A localized transition in the size variation of circular DNA in nanofluidic slitlike confinement

We report strong evidence for a localized transition in the size variation of circular DNA between strong and moderate regimes of slitlike confinement. A novel and rigorous statistical analysis was applied to our recent experimental measurements of DNA size for linear and circular topologies in nanofluidic slits with depths around ≈ 2p, where p is the persistence length. This empirical approach revealed a localized transition between confinement regimes for circular DNA at a slit depth of ≈ 3p but neither detected nor ruled out the possibility for such a transition for linear DNA. These unexpected results provide the first indication of the localized influence of polymer topology on size variation in slitlike confinement. Improved understanding of differences in polymer behavior related to topology in this controversial and relevant system is of fundamental importance in polymer science and will inform nanofluidic methods for biopolymer analysis

Genetic requirements for cell division in a genomically minimal cell

Genomically minimal cells, such as JCVI-syn3.0, offer a platform to clarify genes underlying core physiological processes. Although this minimal cell includes genes essential for population growth, the physiology of its single cells remained uncharacterized. To investigate striking morphological variation in JCVI-syn3.0 cells, we present an approach to characterize cell propagation and determine genes affecting cell morphology. Microfluidic chemostats allowed observation of intrinsic cell dynamics that result in irregular morphologies. A genome with 19 genes not retained in JCVI-syn3.0 generated JCVI-syn3A, which presents morphology similar to that of JCVI-syn1.0. We further identified seven of these 19 genes, including two known cell division genes, ftsZ and sepF, a hydrolase of unknown substrate, and four genes that encode membrane-associated proteins of unknown function, which are required together to restore a phenotype similar to that of JCVI-syn1.0. This result emphasizes the polygenic nature of cell division and morphology in a genomically minimal cell