Ecology of the Invisible. Microbial diversity and sustainability

Could you tell us about the importance of your research for sustainability and mitigation and adaptation to the effects of climate change?
In the Bacterial Ecology Laboratory (LEBac, Spanish initials) at UNAM’s Institute of Ecology, we work in different ecosystems to understand how their microbial diversity is structured and what is their role in the regulation of biogeochemical cycles. Microorganisms are at the base of element cycling, this is the transformation of elements in biochemical processes, and are fundamental in the cycles of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Our research has developed the basic knowledge to determine whether ecosystems are functioning as sources or sinks of greenhouse gases (GHG).

Our work is naturally inter- and transdisciplinary. Since before the pandemic, we have done online cooperative research with colleagues from all over the world and managed to include different research groups.

We are part of several international initiatives, such as the scientific research we are developing in Antarctica, which seeks to characterize communities that form microbial mats and to predict the effect of environmental change on them. We also work on the effect of environmental change on organisms and ecosystems health, in initiatives that seek to understand how wildlife’s holobiome (microbiome plus virome) is structured both in preserved and degraded regions, to predict the occurrence of pandemic events. Other working models include microbialites, which are communities similar to the oldest fossils we know and which help us understand how communities are structured.


Some of your interests are related to microbial research in aquatic environments. Can you tell us about it?
Microbial research in aquatic systems seeks to understand which microorganisms are part of the ecosystems in their different environments (water, sediments, structures) and what their functional role is. Its study makes it possible to recognize how ecosystems are structured and to detect if there are changes in their overall productive state: when there is an increase in available nutrients, this promotes an increase in primary production and leads to an imbalance in the ecosystem that is associated with the release of GHGs. This type of characterization, of both biological and environmental components, allows us to know health state of the water bodies on which the development of the communities depends, which is the basis for promoting sustainable development.


You have also worked with stromatolites, cyanobacteria, and bacterial reefs. How would you explain what they are to a non-specialist audience, and what is their role in their ecosystems sustainability?
LEBac is working on sites harboring stromatolites, entities named after the Greek words: lithos, rock, and stroma, layers. These are structures formed by microbial activity that deposes carbonate minerals. There are some aquatic sites harboring stromatolites in Mexico. These structures form communities that are among the most biodiverse in nature; they have approximately ten million cells per gram and there are more than eight thousand microbial species. Stromatolites are mostly formed by bacteria. Cyanobacteria are the most important bacteria in these structures in terms of biomass, and their role as primary producers is fundamental.

Stromatolites are carbon reservoirs, fundamental in the production of oxygen, responsible for the cycling of carbon, nitrogen, and sulfur in the aquatic systems in which they develop. They also serve as a shelter for juveniles and larvae of many species of fish and invertebrates. This is the reason why their resemblance to reefs has been pointed out, and this is where the concept of “bacterial reefs” comes from.


Part of your work is done in the Bacalar Lagoon in Quintana Roo. What is the importance of biodiversity at the microscopic level at that site?
Bacalar Lagoon is home to the largest freshwater bacterial reef (made of microbialites) in the world. Communities are distributed along more than 45 kilometers of coastline and within its cenotes. The environmental conditions at Bacalar, which include carbonate and sulfate saturation, tropical climate, and crystalline waters, promote the precipitation of carbonate minerals by the microbial communities that form stromatolites.

We have defined two bioregions of stromatolites in Bacalar Lagoon, associated with water conductivity, which, in turn, is defined by circulation in the lagoon. Understanding the diversity of Bacalar’s stromatolites has provided a deeper understanding of the history of the lagoon, the largest body of surface freshwater in the Yucatan Peninsula.

We have also been able to detect the effect of increased nitrogenous and phosphorous nutrients on the lagoon communities, nutrients that come from fields under intensive farming models, which use large amounts of fertilizers and deforest the rainforest. These practices are affecting the lagoon system’s health; stromatolites serve as a biological thermometer to understand these changes so that it is possible to predict associated health problems that affect both human populations and the ecosystem.


This is another area covered by your work: Microbiomes and human health. Could you describe this field of research?
All organisms have a microbiome, made of microorganisms that inhabit our bodies throughout our lives. By characterizing the microbiome of human populations, we have been able to identify how lifestyle (e.g., an agricultural versus an urban lifestyle) affects our microbiomes. This helps us understand the value of different lifestyles for health and to identify which modifications in the microbiome are associated with diseases; for example, with a higher rate of diabetes and metabolic diseases in urban populations.


You told us before about your participation in international research teams in Antarctica. Can you tell us about that experience and the international consortium you collaborate with?
Antarctica represents the last pristine territory of our planet. Only peace research activities are allowed there. Our planet’s health depends on that of the polar regions since it is there where deep ocean waters are formed, and they regulate global climate. Mexico is not a part of the Antarctic Treaty (see box), but from the Mexican Agency for Antarctic Studies, we are seeking to participate in this international effort to preserve and understand the Antarctic polar regions.

In Antarctica, terrestrial ecosystems are defined by patterns of deglaciation and ice formation. As the ice melts in the austral summer, there is water available. Microbial mats are formed in this thaw. Our group is part of international consortia that seek to understand the diversity that forms these mats, how they change over time and their role in biogeochemical cycles. Thanks to Mexico’s international cooperation agreements through Mexican Agency for Cooperation at International Development (AMEXCID, Spanish initials), we have been able to join initiatives with the Antarctic Institutes of Uruguay, Argentina, and Chile. 



Based on information from the Antarctic Treaty Secretariat website (https://www.ats.aq/index_s.html) and the website of the Mexican Agency for Antarctic Studies (https://antartidamexico.org/).

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