Rhizopus microsporus is an early-diverging fungal species with importance in ecology, agriculture, food production, and public health. Pathogenic strains of R. microsporus harbor an intracellular bacterial symbiont, Mycetohabitans (formerly named Burkholderia). This vertically transmitted bacterial symbiont is responsible for the production of toxins crucial to the pathogenicity of Rhizopus and remarkably also for fungal reproduction. Here we show that R. microsporus can live not only in symbiosis with bacteria but also with two viral members of the genus Narnavirus. Our experiments revealed that both viruses replicated similarly in the growth conditions we tested. Viral copies were affected by the developmental stage of the fungus, the substrate, and the presence or absence of Mycetohabitans. Absolute quantification of narnaviruses in isolated asexual sporangiospores and sexual zygospores indicates their vertical transmission. By curing R. microsporus of its viral and bacterial symbionts and reinfecting bacteria to reestablish symbiosis, we demonstrate that these viruses affect fungal biology. Narnaviruses decrease asexual reproduction, but together with Mycetohabitans, are required for sexual reproductive success. This fungal–bacterial-viral system represents an outstanding model to investigate three-way microbial symbioses and their evolution.

Iodine is a highly reactive element with a single natural and stable isotopic form (¹²⁷I). In the biosphere, it is one of the 30 essential elements for life, and its chemical speciation defines its availability and biological activities. The most relevant chemical species are iodate (IO₃⁻) and iodide (I⁻) as the major sources of iodine, with molecular iodine (I₂) and hypoiodous acid (HIO) as the most reactive species, and thyroid hormones (THs) as the representative organic compounds. In human biology, THs are master regulators of metabolism, while inorganic species serve for the iodination of organic molecules and contribute to the innate immune system and the antioxidant cellular defense. Additionally, I⁻, I₂, δ-lactone (6-IL), and α-iodohexadecanal (α-IHDA) have shown therapeutic potential in counteracting oxidative stress, cancer, and inflammation. Both inorganic and organic species have applications in the health science industry, from the manufacturing of disinfection and wound care products to supplements, medicines, and contrast media for radiography. Even after nuclear disasters, intake of high doses of iodine prevents the accumulation of radioactive iodine in the body. Conversely, the controlled production of iodine radioisotopes such as ¹²³I, ¹²⁴I, ¹²⁵I, and ¹³¹I is exploited in nuclear medicine for radiotherapy and diagnostics.

Rhizopus microsporus often lives in association with bacterial and viral symbionts that alter its biology. This fungal model represents an example of the complex interactions established among diverse organisms in functional holobionts. We constructed a Genome‐Scale Model (GSM) of the fungal‐bacterial‐viral holobiont ( i Hol). We employed a constraint‐based method to calculate the metabolic fluxes to decipher the metabolic interactions of the symbionts with their host. Our computational analyses of i Hol simulate the holobiont's growth and the production of the toxin rhizoxin. Analyses of the calculated fluxes between R. microsporus in symbiotic ( i Hol) versus asymbiotic conditions suggest that changes in the lipid and nucleotide metabolism of the host are necessary for the functionality of the holobiont. Glycerol plays a pivotal role in the fungal‐bacterial metabolic interaction, as its production does not compromise fungal growth, and Mycetohabitans bacteria can efficiently consume it. Narnavirus RmNV‐20S and RmNV‐23S affected the nucleotide metabolism without impacting the fungal‐bacterial symbiosis. Our analyses highlighted the metabolic stability of Mycetohabitans throughout its co‐evolution with the fungal host. We also predicted changes in reactions of the bacterial metabolism required for the active production of rhizoxin. This i Hol is the first GSM of a fungal holobiont.

The coordinated efforts to stop the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) include massive immunization of the population at a global scale. The humoral immunity against COVID-19 is conferred by neutralizing antibodies (NAbs) that occur during the post-infection period and upon vaccination. Here, we provide robust data showing that potent neutralizing antibodies are induced in convalescent patients of SARS-CoV-2 infection who have been immunized with different types of vaccines, and patients with no previous history of COVID-19 immunized with a mixed vaccination schedule regardless of the previous infection. More importantly, we showed that a heterologous prime-boost in individuals with Ad5-nCoV (Cansino) vaccine induces higher NAbs levels in comparison to a single vaccination scheme alone.