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July 7, 2019  |  

The ß-lactamase gene profile and a plasmid-carrying multiple heavy metal resistance genes of Enterobacter cloacae.

In this work, by high-throughput sequencing, antibiotic resistance genes, including class A (blaCTX-M, blaZ, blaTEM, blaVEB, blaKLUC, and blaSFO), class C (blaSHV, blaDHA, blaMIR, blaAZECL-29, and blaACT), and class D (blaOXA) ß-lactamase genes, were identified among the pooled genomic DNA from 212 clinical Enterobacter cloacae isolates. Six blaMIR-positive E. cloacae strains were identified, and pulsed-field gel electrophoresis (PFGE) showed that these strains were not clonally related. The complete genome of the blaMIR-positive strain (Y546) consisted of both a chromosome (4.78?Mb) and a large plasmid pY546 (208.74?kb). The extended-spectrum ß-lactamases (ESBLs) (blaSHV-12 and blaCTX-M-9a) and AmpC (blaMIR) were encoded on the chromosome, and the pY546 plasmid contained several clusters of genes conferring resistance to metals, such as copper (pco), arsenic (ars), tellurite (ter), and tetrathionate (ttr), and genes encoding many divalent cation transporter proteins. The comparative genomic analyses of the whole plasmid sequence and of the heavy metal resistance gene-encoding regions revealed that the plasmid sequences of Klebsiella pneumoniae (such as pKPN-332, pKPN-3967, and pKPN-262) shared the highest similarity with those of pY546. It may be concluded that a variety of ß-lactamase genes present in E. cloacae which confer resistance to ß-lactam antibiotics and the emergence of plasmids carrying heavy metal resistance genes in clinical isolates are alarming and need further surveillance.

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July 7, 2019  |  

Whole-Genome and Expression Analyses of Bamboo Aquaporin Genes Reveal Their Functions Involved in Maintaining Diurnal Water Balance in Bamboo Shoots.

Water supply is essential for maintaining normal physiological function during the rapid growth of bamboo. Aquaporins (AQPs) play crucial roles in water transport for plant growth and development. Although 26 PeAQPs in bamboo have been reported, the aquaporin-led mechanism of maintaining diurnal water balance in bamboo shoots remains unclear. In this study, a total of 63 PeAQPs were identified, based on the updated genome of moso bamboo (Phyllostachys edulis), including 22 PePIPs, 20 PeTIPs, 17 PeNIPs, and 4 PeSIPs. All of the PeAQPs were differently expressed in 26 different tissues of moso bamboo, based on RNA sequencing (RNA-seq) data. The root pressure in shoots showed circadian rhythm changes, with positive values at night and negative values in the daytime. The quantitative real-time PCR (qRT-PCR) result showed that 25 PeAQPs were detected in the base part of the shoots, and most of them demonstrated diurnal rhythm changes. The expression levels of some PeAQPs were significantly correlated with the root pressure. Of the 86 sugar transport genes, 33 had positive co-expression relationships with 27 PeAQPs. Two root pressure-correlated PeAQPs, PeTIP4;1 and PeTIP4;2, were confirmed to be highly expressed in the parenchyma and epidermal cells of bamboo culm, and in the epidermis, pith, and primary xylem of bamboo roots by in situ hybridization. The authors’ findings provide new insights and a possible aquaporin-led mechanism for bamboo fast growth.

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