Welcome to The Mejia Lab.
RESEARCH PUBLICATIONS
August 2024
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June 2024
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January 2023
November 2022
September 2022
Entomopathogenic fungi (EPF) infect insects and are of interest for understanding host-pathogen interactions and biological control of insect pests. The fruit fly Drosophila melanogaster offers an excellent model system for exploring the biology of EPF and their interactions with insects. In this review, we describe the advantages of using D. melanogaster as a model system to study EPF and highlight EPF of relevance to agriculture. We also propose possible directions for future research in this area. We predict that in the future, D. melanogaster will continue to be a productive system for understanding the biology of the fungi attacking insects and will no doubt contribute to the future of biological control, conservation and other areas.
March 2022
Hemileia vastatrix is the most important fungal pathogen of coffee and the causal agent of recurrent disease epidemics that have invaded nearly every coffee growing region in the world. The development of coffee varieties resistant to H. vastatrix requires fundamental understanding of the biology of the fungus. However, the complete life cycle of H. vastatrix remains unknown, and conflicting studies and interpretations exist as to whether the fungus is undergoing sexual reproduction. Here we used population genetics of H. vastatrix to infer the reproductive mode of the fungus across most of its geographic range, including Central Africa, Southeast Asia, the Caribbean, and South and Central America.
December 2021
Early in the SARS-CoV-2 pandemic, many national public health authorities implemented non-pharmaceutical interventions to mitigate disease outbreaks. Panamá established mandatory mask use two months after its first documented case. Initial compliance was high, but diverse masks were used in public areas. We studied behavioral dynamics of mask use through the first two COVID-19 waves in Panama, to improve the implementation of effective, low-cost public health containment measures when populations are exposed to novel air-borne pathogens.
November 2021
Salinization of coastal freshwaters (FWs) due to sea-level rise is a significant stressor for FW biodiversity. However, the effect of changes in salinity on the bacterial microbiome of Neotropical FW insects is less known. We combined field collections and common garden experiments to assess how changes in salinity may affect the microbiome associated with fresh and brackish populations of the water strider Telmatometra withei in Panama. The brackish water (BW) population had higher bacterial diversity and the total communities associated with T. withei were different at each site. Common garden experiments showed that both β diversity and the relative abundance of key taxa varied significantly with changes in salinity, but α diversity remained constant.
July 2021
The publication also describes policy and legislative options to facilitate access to genetic resources, the development of products by different industries, and the flow of benefits to the providers of these genetic resources. The book underscores the burgeoning Global ABS Community, which promotes South-South cooperation amongst countries on ABS issues.
This beautifully illustrated report is a visual celebration of our biological, genetic, and cultural diversity. You will be taken on a journey around the world visiting different countries and meeting indigenous peoples and local communities, scientists, and policy makers.
September 2020
The marine bacterial genus Pseudoalteromonas is known for their ability to produce antimicrobial compounds. The metabolite-producing capacity of Pseudoalteromonas has been associated with strain pigmentation; however, the genomic basis of their antimicrobial capacity remains to be explained. In this study, we sequenced the whole genome of six Pseudoalteromonas strains (three pigmented and three non-pigmented), with the purpose of identifying biosynthetic gene clusters (BGCs) associated to compounds we detected via microbial interactions along through MS-based molecular networking.
August 2020
Insects host a highly diverse bacterial community. Although we have a good understanding of the role that this microbiome plays in insects, the composition and diversity of microbiomes associated with Neotropical freshwater insects is virtually unknown. Here, we describe, for the first time, the microbiome associated with six species of Neotropical water striders in Panama.
March 2020
Three new species of Hypoxylon (Hypoxylaceae, Xylariales) are described based on a polyphasic approach that included morphological examination, molecular phylogeny and chemotaxonomic studies of specimens collected in Panama. Specifically, we compared the sexual morph (stromata, asci, and ascospores) of the specimens collected with known species of Hypoxylon and inferred a phylogeny of this genus based on a Randomized Axelerated Maximum Likelihood (RAxML) analysis of partial β–tubulin (TUB2) DNA sequences and the internal transcribed spacer regions (ITS).
February 2020
Interactions between fungal endophytes and their host plants present useful systems for identifying important factors affecting assembly of host‐associated microbiomes. Here we investigated the role of secondary chemistry in mediating host affinity of asymptomatic foliar endophytic fungi using Psychotria spp. and Theobroma cacao (cacao) as hosts.
November 2019
The significance of symbioses between eukaryotic hosts and microbes extends from the organismal to the ecosystem level and underpins the health of Earth’s most threatened marine ecosystems. Despite rapid growth in research on host-associated microbes, from individual microbial symbionts to host-associated consortia of significantly relevant taxa, little is known about their interactions with the vast majority of marine host species. We outline research priorities to strengthen our current knowledge of host–microbiome interactions and how they shape marine ecosystems. We argue that such advances in research will help predict responses of species, communities, and ecosystems to stressors driven by human activity and inform future management strategies.
September 2019
The microbiome plays a key role in the biology, ecology and evolution of arthropod vectors of human pathogens. Vector-bacterial interactions could alter disease transmission dynamics through modulating pathogen replication and/or vector fitness. Nonetheless, our understanding of the factors shaping the bacterial community in arthropod vectors is incomplete. Using large-scale 16S amplicon sequencing, we examine how habitat disturbance structures the bacterial assemblages of field-collected whole-body hematophagous arthropods that vector human pathogens including mosquitoes (Culicidae), sand flies (Psychodidae), biting midges (Ceratopogonidae) and hard ticks (Ixodidae). We found that all comparisons of the bacterial community among species yielded statistically significant differences, but a difference was not observed between adults and nymphs of the hard tick, Haemaphysalis juxtakochi.
August 2019
The significance of mutualisms between eukaryotic hosts and microbes extends from the organismal to the ecosystem level, and mutualistic symbioses underpin the health of Earth’s most threatened marine ecosystems. Despite rapid growth in research on host-associated microbes (microbiomes), very little is known about their interactions for the vast majority of marine host species. We outline research priorities to broaden our current knowledge of host-microbiome interactions and how they shape marine ecosystems. We argue that this research frontier will allow us to predict responses of species, communities, and ecosystems to stressors driven by human activity, and inform future management and mitigation.
June 2019
In this non-exhaustive compendium on our flora and fauna of medical interest, a sample of terrestrial plants, marine organisms, fungi, amphibians, reptiles, scorpions, and insects that can affect human health is included. The descriptions of the selected plants, fungi and animals illustrate us about their habitat, their distribution in the country and about the toxic reactions that can occur when these organisms interact with humans.
March 2019
Background Malaria control in Panama is problematic due to the high diversity of morphologically similar Anopheles mosquito species, which makes identification of vectors of human Plasmodium challenging. Strategies by Panamanian health authorities to bring malaria under control targeting Anopheles vectors could be ineffective if they tackle a misidentified species. Methods A rapid mass spectrometry identification procedure was developed to accurately and timely sort out field-collected Neotropical Anopheles mosquitoes into vector and non-vector species. Matrix-assisted laser desorption/ionization (MALDI) mass spectra of highly-abundant proteins were generated from laboratory-reared mosquitoes using different extraction protocols, body parts, and sexes to minimize the amount of material from specimen vouchers needed and optimize the protocol for taxonomic identification.
February 2019
Mangroves plants and their endophytes represent a natural source of novel and bioactive compounds. In our ongoing research on mangrove endophytes from the Panamanian Pacific Coast, we have identified several bioactive endophytic fungi. From these organisms, an isolate belonging to the genus Zasmidium (Mycosphaerellaceae) showed 91.3% of inhibition against α-glucosidase enzyme in vitro. Results Zasmidium sp. strain EM5-10 was isolated from mature leaves of Laguncularia racemosa, and its crude extract showed good inhibition against α-glucosidase enzyme (91.3% of inhibition).
June 2018
Pseudoalteromonas is a genus of marine bacteria often found in association with other organisms. Although several studies have examined Pseudoalteromonas diversity and their antimicrobial activity, its diversity in tropical environments is largely unexplored. We investigated the diversity of Pseudoalteromonas in marine environments of Panama using a multilocus phylogenetic approach. Furthermore we tested their antimicrobial capacity and evaluated the effect of recombination and mutation in shaping their phylogenetic relationships. The reconstruction of clonal relationships among 78 strains including 15 reference Pseudoalteromonas species revealed 43 clonal lineages, divided in pigmented and non‐pigmented strains
December 2017
The fungus-growing ant-microbe symbiosis is an ideal system to study chemistry-based microbial interactions due to the wealth of microbial interactions described, and the lack of information on the molecules involved therein. In this study, we employed a combination of MALDI imaging mass spectrometry (MALDI-IMS) and MS/MS molecular networking to study chemistry-based microbial interactions in this system. MALDI IMS was used to visualize the distribution of antimicrobials at the inhibition zone between bacteria associated to the ant Acromyrmex echinatior and the fungal pathogen Escovopsis sp. MS/MS molecular networking was used for the dereplication of compounds found at the inhibition zones.
July 2017
It is increasingly recognized that microbiota affect host health and physiology. However, it is unclear what factors shape microbiome community assembly in nature, and how microbiome assembly can be manipulated to improve host health. All plant leaves host foliar endophytic fungi, which make up a diverse, environmentally acquired fungal microbiota. Here, we experimentally manipulated assembly of the cacao tree (Theobroma cacao) fungal microbiome in nature and tested the effect of assembly outcome on host health. Using next-generation sequencing, as well as culture-based methods coupled with Sanger sequencing, we found that manipulating leaf litter exposure and location within the forest canopy significantly altered microbiome composition in cacao.
May 2016
Background The pathogenesis-related (PR) group of proteins are operationally defined as polypeptides that increase in concentration in plant tissues upon contact with a pathogen. To date, 17 classes of highly divergent proteins have been described that act through multiple mechanisms of pathogen resistance. Characterizing these families in cacao, an economically important tree crop, and comparing the families to those in other species, is an important step in understanding cacao’s immune response.