The bacterial flagellar motor is made of a rotor and stators. In Salmonella it is thought that about a dozen MotA/B complexes are anchored to the peptidoglycan layer around the motor through the C-terminal peptidoglycan-binding domain of MotB to become active stators as well as proton channels. MotB consists of 309 residues, forming a single transmembrane helix (30–50), a stalk (51–100) and a C-terminal peptidoglycan-binding domain (101–309). Although the stalk is dispensable for torque generation by the motor, it is required for efficient motor performance. Residues 51 to 72 prevent premature proton leakage through the proton channel prior to stator assembly into the motor. However, the role of residues 72–100 remains unknown. Here, we analyzed the torque-speed relationship of the MotB(Δ72–100) motor. At a low speed near stall, this mutant motor produced torque at the wild-type level. Unlike the wild-type motor, however, torque dropped off drastically by slight decrease in external load and then showed a slow exponential decay over a wide range of load by its further reduction. Since it is known that the stator is a mechano-sensor and that the number of active stators changes in a load-dependent manner, we interpreted this unusual torque-speed relationship as anomaly in load-dependent control of the number of active stators. The results suggest that residues 72–100 of MotB is required for proper load-dependent control of the number of active stators around the rotor.
This study aims to contribute to the existing debate on the impact of corporate social responsibility (CSR) orientation on different measures of business performance through the proposal of a conceptual model. Drawing on stakeholder theory, we conceptualize CSR as a broad and multidimensional construct with seven dimensions: employees, partners, customers, farmers, environment, community, and competition. We also extend the concept of business performance, which includes tangible variables, namely financial performance (FP) and export performance (EXP), as well as intangible variables, namely image and reputation (IR) and the satisfaction of relevant stakeholders (SS). The research context of this study is the agri-food sector in southeastern Spain. This sector has been the focus of attention of numerous researchers due to the relevance that social and environmental aspects have had in its development. To test the proposed model, the partial least-squares technique (PLS-SEM) was applied to data collected by means of a survey from a sample of 107 companies, which represent 81.4% of the turnover of the sector analyzed. The results show that CSR has a positive effect on financial performance, improves the volume and performance of exports, positively affects the corporate image and reputation, and increases the level of satisfaction of relevant stakeholders. Further research should examine the model from the perceptions of other stakeholders (e.g., customers, employees, and suppliers), using a longitudinal research design and exploring other contexts.
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