New collaborative publication analyzing the toxicity of fluorine-free firefighting foams using a soil nematode as a model system

In this study, we used the model organism Caenorhabditis elegans to evaluate the sublethal toxicity of six F-free AFFF alternatives and a current short-chain AFFF in soil invertebrates. We developed a rapid counting and measuring method for assessing sublethal toxicity in C. elegans. Our group took over the establishment of assays following ISO protocols, the maintenance of the nematodes, and the optimization of the approaches for the extractions of living worms from the soil matrix. The results presented in this publication showed that all tested formulations showed adverse impacts on the growth of C. elegans at concentrations lower than or close to the practical application concentration in the field. Also, five of six F-free alternatives caused reduced reproduction in C. elegans. Formulations containing higher concentrations of hydrocarbon surfactants were more toxic than other formulations to C. elegans. This study provides ecotoxicological data that, combined with data from all related ongoing research, should be used in decision-making regarding recommendations for manufacturing and use of candidate F-free foams.

Tested F-free formulations showed adverse effects on the soil nematode C. elegans. Illustration by Javier A. Ceja-Navarro

Javier’s work is featured at the Tech Interactive Museum

Javier’s work is featured at the Tech Interactive Museum ( as part of Solve for the Earth exhibition ( In a set of three videos, Javier describes his path through science, work, and discoveries. The videos were recorded in Spanish with English subtitles to highlight Javier’s commitment to the Latinx community.

Protists community dynamics in the rhizosphere of switchgrass – a video presentation

This video was originally prepared for a conference presentation, but the work that Petr Kosina and I put in the making of little piece made me want to share it more broadly. So here it is, a video in which I describe the concepts and findings of our paper published in the Microbiome Journal.

Protists communities are dynamic and more complex in the rhizosphere

Our new study on the succession of protists in the rhizosphere of switchgrass is now published. This work is part of a multi-institutional collaboration in which my team was in charge of studying soil microfauna – protists, which are microbes too!

The study shows that protists’ community diversity and composition change as the switchgrass plants go through different phenological stages, from early vegetative growth to senescence. The plants were grown in two marginal soil sites managed by the Noble Research Institute. Hence, the study is the result of a field experiment beautifully managed by the Noble scientists. Part of the analysis of protist community dynamics included the reconstruction of co-occurrence networks whose similarity thresholds were not arbitrary by calculated using Random Matrix Theory-based approaches. The results of these analyses show that the networks of protists in the rhizosphere are more complex and dynamic than those of the bulk soil, which remain unchanged from beginning to end of the study (for the most part). We also used iCAMP to analyze the mechanisms that control protist community assembly. We show that dispersal limitation is the mechanism controlling protist assembly in the bulk soil, while homogeneous selection is the mechanism that regulates the assembly of protists in the rhizosphere.

Protists are a type of microbe, and are slowly being recognized as key elements of the soil and rhizosphere microbiome. In this study, protist communities near plant roots were found to respond to the different developmental stages of switchgrass. (Credit: Javier A. Ceja Navarro)

Javier participated in the “Dia de la Ciencia” with the Mexican General Consulate in San Francisco

Javier hosted the forum “Carreras en Ciencia” organized by Science at Cal and the Mexican General Consulate in San Francisco. For the event, six young Latino scientists shared their experiences from their childhood curiosity to becoming scientists.

The event was accompanied by a Q&A section in which the scientists interacted with the public. To see a recording of this event go to:

The Navarro’s lab participated in the 2020 DOE-Genomic Sciences Meeting

Javier Navarro participated in the DOE-Genomic Sciences meeting held in Washington, DC on February 2020. During this meeting, Javier presented his collaborative work with the Lawrence Livermore National Laboratory, and UC Berkeley on the study of soil multitrophic responses to drought.

The Navarro’s lab is participating at the LMU-CAS Lilliputian Workshop in Germany

The complexity of a microbiome is daunting. A human’s gut microbiome may have over 1,000 individual species of bacteria that co-exist stably over years or possibly over generations. We lack an understanding of the forces that contribute to this surprising stability.

On December 5th, Javier Ceja-Navarro will talk about – “Lilliputian Landscapes and Microbial Function: Examples from the Gut of Beetles”