Control of membrane protein synthesis in Bacillus subtilis

A NAD-dependent glutamate dehydrogenase coordinates metabolism with cell division in Caulobacter crescentus

Coupling cell cycle with nutrient availability is a crucial process for all living cells. But how bacteria control cell division according to metabolic supplies remains poorly understood. Here, we describe a molecular mechanism that coordinates central metabolism with cell division in the α-proteobacterium Caulobacter crescentus. This mechanism involves the NAD-dependent glutamate dehydrogenase GdhZ and the oxidoreductase-like KidO. While enzymatically active GdhZ directly interferes with FtsZ polymerization by stimulating its GTPase activity, KidO bound to NADH destabilizes lateral interactions between FtsZ protofilaments. Both GdhZ and KidO share the same regulatory network to concomitantly stimulate the rapid disassembly of the Z-ring, necessary for the subsequent release of progeny cells. Thus, this mechanism illustrates how proteins initially dedicated to metabolism coordinate cell cycle progression with nutrient availability.

Theory of the origin, evolution, and nature of life

Life is an inordinately complex unsolved puzzle. Despite significant theoretical progress, experimental anomalies, paradoxes, and enigmas have revealed paradigmatic limitations. Thus, the advancement of scientific understanding requires new models that resolve fundamental problems. Here, I present a theoretical framework that economically fits evidence accumulated from examinations of life. This theory is based upon a straightforward and non-mathematical core model and proposes unique yet empirically consistent explanations for major phenomena including, but not limited to, quantum gravity, phase transitions of water, why living systems are predominantly CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur), homochirality of sugars and amino acids, homeoviscous adaptation, triplet code, and DNA mutations. The theoretical framework unifies the macrocosmic and microcosmic realms, validates predicted laws of nature, and solves the puzzle of the origin and evolution of cellular life in the universe.

Growth kinetics of individual Bacillus subtilis cells and correlation with nucleoid extension

The growth rate of individual cells of Bacillus subtilis (doubling time, 120 min) has been calculated by using a modification of the Collins-Richmond principle which allows the growth rate of mononucleate, binucleate, and septate cells to be calculated separately. The standard Collins-Richmond equation represents a weighted average of the growth rate calculated from these three major classes. Both approaches strongly suggest that the rate of length extension is exponential. By preparing critical-point-dried cells, in which major features of the cell such as nucleoids and cross-walls can be seen, it has also been possible to examine whether nucleoid extension is coupled to length extension. Growth rates for nucleoid movement are parallel to those of total length extension, except possibly in the case of septate cells. Furthermore, by calculating the growth rate of various portions of the cell surface, it appears likely that the limits of the site of cylindrical envelope assembly lie between the distal tips of the nucleoid; the old poles show zero growth rate. Coupling of nucleoid extension with increase of cell length is envisaged as occurring through an exponentially increasing number of DNA-surface attachment sites occupying most of the available surface.