nai

Project Progress

Cuatro Ciénegas is a unique biological preserve in México (state of Coahuila) in which there is striking microbial diversity, potentially related to extreme scarcity of phosphorus. We aim to understand this relationship via field sampling of biological and chemical characteristics and a series of enclosure and whole-pond fertilization experiments aimed at testing the effects of NP fertilization on the multi-element composition of microbes.

Overview of CC: During 2012 members of our team completed and published several manuscripts reviewing the microbiological and astrobiological attributes of the Cuatro Ciénegas basin; Volume 12, Number 7 of Astrobiology was devoted to eight of these articles. Our work also caught the attention of the New York Times which produced a News article (“Learning About Life on Mars, via a Detour to Mexico”) related to Valeria Souza’s continued work on conservation of the basin and its relevance to astrobiology “http://www.nytimes.com/2012/06/27/world/americas/learning-about-life-on-mars-by-studying-mexico-desert.html?_r=1&”:http://www.nytimes.com/2012/06/27/world/americas/learning-about-life-on-mars-by-studying-mexico-desert.html?_r=1&; June 26 2012.

Phosphorus limitation and element use in microbial communities: During the past year we completed the chemical analyses of samples from the summer 2011 experiment performed in Lagunita, Churince Basin, at Cuatro Cienegas that manipulated P supply and N:P ratio in replicate mesocosms. The responses of water column microbial phototroph biomass to P fertilization were rapid and strong and indicative of NxP synergistic interaction (see Figure CC1). Most data analyses for water column samples are complete while analyses of sediment responses in C:N:P ratios are underway. We have also extracted samples for construction of microbial community structure (¹⁶S ribotag sequencing) and transcriptomic response. These samples are now at JCVI for analysis by Chris Dupont. A manuscript describing the biogeochemical results is now being drafted and an abstract reporting the results was submitted for the February 2013 ASLO meeting.

During summer 2012 we completed the planned “whole pond” P fertilization experiment at Lagunita. Five control mesocosms were installed and then the pond was fertilized periodically (3-5 d intervals) with inorganic P and N to maintain PO₄ at a target of 1 uM. The response of water column phototroph biomass was substantial and immediate (Figure CC2). Prior to fertilization, a set of samples was taken for processing for metagenomic analysis; at the end of the 7-week fertilization period, another set was taken for metagenomic and transcriptomic analysis. Biogeochemical and genomic samples are now being processed.

Calcification, nutrient cycling, and microbial community structure in Río Mezquites stromatolites

PhD candidate Jessica Corman continued her work to understand formation of, and nutrient cycling processes associated with, oncoid stromatolites. During summer 2012, she sampled phenotypically distinct oncoid stromatolites for nutrient and microbial community analysis. Dr. Amisha Poret-Peterson and Corman, along with undergraduate Alisa Glukhova are characterizing the response of oncoid microbial communities to changes in nutrient and light availability with T-RFLP analysis.

Environmental, microbial, and stoichiometric diversity at Cuatro Ciénegas
In continuation of regular environmental sampling, PhD students Jessica Corman and Jorge Ramos sampled over 30 distinct water bodies in the valley during summer 2012. Water and sediment samples were collected for major and minor elemental analysis. Jessica Corman also continued the ecological and microbiological monitoring of succession in the Pozas Rojas, an area of saline pools that was affected by a massive flood in July 2010. Initial results of these studies were presented at the 2012 Ecological Society of America (ESA) Annual Meeting.

Environmental microbiology. UNAM researcher Valeria Souza continued to advance studies in association with the NASA NAI project to describe the genetic composition and microbial community structure of various ecosystems at Cuatro Ciénegas, including soil and sediment microbes as well as the microbes composing various stromatolite structures in the basin. Publications from this work include those featured in the special issue of Astrobiology mentioned earlier.