The biofilms that cover the walls of the “La Cueva del Escalón” cave, located in the Ason Valley (Cantabria, Spain), have proved to be a treasure trove of microbial biodiversity. They are mostly made up of a complex and varied tapestry of cyanobacteria, many of them little known, and which are currently being investigated in several projects.
The "Ares Station" is an operational center of the "Astroland Agency" company, installed inside the cave itself, from where part of the research work on biofilm takes place and basically acts as a support for sampling activities. These are environmentally friendly structures in which they are located, and from where an interesting astrobiology program is developed, in which different protocols related to microbiological research and the appearance of life on our planet are tested, or looking for signs of life on Mars.
Among the multicolored jellies that form the dense tapestry that covers the walls of the cave, those of the cyanobacterium Schizothrix are characterized by their green color and can appear by spraying irregularly other jelly-like masses of pink, grayish, and other various colors, or occur among other masses cyanobacteria showing fibrous structures.
Fig. 1. Macroscopic appearance of Schizothrix calcicola colonies, seen as green gelatinous masses among other filamentous cyanobacteria such as Scytonema julianum.
Under the microscope, using the Motic Panthera equipment, the filaments of Schizothrix calcicola, using objectives of different magnifications, reveal themselves as tenuous, narrow, and fragile structures, and appear to be formed by cells of just over a micron in width and four or five microns in diameter in length. One after another, these cells gently curve their long chains as they tangle.
Fig. 2. Aspects presented by filamentous colonies of Schizothrix calcicola when viewed with an epifluorescence microscope at 400X magnification and in a specimen that has been in a cold cell for 5 months in the dark. The photographs were taken with a Motic Panthera CC trinocular equipment with the Motic FLED fluorescence module. Image captured with a 40X / 0.65 / S (WD 0.6mm) objective.
All these strands are wrapped in thick sheaths of transparent and fibrous gelatin, which end in a long tip and protect the Schizothrix groups by preventing them from drying out.
The filaments in Schizothrix calcicola are irregularly arranged to form a mucilaginous, unincorporated thallus; with 1 - 2 (3) trichomes per pod, parallel and sometimes slightly curved. Colorless pods closed apically and sharp. Trichomes can be 0.7 - 1.5 (2) μm in diameter, are pale bluish-green in color with cells longer than wide, (1) 2 - 4.4 μm in length, and terminate in an apical cell rounded.
Fig.3. Schizothrix calcicola filaments photographed at 1000x magnification with the brightfield technique using the Motic 100X / 1.25 / S-Oil immersion objective (WD 0.16 mm).
All this tangle, which appears inert when viewed under brightfield illumination, turns out to be completely different when viewed illuminated with Motic's FLED fluorescence module and reveals its life by emitting a red-orange light that resembles the colors of a flame. in the form of filaments.
Fig. 4. Filaments of Schizothrix calcicola from a sample stored in cold storage and in the dark after 5 months. Images taken at 400x magnification with the epifluorescence technique, with the FLED module and the Motic 40X / 0.65 / S dry objective (WD 0.6mm). In the lower part can be seen the cells of some colonies of Gloeobacter violaceus colored with intense yellow color.
The name Schizothrix calcicola includes a complex of at least twenty morphological and genotypic varieties awaiting revision and which in Europe live on humid limestone rocks in temperate regions. In this cave of Escalón it is part of the flora that covers the wet walls in the areas near the entrance.
The images, taken at 400 and 1000 magnifications, with brightfield and epifluorescence techniques, with Motic Panthera CC trinocular equipment, come from samples collected inside the Escalón cave, near the Ares station, in a very poorly lit area in that the "Astroland Agency" is developing in its approximation project to the knowledge of Mars.
Fig. 5. Filaments of Schizothrix calcicola from a fresh specimen. Images taken at 400x magnification with the epifluorescence technique, with the FLED module and the Motic 40X / 0.65 / S dry objective (WD 0.6mm). Other cyanobacterial forms of different genera can be seen around the reddish filaments of Schizothrix calcicola, showing another coloration.
It is striking how these samples observed today and collected in late June 2021 continue to maintain vital and photosynthetic activity after being in a cold room for almost six months.
Fig. 6. Observation of samples of Schizothrix calcicola with the FLED module and the Motic 40X / 0.65 / S (WD 0.6mm) dry objective. Students of the subject Scientific culture at the high school "Escultor Daniel" (Spain)
Today these cyanobacteria are shown again to the readers of this publication and for the 1st year the students of the "Escultor Daniel" high school in Logroño (Spain), who participated in these observations learning to handle the Motic equipment, both with conventional brightfield illumination, as with the FLED epifluorescence module, essential for detecting the presence of photosynthetic activity in any sample of cyanobacteria.
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