Genetic Dissection of a Prevalent Plasmid-Encoded Conjugation System in Lactococcus lactis

Plasmid pNP40, which was first identified nearly 40 years ago in Lactococcus lactis subsp. lactis biovar diacetylactis DRC3, encodes functions such as heavy metal-, bacteriophage-, and nisin-resistance, as well as plasmid transfer ability by conjugation. Here, we report an optimized conjugation protocol for this plasmid, yielding a transfer frequency that is approximately 4,000-fold higher than those previously reported in literature, while we also observed high-frequency plasmid co-mobilization. Individual mutations in 18 genes that encompass the presumed conjugation cluster of pNP40 were generated using ssDNA recombineering to evaluate the role of each gene in the conjugation process. A possible transcriptional repressor of this conjugation cluster, the product of the traR gene, was identified in this manner. This mutational analysis, paired with bioinformatic predictions as based on sequence and structural similarities, allowed us to generate a preliminary model of the pNP40 conjugation machinery.

Plant pathogenic bacterium can rapidly evolve tolerance to an antimicrobial plant allelochemical

Crop losses to plant pathogens are a growing threat to global food security, and hence, more effective control strategies are urgently required. Biofumigation, an agricultural technique, where Brassica plant tissues are mulched into soils to release antimicrobial plant allelochemicals called isothiocyanates (ITCs), has been proposed as an environmentally friendly alternative to synthetic agrochemicals. While biofumigation has been shown to suppress a range of plant pathogens, its effects on plant pathogenic bacteria remain largely unexplored. Here we used a laboratory model system to compare the efficacy of different types of ITCs against Ralstonia solanacearum plant bacterial pathogen. Additionally, we evaluated the potential for ITC-tolerance evolution under high, intermediate and low transfer frequency ITC exposure treatments. We found that allyl-ITC was the most efficient compound at suppressing R. solanacearum growth, and its efficacy was not improved when combined with other types of ITCs. Despite consistent pathogen growth suppression, ITC tolerance evolution was observed in the low transfer frequency exposure treatment. Mechanistically, tolerance was associated with parallel mutations in a gene linked to glucose/sorbonose dehydrogenase, resulting in cross-tolerance to ampicillin beta-lactam antibiotic. Interestingly, pathogen adaptation to the growth media also indirectly selected for increased ITC tolerance through potential metabolic adaptations linked with cell wall structure (serine/threonine kinase) and DNA replication, recombination and repair (deoxyribonucleases). Together, our results suggest that R. solanacearum can rapidly evolve tolerance to allyl-ITC plant allelochemical, which could constrain the long-term efficiency of biofumigation biocontrol and potentially shape pathogen evolution with plants.

Screening of heavy metal and antibiotic resistance among Proteus vulgaris isolates from hospital wastewater of Northern India

Background: Microbial resistance to antibiotics and heavy metals is a rising problem in the world today. All the Proteus vulgaris isolates showed their MIC in between 50-1600 µg/ml. Of 70% and 46% of the isolates showed their MIC at 800-1200 µg/ml against Zn2+ and Cu2+ while 80% of the isolates showed their MIC at 100-200 µg/ml against Ni2+, respectively. All Proteus vulgaris isolates also exhibited multiple resistance patterns (2-7 heavy metals) in different combination of metals. The Multi metal resistance Index (MHMR) ranges were found (0.04-0.5). Methods: A high level of antibiotics resistance was observed against Methicillin (100%) and least to Oflaxicin (6%), Gentamycine and Neomycin (10%). All Proteus vulgaris isolates also showed multiple drug resistance patterns (2-12 antibiotics) in different combination of antibiotics. The MAR index ranges were found (0.02-0.7). Of 98%, 84% and 80% of the total isolates showed urease, gelatinase and amylase activity. Results: The Proteus vulgaris isolates contained plasmid of size ranging from 42.5 to 57.0kb and molecular weight of plasmids ranged from 27.2 to 37.0 MD. Incidences of resistance transfer, 7 pairs of isolates were assessed for the transfer of the antibiotic/ heavy metal resistance markers. The higher (4.4x10-1 and 3.4x10-1) transfer frequency was observed among antibiotic and heavy metal while lower transfer frequency were (5.0x10-2 and 1.0x10-2) showed against antibiotic and heavy metal in both the medium from the entire site tested, respectively. Conclusion: Indicating the high threat of environmental pollution and appearance of heavy metal resistance which may support the enlargement of resistance to antibiotics among the pathogens.

Simulation Analysis of Knowledge Transfer in a Knowledge Alliance Based on a Circular Surface Radiator Model

Based on the theory of acoustic waves, a circular surface radiator model is introduced as a basis for constructing a knowledge transfer model for a knowledge alliance. The three main variables in the model are chosen to be the number of enterprises in knowledge alliance, the frequency of knowledge transfer, and the relationship distances between the knowledge bodies. The internal mechanism of knowledge transfer in a knowledge alliance is studied, and the direct relationships among the internal influencing factors are explored. The results show that the number of enterprises in knowledge alliance, knowledge transfer frequency, and knowledge transfer effect are positively correlated. The “Rayleigh distance” in the knowledge field is the appropriate relationship distance measure for assessing knowledge transfer within the alliance. The Rayleigh distance is highly correlated with the number of enterprises in knowledge alliance and knowledge transfer frequency. Moreover, the number of enterprises in knowledge alliance and knowledge transfer frequency are interrelated.

Intrinsic nature of photocatalysis by comparing with electrochemistry

The kinetics of photocatalysis was discussed based on the calculated surface electric field, the limited electron transfer frequency and the irreversibility.

An Enhanced Inference Algorithm for Data Sampling Efficiency and Accuracy Using Periodic Beacons and Optimization

Transferring data from a sensor or monitoring device in electronic health, vehicular informatics, or Internet of Things (IoT) networks has had the enduring challenge of improving data accuracy with relative efficiency. Previous works have proposed the use of an inference system at the sensor device to minimize the data transfer frequency as well as the size of data to save network usage and battery resources. This has been implemented using various algorithms in sampling and inference, with a tradeoff between accuracy and efficiency. This paper proposes to enhance the accuracy without compromising efficiency by introducing new algorithms in sampling through a hybrid inference method. The experimental results show that accuracy can be significantly improved, whilst the efficiency is not diminished. These algorithms will contribute to saving operation and maintenance costs in data sampling, where resources of computational and battery are constrained and limited, such as in wireless personal area networks emerged with IoT networks.