Functional viromic screens uncover regulatory RNA elements.

The number of sequenced viral genomes has surged recently, presenting an opportunity to understand viral diversity and uncover unknown regulatory mechanisms. Here, we conducted a screening of 30,367 viral segments from 143 species representing 96 genera and 37 families. Using a library of viral segments in 3' UTR, we identified hundreds of elements impacting RNA abundance, translation, and nucleocytoplasmic distribution. To illustrate the power of this approach, we investigated K5, an element conserved in kobuviruses, and found its potent ability to enhance mRNA stability and translation in various contexts, including adeno-associated viral vectors and synthetic mRNAs. Moreover, we identified a previously uncharacterized protein, ZCCHC2, as a critical host factor for K5. ZCCHC2 recruits the terminal nucleotidyl transferase TENT4 to elongate poly(A) tails with mixed sequences, delaying deadenylation. This study provides a unique resource for virus and RNA research and highlights the potential of the virosphere for biological discoveries.

Spatially Organized Films from Bdellovibrio bacteriovorus Prey Lysates.

Bdellovibrio bacteriovorus is a Gram-negative predator of other Gram-negative bacteria. Interestingly, Bdellovibrio bacteriovorus 109J cells grown in coculture with Escherichia coli ML-35 prey develop into a spatially organized two-dimensional film when located on a nutrient-rich surface. From deposition of 10 µl of a routine cleared coculture of B. bacteriovorus and E. coli cells, the cells multiply into a macroscopic community and segregate into an inner, yellow circular region and an outer, off-white region. Fluorescence in situ hybridization and atomic force microscopy measurements confirm that the mature film is spatially organized into two morphologically distinct Bdellovibrio populations, with primarily small, vibroid cells in the center and a complex mixture of pleomorphic cells in the outer radii. The interior region cell population exhibits the hunting phenotype while the outer region cell subpopulation does not. Crowding and high nutrient availability with limited prey appear to favor diversification of the B. bacteriovorus population into two distinct, thriving subpopulations and may be beneficial to the persistence of B. bacteriovorus in biofilms.