Bioprospecting the Solar Panel Microbiome: High-Throughput Screening for Antioxidant Bacteria in a Caenorhabditis elegans Model

First characterization of cultivable extremophile Chroococcidiopsis isolates from a solar panel

Introduction

Microorganisms colonize a wide range of natural and artificial environments. Even though most of them are unculturable in laboratory conditions, some ecosystems are ideal niches for bioprospecting extremophiles with unique properties. Up today, there are few reports concerning microbial communities found on solar panels, a widespread, artificial, extreme habitat. Microorganisms found in this habitat belong to drought-, heat- and radiation-adapted genera, including fungi, bacteria, and cyanobacteria.

Methods

Here we isolated and identified several cyanobacteria from a solar panel. Then, some strains isolated were characterizated for their resistance to desiccation, UV-C exposition, and their growth on a range of temperature, pH, NaCl concentration or diverse carbon and nitrogen sources. Finally, gene transfer to these isolates was evaluated using several SEVA plasmids with different replicons to assess their potential in biotechnological applications.

Results and discussion

This study presents the first identification and characterization of cultivable extremophile cyanobacteria from a solar panel in Valencia, Spain. The isolates are members of the genera Chroococcidiopsis, Leptolyngbya, Myxacorys, and Oculatella all genera with species commonly isolated from deserts and arid regions. Four of the isolates were selected, all of them Chroococcidiopsis, and characterized. Our results showed that all Chroococcidiopsis isolates chosen were resistant up to a year of desiccation, viable after exposition to high doses of UV-C, and capable of being transformed. Our findings revealed that a solar panel is a useful ecological niche in searching for extremophilic cyanobacteria to further study the desiccation and UV-tolerance mechanisms. We conclude that these cyanobacteria can be modified and exploited as candidates for biotechnological purposes, including astrobiology applications.

Kineococcus vitellinus sp. nov., Kineococcus indalonis sp. nov. and Kineococcus siccus sp. nov., Isolated Nearby the Tabernas Desert (Almería, Spain)

Three novel Gram-positive, aerobic, chemoheterotrophic, motile, non-endospore-forming, orange-pigmented bacteria designated strains T13T, T90T and R8T were isolated from the Tabernas Desert biocrust (Almería, Spain). Cells of the three strains were coccus-shaped and occurred singly, in pairs or clusters. The three strains were oxidase-negative and catalase-positive, and showed a mesophilic, neutrophilic and non-halophilic metabolism. Based on the 16S rRNA gene sequences, the closest neighbours of strains T13T, T90T and R8T were Kineococcus aurantiacus IFO 15268T, Kineococcus gypseus YIM 121300T and Kineococcus radiotolerans SRS 30216T (98.5%, 97.1% and 97.9% gene sequence similarity, respectively). The genomes were sequenced, and have been deposited in the GenBank/EMBL/DDBJ databases under the accession numbers JAAALL000000000, JAAALM000000000 and JAAALN000000000, respectively, for strains T13T, T90T and R8T. The average nucleotide identity (ANIb) and digital DNA-DNA hybridization (dDDH) values confirmed their adscription to three new species within the genus Kineococcus. The genomic G + C content of strains T13T, T90T and R8T ranged from 75.1% to 76.3%. The predominant fatty acid of all three strains was anteiso-C15:0. According to a polyphasic study, strains T13T, T90T and R8T are representatives of three new species in the genus Kineococcus, for which names Kineococcus vitellinus sp. nov. (type strain T13T = CECT 9936T = DSM 110024T), Kineococcus indalonis sp. nov. (type strain T90T = CECT 9938T = DSM 110026T) and Kineococcus siccus sp. nov. (type strain R8T = CECT 9937T = DSM 110025T) are proposed.

Microbial communities of the Mediterranean rocky shore: ecology and biotechnological potential of the sea-land transition

Microbial communities from harsh environments hold great promise as sources of biotechnologically relevant strains and compounds. In the present work, we have characterized the microorganisms from the supralittoral and splash zone in three different rocky locations of the Western Mediterranean coast, a tough environment characterized by high levels of irradiation and large temperature and salinity fluctuations. We have retrieved a complete view of the ecology and functional aspects of these communities and assessed the biotechnological potential of the cultivable microorganisms. All three locations displayed very similar taxonomic profiles, with the genus Rubrobacter and the families Xenococcaceae, Flammeovirgaceae, Phyllobacteriaceae, Rhodobacteraceae and Trueperaceae being the most abundant taxa; and Ascomycota and halotolerant archaea as members of the eukaryotic and archaeal community respectively. In parallel, the culture-dependent approach yielded a 100-isolates collection, out of which 12 displayed high antioxidant activities, as evidenced by two in vitro (hydrogen peroxide and DPPH) and confirmed in vivo with Caenorhabditis elegans assays, in which two isolates, CR22 and CR24, resulted in extended survival rates of the nematodes. This work is the first complete characterization of the Mediterranean splash-zone coastal microbiome, and our results indicate that this microbial niche is home of an extremophilic community that holds biotechnological potential.