The generation of self-organized ring patterns of gene expression in the absence of a morphogen gradient was demonstrated using bacteria programmed by a synthetic gene circuit. This work presents a timing mechanism of pattern formation.

Summary Scale invariance refers to the maintenance of a constant ratio of developing organ size to body size. Though common, its underlying mechanisms remain poorly understood. Here we examined scaling in engineered E. coli that can form self-organized core-ring patterns in colonies. We found that the ring width exhibits perfect scale invariance to the colony size. Our analysis revealed a collective space-sensing mechanism, which entails sequential actions of an integral feedback loop and an incoherent feedforward loop. The integral feedback is implemented by the accumulation of a diffusive chemical produced by a colony. This accumulation, combined with nutrient consumption, sets the timing for ring initiation. The incoherent feedforward is implemented by the opposing effects of the domain size on the rate and duration of ring maturation. This mechanism emphasizes a role of timing control in achieving robust pattern scaling and provides a new perspective in examining the phenomenon in natural systems.

Biodiversity, or the relative abundance of species, measures the persistence of an ecosystem. To better understand its modulation, we analyzed the spatial and temporal dynamics of a synthetic, chemical-mediated ecosystem that consisted of two engineered Escherichia coli populations. Depending on the specific experimental conditions implemented, the dominant interaction between the two populations could be competition for nutrients or predation due to engineered communication. While the two types of interactions resulted in different spatial patterns, they demonstrated a common trend in terms of the modulation of biodiversity. Specifically, biodiversity decreased with increasing cellular motility if the segregation distance between the two populations was comparable to the length scale of the chemical-mediated interaction. Otherwise, biodiversity was insensitive to cellular motility. Our results suggested a simple criterion for predicting the modulation of biodiversity by habitat partitioning and cellular motility in chemical-mediated ecosystems.

Synopsis 1,ow t miperat iirc gaseiiis 1d:isiii:is of ammoiii;i or tiit iugeti-hydrogcti inixt iires coiiLaiii -KH2 groiips, or prwiii'sors t hereof, formed i i i the plwrn:i, which esperimeiital evideiicx! sti.oiigly siiggests, ciiti add t o various polymer sril~faces. The plasmas were est:thlished i i i the 0.3-1..7 t o n raiige by radiofiqiieiicy (13..>6 3IHx) elect.r~idelcss csritntioii at. poaei-s raiigitig from .iO to >OO \V. Samples of polypropyleiie, poly(viiiy1 chloritlc), polytct iafliiorethyleiie, polycartxmat e, polyiirethaiie, and pcily(niethy1 met hitcrylate) were iiivcstigated. All these polyriiers added amiiio groiips t.o varyiiig d o g i w~ of : i i i i i i i i ) site deiisities depeiidiiig on the rhoire of plasma paramet,ers a i d the reartivity o f the polymer itself. I n every itistaiice the polymer w a s rendered more wettable, althoiigh i i o qiiaiititative nettability measiiremeiits were made. Following the p1nsiri:t treatment, degrees of amiiio attachmeiit to the polymer were followed mdiometrically arid reported iii terms of "heparin thicliiwscs" i e d t i i i g from ionic hepariii -358 attarhmeiit t o c1iiateriiai.y sites piwliiced from the nmitio groups. Two implicat iiitis of siich a surface mrrdific:itioii :ire t o :idhesioii wid hlood rompat ihle materials p i q x i i x t ioti.

The active agent within coal appears to be iron, not quartz. By identifying components of coal before mining activities, the risk of developing CWP may be reduced.