No abstract

Yarrowia lipolytica is categorized as a generally recognized as safe (GRAS) organism and is a heavily documented, unconventional yeast that has been widely incorporated into multiple industrial fields to produce valuable biochemicals. This study describes the construction of a CRISPR-Cas9 system for genome editing in Y. lipolytica using a single plasmid (pCAS1yl or pCAS2yl) to transport Cas9 and relevant guide RNA expression cassettes, with or without donor DNA, to target genes. Two Cas9 target genes, TRP1 and PEX10, were repaired by non-homologous end-joining (NHEJ) or homologous recombination, with maximal efficiencies in Y. lipolytica of 85.6 % for the wild-type strain and 94.1 % for the ku70/ku80 double-deficient strain, within 4 days. Simultaneous double and triple multigene editing was achieved with pCAS1yl by NHEJ, with efficiencies of 36.7 or 19.3 %, respectively, and the pCASyl system was successfully expanded to different Y. lipolytica breeding strains. This timesaving method will enable and improve synthetic biology, metabolic engineering and functional genomic studies of Y. lipolytica.

No abstract

Acinetobacter baumannii resistance to carbapenem antibiotics is a serious clinical challenge. As a newly developed technology, silver nanoparticles (AgNPs) show some excellent characteristics compared to older treatments, and are a candidate for combating A. baumannii infection. However, its mechanism of action remains unclear. In this study, we combined AgNPs with antibiotics to treat carbapenem-resistant A. baumannii (aba1604). Our results showed that single AgNPs completely inhibited A. baumannii growth at 2.5 μg/mL. AgNP treatment also showed synergistic effects with the antibiotics polymixin B and rifampicin, and an additive effect with tigecyline. In vivo, we found that AgNPs–antibiotic combinations led to better survival ratios in A. baumannii -infected mouse peritonitis models than that by single drug treatment. Finally, we employed different antisense RNA-targeted Escherichia coli strains to elucidate the synergistic mechanism involved in bacterial responses to AgNPs and antibiotics.

Gut microbiota dysbiosis is closely associated with primary hepatocellular carcinoma (HCC). Recent studies have evaluated the early diagnosis of primary HCC through analysis of gut microbiota dysbiosis. However, the relationship between the degree of dysbiosis and the prognosis of primary HCC remains unclear. Because primary HCC is accompanied by dysbiosis and dysbiosis usually increases the circulatory concentrations of endotoxin and other harmful bacterial substances, which further increases liver damage, we hypothesized that level of dysbiosis associated with primary HCC increases with the stage of cancer progression. To test this hypothesis, we introduced a more integrated index referred to as the degree of dysbiosis ( D dys ); and we investigated D dys of the gut microbiota with the development of primary HCC through high-throughput sequencing of 16S rRNA gene amplicons. Our results showed that compared with healthy individuals, patients with primary HCC showed increased pro-inflammatory bacteria in their fecal microbiota. The D dys increased significantly in patients with primary HCC compared with that in healthy controls. Moreover, there was a tendency for the D dys to increase with the development of primary HCC, although no significant difference was detected between different stages of primary HCC. Our findings provide important insights into the use of gut microbiota analysis during the treatment of primary HCC.