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771.
Ryszard Soluch Nils F. Hülter Devani Romero Picazo Ezgi Özkurt Eva H. Stukenbrock Tal Dagan 《Environmental microbiology》2021,23(4):2260-2273
Plants are colonized by microbial communities that have diverse implications for plant development and health. The establishment of a stable plant–bacteria interaction depends on a continuous coexistence over generations. Transmission via the seed is considered as the main route for vertical inheritance of plant-associated bacteria. Nonetheless, the ecological principles that govern the plant colonization by seed endophytes remain understudied. Here we quantify the contribution of arrival time and colonization history to bacterial colonization of the wheat root. Establishing a common seed endophyte, Pantoea agglomerans, and wheat as a model system enabled us to document bacterial colonization of the plant roots during the early stages of germination. Using our system, we estimate the carrying capacity of the wheat roots as 108 cells g−1, which is robust among individual plants and over time. Competitions in planta reveal a significant advantage of early incoming colonizers over late-incoming colonizers. Priming for the wheat environment had little effect on the colonizer success. Our experiments thus provide empirical data on the root colonization dynamics of a seed endophyte. The persistence of seed endophyte bacteria with the plant population over generations may contribute to the stable transmission that is one route for the evolution of a stable host-associated lifestyle. 相似文献
772.
773.
Tal Perevolotsky Christopher H. Martin Asaph Rivlin Roi Holzman 《Proceedings. Biological sciences / The Royal Society》2020,287(1938)
Herbivorous fishes form a keystone component of reef ecosystems, yet the functional mechanisms underlying their feeding performance are poorly understood. In water, gravity is counter-balanced by buoyancy, hence fish are recoiled backwards after every bite they take from the substrate. To overcome this recoil and maintain contact with the algae covered substrate, fish need to generate thrust while feeding. However, the locomotory performance of reef herbivores in the context of feeding has hitherto been ignored. We used a three-dimensional high-speed video system to track mouth and body kinematics during in situ feeding strikes of fishes in the genus Zebrasoma, while synchronously recording the forces exerted on the substrate. These herbivores committed stereotypic and coordinated body and fin movements when feeding off the substrate and these movements determined algal biomass removed. Specifically, the speed of rapidly backing away from the substrate was associated with the magnitude of the pull force and the biomass of algae removed from the substrate per feeding bout. Our new framework for measuring biting performance in situ demonstrates that coordinated movements of the body and fins play a crucial role in herbivore foraging performance and may explain major axes of body and fin shape diversification across reef herbivore guilds. 相似文献
774.
775.
The EMG pattern in the elbow flexors during the performance of relatively slow (non-ballistic) targeted flexor and extensor
movements with different velocities and amplitudes and subsequent fixation of a reached position was studied in healthy humans.
Using a servocontrolled mechanostimulator, steady external loading was applied to the arm, which provided performance of the
movements and their termination exclusively by the flexor activity, leaving the extensors passive. In all cases, even at very
slow movements, EMG activity of the flexors at transition of the joint from one equilibrium state to another was shown to
contain a clear dynamic phase followed by a phase of stationary activity. The level of the latter, generated during fixation
of a reached position, was practically independent of the amplitude of a movement within the 0–60° range of the joint angles.
Thus, the force developed by the flexors at the dynamic EMG phase became fixed when a new equilibrium joint position was reached
and did not decrease in the course of a considerable drop in the efferent activity level, when the stationary phase of this
activity began. The dynamic EMG phase included two components. The first component was related to leaving the equilibrium
state with a certain acceleration, while the second component was probably involved in the velocity control and stoppage of
the joint in a new equilibrium position. We suppose that retention of the joint in the equilibrium state is not provided exclusively
by formation of a certain equilibrium level of efferent activity (as it is postulated by the equilibrium point hypotheses);
it results from some coordinated modifications of the dynamic muscle activity that provide achievement of equilibrium in a
certain position within a certain stage of the movement. 相似文献