In the frame of the project “Phylogeny and survival strategies of photosynthetic extremophilic microorganisms, PRIN-MIUR the aim of the research is to study species of extremophilic terrestrial cyanobacteria adapted to conditions of water stress and low irradiance. The first task is to characterize isolates of the genus Chroococcidiopsis isolated from hot and cold deserts and isolates of epilithic cyanobacteria from hypogean environments, taking into account their molecular phylogeny and the mechanisms underlying their ability to survive desiccation and low irradiance. The biodiversity of these isolates is evaluated according two molecular approaches : the first based on the analysis of the 16S rRNA sequence and of the internal transcribed spacer (ITS). The second one is based on the employment of a genomic PCR fingerprinting technique based on the use of primers derived from cyanobacterial repeated sequences, namely short tandemly repeated repetitive (STRR), long tandemly repeated repetitive (LTRR) and the highly iterated palindrome (HIP1) sequences. This technique allows the identification and typing of different isolates belonging to the same species as well as provides evidence on the presence of repeated sequences in their genome, giving thus information on its plasticity, contributing, thus, to highlight the molecular mechanisms of their capability to survive to environmental stresses. The second task is to evaluate the effects of various experimental conditions of water stress and low irradiance by means of morphological characterizations and analysis of the variation in their photosynthetic apparatus along with the measurement of the photosynthetic activity in the various experimental conditions. The third task consists in the characterization by HPLC and Circolar Dicroism of the composition of the capsular polysaccharides (CPS) extracted from the cyanobacterial cultures and in the evaluation of the polysaccharides production and their biochemical characteristics in relation to water stress and low-light availability.  

Genomic PCR fingerprinting of two Leptolyngbya strains with primers: (a) STRR2/STRR3, (b) STRR1/STRR3 and (c) LTRR1/LTRR2. The band profiles obtained allowed to distinguish between the two strains. Lanes M, 100 bp

Chroococcidiopsis molecular phylogeny

Few data are available on the genetic biodiversity of Chroococcidiopsis strains isolated from hot and cold deserts, and a preliminary phylogenetic analysis based upon partial 16S RNA gene sequencing suggested that hot and cold desert strains of Chroococcidiopsis form a distinct cluster, though at this time it is not yet clear whether these diverse forms should be regarded as species or perhaps genera. To elucidate the molecular phylogeny of desert strains of Chroococcidiopsis a polyphasic approach based on almost complete 16S RNA gene sequencing and genome PCR fingerprinting is currently employed. The research takes advantage of the fact that Daniela Billi is entrusted of maintaining Chroococcidiopsis isolates and related genera of the Culture Collection of Microorganisms from Extreme Environments (CCMEE), established by E.I. Friedmann as Polar Desert Research Center Director (Florida State University, Thallahassee, USA).

Leptolyngbya molecular phylogeny

Six strains of Leptolyngbya, three red and the other three green in colour, isolated from five different Roman hypogea were investigated by combining morphological and ultrastructural observations with the 16S rRNA gene and ITS sequencing and the total genomic PCR fingerprinting. The three red strains resulted as different isolates of the same species, while two of the green strains belong to the same species and the other one to a different one. In addition, the 16S rRNA gene sequencing suggested that the aerophytic epilithic strains of Leptolyngbya from extreme environments cluster within a clade that is divergent from that containing the aquatic form of Leptolyngbya, namely L. foveolarum and L. boryana.