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E. coli is well equipped for living in rapidly changing conditions of its natural ecosystem. For example, it is able to navigate by modulating the rotation of the bidirectional flagellar motor, and it has the ability of switching to anaerobic respiration that involves fumarate reduction, when oxygen is limited. A decade ago it was discovered that there is a crosstalk between the fumarate reduction system and the flagellar motor: fumarate reductase (FRD) was found to be required for flagellar clockwise (CW) rotation, which is essential for the navigation process. Here, by combining biochemical techniques with super resolution microscopy, we found that FRD affects the motor via its cytosolic subunit FrdA, and that this subunit preferentially binds to the CW state of the flagellar rotary unit FliG. This suggests that FrdA stabilizes the CW state of individual FliG subunits, thus increasing the probability of CW-conformational spread over the entire rotor. We further found that a natural increase in FrdA expression levels during microaerophilic growth conditions increases the probability of CW rotation to a level shown earlier to be more efficient for navigation. Thus, FrdA-motor interaction may be a mean of adjusting the navigation efficiency to the microaerophilic conditions found in the mammalian gut.

We derive a spectral sum rule in the shear channel for conformal field theories in general d> 2 dimensions held at finite temperature. The sum rule result from the OPE of the stress tensor at high frequency as well as the hydrodynamic behaviour of the theory at low frequencies. The sum rule states that a weighted integral of the spectral density over frequencies is proportional to the energy density of the theory. We show that the proportionality constant can be written in terms the Maldacena-Hofman variables t_2, t_4 which rely on data which determines the three point function of the stress tensor of the CFT. For theories which admit a two derivative gravity dual this proportionality constant is given by d/2(d+1) . We then use causality constraints and obtain bounds on the sum rule which are valid for any conformal field theory. We illustrate the sum rule by applying it to well studied conformal field theories in d=3, 4, 6. dimensions

Ecosystem responses to climatic droughts range from increased frequency of stomatal closure and declines in carbon assimilation to plant mortality and increased vulnerability to insects/pathogens and fire. Forest thinning is often posited as a management practice that can reduce mitigate these forest drought responses and may have implications for groundwater recharge and streamflow. There are still relatively few field-based studies of thinning impacts on forest water use. Most of these studies focus only on responses in the first 1-2 years following thinning and show substantial cross-site differences in responses. To extend and better understand field-based findings, we utilize a fully coupled model of ecosystem carbon cycling and hydrology to estimate forest water use, carbon sequestration, regrowth rates and indicators of water stress for different thinning densities. We compare results across climate, topography and soils. For the California Sierra, results emphasize the importance of plant accessible subsurface water storage capacity (PAWSC). We find that a first-order control on system response to thinning is the interactions between PAWSC and climate. We also show that a critical information gap is estimates of the degree to which neighboring trees share water. We conclude by suggesting model applications and new measurements that could be used to help guide decision-making with respect to thinning by accounting for how these multiple controls on thinning ecohydrology interact.