Evidence for Widespread Associations between Neotropical Hymenopteran Insects and Actinobacteria

The evolutionary success of hymenopteran insects has been associated with complex physiological and behavioral defense mechanisms against pathogens and parasites. Among these strategies are symbiotic associations between Hymenoptera and antibiotic-producing Actinobacteria, which provide protection to insect hosts. Herein, we examine associations between culturable Actinobacteria and 29 species of tropical hymenopteran insects that span five families, including Apidae (bees), Vespidae (wasps), and Formicidae (ants). In total, 197 Actinobacteria isolates were obtained from 22 of the 29 different insect species sampled. Through 16S rRNA gene sequences of 161 isolates, we show that 91% of the symbionts correspond to members of the genus Streptomyces with less common isolates belonging to Pseudonocardia and Amycolatopsis. Electron microscopy revealed the presence of filamentous bacteria with Streptomyces morphology in brood chambers of two different species of the eusocial wasps. Four fungal strains in the family Ophiocordycipitacea (Hypocreales) known to be specialized insect parasites were also isolated. Bioassay challenges between the Actinobacteria and their possible targeted pathogenic antagonist (both obtained from the same insect at the genus or species level) provide evidence that different Actinobacteria isolates produced antifungal activity, supporting the hypothesis of a defensive association between the insects and these microbe species. Finally, phylogenetic analysis of 16S rRNA and gyrB demonstrate the presence of five Streptomyces lineages associated with a broad range of insect species. Particularly our Clade I is of much interest as it is composed of one 16S rRNA phylotype repeatedly isolated from different insect groups in our sample. This phylotype corresponds to a previously described lineage of host-associated Streptomyces. These results suggest Streptomyces Clade I is a Hymenoptera host-associated lineage spanning several new insect taxa and ranging from the American temperate to the Neotropical region. Our work thus provides important insights into the widespread distribution of Actinobacteria and hymenopteran insects associations, while also pointing at novel resources that could be targeted for the discovery of active natural products with great potential in medical and biotechnological applications.National Science Foundation/[MCB-0702025]/NSF/Estados UnidosUniversidad de Costa Rica/[801-B0-538]/UCR/Costa RicaUniversidad de Costa Rica/[810-B3-185]/UCR/Costa RicaNational Institute of Health/[U19 Al109673]/NIH/Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Estructuras Microscópicas (CIEMIC)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biología Celular y Molecular (CIBCM)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Centro de Investigación en Enfermedades Tropicales (CIET)UCR::Vicerrectoría de Docencia::Salud::Facultad de Medicin

ENSO‐Influenced Drought Drives Methane Flux Dynamics in a Tropical Wet Forest Soil

Global atmospheric methane growth rates have wildly fluctuated over the past three decades, which may be driven by the proportion of tropical land surface saturated by water. The El Niño/Southern Oscillation Event (ENSO) cycle drives large‐scale climatic trends globally, with El Niño events typically bringing drier weather than La Niña. In a lowland tropical wet forest in Costa Rica, we measured methane flux bimonthly from March 2016 to June 2017 and using an automated chamber system. We observed a strong drying trend for several weeks during the El Niño in 2016, reducing soil moisture below normal levels. In contrast, soil conditions had high water content prior to the drought and during the moderate La Niña that followed. Soil moisture varied across the period studied and significantly impacted methane flux. Methane consumption was greater during the driest part of the El Niño period, while during La Niña and other time periods, soils had lower methane consumption. The mean methane flux observed was −0.022 mg CH4‐C m−2 hr−1, and methane was consumed at all timepoints, with lower consumption in saturated soils. Our data show that month studied, and the correlation between soil type and month significantly drove methane flux trends. Our data indicate that ENSO cycles may impact biogenic methane fluxes, mediated by soil moisture conditions. Climate projections for Central America show dryer conditions and increased El Niño frequency, further exacerbating predicted drought. These trends may lead to negative climate feedbacks, with drier conditions increasing soil methane consumption from the atmosphere.National Science Foundation/[DEB‐1624623]/NSF/Estados UnidosNational Science Foundation/[DEB‐1442537]/NSF/Estados UnidosNational Science Foundation/[DEB‐1624658]/NSF/Estados UnidosNational Science Foundation/[DEB‐1442714]/NSF/Estados UnidosUnited States Department of Agriculture-National Institute of Food and Agriculture/[CA‐R‐PPA‐5093‐H/1005159]/USDA NIFA/Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biología Celular y Molecular (CIBCM)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Estructuras Microscópicas (CIEMIC

Evidence for Widespread Associations between Neotropical Hymenopteran Insects and Actinobacteria

The evolutionary success of hymenopteran insects has been associated with complex physiological and behavioral defense mechanisms against pathogens and parasites. Among these strategies are symbiotic associations between Hymenoptera and antibiotic-producing Actinobacteria, which provide protection to insect hosts. Herein, we examine associations between culturable Actinobacteria and 29 species of tropical hymenopteran insects that span five families, including Apidae (bees), Vespidae (wasps), and Formicidae (ants). In total, 197 Actinobacteria isolates were obtained from 22 of the 29 different insect species sampled. Through 16S rRNA gene sequences of 161 isolates, we show that 91% of the symbionts correspond to members of the genus Streptomyces with less common isolates belonging to Pseudonocardia and Amycolatopsis. Electron microscopy revealed the presence of filamentous bacteria with Streptomyces morphology in brood chambers of two different species of the eusocial wasps. Four fungal strains in the family Ophiocordycipitacea (Hypocreales) known to be specialized insect parasites were also isolated. Bioassay challenges between the Actinobacteria and their possible targeted pathogenic antagonist (both obtained from the same insect at the genus or species level) provide evidence that different Actinobacteria isolates produced antifungal activity, supporting the hypothesis of a defensive association between the insects and these microbe species. Finally, phylogenetic analysis of 16S rRNA and gyrB demonstrate the presence of five Streptomyces lineages associated with a broad range of insect species. Particularly our Clade I is of much interest as it is composed of one 16S rRNA phylotype repeatedly isolated from different insect groups in our sample. This phylotype corresponds to a previously described lineage of host-associated Streptomyces. These results suggest Streptomyces Clade I is a Hymenoptera host-associated lineage spanning several new insect taxa and ranging from the American temperate to the Neotropical region. Our work thus provides important insights into the widespread distribution of Actinobacteria and hymenopteran insects associations, while also pointing at novel resources that could be targeted for the discovery of active natural products with great potential in medical and biotechnological applications

Phylogenetic analyses of antibiotic-producing Streptomyces sp. isolates obtained from the stingless-bee Tetragonisca angustula (Apidae: Meliponini)

Many insects have been associated with actinobacteria in protective symbiosis where antimicrobial metabolites inhibit host pathogens. However, the microbiota of neotropical insects such as the stingless-bee Tetragonisca angustula is poorly explored. T. angustula is a meliponid bee widely distributed in Latin America, its honey is traditionally exploited because of its ethno-pharmacological properties and its antimicrobial activity has been demonstrated. Also, the well-structured nest of this species allows exploration of the microbiota of its different components. Even though Streptomyces spp. have been cultured from stingless-bees, little is known about their role in this insect–microbe relationship. In this study, we examined the association between culturable actinobacteria and T. angustula, and evaluated the isolates’ potential as antimicrobial producers. We isolated 51 actinobacteria from adult bees and different substrates of the hive of T. angustula (pollen and honey storage, garbage pellets and cerumen). We then performed a 16S rRNA phylogenetic analysis that clusters the bacteria to previously described lineages of host-associated Streptomyces. In addition, all the isolates were classified according to their antibacterial activity against human pathogens, measured by a growth inhibition test based on diffusion in agar. More than 50 % of our isolates exhibit antimicrobial activity, mainly to Gram-positive bacteria and fungi and only two against Gram-negative bacteria. Additionally, we obtained electron micrographs of adult bees with what appears to be patches of hyphae with Streptomyces-like cell morphology on their body surface. Our results suggest that T. angustula possibly uptakes and transfers actinobacteria from the environment, acting as vectors for these potentially beneficial organisms. This research provides new insights regarding the microbiota associated with T. angustula and justify future studies exploring the full diversity of the microbial community associated with the hive and the possible exchange of microbes with the crops they pollinate.Universidad de Costa Rica/[810-B3-185]/UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Estructuras Microscópicas (CIEMIC)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro en Investigación en Contaminación Ambiental (CICA)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biología Celular y Molecular (CIBCM)UCR::Vicerrectoría de Docencia::Salud::Facultad de Medicina::Escuela de MedicinaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones en Productos Naturales (CIPRONA

Streptomyces sp. M54: an actinobacteria associated with a neotropical social wasp with high potential for antibiotic production

Abstract Streptomyces symbionts in insects have shown to be a valuable source of new antibiotics. Here, we report the genome sequence and the potential for antibiotic production of ‘‘Streptomyces sp. M54’’, an Actinobacteria associated with the eusocial wasp, Polybia plebeja. The Streptomyces sp. M54 genome is composed of a chromosome (7.96 Mb), and a plasmid (1.91 Kb) and harbors 30 biosynthetic gene clusters for secondary metabolites, of which only one third has been previously characterized. Growth inhibition bioassays show that this bacterium produces antimicrobial compounds that are active against Hirsutella citriformis, a natural fungal enemy of its host, and the human pathogens taphylococcus aureus and Candida albicans. Analyses through TLC-bioautography, LC–MS/MS and NMR allowed the identification of five macrocyclic ionophore antibiotics, with previously reported antibacterial, antitumor and antiviral properties. Phylogenetic analyses placed Streptomyces sp.M54 in a clade of other host-associated strains taxonomically related to Streptomyces griseus. Pangenomic and ANI analyses confirm the identity of one of its closest relatives as Streptomyces sp. LaPpAH-199, a strain isolated from an ant-plant symbiosis in Africa. In summary, our results suggest an insect-microbe association in distant geographic areas and showcase the potential of Streptomyces sp. M54 and related strains for the discovery of novel antibioticsUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones en Productos Naturales (CIPRONA