An analysis of the genome of the Australian lungfish is reported in Nature this week, revealing new insights into the transition of vertebrate life from water to land, as well as the structures of giant genomes. Lungfish are lobe-finned fish capable of breathing air through lungs, a capability they share with land-dwelling vertebrates, and are also known to have the largest animal genome. To better understand these unique organisms, scientists from the University of Konstanz and collaborators sequenced, assembled, and annotated the Australian lungfish genome, finding evidence of a number of pre-adaptations for living on land such as gaining limb-like expression of developmental genes in their lobed fins. Other findings include rates of evolution and duplication of genes associated with obligate air-breathing and the detection of air-borne odors.
Using the gene-editing technology CRISPR, scientists from the Institut Pasteur investigate the effects of genetic diversity on gene essentiality in Escherichia coli, an organism whose core genome represents only about half the number of genes in different strains of the bacteria. The team developed a CRISPR interference platform for high-throughput gene repression to assess the importance of about 3,400 genes that are nearly ubiquitous in E. coli under different growth conditions in 18 strains. As reported in Nature Microbiology, the researchers find extensive variations in gene essentiality between strains and conditions, and show that epistatic interactions with mobile genetic elements can influence these variations. For example, they demonstrate that prophage-encoded defense systems against phage infection can trigger the essentiality of persistent genes that are usually non-essential. "Our study highlights the importance of studying the contribution of genes to fitness in many strains and environments, which is now made possible by recent advances in bacterial genomics," they write.