Bacterial cell walls’ functions: from protection to sensing

 

Surface layers (S-layers) in extremophilic bacteria

S-layer are paracrystalline arrays of proteins associated to the external side of the cell wall and they cover the surface of many bacterial species. We are interested on the structural and functional characterisation of S-layers and their associated membrane protein complexes. In particular, we investigated these protein components in extremophiles such as Deinococcus radiodurans, Thermus thermophilus, Haloferax volcanii. Our aim is to uncover the role of these bacterial structures by a deep understanding of their protein and cofactor composition.

 

S-layers as vestigial structures from primordial Earth

By studying the S-layer of Deinococcus radiodurans, we discovered that the major protein component was the protein DR_2577, which bind a carotenoid cofactor, the deinoxanthin, which is specific of this bacterium. The UV- and desiccation-resistance features of this protein prompted us to further investigate their matching with primordial Earth’s conditions. We are interested in elucidating the evolution of S-layer structures and functions in a wide range of extremophilic bacteria which are adapted to extreme conditions similar to the ones characterising the primordial Earth and, nowadays, the other exoplanets.

 

Rhizobiology

We study the early pre-nodulation events associated to the imbibing and germinating phases in legumes. In particular, we are investigating the chemotactic response of rhizobacteria to components released in the soil by seeds, in order to understand the early-symbiotic processes occurring before the development of the nodule.

 

For details, please see:

Farci D, Esposito E, El Alaoui E, Piano D. S-layer proteins as a source of carotenoids: isolation of the protein cofactor deinoxanthin from its S-layer protein DR_2577. Food Res Intern, 2016, in press. doi:10.1016/j.foodres.2016.10.003.

Farci D, Slavov C, Tramontano E, Piano D. The S-layer protein DR_2577 binds the carotenoid deinoxanthin and under desiccation conditions protect against UV-radiation in Deinococcus radiodurans. Frontiers in Microbiology, section of Extreme Microbiology, research topic Photobiology of Extremophiles, Front Microbiol. 2016, 7:155. doi: 10.3389/fmicb.2016.00155.

Farci D, Bowler MW, Esposito F, McSweeney S, Tramontano E, Piano D. Purification and characterization of DR_2577 (SlpA) a major S-layer protein from Deinococcus radiodurans. Front in Microbiol, 2015, 6:414. doi:10.3389/fmicb.2015.00414.

Farci D, Bowler MW, Kirkpatrick J, McSweeney S, Tramontano E, Piano D. New features of the cell wall of the radio-resistant bacterium Deinococcus radiodurans. Biochim. Biophys. Acta – Biomembranes. 2014, 1838: 1978-84. doi:10.1016/j.bbamem.2014.02.014.

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