Biology subjects

Rojas-Gätjens, D.

Publications and source records attributed to Rojas-Gätjens, D..

3 recordsLinked to original sources

bioRxiv2020

Rapid shift in microbial community structure in a neutral hydrothermal hot spring from Costa Rica

In this work, we characterize the geochemistry and microbial community of Bajo las Penas, a neutral (pH 6.5-7.4), hot spring (T = 62.0-68.0{degrees}C) located near Turrialba Volcano, Costa Rica. The microbiota at its two sources belongs mainly to the family Aquificae, comprising OTUs closely related to the genera Sulfurihydrogenibium, Thermosulfidibacter, Thermodesulfovibrio and Thermocrinis which is consistent with the presence of moderate levels of sulfate (243-284 mg/L) along the stream. We determined a dramatic shift in the microbial community just a few meters downstream of the sources of the hot spring (15-20 meters), with a change from sulfur related chemoautotrophic (e.g. Sulfurihydrogenibium and an OTU closely related to Thermodesulfovibrio) to chemoheterotrophic prokaryotes (e.g. Meiothermus, Nitrososphaera, Thermoflexus, Thermus). Thus, in this neutral hot spring, the first level of the trophic chain is associated with photosynthesis as well other anaerobic CO2 fixing bacteria. Then, thermotolerant chemoheterotrophic bacteria colonize the environment to degrade organic matter and use fermentative products from the first level of the trophic chain. Our data demonstrate how quickly the microbial community of an ecosystem can change in response to environmental variables and sheds light on the microbial ecology of less common circumneutral pH hot springs.

microbiology↗

bioRxiv2020

Temperature and elemental sulfur shape microbial communities in two extremely acidic aquatic volcanic environments

Aquatic environments of volcanic origin provide an exceptional opportunity to study the adaptations of microbial communities to early planet life conditions such as high temperatures, high metal concentrations, and low pH. Here, we characterized the prokaryotic communities and physicochemical properties of seepage sites at the bottom of the Poas Volcano crater and the Agrio River, two geologically related extremely acidic environments located in the Central Volcanic mountain range of Costa Rica. Both locations hold a very low pH (pH 1.79-2.20) and have high sulfate and iron concentrations (Fe = 47-206 mg/L, SO42- = 1170-2460 mg/L measured as S), but significant differences in their temperature (90.0-95.0{degrees}C in the seepages at Poas Volcano versus 19.1-26.6 {degrees}C in Agrio River) and in the abundance of elemental sulfur. Based on the analysis of 16S rRNA gene sequences, we determined that Sulfobacillus spp., sulfur-oxidizing bacteria, represented more than half (58.4-78.4%) of the sequences in Poas Volcano seepage sites, while Agrio River was dominated by the iron- and sulfur-oxidizing Leptospirillum (7.4-55.5%) and members of the archeal order Thermoplasmatales (16.0-58.2%). Both environments share some chemical characteristics and part of their microbiota, however the temperature and the presence of reduced sulfur are likely the main distinguishing feature ultimately shaping their microbial communities. Our data suggest that in the Poas Volcano-Agrio River system there is a common metabolism but with specialization of species that adapt to the physicochemical conditions of each environment.

microbiology↗

bioRxiv2020

C1 compounds shape the microbial community of an abandoned century-old oil exploration well.

The search for microorganisms that degrade hydrocarbons is highly relevant because it enables the bioremediation of these substances cheaply and without dangerous by-products. In this work, we studied the microbial communities of an exploratory oil well, abandoned a century ago, located in the Cahuita National Park of Costa Rica. Cahuita well is characterized by a continuous efflux of methane and the presence of a mixture of hydrocarbons including C2-dibenzothiophene, phenanthrene or anthracene, fluoranthene pyrene, dibenzothiophene, tricyclic terpanes, pyrene, sesquiterpenes, sterane and n-alkanes. Based on the analysis of 16S rRNA gene amplicons, we detected a significant abundance of methylotrophic bacteria (Methylobacillus (6.3-26.0 % of total reads) and Methylococcus (4.1-30.6 %)) and the presence of common genera associated with hydrocarbon degradation, such as Comamonas (0.8-4.6 %), Hydrogenophaga (1.5-3.3 %) Rhodobacter (1.0-4.9 %) and Flavobacterium (1.1-6.5 %). We evidenced the presence of methane monooxygenase (MMO) activities, responsible for the first step in methane metabolism, by amplifying the pmo gene from environmental DNA. We also isolated a strain of Methylorubrum rhodesianum, which was capable of using methanol as its sole carbon source. This work represents a contribution to the understanding of the ecology of communities of microorganisms in environments with permanently high concentrations of methane and hydrocarbons, which also has biotechnological implications for the bioremediation of highly polluting petroleum components.

microbiology↗