Bacterial isolates from Canary Islands (Spain) and the Selvagens Islands (Portugal) lava tubes

Volcanic caves are distributed worldwide. Numerous studies have revealed highly diverse microbial communities in lava tubes, forming colored microbial mats on the walls and ceilings of these caves. Several studies on bacterial biodiversity in lava tubes based on molecular techniques have been conducted, but there is limited information available on the diversity of culturable bacteria present in these caves. Culture-dependent techniques and molecular analyses were used in this study to characterize the microbial biofilms found in several lava tubes located in the Canary Islands (Lanzarote, Spain) and the Selvagens Islands (Portugal). One hundred and thirty-seven bacterial isolates were obtained thus far, mainly distributed within the phylum Bacillota. Most of the bacteria isolated from the lava tubes of Lanzarote and Selvagens Islands tolerate high salt concentrations, and some of them can produce antibiotics, such as Bacillus paralicheniformis and Streptomyces zaomyceticus (isolated from Selvagens Islands) or enzymes of industrial importance such as cellulose produced by Alkalihalobacillus akibai, urease produced by Sporosarcina newyorkensis (isolated from Lanzarote) or pectinase made by Sinomicrobium pectinilyticum (isolated from Selvagens Islands). Other interesting strains present in the lava tubes of the Selvagens Islands were Arthrobacter bussei and Kocuria palustris due to their antioxidant and fungicidal activity. The characterization of the microbial communities present in these lava tubes will help to better understand their diversity and the conservation of these volcanic cavity. Lava tubes could also be a good scenario to study the characterization of new bacterial species and to study the production of bioactive substances produce by these bacteria.