a rapid (1 min) incubation step, along with minimal sample handling (no grinding) of the dried mushroom tissue. We present an extraction protocol that saves time, reduces equipment contamination, and minimizes risk to the researcher. The impact of this faster, safer method may help produce these important toxins faster, for both research and medical use.