In Situ Nitrogen Fixation by Cyanobacteria at the Andragulla Cave, Spain

Abstract

Andragulla Cave is 2 m high, 6 m wide, and 2 m long (deep). Its lack of depth means that it is not isolated from external influences, and the microclimate is very similar to that experienced externally. The common stress factors on the growth of cyanobacterial communities on walls inside of Andragulla Cave include excess light, dryness, lack of nutrients, and cold temperatures. Nitrogen fixation, photon flux, relative humidity, and temperature in Andragulla Cave were measured hourly over 24 hours in winter. Nitrogen fixation by the reddish-brown mat formed by both cyanobacteria Scytonema mirabile and Gloeocapsa sanguinea in cave-like environments was measured in situ for the first time by acetylene reduction. The mat-specific rates (1.6 to 7.5 nmol C 2 H 4 m 22 s 21 ) were lower compared to published values from laboratory measurements of rehydrated samples from different environments. Daytime fixation was slightly higher than nighttime fixation, where nitrogen fixation by Gloeocapsa sanguinea played an important role. The most influential parameters for environmental nitrogen fixation in Andragulla Cave were photon flux for daytime fixation, temperature for nighttime fixation, and relative humidity for both. Nitrogen fixation by cyanobacteria may be significant in these N-poor ecosystems.

Molecular characterization of Geitleria appalachiana sp. nov. (Nostocales, Cyanobacteria) and formation of Geitleriaceae fam. nov.

“…Most Nostocales have the ability to fix nitrogen, and the absence of that ability has not been definitively proven. Cave environments are limited in nitrogen and cyanobacterial lineages in caves, such as Scytonema and Gloeocapsa, are known to fix atmospheric nitrogen (Asencio & Aboal 2011). Nitrogen fixation is normally accomplished by spatial separation of the enzyme nitrogenase from oxygen by the formation of a thick-walled heterocyte.…”

Polyhydroxybutyrate-producing cyanobacteria from lampenflora: The case study of the “Stiffe” caves in Italy

“…They are well adapted to extreme environments due to their ability to withstand high osmotic pressure, low temperatures, arid conditions, and UV radiations ( Sechrest and Brooks, 2002 ; Satyanarayana et al, 2005 ; Chrismas et al, 2015 ; Rasouli-Dogaheh et al, 2022 ). Many authors have described their presence in caves as most close to entrances lit by direct or indirect sunlight or by artificial light in those open to tourists ( Pentecost, 1992 ; Giordano et al, 2000 ; Asencio and Aboal, 2011 ; Czerwik-Marcinkowska and Mroziñska, 2011 ; Albertano, 2012 ; Czerwik-Marcinkowska, 2013 ; Pfendler et al, 2018 ; Puente-Sánchez et al, 2018 ; Behrendt et al, 2020 ; Havlena et al, 2021 ; Panou and Gkelis, 2022 ).…”