Novel Transcription Factor CXRD Regulates Cellulase and Xylanase Biosynthesis in Penicillium oxalicum under Solid-State Fermentation.

Penicillium oxalicum produces an integrated, extracellular cellulase and xylanase system, strictly regulated by several transcription factors. However, the understanding of the regulatory mechanism of cellulase and xylanase biosynthesis in P. oxalicum is limited, particularly under solid-state fermentation (SSF) conditions. In our study, deletion of a novel gene, cxrD (cellulolytic and xylanolytic regulator D), resulted in 49.3 to 2,230% enhanced production of cellulase and xylanase, except for 75.0% less xylanase at 2 days, compared with the P. oxalicum parental strain, when cultured on solid medium containing wheat bran plus rice straw for 2 to 4 days after transfer from glucose. In addition, the deletion of cxrD delayed conidiospore formation, leading to 45.1 to 81.8% reduced asexual spore production and altered mycelial accumulation to various extents. Comparative transcriptomics and real-time quantitative reverse transcription-PCR found that CXRD dynamically regulated the expression of major cellulase and xylanase genes and conidiation-regulatory gene brlA under SSF. In vitro electrophoretic mobility shift assays demonstrated that CXRD bound to the promoter regions of these genes. The core DNA sequence 5'-CYGTSW-3' was identified to be specifically bound by CXRD. These findings will contribute to understanding the molecular mechanism of negative regulation of fungal cellulase and xylanase biosynthesis under SSF. IMPORTANCE Application of plant cell wall-degrading enzymes (CWDEs) as catalysts in biorefining of lignocellulosic biomass into bioproducts and biofuels reduces both chemical waste production and carbon footprint. The filamentous fungus Penicillium oxalicum can secrete integrated CWDEs, with potential for industrial application. Solid-state fermentation (SSF), simulating the natural habitat of soil fungi, such as P. oxalicum, is used for CWDE production, but a limited understanding of CWDE biosynthesis hampers the improvement of CWDE yields through synthetic biology. Here, we identified a novel transcription factor CXRD, which negatively regulates the biosynthesis of cellulase and xylanase in P. oxalicum under SSF, providing a potential target for genetic engineering to improve CWDE production.

[Clinical characteristics and antibiotic resistance in children with invasive Acinetobacter baumannii infection].

OBJECTIVE: To analyze the clinical characteristics and antibiotic resistance in children with invasive Acinetobacter baumannii infection (IABI). METHODS: A retrospective analysis was performed on the clinical and drug sensitivity data of 52 children with IABI between January 2004 and December 2011. RESULTS: Of the 52 children with IABI, 35 (67%) were less than one year old and 35 (67%) had IABI in the summer and autumn, 19 (37%) of these children were clinically diagnosed with septicemia, 16 (31%) with urinary tract infection, and 12 (23%) with skin and soft tissue infection, and 38 (73%) of them suffered from underlying diseases. The incidence rates of hospital-acquired and community-acquired IABIs were 90% and 10% respectively; 44 cases (85%) were cured or showed improvement in symptoms, and 8 cases (15%) died. All the IAB strains isolated from these children were sensitive to amikacin, 82% of them were sensitive to imipenem, more than 70% were sensitive to fluoroquinolone and to cefoperazone/sulbactam, 13% were sensitive to cefoperazone, 8% were sensitive to aztreonam, 21% developed multidrug resistance, and 17% developed pan-drug resistance. CONCLUSIONS: IABI occurs more frequently in children under one year of age, and most children with IABI have underlying diseases. IABI mainly results in septicemia, urinary tract infection and skin and soft tissue infection and is mostly hospital-acquired. Multi-drug resistance and pan-drug resistance are severe in IAB strains.