Elementor #27092


Institute for Integrative Biology of the Cell

Plant endosymbionts defend themselves against the hostile host environment

The nitrogen fixing symbiosis of legumes with rhizobium bacteria has a predominant ecological role in the nitrogen cycle and has the potential to provide the nitrogen required for plant growth in agriculture. The host plants allow the nitrogen-fixing rhizobia to colonize the cells of specific symbiotic organs, the nodules, in very large numbers in order to produce sufficient reduced nitrogen for the plant needs. Some legumes, including Medicago spp., produce massively antimicrobial peptides to keep this large bacterial population in check. These peptides, known as NCRs, have the potential to kill the rhizobia but in the nodule cells, they rather inhibit the division of the endosymbionts and trigger them into a morphologically differentiated state, resulting in a high nitrogen fixing activity. In this study published in mBio, the Plant-Bacteria Interactions team of I2BC shows that the bacterial resistance to the antimicrobial activity of the NCR peptides in the Medicago symbiont Sinorhizobium meliloti is multifactorial and requires peptide transporters, the lipopolysaccharide outer membrane and the stress response regulator RpoH1.


Contact: Peter MERGAERT (peter.mergaert@i2bc.paris.saclay.fr)

Zeiss truck on I2BC campus!

Tradeshows and conferences are ideal opportunities to discover new products and witness innovations firsthand. A real-time experience in an individual hands-on session will be offer to you to test new functionalities and give you the opportunity to talk to an expert about your needs. With Zeiss on your campus Truck,you can have the opportunity to experience microscopy workflows at first hand. Near your place of practice and taking into account the applicable hygiene measures, you can individually test the ZEISS instruments and solutions.


Temporal compartmentalization of viral infection in bacterial cells

Virus lytic infection imposes a major biosynthetic effort to the host cell and takes over significant cellular space. Viruses of prokaryotes must meet the challenge to restructure the cytoplasm open space of a small-sized cell. A study published in the Proceedings of the National Academy of Sciences USA reports the discovery that bacteriophage SPP1 infection leads to biogenesis of two types of membraneless compartments in the cytoplasm of the bacterium Bacillus subtilis. One is a single viral DNA compartment and others are warehouses for storage of viral particles. These compartments are temporal and spatially independent.
The DNA compartment sequesters machines operating viral DNA transactions. Multiple hybrid DNA replication centers, containing both phage replication proteins and hijacked bacterial replisomes, operate at different sub-locations within the compartment for parallelized synthesis of viral DNA. DNA is subsequently packaged in virion precursors without DNA (procapsids) at the compartment edges. Viral DNA-filled capsids then segregate from the DNA compartment, bind phage tails, and the resulting virions build warehouse compartments.
This spatial partition of the B subtilis cell responds to the requirements for exponential replication of SPP1 genomes and for the assembly of hundreds of viral particles. Its similarities to remodelling of the cell nucleus by herpesviruses led to the hypothesis that ancestral strategies used by viruses to invade the cell space were conserved to infect hosts of different Domains of Life.
Part of this work is from the PhD thesis of Audrey Labarde at Université Paris-Saclay.


Contact: Paulo TAVARES (paulo.tavares@i2bc.paris.saclay.fr)

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