Pyruvate accelerates palladium reduction by regulating catabolism and electron transfer pathway in Shewanella oneidensis.

Shewanella oneidensis is a model strain of the electrochemical active bacteria (EAB) because of its strong capability of extracellular electron transfer (EET) and genetic tractability. In this study, we investigated the effect of carbon sources on EET in S. oneidensis by using reduction of palladium ions (Pd(II)) as a model and found that pyruvate greatly accelerated the Pd(II) reduction compared with lactate by resting cells. Both Mtr pathway and hydrogenases played a role in Pd(II) reduction when pyruvate was used as a carbon source. Furthermore, in comparison with lactate-feeding S. oneidensis, the transcriptional levels of formate dehydrogenases involving in pyruvate catabolism, Mtr pathway, and hydrogenases in pyruvate-feeding S. oneidensis were up-regulated. Mechanistically, the enhancement of electron generation from pyruvate catabolism and electron transfer to Pd(II) explains the pyruvate effect on Pd(II) reduction. Interestingly, a 2-h time window is required for pyruvate to regulate transcription of these genes and profoundly improve Pd(II) reduction capability, suggesting a hierarchical regulation for pyruvate sensing and response in S. oneidensis IMPORTANCE The unique respiration of EET is crucial for the biogeochemical cycling of metal elements and diverse applications of EAB. Although a carbon source is a determinant factor of bacterial metabolism, the research into the regulation of carbon source on EET is rare. In this work, we reported the pyruvate-specific regulation and improvement of EET in S. oneidensis and revealed the underlying mechanism, which suggests potential targets to engineer and improve the EET efficiency of this bacterium. This study sheds light on the regulatory role of carbon sources in anaerobic respiration in EAB, providing a way to regulate EET for diverse applications from a novel perspective.

Reduction pathway and mechanism of chloronitrobenzenes synergistically catalyzed by bioPd and Shewanella oneidensis MR-1 assisted by calculation.

Although microbial synthesized palladium nanoparticles (bioPd) have been demonstrated to exhibit a great activity toward dechlorination of several chlorinated pollutants, there is no systematic investigation into the substituent effect on dechlorination. Chloronitrobenzenes are widely used for manufacturing and known as persistent pollutants with recalcitrance of biodegradation for nitro groups. In this work, bioPd was synthesized by Shewanella oneidensis MR-1. The dechlorination of 2-chloronitrobenzene, 4-chloronitrobenzene and 2,4-dichloronitrobenzene catalyzed by bioPd were investigated. Simultaneous dechlorination and nitro reduction were observed by synergistic catalysis of bioPd and S. oneidensis MR-1. Pd concentration was optimized for the reduction. Producing profiles of intermediates changed with the ratio of Pd to cell, supporting a size- or shape-controlled catalytic activity of bioPd. The removal of chloro atoms at para-position was easier than that at ortho-position in 2,4-DCNB, suggesting a position effect on the reduction, which was further supported by the frontier molecular orbital and frontier electron density of 2,4-DCNB according to density functional theory.

[Early screening of cerebral palsy during infancy using 'Infant Motor Malfunction Profile' in the communities of two cities].

OBJECTIVE: To evaluate the prospective validity and predictive value of cerebral palsy during infancy, using 'Infant Motor Malfunction Profile'. METHODS: Items of motor milestone in the profile was used as the first step to screen cerebral palsy on 8137 infants who were screened at 3, 6, 9, 12 months of age. The positive cases who had one of 7 developmental abnormal motor milestone items were examined using the items of primitive reflexes or postural reaction as the secondary step of cerebral palsy screening. The cases who had at least one abnormal item of primitive reflex or postural reaction received neurological examination by doctors to diagnose cerebral palsy. RESULTS: According to our data, sensitivity, specificity, positive prospective value, positive and negative likelihood ratio of the profile in screening cerebral during infancy were 94.1%, 99.8%, 48.5%, 449.6 and 0.06, respectively. CONCLUSION: The profile seemed to be an acceptable instrument for early identification of cerebral palsy.